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  1. You are so right that statistical models “… aren’t much good for predictions if you know the underlying system is changing …” The ability of statistics to interpolate within the range of known behavior is impressive, but extrapolation into unknown territory is very risky business.

    Comment by tamino — 3 Nov 2008 @ 7:18 AM

  2. What are the major differences between climate models and weather models? Strengths and limitations of both?

    [Response: Conceptually they are very similar, but in practice they are used very differently. Weather models use as much data as there is available to start off close to the current situation and then use their knowledge of physics to step forward in time. This has good skill for a few days and some skill for a little longer. Because they are run for short periods of time only, they tend to have much higher resolution and more detailed physics than climate models (but note that the Hadley Centre for instance, uses the same model for climate and weather purposes). Weather models develop in ways that improve the short term predictions – but aren’t necessarily optimal for long term statistics. – gavin]

    Comment by Bud Ward — 3 Nov 2008 @ 7:48 AM

  3. >>

    On what basis then do I consider or assess expensive climate policy proposals that are supposedly justified by (putative/speculative) climate impacts on my home?

    I.O.W. if I do not know what will happen in 100 years time around here where I live, how do I know what to do about it? Or whether I even should do something?

    Comment by Clive van der Spuy — 3 Nov 2008 @ 8:55 AM

  4. Question: Can GCMs predict the temperature and precipitation for my home?

    Answer: No

    On what basis then do I consider or assess expensive climate policy proposals that are supposedly justified by (putative/speculative) climate impacts on my home?

    I.O.W. if I do not know what will happen in 100 years time around here where I live, how do I know what to do about it? Or whether I even should do something?

    Comment by Clive van der Spuy — 3 Nov 2008 @ 9:06 AM

  5. Sorry but I am having difficulty copying and pasting from your site – it does not come through on the final post that appears. My posts also do not seem to reflect.

    Post 1 was in response to:

    FAQ: Can GCMs predict the temperature and precipitation for my home?
    Answer: No

    Comment by Clive van der Spuy — 3 Nov 2008 @ 9:24 AM

  6. Very nice FAQ. I have wondered how the inputs are handled as the models step forward into the future. Do they use the length of the day for the solar input? How do they handle future solar variability as an input? What about the distance of the Earth from the Sun – is than an input (or is that to long term to model in the climate models?) Do the models input the PDO or ENSO, or does that sort of fall out of the models themselves. Thanks in advance for any response.

    [Response: The effect of the orbit is fully taken into account – and indeed variations in the orbit on multi-thousand year timescales are one of the key tests of the model in matching past climate data. Variations in the tropical Pacific arise naturally as part of the model solutions, but getting that variability to match observations is still a huge challenge. – gavin]

    Comment by RickA — 3 Nov 2008 @ 10:21 AM

  7. As a television meteorologist I frequently encounter the comment that because climate models are using “bad” data they are biased and do not reflect reality, therefore cannot be trusted and global warming either does not exits or exists an there is no anthropogenic influence.

    My approach is to explain that the models are not dependent on observed data. I also explain that given any set of initial weather conditions (wintin reason) a good model will eventually reproduce realistic climate patterns.

    To simplify I restrict the initial conditions under consideration to global temperature only. My example usually sets global temperature to a uniform 10C (50F) with all other variables at realistic values. I tell the viewer that given this scenario, if run for a sufficient amount of time (both model time and computational time of course). the model will reproduce realistic global temperature distributions.

    My experience with the curious but uneducated in climate science reinforces the “keep it simple” approach.

    Ten celsius (50F) works well because that temperature seems to be too cool for equatorial regions and too warm for polar regions in the mind of the average viewer.

    I then explain that a climate model, as the computations are made will warm equatorial regions and cool polar regions.

    The point then is that the model is not dependent on the observed data and because it is a representation of the physical processes governing the climate system the model eventually gets earth’s climate to where it is.

    Often this is as far as I can go without getting a blank stare. For those who remain with me, this point is a great jumping off point to discuss how the same thing can be done with greehhouse gas concentrations.

    If initial conditions are a realistic representation of 1960 earth and the only change made is by increasing greenhouse gasses by the amount that can be attributed to human activity the planet warms.

    I am still met with skepticism in some cases but I feel I have at least exposed members of the public to a very basic look at how this all works.

    1. Anyone see a flaw in the reasoning above?
    2. Anyone have suggestions for improving the approach?
    3. Anyone have and idea for taking this approach farther?

    Recall the average American is barely functionally literate in science so simple is important.

    Thanks for your time,
    Steve Horstmeyer

    Comment by Steve Horstmeyer — 3 Nov 2008 @ 10:28 AM

  8. “GCM – General Circulation Model (sometimes Global Climate Model) which includes the physics of the atmosphere and often the ocean, sea ice and land surface as well.”

    ‘THE’ physics? Hardly. Your bias is showing. ‘Some’, ‘much’ ‘ or simply ‘physics’ will do.

    Comment by auntiewiggly — 3 Nov 2008 @ 11:14 AM

  9. “Initial Condition Ensemble – a set of simulations using a single GCM but with slight perturbations in the initial conditions.”

    Bad definition. An ‘initial condition ensemble’ is exactly what it says – a collection of initial conditions which may or may not be close. You are in fact trying to define something akin to the microcanonical ensemble of statistical physics – a set of states consistent with the external contstraints imposed on the system.

    Comment by auntiewiggly — 3 Nov 2008 @ 11:27 AM

  10. Here’s another question.

    Is it true that the climate models do not reproduce the the abrupt climate changes that happened in the Northern Hemisphere at the start of the Booling-Allerod interstadial and at the start of the Holocene Epoch?

    If so, how can we be sure that a similar event will not happen in the near future?

    Cheers, Alastair.

    Comment by Alastair McDonald — 3 Nov 2008 @ 11:28 AM

  11. OT: this page says it is valid XHTML, but the validator says it has 57 errors.

    Comment by Douglas McClean — 3 Nov 2008 @ 11:48 AM

  12. hey something that works on windows!! Now I have a new toy to keep me busy for a while. Great post.

    Comment by Chris Colose — 3 Nov 2008 @ 12:20 PM

  13. Do any of the GCM models include a negative feedback mechanism as described in the attached link?

    The study found that the cooling effect of the trees is attributed to the release of chemicals that react to form aerosols and convert water vapour into clouds.

    Perhaps the slight warming we’ve seen over the last 100 years is attributable to all the forests that have been cleared all over the world rather than CO2.

    Comment by Ed — 3 Nov 2008 @ 12:21 PM

  14. Hi,
    when I am discussing with climate skeptics, they often refer to the third report of the IPCC (page 774): “In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”
    I don’t now what to answer. Perhaps you can help me and explain how the quote ist correctly to be understand?


    [Response: There are at least two aspects to this question. First, how well do we know the forcing into the future? We can’t do a very good job at estimating the future trajectory of technology for instance, or economic development, and so regardless of how well we understand climate, our ability to predict exactly what will happen is limited. Secondly, we don’t have full information about the current conditions, and so, like for weather forecasts, if there are aspects of climate change that are chaotic, we can’t predict those over the long term. However, it is worth pointing out that the statement does not imply that we can’t know anything about the climate system in the future. We know that if there is a big volcano, the climate will cool – and many aspects of the resulting changes will have been predictable. The same is true for increasing GHGs – the climate will warm. Models can’t tell you exactly what will happen where, but there is a lot they can say. – gavin]

    Comment by Samson — 3 Nov 2008 @ 12:29 PM

  15. My question concerns the interplay of forcings and feedbacks to produce a “climate sensitivity”:

    As I understand it, the warming resulting from a doubling of [CO2] is around 1.1 oC from an increased forcing near 4 Wm-2. This warming will be amplified by feedbacks (assuming a net positive feedback). If the enhanced atmospheric warming from a CO2-induced temperature rise of 1 oC results in enhanced water vapour that gives an additional warming of say x oC, the overall warming (doubled CO2 + water vapour feedback; leaving out other feedbacks for now) will be something like 1.1*(1 + x + x2 + x3…) or 1.1/(1-x)].

    QUESTION: Is there a good estimate for the value of “x”? e.g. “x is greater than 0.2 oC and less than 0.5 oC”? Is that a meaningful question to ask?

    Presumably the water vapour feedback in models is dealt with by determining/estimating/calculating the radiative forcing from water vapour and then making some assumption about the water vapour response to atmospheric warming (e.g. assuming constant relative humidity). If so, then an estimate for “x” above should be an accessible/calculable number (?)

    What I’m trying to get at is some simplistic estimate of the water vapour feedback that results from an enhanced CO2-induced warming of say 1.1 oC from the CO2 RF of around 4 Wm-2. One of the things that people (particularly from an engineering background) have trouble with is the idea that the feedback from a small amount of warming can give rise to a much larger amount of warming, and this seems, from an “enginering perspective” on the meaning of “feedback”, to result in an uncontrolled “runaway” response.

    My understanding is that many of the feedbacks in relation to atmospheric physics are better considered as “amplifications”, since the response doesn’t necessarily feedback into the input (i.e. the feedbacks resulting from raised [CO2] don’t result in very much in the way of further enhanced CO2 concentrations although this happens a bit and is important during Milankovitch warming where enhanced [CO2] is itself an important feedback). Therefore one can essentially add up the “feedbacks”/amplifications.

    Is that a good way of thinking about climate feedbacks in relation to climate sensitivity? ..anyone know of a better way of explaining this to recalcitrant engineers?

    Comment by Chris — 3 Nov 2008 @ 1:11 PM

  16. Alastair McDonald (8) — Those abrupt warmings are related to the collapse of massive ice sheets:

    and, in seems, not global nor as rapid as in Greenland.

    In any case, there are no massive ice sheets going to rapidly collapse at any time in the readily foreseeable future.

    Comment by David B. Benson — 3 Nov 2008 @ 1:35 PM

  17. Question: How are clouds parametrized in the models? How are the parameterizations evaluated? The IPCC reports considerable uncertainty associated with cloud and aerosol forcings. What is being done to address them?

    Comment by James C Wilson — 3 Nov 2008 @ 1:37 PM

  18. Sampson, #12. The response is “how do you know that any errors are there to make the problem disappear?”.

    I may have an error in measuring out the weight of produce of 5% but this doesn’t mean it only ever goes 5% in my favour.

    Then ask if they would have complained about how these scientists were hiding problems with the model if they didn’t say this statement, whether they knew if there were errors or not.

    Comment by Mark — 3 Nov 2008 @ 1:51 PM

  19. Ed.

    Try doing the maths.

    How much would these clouds cool the atmosphere? Remember that a clear night is colder by far than a cloudy one, and whether a cloud is cooling or warming depends on how high it is: high clouds radiate back out into space, low clouds are just “high ground” as far as warming the air is concerned.

    Then if you can’t be bothered to do the sums and put them here for checking, take as read that no, they don’t make the difference.

    Comment by Mark — 3 Nov 2008 @ 1:53 PM

  20. re #8.

    How do we know that an asteroid will hit the earth, splitting it apart and removing the earth from its orbit.

    After all, there’s no model for how this CAN’T happen.

    Check out the phrase “clutching at straws”.

    Comment by Mark — 3 Nov 2008 @ 1:55 PM

  21. 3. Steve Horstmeyer: Maybe go even simpler: Start with the 19th century laboratory measurements of the absorption of infrared by CO2 at various pressures. Cite the MIT Wavelength Tables, an encyclopedia-sized resource. Tell them about the thermal runaway on Venus. Talk about the measurement of CO2 concentration that has been going on in Hawaii since 30 or 40 years ago. It is really hard to understand how anybody could avoid the idea that the absorption bands of every gas have been cataloged and re-measured about a jillion times. Perhaps all high school students should be required to take 4 years of physics in which they spend about a semester measuring the spectra of CO2 and other things.

    We have known since the 19th century that CO2 absorbs infrared. Oxygen and nitrogen have windows where CO2 does not. That is how we know that it is CO2 and other gasses that are causing global warming.

    We have satellites that are measuring the solar energy coming in and the heat radiation going out. More is coming in than going out, so the earth has to be getting warmer.

    Maybe talk about how much less ice there is in the Arctic Ocean recently. You have to tell them that the “Normal” temperature displayed on your 5 day weather prediction is a running average of only the last 10 years. You have to say this is because the George W. Bush Administration won’t let you use all of the data since 18?? when that data was first recorded in your area. In other words, you have to admit that the W. government requires you to lie to cover up global warming. You have to remind them that it is global not local, a small number of degrees, and an average not an absolute. Then say: “The GCMs use the laboratory data on the absorption of infrared by CO2 and a whole lot more science to try to make climate predictions. The problems are that computers aren’t ‘big’ enough to take everything into account, and the butterfly problem happens.”

    Tell them the following: Global Warming Has Already Happened. In the mid 19th century, the Mississippi river froze over in the winter so you could drive on it at St. Louis. That’s how St Louis became known as the gateway to the west. Now the Mississippi river is ice-free at Davenport, Iowa. If you want to drive on the river, you have to go at least as far North as Minnesota. Cattaraugus County New York [Olean, Little Valley] got 450 inches [37.5 feet] of snow per year in the 1950s and 1960s. Now it gets only 96 inches of snow per year. At Barrow, Alaska, the grave yard washed away because the fast[ened to the land] sea ice melted. We humans have caused 1.3 degrees Fahrenheit of global warming since we started burning coal in 1750.

    In other words, you have to try to teach a little basic science to people who weren’t smart enough to be able to take science courses when they were in high school. In addition to the IQ problem and the amazing ignorance problem, some of them may be coal miners or other coal industry involved people who want to keep on mining coal.

    You could give them a list of URLs, such as:

    Remind them that the coal industry puts up a lot of phony web sites to distract them.
    You could list some books, but my guess is that you are talking to people who have marginal reading skills and no plans to read books.

    Comment by Edward Greisch — 3 Nov 2008 @ 1:56 PM

  22. Bud, the differences are:

    Weather. Small scale transients. The result of input operating under chaos.
    Climate. Large scale time invariants. The result of inputs operating under forcings.

    Think of rolling a rugby ball from the top of a hill. There are dips, bumps, hedges, bushes and the occasional dog on the slope.

    Where is it going: Downhill.
    What path will it take: Uh, depends, really.

    Climate=where is it going
    Weather=what path will it take

    Just because you think it *might* hit that bush and go *that* way but with low confidence and none further down the hill doesn’t mean the ball will roll uphill.

    Comment by Mark — 3 Nov 2008 @ 2:00 PM

  23. Anything on paleo climate models, especially the proprietary ones used in petroleum exploration, would be welcome. Tidbit here:

    Comment by Hank Roberts — 3 Nov 2008 @ 2:09 PM

  24. VERY VERY good post! Thanks!

    Is there any sense of how, how much, if, or which parameters ‘tuned’ for emergent properties in the average climate might change with climate change? Could comparing different months, seasons, and years help in that?

    Could the climate forcing itself, such as increasing GHGs, affect parameterizations independently of the larger scale climate changes (for example, by changing thermal damping of various kinds of waves, or by changing the differences of radiative effects between different amounts and kinds of clouds)?

    Would there be any advantage to having seperate models at seperate scales, where smaller scale processes would be modelled at fine resolution, and the larger scale model would, for each unit grid and time, search the results of the smaller model based on similarity of input conditions, perhaps interpolating and if necessary using a randomly chosen result based on probability distributions, and in the ocassion where the results of the smaller model are too sparse, telling the smaller scale model to do a new run (as time goes on this would happen less often)?

    Has there been any success with models that would attempt to model climate ‘directly’ via some theoretically or otherwise justified parameterization of all weather?

    To what extent can model results be explained conceptually via cause and effect relationships (for example, the storm tracks move here because the tropopause did this…) and where could I go to find more of that?

    Comment by Patrick 027 — 3 Nov 2008 @ 2:14 PM

  25. Simple logistics question – With today’s higher speed computers, about how long does it take to complete a single GCM model run simulating 100-150 years?

    [Response: It’s always taken about the same amount of time (roughly a month). As computers get faster, we add in more stuff. – gavin]

    Comment by Bob North — 3 Nov 2008 @ 2:24 PM

  26. Well said. The models are increasing in complexity and are at least approaching more true to life climate conditions. To echo tamino, statistical methods cannot factor in all the real time changes. The signal-noise ratio can be a confounding thing indeed when analyzing the raw stats. Still besides empirical observations and good inferences, the models are what are available to work with, and they serve several purposes quite well and they are the basis for improved models in the future.

    Comment by jcbmack — 3 Nov 2008 @ 2:39 PM

  27. I have stumbled across the recorded global temperature increase chart for the last century. The wiggles are smoothed with five-year averaging. The graph shows clearly three things. It can be divided into roughly three equal parts. The first is a straight line increase. The second is a temperature plateau, even decreasing slightly. The third is another straight line increase at the same gradient as the first one. What caused the plateau? This is a significant matter, since the century is center to the manmade carbon dioxide creation. We all know the hockey stick curve steep increase of CO2, and its latency in the atmosphere. Since the general proclamation is a direct causal, albeit somewhat delayed rise in global temperature, where does the plateau come from? This 30-plus year phenomenon is not just an insignificant kink in the straight-line curve. Something bent the curve drastically. With all the theories, clamor, explanations of global temperature rise I have not found a single reasoning for this plateau. Why is this important? Well, aren’t there real doomsday numbers being credibly disseminated, of 5 to 10 degrees Celsius increase within the next 100 years? Could we not see another plateau, a stoppage, a real drop-off? Please, can someone give me a simple explanation, and not a “definite may-be” obfuscation?

    Comment by Dietrich Hoecht — 3 Nov 2008 @ 4:20 PM

  28. I presume we are now running models which assume a lot more open water in the Arctic. How do the models then play out? Not obvious to me. Does the reduced albedo of the ocean mean that more energy is absorbed instead of reflected? Or does the increased evaporation cause more snow on the neighboring land and hence more reflection? This question seems important to me because we notice that temperatures rose through the previous interglacial (which was warmer than this one), then crashed: so it seems natural to look for some switch that got flipped. Snow and ice on land can build up, unlike ice on water.

    Comment by Robert Smart — 3 Nov 2008 @ 4:44 PM

  29. Nice summary post. Re#8, any changes in climate over glacial-interglacial timescales have to take into account an additional component: the biogeochemical cycling of atmospheric gases.

    The climate models as described here won’t produce glacial/interglacial cycles if run for a long time, and that is because they treat the atmospheric content of trace IR-absorbing gases (CO2, methane and N2O) as external forcings. Thus, for a 100-yr climate model run, the year-by-year atmospheric CO2 content is set by the researcher.

    There are many reasons that the atmospheric gas content can change. Purely physical processes like wind-driven mixing can increase the uptake of CO2 by the oceans, but biological processes also play an important role, as does the temperature difference between the air and the water:

    This kind of biogeochemical analysis is needed to understand the overall role of CO2 and methane in the global climate. It is also needed to evaluate the effectiveness of any carbon trading programs designed to limit CO2 buildup in the atmosphere.

    For example, a biogeochemical model can be used to show that dumping iron in the oceans will have no effect on atmospheric CO2, as any increase in algal growth will be accompanied by increases in remineralization of algal biomass in the water column. The only way to permanently remove the biomass is to bury it beneath sediment.

    You also need a biogeochemical approach to answer questions like “what gases will the melting permafrost add to the atmosphere?” The main control over microbial activity is temperature, so as northern soils and permafrost warm, there should be a flux of CO2 and/or methane to the atmosphere. If it is very wet, that encourages methane formation. The process is entirely analogous to slowly defrosting a freezer full of food – it starts to outgas as microbial decomposition sets in.

    Any estimate of the effect that preserving a forest has on the atmospheric CO2 also must be based on some kind of biogeochemical approach. In northern forests, the average age of leaf litter might be 5 years, but in tropical regions, that might just be six months. The difference is mostly temperature – microbial decomposition never lets up in the tropics. A standing forest, in that respect, is a bit like a living coal field – or a coal field is a fossilized forest. In either case, the carbon accounting is done the same.

    This is all discussed in the IPCC ( but is usually left out of news reports, which typically fail to discuss the fundamental differences between CO2 emissions from living biomass, deforestation emissions, permafrost emissions, and fossil fuel CO2 emissions. Not all carbon dioxide emissions are the same, not by a long ways!

    Fossil fuel carbon last saw the atmosphere millions of years ago, and that’s why burning it leads to a net accumulation of CO2 in the atmosphere. It’s a basic but widely misunderstood point.

    Comment by Ike Solem — 3 Nov 2008 @ 4:54 PM

  30. How are solar variations represented in the models?

    Comment by Jim Cross — 3 Nov 2008 @ 5:29 PM

  31. Guess what? You have described very well the economists/bankers mathematical models that predicted everything was rosy in this best of all possible worlds. Trouble is it turned out to be a house of cards, and there is no evidence that climate models are any better, and even less evidence that they should be used as the basis for policy decisions.

    Comment by Dave Andrews — 3 Nov 2008 @ 5:37 PM

  32. Thank you – the FAQ has added to my knowledge considerably.

    Two questions:

    (1) I believe that the global mean temperature in the 00s has increased less quickly (if at all) in the last 10 years or so, compared to the previous two decades. Have any of the models been adjusted in the light of measurements from the last 10 years? Do newer models fit that data better than older ones?

    (2) What proportion of model runs from a multi-model ensemble produce global mean temperatures at or below (on average) the actual measurement for the last 10 years?

    Comment by Neil McEvoy — 3 Nov 2008 @ 5:52 PM

  33. My Climatology professor says GCMs that predict global warming are based on a doubling of CO2 from 350-700 PPM in the next 50-100 years. Is this correct, and if so, why is a doubling assumed when CO2 has increased approximately 100 PPM since pre-industrial times? If someone can point me to a source that explains why 700 PPM is a valid prediction and input, I would be much obliged.

    [Response: Look up the IPCC SRES scenarios to get a handle on what CO2 emissions could plausibly lead to. – gavin]

    Comment by Mae Frantz — 3 Nov 2008 @ 6:15 PM

  34. Samson (#12 3 November 2008 at 12:29 PM):

    You could try quoting the very next sentence to them: “The most we can expect to achieve is the prediction of the probability distribution of the system’s future possible states by the generation of ensembles of model solutions.”

    I’d have thought a probability distribution of the system’s future possible states would be enough to inform rational decision-making, though of course some people will never be satisfied.

    Comment by Garry S-J — 3 Nov 2008 @ 6:18 PM

  35. Dave Andrews (27) — The important difference is that the climate models are based on physics whilst the economic ones are not.

    Comment by David B. Benson — 3 Nov 2008 @ 6:36 PM

  36. 23 Clarification:

    “(for example, by changing thermal damping of various kinds of waves, or by changing the differences of radiative effects between different amounts and kinds of clouds)?”

    Regarding the second part, I didn’t mean to imply that that would be parameterized; but it’s an example of what could change. As for the first part, I got the impression that it might in some cases be parameterized, but I’m not sure if there’s much of an effect.

    Other questions:

    Do climate models currently take into account the solar UV -stratosphere-ozone aspect of solar forcing?

    What might change (educated guesses) in model output if the dynamics of the upper atmosphere were better resolved?

    Comment by Patrick 027 — 3 Nov 2008 @ 6:53 PM

  37. Dave Andrews:

    GCMs are able to do hindcasts – i.e. they are able to fairly accurately replicate both recent and ancient past climates and climate shifts.

    I would be fascinated to hear of any economic models that are capable of doing this – e.g by replicating the great depression, the Dutch tulip bubble or the impacts on each national economy of the abolition of slavery.

    Comment by Craig Allen — 3 Nov 2008 @ 6:54 PM

  38. The data ultimatley dictates everything, but the models are very useful. No matter what stats are used, eventually the accuracy and is determined, the models are coming along nicely. Even if one were to use a lowe end estimate, global warming is a major issue, not in great dispute, even non peer reviewed data is useful, just that the peer reviewed data and model designs have been shown to have a lot of relevance.

    Comment by jcbmack — 3 Nov 2008 @ 7:50 PM

  39. #14 Chris

    Since climate feedbacks are a converging series, the value of x as you set it up must lie on an internal from zero to one. Though, the effect is generally expressed in units W/m**2/K to express the change in the top-of-atmosphere radiative balance…where the longwave and shortwave components of water vapor feedback is roughly 1.13 and 0.27, respectively (Soden et al 2008). The water vapor feedback itself roughly doubles the sensitivity of climate, but note that its magnitude also depends on other feedbacks. Whether or not relative humidity is conserved is going to effect its magnitude, but this is not an assumption as you put it, but an emergent property of models.

    Comment by Chris Colose — 3 Nov 2008 @ 7:52 PM

  40. Edward # 20, well said! It is apalling how many websites and papers are put out by company funded projects in the name of “science.”

    Comment by jcbmack — 3 Nov 2008 @ 7:54 PM

  41. Chris # 14 Airplane ingineers deal with forces of great magnitude all the time. For example wind shear can be quite powerful and ingineers rely upon data and careful calculations to design a plane that will not have a cockpit that will snap off. In this sense, the airplane may be “sensitive,” to some sort of force of some magnitude and vector, (consider also tail winds, cross winds and head winds) Usually ingineers do not work in values of x. The Earth is a natural system with both natural and artificial influences, but inputs can be greatly magnified; if one were to ‘ingineer,’ a sound system that amplifies sound volume (apmlitude) and enhances pitch (a function of frequency) does the volume run away? The climate sensitivty of the planet can be greatly increased by both precipitating events and positive feedback being greater or more abundant than negative; slower to develop as well. Constant relative humidity? Could you expand on that?

    Comment by jcbmack — 3 Nov 2008 @ 8:14 PM

  42. PS to Dave Andrews re economic vs climate models:

    Also, James Hansen successfully predicted in 1981 the trend of the past several decades of global warming, including a good approximation of the noise around the trend. And he did so with a climate model that was far less sophisticated than those of today.

    Can you provide an example of any economic model that has been anywhere near as successful?

    Comment by Craig Allen — 3 Nov 2008 @ 8:34 PM

  43. Gavin – thanks for your quick response to my question (#24). That is actually a good bit longer than I expected.

    Comment by Bob North — 3 Nov 2008 @ 8:38 PM

  44. Since models are about 100×100 KM^2 horizontally, or even somewhat less, the grids would contain elements like forested and/or farm areas,cloud cover and urban areas that are smaller than the grid, that effect climate in the grid as a whole. How would models generally treat the entire grid to account for these effects?
    My take is that the statistical downscaling described by Rasmus in his post on Regional Climate Projections, doesn’t apply to entire grids.

    Comment by Lawrence Brown — 3 Nov 2008 @ 9:12 PM

  45. On a short note I have to say this site is the best for information and blogging on GW issues.

    Comment by jcbmack — 3 Nov 2008 @ 10:47 PM

  46. Re: Edward Greisch #21

    Ed – you have a lot of useful information and good links, why mix in some falsehoods and BS? Reported normals on weather forecasts are for 30 year averages, not 10 years, and have been for a long time. Dubya has nothing to do with it and isn’t requiring any weather people to lie to cover up Global warming.

    Although I can’t say whether the Mississippi froze at Saint Louis regularly during the 19th century, I am sure that is not how St. Louis got the nickname of “Gateway to the West”. I don’t know where you got the idea that Cattaragaus County in NY routinely got 450 inches of snow during the 50s and 60s since the record annual snowfall in NY is 379.5″ at Hooker 12 NNW (in 1979), which is nowhere near Cattaragaus county, but in the snowbelt east of Lake Ontario.

    Just stick to the facts and don’t embellish.

    Comment by Bob North — 3 Nov 2008 @ 11:01 PM

  47. Regarding response to #33.

    Gavin, are you aware of the complete disconnect between SRES estimates of fossil fuel reserves, which are based on a single review paper by Roger in 1997, and more recent views regarding peak oil, peak gas, and peak coal? Ever read about this stuff, e.g., Dave Rutledge or James Hansen work?

    Not that I think it matters too much…there’s far too much co2 in the air already, but SRES is a joke in my view. Economic growth forever? Come on.

    [Response: I was simply answering the question. Scenarios are being updated all the time, but the only thing that is clear is that there is plenty enough carbon to take us significantly above where we are now. Oil, coal, shales, hydrates or whatever. Peak oil is not going to save us – and I know that Hansen doesn’t think so. – gavin]

    Comment by Jason — 3 Nov 2008 @ 11:17 PM

  48. Re #33

    If CO2 production grows at 2% annually, that is a doubling about every 30 years. But take a moment to think about what a doubling power series really means – it took me a while to get my head around this, and I think most people don’t appreciate the magnitude of such growth – but the effect is that every 30 year period results in as much CO2 as the ENTIRE PREVIOUS HISTORY (since the exponential growth began).

    Comment by William — 4 Nov 2008 @ 12:02 AM

  49. How do you model clouds?

    Comment by jim norvell — 4 Nov 2008 @ 12:06 AM

  50. Thank you for the chance to ask some basic questions.

    This has bothered me in the past. You say that the hindcasts are true hindcasts, and that parameters are not fit to match the historical trends. That’s all very well and good.

    So can you help me understand what is happening here?

    All the GCMS do a decent job of the hindcast, yet diverge in the forecast. They’re all using the same scenario here, so the forcings ought to be the same.

    If the GCMs have slightly different physics, why would that show in the future, but not the past?

    [Response: One issue is the inertia in the oceans which means that the 20th century changes are not in equilibrium. Therefore, the changes so far aren’t impacted by the full equilibrium sensitivity. Transient sensitivities are much closer across the models than the equilibrium value. But as the signal gets larger, the models will diverge a little more. – gavin]

    Comment by tharanga — 4 Nov 2008 @ 12:09 AM

  51. Re Dave Andrews @31: “You have described very well the economists/bankers mathematical models that predicted everything was rosy in this best of all possible worlds.”

    Did you even read the post? The very first “Question” outlines the fundamental difference between a statistical model (your economists/bankers mathematical model) and a dynamic physical model (general circulation model) based on physical laws and properties.

    Ignorance is correctable. Will ignorance is inexcusable.

    Comment by Jim Eager — 4 Nov 2008 @ 12:19 AM

  52. Dietrich Hoecht #27:

    the plateau is commonly, and credibly, attributed to industrial aerosols produced by Northern hemisphere industrialized countries. (Not to be confused with stratospheric aerosols due to large volcanic eruptions.) See, e.g., Figure 9.5 in the IPCC AR4 WG1 report. Or

    It was the cooling produced by these areosols that offset the greenhouse warming and even led (in the popular press, not the scientific literature) to the “ice age scare” of the 1970’s:

    With all the theories, clamor, explanations of global temperature rise I have not found a single reasoning for this plateau.

    Yes, googling is an art :-)

    Comment by Martin Vermeer — 4 Nov 2008 @ 12:34 AM

  53. Mae (#33). Predictions of global warming are not “based on” doubling of CO2. Even the present 387 ppm would lead to further climate change, and ideas on a relatively ‘safe’ level range from 350 to 450 ppm. At the moment the CO2 concentration is increasing by approx. 3 ppm per year, so at this rate it would reach 450 ppm in little more than 20 years:

    Comment by Ark — 4 Nov 2008 @ 12:43 AM

  54. It’s semantics, but for cross-discipline understanding, you might reconsider that “physical model” coinage (yours?). I understand you to mean “a model built to represent basic physical principles”, but others could be confused.

    The term physical model is widely used in engineering to mean a model built from actual physical stuff, usually to scale; sometimes in quite complex ways. Believe it or not such models are still widely used to predict the behavior of things which are computationally difficult or even intractable. Examples include hydraulic structure models (eg dykes to resist hurricane waves and rising sea levels!) and the wind tunnel models used in aeronautics. In engineering jargon, A GCM would be a numerical model, so I guess the term you’d be looking for would be physically-based numerical model

    [Response: See #66 – I’ve gone with physics-based. Thanks – gavin]

    Comment by GlenFergus — 4 Nov 2008 @ 1:03 AM

  55. Are there measurements of “Earthlight”? Do we have experimental records demonstrating the atmosphere is not CO2 saturated?

    Comment by Richard C — 4 Nov 2008 @ 5:29 AM

  56. Re #47 It might not save us but it will potentially disrupt the global economy and political order enough to make AGW a problem for future generations and not this one.

    If economic growth is the reason detre of the present globalized world then its a pipe dream. Tar and shale sands cannot scale in time and neither can coal for peak oil to make a large scale impact. Recently at $147 a barrel it was starting to hurt but when we cannot pump more oil and a depression is not on the cards and demand is growing it will spell significant issues for the world.

    Comment by pete best — 4 Nov 2008 @ 5:35 AM

  57. On economic models, in 2004 representatives (Hank Paulson, then the CEO of Goldman Sachs, was one of them) of some the investment banks met with the SEC to request a change in their required capital reserves. There was one dissenting opinion, mailed in from a guy with a PO box:

    Comment by JCH — 4 Nov 2008 @ 8:32 AM

  58. Mark writes:

    How do we know that an asteroid will hit the earth, splitting it apart and removing the earth from its orbit.

    After all, there’s no model for how this CAN’T happen.

    Asteroids are very small compared to the Earth and would have great difficulty changing Earth’s orbit noticeably, even with a major impact.

    Comment by Barton Paul Levenson — 4 Nov 2008 @ 9:16 AM

  59. Dietrich Hoecht writes:

    Since the general proclamation is a direct causal, albeit somewhat delayed rise in global temperature, where does the plateau come from?

    The plateau of temperature from about 1940 to 1970 is generally attributed to an increase in high-altitude aerosols due to the tremendous ramping up of industry in response to World War II. When pollution controls began to be introduced in the 1970s, the temperature began rising again.

    Comment by Barton Paul Levenson — 4 Nov 2008 @ 9:26 AM

  60. Dave Andrews writes:

    there is no evidence that climate models are any better, and even less evidence that they should be used as the basis for policy decisions.

    There is considerable evidence that climate models are better. Just because you’re not familiar with it doesn’t mean the evidence doesn’t exist. You really ought to research these things more thoroughly before making pronouncements about them.

    Global climate models have successfully predicted the rise in temperature as greenhouse gases increased, the cooling of the stratosphere as the troposphere warmed, polar amplification due the ice-albedo effect and other effects, greater increase in nighttime than in daytime temperatures, and the magnitude and duration of the cooling from the eruption of Mount Pinatubo.

    Comment by Barton Paul Levenson — 4 Nov 2008 @ 9:30 AM

  61. Richard C writes:

    Do we have experimental records demonstrating the atmosphere is not CO2 saturated?

    How would it get CO2 saturated? What does that even mean?

    Comment by Barton Paul Levenson — 4 Nov 2008 @ 9:35 AM

  62. 14 Samson

    The best result I had discussing chaos with a climate skeptic was to show him two pictures of Jupiter taken 21 years apart. (From Voyager 1 and Cassini I think). At the large scale the images are almost identical it is the small scale weather type stuff that is different.

    I’m sure that you can find better images than the ones above.

    Another approach is to point out that the Earths orbit around the Sun is also chaotic (along with the other planets) but we can still sling shot a space proba around Jupiter or Saturn very accurately.

    Comment by Jaydee — 4 Nov 2008 @ 9:51 AM

  63. Do you think it possible for the chaotic “weather” unsteadiness to modify the external forcings?

    For example: could different oceanic circulation rates change the oceanic CO2 sink/source behaviour, or could different atmospheric conditions change the mixing rates of atmospheric gases hence modify their affect on the solar forcing?

    [Response: Those would be feedbacks in the full system. – gavin]

    Comment by Richard — 4 Nov 2008 @ 10:54 AM

  64. You indicate it is suprising that multi-model ensembles give a better match to climatological observations. Why should that be suprising, and how exactly does it happen that multi-models give better matches?

    [Response: It’s surprising because the different models are not really a random selection from the space of all possible models, and so wouldn’t necessarily be expected to conform to the central limit theorem or similar. The paper by Reichler and Kim in BAMS this year has some of the details. – gavin]

    Comment by Hank — 4 Nov 2008 @ 1:53 PM

  65. Richard #55. Yes.

    Go high enough and there isn’t enough CO2 to be saturated in ANY band. Yet you are still in the atmosphere.

    Even at the ground level, the width of the saturated bands will get wider as you put more CO2.

    Alternatively, since your wording is ATROCIOUS, yes, since anything less than 100% CO2 is a non-CO2 saturated atmosphere, then we don’t have CO2 saturated atmosphere.

    Write your questions CORRECTLY.

    [edit – stay polite]

    Comment by Mark — 4 Nov 2008 @ 2:11 PM

  66. Glen, #54. How about “physics based model”?

    [Response: I concur. I’ve changed it above. – gavin]

    Like the old looking glass Flight Sim (forget the name) it was based on not a model of how a plane acts but on a full physical simulation of airflow over the aircraft.

    VERY computationally expensive and they only managed a few air frames to simulate.

    The next one used a model where it said things like “if you have the thrust at THIS level, operate like THIS if you are in THIS configuration”. Which is computationally MUCH simpler but you have to change the model for each airframe you want to include. This is the form all the other flight sims on PC used.

    One used just the physics and simulated the situation. A physics based model (or Physical Model in this topic, see how you CAN get that as a perfectly cromulent word?). Or what I call a simulation. Anything you get is an emergent property of the physics involved (or errors in your discrete analogue needed for making a numerical model of the continuous equations).

    The other used a constraint model that was based on finding the operating characteristics of real aircraft. A statistical model. Or what I call a real model: it does what you tell it to, the only surprises are emergent properties.

    Comment by Mark — 4 Nov 2008 @ 2:18 PM

  67. RE #42 Craig
    One example would be the Laffer Curve. Cutting taxes increases overall tax revenues.

    Comment by Ed — 4 Nov 2008 @ 3:06 PM

  68. jcbmack (41) — Suppose the relative humidity goes up; then the water vapor is more likely to condense and percipitate out. Suppoe the relative humidity goes down; less likely.

    There is a recent study tending to demonstrate that the average relative humidity is indeed close to constant.

    Comment by David B. Benson — 4 Nov 2008 @ 3:14 PM

  69. Steve (7), you’re better off keeping your audience ignorant rather than teaching them science and then hitting ’em with Edward’s non-scientific litany of trivial individual cherry-picked anecdotes (21). “Podunk set a new September high temperature record two years in a row. Game over! World’s getting hotter!” There needs to be some level of knowledge, though not much, to see through that inductive logic as proof. Or, the argument that all sceptics are devils makes some proponents feel good but usually falls quite short of scientifically swaying others.

    Comment by Rod B — 4 Nov 2008 @ 3:24 PM

  70. Very helpful informative post. Thanks

    Comment by Rod B — 4 Nov 2008 @ 3:27 PM

  71. “One example would be the Laffer Curve. Cutting taxes increases overall tax revenues. …”

    First, it was not a model. He famously drew it on a napkin, and correctly admits it was not his idea.

    “[T]he whole California gang had taken [the Laffer curve] literally (and primitively). The way they talked, they seemed to expect that once the supply-side tax cut was in effect, additional revenue would start to fall, manna-like, from the heavens. Since January, I had been explaining that there is no literal Laffer curve. …” – David Stockman, President Ronald Reagan’s budget director

    Comment by JCH — 4 Nov 2008 @ 3:33 PM

  72. Timely post. Just read “Telling the truth about climate change has become a revolutionary act” at

    Even supposing the models “lie,” they might be underestimating the problem. Why is it with denialists that if climate science is wrong, it’s got to be wrong in overestimating GW? (that’s just a frustrated rhetorical Q)

    And I haven’t seen any “collective delusions and hysterical illness” like people trampling each other at Home Depot to buy compact fluorescent bulbs.

    Comment by Lynn Vincentnathan — 4 Nov 2008 @ 3:34 PM

  73. Mark #66, well put. Of course emerging properties will foul up predictions verus actual results.

    Comment by jcbmack — 4 Nov 2008 @ 3:50 PM

  74. David B. Bension #68, could you point me in the direction of this study- thanks.

    Comment by jcbmack — 4 Nov 2008 @ 3:55 PM

  75. #67: One example would be the Laffer Curve. Cutting taxes increases overall tax revenues.

    Only true on the right hand side of the curve. Empirically Sweden (I think) found it to be at around 70-80% of GDP taken in taxes. Note the curve is usually drawn very incorrectly – 100% tax could be considered communism, and while that tends to drop productivity significantly, it certainly doesn’t go to 0.

    Comment by Stuart — 4 Nov 2008 @ 4:00 PM

  76. # 67 & 71 Ofcourse in the Laffer curve, tax increases positively increased revenues, until passing the optimum point, then reducing taxes increases revenues. So revenues are a function of taxes. Then again, Roosevelt’s new deal where currency becomes devalued to increase the value of the gold backing it, during the great depression, (1933) even if arbitrarily carried out, worked with no graph; the empirical observations of its effectiveness was enough.

    The models in the case of AGW, are a little more scientific than either approach/;, the variables cannot all be counted for, but they do provide insights to the totality of the research, and the models, (and data fed into the models)satellite data and observations from researchers in the geographical areas affected by GW, agree more than do not, as long as the averages are taken into account.

    Comment by jcbmack — 4 Nov 2008 @ 4:09 PM

  77. For clarity, the “Hank” at 4 novembre 2008 at 1:53 PM isn’t me. Not complaining; just to avoid confusion.

    Comment by Hank Roberts — 4 Nov 2008 @ 4:15 PM

  78. jcbmack (74) — Unfortunately, no. I saw in mentioned in some comment of some thread on one of the many climate blogs I frequent. You could try Google School to search.

    A good general overview of water vapor is in CaltechWater.pdf on Ray Pierrehumbert’s web site.

    Comment by David B. Benson — 4 Nov 2008 @ 4:28 PM

  79. Question: before talking about simulating climate CHANGE, how long does the climate science community expect it to take before GCM’s can reproduce the real world climate PRIOR to human induced CO2 perturbation in terms of:
    – “equilibrium point”, i.e. without artificial flux adjustment to avoid climatic drift,
    – “natural variability”, in terms of, for instance, the Hurst coefficient at different locations on the planet?

    Comment by Nonlinear guy — 4 Nov 2008 @ 4:41 PM

  80. Question: What is wrong with this reply by Roger A. Pielke Sr.?

    … “I think the IPCC was basically a very narrowly focused document. In fact it was basically written mostly by atmospheric scientists. And they’re focusing on a very narrow issue where the atmospheric increase of CO2 feeds down to affect the climate that has all these effects on resources, and I think that is so narrowly confined as to be of little use to policymakers in terms of what’s really going to happen.”

    [Response: He isn’t reading the same report as everyone else. – gavin]

    Comment by Pat Neuman — 4 Nov 2008 @ 5:07 PM

  81. BPL, #60,

    Come on, you KNOW the models can hindcast if the right parameters are put in but they are pretty atrocius at forecasting.

    I don’t suppose economic models were designed to hindcast, but, as in climate science, a whole world view was built upon their supposed mathematical and statistical prowess.

    I do not doubt the sincerety and expertise of the climate modellers, but seriously question the policy actions that are based upon the models.

    Comment by Dave Andrews — 4 Nov 2008 @ 5:24 PM

  82. Dave, your suppositions continue to show you don’t bother to look things up. Why not try?
    Simple Google turns up quite a few studies of the sort you suppose don’t exist. From the first page, using a search string taken directly from your posting above, just as an example of what you can find out if you bother to check your suppositions:

    The Forecasting Power of Economic Growth Models

    … In economics, forecasting power may be decisive for the success or failure of a particular policy. The forecasting power of economic growth models is investigated in this study. … Forecasts/hindcasts from the statistical model were tested ….”

    Try facts. They help.

    One of the problems the authors discuss with those failing economic models is that they relied on their theoretical beliefs instead of using facts.

    What you say you wish were being done is being done by the very people you claim aren’t doing it.

    Comment by Hank Roberts — 4 Nov 2008 @ 6:22 PM

  83. Barton #61, Mark #65

    Apologies for the lousy phrasing. I’ve been arguing with a skeptic on a different blog. If you thought my terminology was bad you ought to try listening to a skeptic making analogies using Pandas and bamboo! I think the saturation in question is based upon a mis-application of the Beer-Lambert law, i.e. an excess of CO2.

    Are there any measurements made by satellites giving a time based record that shows variation in outgoing longwave radiation dependent on the amount of CO2 in the atmosphere? Is that better?

    Comment by Richard C — 4 Nov 2008 @ 6:28 PM

  84. Should the turbulent Prandtl and Schmidt numbers be treated as constants or variables and does the choice have any effect on the performance of GCM simulations?

    Comment by Richard — 4 Nov 2008 @ 6:36 PM

  85. Here’s a potential FAQ question: what do you mean when you say model has “skill”?

    Another: although physical and statistical models are different, there is a statistical component to physical models (eliminating noise and skewing effects such as urban heat islands): to what extent do these statistical components add to uncertainties in physical models?

    Another: how much can we learn from the paleoclimate, e.g., previous periods of rapid sea level rise or rapid greenhouse gas increases? (This question would be a useful riposte to those pulling up ice core data purporting to show that CO2 rise always follows temperature rise.)

    Comment by Philip Machanick — 4 Nov 2008 @ 7:04 PM

  86. Is computer processing power a major limitation? In the future will simulations become more accurate with increasing processing power?

    I imagine even with todays super computers that some simulations would take a long time….days? weeks? years?

    [Response: Most simulations (say 100 years of model time) take on the order of a month. We definitely want to be doing longer runs (the last millenium, the Holocene, the deglaciation, ice age cycles), but simulations that take longer than 6 months (or maybe a year) don’t tend to get started (because you know that if you wait, you’ll be able to do the same thing twice as fast). So longer runs tend to be made with slightly less complicated models. – gavin]

    Comment by David W — 4 Nov 2008 @ 8:10 PM

  87. This RC areticle from last year answers some questions as well:

    27 May 2007
    Why global climate models do not give a realistic description of the local climate

    Comment by jcbmack — 4 Nov 2008 @ 8:35 PM

  88. I have looked at the models and the information provided here and I do not see where changes in the sun are calculated into these models. My question is as follows;

    How are cyclical changes in the sun reflected in these models?

    [Response: They are imposed directly as cyclic changes in the amount (and spectra) of the incoming solar radiation. – gavin]

    Comment by Bob H — 4 Nov 2008 @ 8:58 PM

  89. And, Dave, I expect many are in agreement with you about watching _policy_ decisions.

    Estimating fossil CO2 produced from, for example, a grain ethanol program takes attention from voters, including scientists. But that would belong on another blog (like a better filtered DotEarth maybe?).

    Comment by Hank Roberts — 4 Nov 2008 @ 9:13 PM

  90. Ok in response to relative humidity being at or near constant, it is the models which tend to represent it as so, due to the input assumption as so. The real conditions flucuate quite a bit. Relative humidity is the ratio of the actual vapor pressure and the saturated vapor pressure at a given air temperature expressed as a percentage. Or how close to saturation the air is. Google provides plenty of research, some credible, some not, but what is revealed is that the relative humidity is not constant in the real system.

    Now the amount of oxygen in the atmosphere is fairly constant, not water vapor levels. The models again do not factor in constant or rapid changes so well, but what they do is provide a guide with other data. Unsaturated air in the real system does produce questions of the models.

    Without doing the math here, look up the Clausius-Clapeyron relation OLR effects,and just how important CO2 is in ineracting with this major GHG.

    Just like any model, there are limits to what can be precisely and acuurately shown, based upon assumptions, holding anything to a constant to get a clearer depiction will skew the representation, regardless. In the absence of models AGW is in tact, the issue is how long, how much money and what inputs are necessary to make the models more in tune or close to real time and conditions. As I stated in another blog, ideal conditions (or gases) do not give the full picture. Now the MME’s have shown practical and revealing possibilites, this is true, but they still do not represent the dynamics of the atmospheric system or oecean atmosphere interface. Just like models for evolution do not capture all of the dynamics, or simulated models of flight (no matter how complex) do not take into account dry versus wet runway conditions, or sudden changes from cold fronts etc… The models, however, have been useful in light of several other resources.

    So let us not assume constant or near constant relative humidity.

    Comment by jcbmack — 4 Nov 2008 @ 10:35 PM

  91. The policies that do not work or the ones that I question include: corn based ethanol, (and other agriculturally based)carbon capture into the ground, and burying garbage into the ground to produce electricity, (you cannot trustwhat they are putting there to produce the methane, some of that garbage could cause problems)and the slow rate at which wind mills are being constructed, there are a few technical problems, but the aesthetic one is ridiculous on light of being placed mostly in the middle of nowhere, and I have worked out the basic problems the applications faced, not difficult to figure out; the problem is this is a wikipedia world in instead of a Brittanica and howstuffworks one. Bacteria could be applied in other modalities, but the application that is quite possible and safe for carbon capture has not been tried as of yet. I digress for now, however, to do more reading of my fellow posters, I am relatively new to this site and with some down time, it certainly passed mine:)

    Comment by jcbmack — 4 Nov 2008 @ 11:47 PM

  92. Dave Anderson, One of the things I have never understood about denialits is the delight they take in the possibility that the models might be unreliable. Have you considered that once a threat is deemed credible, the models are crucial for limiting the the risk. If the models are unreliable, then what you have is effectively unlimited risk, and any amount of mitigation can be justified.
    Simple physics plus the paleoclimatic record are sufficient to make the threat credible. If you favor a measured response to climate change, you had better hope and pray you’ve got decent models go guide you.

    Comment by Ray Ladbury — 5 Nov 2008 @ 1:00 AM

  93. The modes assume near constant leves of water vapor, but they are not necessarily so close, however, water tends towards equilibrium, so in the long run, the mode averages may not be far off in that regard, but relative humidity does vary greaty, especially during shorter periods of time.

    Comment by jcbmack — 5 Nov 2008 @ 2:00 AM

  94. Ray Ladbury always good to see your posts!

    Comment by jcbmack — 5 Nov 2008 @ 2:45 AM

  95. The modes assume near constant leves of water vapor (snip)

    Doesn’t this rambling qualify as technobabble?

    I know it’s been a long night, but …

    Captcha : admits to

    Comment by Thomas Lee Elifritz — 5 Nov 2008 @ 2:55 AM

  96. “Multi-model Ensemble – a set of simulations from multiple models. Surprisingly, an average over these simulations gives a better match to climatological observations than any single model.”

    Is there a reference for this that does NOT use RMS error to measure model performance (RMS error will always reward simulations with less variability)?

    Comment by Ed Tredger — 5 Nov 2008 @ 3:39 AM

  97. Just to say a sincere ‘THANK YOU’ to all AMERICANS fo making the RIGHT choice for the countries future but also the WORLD’S future. I think it’s obvious that for a country that basically single handedly caused climate change or at the least had the most influence in it’s creation that now you have a smart, switched on leader who will I’m sure make the CORRECT decisions to lead the world to dramatic and vital emissions reduction. You have now In my opinion the best hope you are ever going to get to get this right or in his term (hopefully 8 years) to lay the strongest global foundations for all countries to adhere to. Why we have had such a lukewarm response from world leaders in re: to CC is because they were looking to America for leadership and found ‘absolutely nothing’. Now we have a competant steward to sail planet earth through the eye of the perfect storm and out the other side battered and damaged but still afloat, still able to be repaired.

    Comment by Lawrence Coleman — 5 Nov 2008 @ 3:49 AM

  98. Richard #83. Sorry for being so piggin annoyed. However, although I love a good argument (even if I’m proven wrong or at best mistaken) I really loath it when someone can’t even manage to ask a question properly. You spend a lot of time trying to ask fifteen questions that they could have meant and then answering them.

    REALLY annoying.

    Comment by Mark — 5 Nov 2008 @ 4:01 AM

  99. Richard #63, for that weather to last long enough to become a climatological forcing (it would have to take gigatons of carbon out of one system and dump it into another) it would either have to be a catastrophic event (clathrates suddenly erupting, supervolcano erupting, etc) or long lasting (in which case open to climatological statistics rather than weather chaotics).

    So no, but such a case is on the same level as aliens finding us and giving us new technologies (or making us work in their salt mines).

    Comment by Mark — 5 Nov 2008 @ 4:10 AM

  100. BPL #58. But a BIG asteroid (say, for example, Ceres) could split us. Something as big coming from the Ooort cloud would be going MUCH faster than Ceres (about 8km/s I think, compared to ~1km/s) and the energy to convert 64 times greater.


    PS Turn up the sarcasm detector.

    Comment by Mark — 5 Nov 2008 @ 4:14 AM

  101. About “Tuning”:
    “…It is important to note that these exercises are done with the mean climate (including the seasonal cycle and some internal variability) – and once set they are kept fixed for any perturbation experiment..”
    With “mean climate”, surely the model ensemble mean is meant, however the “real data” to base the tuning on by definition is restricted to the single realisation of Earth’s climate (including cloud cover caused by, for instance, multi-decadal oscillations instead of AGW feedback). How is this taken into account in the estimation of the climate sensitivity?

    Comment by Nonlinear guy — 5 Nov 2008 @ 5:26 AM

  102. This is a very helpful post on a great site, thank you.

    If you do requests, I’d also like to learn more about the chaos topic broached here in #14 (Samson + Gavin’s reply) and in #34 (Garry S-J).

    That is: Is climate chaotic? Is climate change? In what way?(Gavin said: “…if there are aspects of climate change that are chaotic…”) What does that actually mean? In particular, what are the implications for climate modeling, and what do you tell a skeptic who pooh-poohs the models because “it’s chaotic”? Is there an easy-to-grasp example that helps unpack the point?

    Gavin’s and Garry’s responses here are helpful. But I’d really appreciate a dedicated post — or failing that, a reading tip — amplifying on this.

    Comment by CM — 5 Nov 2008 @ 6:04 AM

  103. Ed writes:

    One example would be the Laffer Curve. Cutting taxes increases overall tax revenues.

    Only if you start out on the upper half of the curve. If you don’t, then cutting taxes cuts overall tax revenues.

    Comment by Barton Paul Levenson — 5 Nov 2008 @ 6:33 AM

  104. Not sure who to take for granted with the published numbers:

    NSIDC/NOAA posted their numbers yesterday for October 2008:

    Extent: 8.40 million km square, where the JAXA 31 days daily averages 7.21
    Area: 5.72 million km square, including the 0.31 million km square for the blind spot. Cryosphere Today from the iPhone 31 dailies averages to 5.0 million km square.

    What is “bad” is that the NOAA/NSIDC numbers suggest there was 2.68 million km square average water within their extent implying a major major break up / dispersal.

    Comment by Sekerob — 5 Nov 2008 @ 7:36 AM

  105. Ray Ladbury, one thing that puzzles me is the assumption that human action to curb human emissions is generally presented as being risk-free.

    Among the consequences of the rush to bio-fuels appears to be food shortage and accelerated de-forestation.

    Whatever the merits of the pro and anti AGW arguments, we need to be extremely wary of the law of unintended consequences. Hubris is always punished severely in the end.

    Comment by Mark Smith — 5 Nov 2008 @ 7:59 AM

  106. With increasing sophistication of the models and increasing precision and completeness of boundary conditions will there be a reduction of the “wiggles at almost all time scales”? Can this be expected for large scale phenomena like Enso, zonal winds etc. and could this lead in the long-term also to better local climate forecasts and even weather forecasts?

    [Response: No. The ‘wiggles’ are real phenomena. As we get better models, the realism and structure of those wiggles will likely become more realistic – but in the end they define the limits to what we will be able to predict at regional/decadal scales. – gavin]

    Comment by Klaus Ragaller — 5 Nov 2008 @ 8:30 AM

  107. Dear realclimate crew.

    I was wondering for some time now, how much the findings of the work of scientists, be it the IPCC, be it the PIK in Potsdam or what have you, can be taken for granted in order for policy makers to make valuable decisions (e.g. cutting carbon emissions by half by 2050) and if the uncertainties in the models might outweigh certain decisions to reduce carbon emissions so that in the end it might happen that these uncertainties make these decisions obsolete, because they do not suffice to avoid “dangerous climate change”? So, are the data and models reliable enough to ensure feasible decisions?


    Comment by Nico — 5 Nov 2008 @ 10:39 AM

  108. Ray (92), the fact that “…the models are crucial for limiting the risk…” or that anyone is hoping and praying for decent models does not, by themselves, make the models any less inaccurate or unreliable.

    Comment by Rod B — 5 Nov 2008 @ 10:42 AM

  109. I am back, re. #27 and #52, the temperature plateau caused by aerosols. I read through the feedback references, and am still intrigued. Taking my ruler and extending the warming line, bypassing the plateau, I get somewhere around 0.5 to 0.8 deg Celsius prevention of thermal rise! Thanks aerosols! Here are more thoughts: if North America’s dirty industries, like steel mills, were the culprit, then we should be able to trace back to those times a significant regional cooling differential in the downwind regions of places like Pittsburgh, PA. This cooling differential should be readable relative to today and surrounding regions outside the downwind aerosol cones. Remember, these aerosols are short lived, and, theoretically, the effect and changes should be obvious. Further, since these industrial pollution centers have had widespread aerosol thermal changes, the localized effects would have shown ‘hotbeds’ of cooling (sorry). Are there any good studies on this? Actually, cherchez le acid rain, since those were the the times BC (before clean-up) and BS (before scrubbers). Come to think of it, if nowadays we were to re-tune all jet engines for sooty output (large particles to avoid breathing health hazards) we might mitigate all of the carbon curb hoopla (sorry again, but I could not resist)!
    Now, I want to contrast these relatively drastic temperature influences with the recent (around 2003) surprising thermal rise in Europe. It was measured (Philipona et al) and found to be predominantly tracking increased water vapor. Wow, a totally different singular cause. So that begs the question how the earlier aerosol effects might have interacted with the increased steam and water vapor emissions that accompany aerosol emitting processes. Coal powerplans burn slurries and use lots of cooling water for their turbines; Bessemer steel furnaces use lime and iron ore with lots of trapped water. Lastly, today, i.e. over the last 30 years, we should be able to observe the identical localized aerosol caused cooling over the Chinese industrial zones, which are known for their constant brown haze. However, if I read the regional temperature distribution correctly, there is only warming. Where am I wrong?

    Comment by Dietrich Hoecht — 5 Nov 2008 @ 10:46 AM

  110. Lawrence Coleman (97), which also cuts through your all’s canard of maintaining or even improving economic well being, which is hard to do by “bankrupting” (his words) the entire US coal industry as fast as can be by, in effect, shutting off 50% of all of our electricity production nearly over night.

    Comment by Rod B — 5 Nov 2008 @ 10:57 AM

  111. Re “the” Laffer curve;

    If it did in fact represent the output of an economic model instead of a sketchy idea drawn on a napkin, it would be an ensemble of models with different underlying policy decisions regarding the distribution of tax expenditures. In scenario A, a higher percentage of tax revenues spent on things that increase productivity, such as health care, infrastructure such as more efficient transportation and power generation, and R & D which results in such advances as the internet, has an optimum tax rate that is higher than scenario B, where a higher percentage is spent on the military, which a soldier once told me is fundamentally set up to “break things and kill people.”

    Not only are the underlying policy decisions mutable and arbitrary, the government doesn’t allocate spending as a percent of revenue, but as differing amounts unrelated to receipts. When expenditures exceed receipts (currently the case, arguably due to higher military costs), the government simply borrows or prints more money.

    These hypothetical Laffer models(GCMs) have the tax revenues(global temperatures) decoupled from expenditures(OLR) by arbitrary policy decisions(denialist handwaving).

    Comment by Brian Dodge — 5 Nov 2008 @ 11:15 AM

    “police instantly” says ReCaptcha

    Comment by Hank Roberts — 5 Nov 2008 @ 11:39 AM

  113. Brian (111), you make some good points (though I admit not fully understanding your analogy with Laffer and GCM modelling), but why do you think military spending does not improve productivity, i.e the economy? It got us out of the depression of the 30s. It does much productive R&D (your example of the [early] internet, e.g.), indirectly supports even Gavin and company (a little maybe) by being NASA’s largest customer, and tons of other stuff (even though you could probably find pieces of the military budget that one would be hard-pressed to claim productive).

    The military IS “fundamentally set up to “break things and kill people.””. What’s your point?

    Comment by Rod B — 5 Nov 2008 @ 12:06 PM

  114. Rod, #113: Who gets the lions share of the money?

    Those big investors (with lots of money) and the directors/C*O that get paid lots of money.

    The rich invest money in things to get it from people who can’t afford a cash transaction (loa ns and mort gages) and so accrue more of the capital to themselves.

    You need money to make money. And these guys have lots.

    They don’t *spend* money, though.

    If all your money goes on fags, booze, rent, food and clothes, you can’t afford NOT to spend all your money (the first two are to take your mind off the fact that you can only afford fags, booze, rent, food and clothes). However, the rich spend a lot of money, but not as much as if that money were in poor people’s hands.

    E.g. Despite having given away billions, Bill Gates was still richer six years later than he was when he committed to spending all his money on charity before he dies.

    And in the modern age, “defense spending is good” can be removed by one simple name:


    Investors and the senior management have made out like bandits. They’ve LOST billions upon billions. That money didn’t go back into the US economy.

    You can’t say defense spending improves productivity.

    Each Fox One shot at a target is 3 grand blown up. And the cash isn’t moving around in the economy, it’s sitting as some rich beggar’s Mona Lisa print sat in their bathroom…

    Comment by Mark — 5 Nov 2008 @ 12:59 PM

  115. Nico, #107

    All of it, if they like.

    This is why the summary and reports include all the uncertainties in the outputs. So that the politicians can treat it ALL as a given, since it already shows the possible errors in assumptions.

    Then the summary is written BY those politicians, so you think they are going to say “How much of this what I wrote should I believe”?

    Comment by Mark — 5 Nov 2008 @ 1:02 PM

  116. OT: Michael Crichton passed away. He was the classic, anti-science denialist.

    Comment by Dan — 5 Nov 2008 @ 1:09 PM

  117. “This post is designed to be a FAQ for climate model questions … so that we can have a resource for future discussions. (We would ask that you please focus on real questions that have real answers and, as always, avoid rhetorical excesses).” — the first post here.


    Comment by Hank Roberts — 5 Nov 2008 @ 1:19 PM

  118. jcbmack — Near constant average relative humidity (averaged over space and time) is surely correct, due to the negative feedbacks I previously indicated.

    A bit more puzzling is the global precipitation product producing by a group in Italy. Twenty-eight years on, the global precipitation has been essentially constant on an annual basis. There will be another paper (for 29 years on) at the Fall AGU meeting (held in December, so I think of it as the winter AGU meeting. Oh well.)

    This seems in disagreement with the argument in CaltechWater.pdf (and surely elsewhere) that with global warming prcipitation ought to increase. However, aerosols are throught to decrease precipitation, so maybe this (partly) explains the situation. But then I would think then that cloudiness would increase. Dunno.

    Comment by David B. Benson — 5 Nov 2008 @ 1:25 PM

  119. I have one question with two parts, is there a limit to how much regional downscaling can be done:

    When GCMs are used to model atmospheric conditions and spatial grid size is reduced is there a scale at which chaotic conditions prevail and make modeling difficult in the same way that weather is harder to model than climate? For example going from 100km x 100km squares to 50km x 50km is possible to model but 10km x 10km is not.

    Does introducing regional geographical features make modeling more complex but theoretically achievable, or are there built in barriers, again like weather vs climate. For example an area with complex topography can’t be modeled but areas with relatively simple topography simple can.

    recaptcha “drained reviewer” I hope my usually off-topic comments haven’t been to taxing on the people who must read them and decide to let them through. The oracle has spoken again.

    Comment by Joseph O'Sullivan — 5 Nov 2008 @ 1:56 PM

  120. #95 it helps to talk it through; denialists see a paper or research are making assumptions, and they have no idea why these ‘assumptions’are made they automatically assume themselves, a grave error. Also without looking at the facts, people miss the point of the models. Sometimes both the argument for and against must be presented. I know that modelling always plays an important role in science and global climate change, such a vast phenomenon needs all the relevant research that is available, for the blind men (people in general) to understand the elephant:)The models are a necessary component, and interestingly some of these assumptions are based upon physics and chemsitry just the same, otherwise the models would be really far off.

    Comment by jcbmack — 5 Nov 2008 @ 2:22 PM

  121. Although average relative humidity may be constant, average melt rates are increasing (increasing latent heat of condensation and increasing temperatures), so why do models ignore increasing latent heat effects on thaw of snow and ice?

    Comment by Pat Neuman — 5 Nov 2008 @ 3:10 PM

  122. David # 118 absolutely, just wanted to talk it out so denialists do not get the wrong idea. Regarding the other research you cite, I will read what I can find first before I comment,but aersols are relatively temporary in their effects in this matter. Thanks for the references.

    Comment by jcbmack — 5 Nov 2008 @ 3:16 PM

  123. Re 113,

    “The military IS “fundamentally set up to “break things and kill people.””. What’s your point?”

    Well, breaking things and killing people is destroying value, for one thing. So when the military is in use, you have negative value as a “product”, and during peacetime you have no product.

    Admittedly, the question of *whose* negative value–ours or, say, North Korea’s–is the whole point of having a military. But I believe it was Adam Smith himself who first characterized the military as an economic drag–not some raving leftist. The fact that you can use the military to deliver economic stimulus doesn’t mean it is the most efficient means of doing so.

    Comment by Kevin McKinney — 5 Nov 2008 @ 3:17 PM

  124. Mark, so contracting out millions-billions so outfits can hire thousands of workers building tanks, carriers, rifles, airplanes, ships, uniforms, boots, etc, etc, etc does nothing for the pure poor little guy? How about the billions of wages we pay members of the military? Or did someone tell you that only greedy Generals get paid? Etc? Etc, ad infinitum? Or did someone tell you that none of this stuff is any help to the economy and productivity? Silly.

    Comment by Rod B — 5 Nov 2008 @ 3:56 PM

  125. On second thought, I should probably admit that in his own day, Smith arguably *was* a “raving leftie.”

    Comment by Kevin McKinney — 5 Nov 2008 @ 3:58 PM

  126. Hank Roberts (117), point well taken. Sorry

    Comment by Rod B — 5 Nov 2008 @ 3:59 PM

  127. Kevin (123)

    “The fact that you can use the military to deliver economic stimulus doesn’t mean it is the most efficient means of doing so.”

    Perhaps you should just give everyone in the country $1 million and stimulate the economy that way :-)

    Comment by Dave Andrews — 5 Nov 2008 @ 4:28 PM

  128. Hank

    … In economics, forecasting power may be decisive for the success or failure of a particular policy. The forecasting power of economic growth models is investigated in this study. … Forecasts/hindcasts from the statistical model were tested ….”

    Well there you go, the economic models were rubbish at forecasting even though they could hindcast. Bit like the climate models really

    Comment by Dave Andrews — 5 Nov 2008 @ 4:37 PM

  129. Mark Smith, if you are looking for someone to blame for the push to biofuels, you’ve come to the wrong guy. Corn Ethanol doesn’t make sense. It is mainly driven by US farm belt (read agribusiness) politics. Sugar cane ethanol makes sense in Brazil mainly because they have a large, poor labor force to harvest the cane. It is as much a job creation program in the poor Nordeste as it is an energy program. Cellulosic ethanol makes a great deal more sense, but has a way to go before it is practical. Conservation, on the other hand, pretty much always makes sense and we still have LOTS of low hanging fruit there.
    Look, if people are going to adopt stupid mitigation strategies and say, “Doctor, doctor, it hurts when I adopt stupid mitigation strategies,” I’m going to say, “Don’t adopt stupid mitigation strategies.”

    I’m sorry, but I think that when you are confronted with a real threat, the argument that you can’t intervene because you might screw it up is a pretty piss poor one. Just don’t screw it up.

    Comment by Ray Ladbury — 5 Nov 2008 @ 5:25 PM

  130. Rod B., You miss my point. The models actually perform remarkably well, yet the only folks who are denying this are precisely those arguing for “a measured response,” which can only be justified based on output from the very models they distrust. Kinda mavericky, huh?

    Comment by Ray Ladbury — 5 Nov 2008 @ 5:27 PM

  131. The production of ethanol is concentrated in the Central and Southeast regions of the country, which includes the main producer, São Paulo State. … machines will gradually replace human labor as the means of harvesting cane, except where the abrupt terrain does not allow for mechanical harvesting. However, 150 out of 170 of São Paulo’s sugar cane processing plants signed in 2007 a voluntary agreement with the state government to comply by 2014. Independent growers signed in 2008 the voluntary agreement to comply, … As production sparks in other states in Brazil, mainly in the Northeast Region, where lack of job positions and social issues amount much further, to give incentives to coming sugarcane producers as long as they employ harvest workers instead of implementing less labor intensive and more modern techniques


    [reCHAPTCHA entonees “stick legislation”]

    Comment by David B. Benson — 5 Nov 2008 @ 5:57 PM

  132. David, most of the sugar cane is grown in the Northeast–Bahia and Northwards. This area has been depressed since the collapse of the last sugar boom in the early 1900s. I’m not as familiar with the industry in Sao Paolo, which I tend to avoid when I’m in Brazil. However, it’s interesting to hear about the shift to mechanized harvesting. Cane cutting is backbreaking work, but it’s been the only work available for many of the poor in Brazil.

    Comment by Ray Ladbury — 5 Nov 2008 @ 6:58 PM

  133. > Dave Andrews … 5 November 2008 at 4:37 PM
    > … much like climate models

    Dave, if you’d read even the abstract, or the previous comments to you, you’d understand the difference.

    You can’t be credible commenting on policy while you insist on making up your own facts about things you could easily read and understand.

    Jim aske dyou earlier:

    “Did you even read the post? The very first “Question” outlines the fundamental difference between a statistical model (your economists/bankers mathematical model) and a dynamic physical model (general circulation model) based on physical laws and properties.”

    Try reading. It will improve your ability to comment.
    You have a lot of energy. Focus and be useful, there’s work everyone can do to figure this stuff out.

    Comment by Hank Roberts — 5 Nov 2008 @ 7:48 PM

  134. Ray Ladbury (132) — Your information about Brazil’s Northeast region does not agree with the Wikipedia article, which has 92 references and which includes this map:

    Comment by David B. Benson — 5 Nov 2008 @ 8:56 PM

  135. I am totally confused with your definitions. What exactly is “forcing”? What do you mean under “imposed from the outside”? Do you “impose” new boundary conditions on the “physics-based” equations? Or do you change a parameter in a differential equations like a gas mix ratio? Is there any “forcing” if the atmosphere mix stays constant, and the Sun shines steady?

    What do you mean under “Feedbacks are changes in the model that occur in response…”? Did you mean “changes in the state variables of the physics-based model”? What is “initial forcing”? The only forcing I am familiar with is a constant flux of SW solar energy. What are the other “forcings”?

    What do you mean under “physics-based”? You mentioned F=ma, but for a continuous media, the physical equivalent of the conservation laws would be Navier-Stokes Equations (NSE). Do you mean that GCMs directly emulate NSE by numerically iterating some finite-difference (or spectral) approximation of NSE?

    What is the definition of “process-level parameterization”?

    Comment by Alexi Tekhasski — 5 Nov 2008 @ 9:08 PM

  136. When are we going to see “the physics” of ice sheets on Greenland and Antarctica added to the models?

    What is the center of rotation in the models? If it is not yet the Earth’s actual axis of rotation, are there plans to correct that little bit of physics in hopes of getting a better handle on heat flows over and around Greenland?

    Comment by Aaron Lewis — 5 Nov 2008 @ 10:44 PM

  137. Does a model or another replicate the Stratospheric Polar Vortex? And how successful are they in actually predicting their size and magnitude?

    Comment by wayne davidson — 5 Nov 2008 @ 11:11 PM

  138. David, I won’t argue with Jose. He’s a good guy (I had an opportunity to interact with him a bit when he wrote an article for Physics Today). My impression was based on my own travels in Brazil and conversations with Brazilians I met, and I haven’t traveled in the northeast recently. My sources had said that the alcohol boom had brought employment if not prosperity to the northeast. So I’m willing to be wrong on this. Jose’ ought to know better than I do.

    Comment by Ray Ladbury — 5 Nov 2008 @ 11:19 PM

  139. Why is anyone still using wikipedia?

    Comment by jcbmack — 5 Nov 2008 @ 11:45 PM

  140. RE 133, Good point hank! dave andrews should start by reading this.
    you might as well. It a good place to start…to frame some questions.

    Comment by steven mosher — 6 Nov 2008 @ 12:59 AM

  141. One thought, a lot of the FAQ suggestions like some of Alexi’s are good ones for a collection of the very frequently asked and answered.

    Some might be answered with a picture first rather than text first, then answer questions people ask about the picture. Example:

    What are climate “forcings”?

    Some people will get that just from looking. Others will need more.

    Comment by Hank Roberts — 6 Nov 2008 @ 1:07 AM

  142. Alexi, Gravity is a forcing. Air resistance is a forcing. Drop a feather.

    It WILL go down. Gravity. It will go slowly. Air resistance. Its path will be chaotic. Like weather, because its path is based on the very fine small difference between air resistance and gravity.

    Boundary condition: the sun is hot. What about when there’s a CME? You change the external boundary condition contributed by that sun. We don’t simulate the sun in a GCM.

    Feedbacks: the warmer the air the more water it can hold before raining it out. The warmer it is and the sunnier it is, the more water evaporates. CO2 can cause it to be warmer. Water gets sucked into the air and that causes warming. And more water makes it warmer. Which makes more water get sucked up into the air. Which makes it warmer. Which …


    Yes. That’s what’s done. But not just that. The blocking of IR from the earth doesn’t obey Navier Stokes.

    Winds across the earth are slowed more and this slows air higher up the atmosphere if it travels over trees than grassland. But in a 100km square you can’t model the disrupted airflow over each and every tree, bush, kangaroo or ant. So you paraeterise the entire effect of all the trees, grass, houses and rivers into a overall effect. Much like an army cook doesn’t try and work out how much each and every squaddie will eat that day (it varies) but go “A squaddie will eat this many calories on average and we have X sqaddies to feed. We need Y calories.” and then work out how many tins of beans need to be purchased for stores. A small difference is that you can’t have squaddies without food, so you over order, but you also parameterise this figure so that you aren’t dinged by stores for wasting food.

    Comment by Mark — 6 Nov 2008 @ 4:07 AM

  143. Rod 124. Thanks for taking the answer and making a straw man out of it.

    Did I say it did NOTHING for them? No. It does a heck of a lot less than if that moeny was just given to all the poor people (who have to spend it all because they are poor and can’t afford all the thinks the middle classes take for granted).

    Are you saying that rich people spend all their money? If so, why do they hate inheritence tax?

    (just thought I’d use the straw left over myself)

    Comment by Mark — 6 Nov 2008 @ 4:12 AM

  144. Joseph #119. Actually parameterisation models are made. Microclimate really DO measure the turbulence around a scotts pine on its own and in a forest, checking what effect that has on cloud formation, convective lift and lots of other things.

    These models are then used to make parameterisations to go in the big models.

    The main reason for a limit to how small I would say is that for every halving of the grid size you have 16x as much work (cube 1/2 on a side and your timestep has to halve at least).

    Comment by Mark — 6 Nov 2008 @ 4:16 AM

  145. Unrelated note: Can anyone explain why the RC wiki is so thoroughly locked down? I found the Crichton page, and wanted to update it to A) mention his death, and B) update a couple of links that have gone stale. Even after creating an account, I found that everything was locked to prevent editing (which sort of defeats the purpose of a wiki).

    [Response: The wiki is only editable by approved accounts, email the contact address to inform us of your background and what you’d like to edit and we’ll see. But please note that the wiki is basically just a clearing house for links to existing rebuttals/discussions of the contrarian arguments – it is not an encyclopedia, and the details of Crichton’s life are not relevant. – gavin]

    Comment by Bryce Anderson — 6 Nov 2008 @ 4:59 AM

  146. There has been a lot of mention about the parameterisations within models, initial boundary conditions, various forcing mechanisms, etc. Do all models assume the same boundary conditions? And if so, what are these conditions? How are they calculated? There are hundreds of factors that influence the climate in different ways, how do you manage to cram all of these into the calculations within the model to accurately (as far as possible) represent the climate? Is there an average number of conditions that imposed on models, and how do you decide which forcings and limitations are to be imposed on the models?

    Comment by jo — 6 Nov 2008 @ 6:03 AM

  147. I’m sorry — in #102 I suggested a post on chaos and climate, without noticing you already ran one in 2005:

    But perhaps a statement about this would be a useful part of this FAQ?

    Comment by CM — 6 Nov 2008 @ 7:42 AM

  148. Dietrich Hoecht #109:

    Taking my ruler and extending the warming line, bypassing the plateau, I get somewhere around 0.5 to 0.8 deg Celsius prevention of thermal rise! Thanks aerosols!

    Hmmm yes… but I suspect that what you did was place your ruler through the pre-1950 temperature curve, which is somewhat affected by a lull in volcanism 1920-1950. See the following graphs:

    The grey curve “stratospheric aerosols” represents volcanism.

    If you look at the tropospheric aerosol effect, you have to add the light blue and the purple dotted curve, yielding -1.8 W/m^2. Scale that to the total forcing of 2 W/m^2 (right figure) which has produced so far (through feedbacks, and attenuated by ocean thermal inertia) a warming of 0.7 degrees. So yes, something like 0.5…0.6 degrees.

    Come to think of it, if nowadays we were to re-tune all jet engines for sooty output (large particles to avoid breathing health hazards) we might mitigate all of the carbon curb hoopla

    Only for a while. Remember they are short lived (longer lived if you put them in the stratosphere, but even there only a few years) and not cumulative. CO2 is.

    Something like this has been seriously proposed as “geo-engineering” (but using sulphuric acid rather than soot), see elsewhere on RC. It’s not really a solution, rather a balancing act (like drinking a lot of black coffee after a boozing spree).

    So that begs the question how the earlier aerosol effects might have interacted with the increased steam and water vapor emissions that accompany aerosol emitting processes.

    Human water vapour emissions are irrelevant, as water vapour is in dynamic equilibrium with ocean water, an equilibrium controlled by global mean temperature, i.e., other greenhouse gases etc. In other words, H2O is a feedback, not a forcing. Also discussed elsewhere on RC.

    Lastly, today, i.e. over the last 30 years, we should be able to observe the identical localized aerosol caused cooling over the Chinese industrial zones, which are known for their constant brown haze. However, if I read the regional temperature distribution correctly, there is only warming. Where am I wrong?

    Perhaps that, while short lived, these aerosols nevertheless spread around the globe, especially the small particles, which play a role in modifying cloud formation (the “indirect aerosol effect” in the above graph). So the most visible part of the aerosol emissions may not be the most climatically relevant. My guess. But the experts on this site should know best.

    Hope this helps.

    Comment by Martin Vermeer — 6 Nov 2008 @ 8:08 AM

  149. Does anybody here know roughly how many tonnes of CO2 is released into the global atmosphere daily by just the consumption of carbonated drinks, eg: coke,fanta even sparkling mineral water and all the aerosol cans that use compressed CO2 as the propellant. Say 1 in every 6-7 people on earth drink 1L of soda drinks/day….? How does that stack up against the emissions from vehicles say? I just drank a can of coke and burped and immediately felt somewhat guilty.

    Comment by Lawrence Coleman — 6 Nov 2008 @ 10:15 AM

  150. Re #141 and 142: Mark and Hank, I am afraid you misunderstood my questions. I do not understand your terms like “gravity” and “air resistance”, “and the sunnier it is, the more water evaporates” when we are talking about numeric calculations. Here is an example of description of a GCM model in normal scientific terms I can understand:
    Still, this description is incomplete and requires additional information from articles published in 1959 and 1974, and it never mentions the term “feedback” (except once in the Reference to other articles).
    So, my questions are: given the equations shown in the above document, which particular terms (or coefficients, or else) do “you” call as “forcings”, and which one are the “feedbacks”. Thanks.

    Comment by Alexi Tekhasski — 6 Nov 2008 @ 12:31 PM

  151. Do GCMs model the 1.4C difference in annual temperature between NH and SH ?

    If they do, what prinipally causes this phenomenon ?
    If they don’t…… why not ?

    Comment by Cumfy — 6 Nov 2008 @ 12:40 PM

  152. Well, Alexi, you should have said.

    You did not say that.

    So please say what in mathematical terms you wish to know so it can be answered in mathematical terms.

    We can’t read your mind. Only your english.

    So try again.

    What mathematically are you looking for?

    NOTE: be accurate. For some versions of what you’re looking for, this

    is correct.

    Comment by Mark — 6 Nov 2008 @ 1:04 PM

  153. Lawrence, look it up. From a quick google:

    CO2 per can of soda 6g CO2.

    22 cans a week is a lot, so say 4 cans average.

    4Billion people.

    4×10^9x4x50x6g = 5×10^12g = 5×10^9kg = 5x106T = 5Million tons.

    Comment by Mark — 6 Nov 2008 @ 1:15 PM

  154. I’m not trying to be argumentative, but a response might be interesting. I read a comment by a skeptic that because climate model projections are “averaged over time” (ie. “linear” in nature), they don’t show possible future tipping points (chaotic tipping point reactions like the climate system actually likes to operate in).

    As a result, this might lull the mainstream climate communtity into a false sense of complacency as they look at climate model’s future “linear” reponses. How big an effect do you feel that this is having on mainsteam climate science’s “global warming” projections?


    [Response: It makes no sense. Models are full of non-linearities and aren’t ‘made linear’ by averaging in time. There may be physics that isn’t included in the models that might lead to dramatic changes (c.f. the ozone hole physics that were not included in the first models of ozone depletion). But that has little to do with how non-linear the models are. – gavin]

    Comment by Richard Ordway — 6 Nov 2008 @ 1:56 PM

  155. Feedback:

    rate of accretion of mass in a diffuse nebula.

    4/3 pi r^3 dt

    This is the volume of possible capture for a mass in space.

    dt is the delta time.

    But masses can move during that time only s=ut+1/2at^2.

    And a is the gravitational accelleration toward that mass.

    So you can do the maths yourself, but the rate of accretion depends on the mass of that object.

    But dt seconds later, the mass has gone up, so “r” is bigger and so the next dt seconds later, the growth of the mass is higher than it was one timestep ago.

    This is called FEEDBACK. Notice how feedback didn’t need to be mentioned to introduce the mathematics (or, indeed, the model of speed of accretion)?

    Now, what don’t you understand, Alexi?

    You have the start of one feedback equation. You have already been told one feedback mechanism that is relevant in climate models. Are you unhappy because it doesn’t *mention* feedback in the model description you have hold of? Well, get hold of the source code for a model with feedback.

    Within that source code you will see the maths.

    If you know your maths, you will see how the code sets up an iterative process. This iterative process doesn’t have “feedback” in the name because the feedback is a RESULT of running the model, not the aim of the model itself.

    Similarly with the other things “you don’t know”.

    Comment by Mark — 6 Nov 2008 @ 2:02 PM

  156. Sigh. Without a real mechanism for putting in equations, you miss spotting.

    r^3. Should be the size of the shell around the mass considered, so you need to differentiate it.

    So sue me, I’m an astrophysicist. We don’t model how stars form, just how the grow and die.

    Comment by Mark — 6 Nov 2008 @ 2:04 PM

  157. Cumfy, Land.


    The NH has lots of land, not a lot of water. SH has not a lot of land which leaves a lot of room for water.

    Land warms up to a shallow depth (ask a gardener, no need to trust a scientist). The ocean warms to a much greater depth.

    That’s one element. A real climatologist will tell you more.

    Comment by Mark — 6 Nov 2008 @ 2:07 PM

  158. Well, Mark, I am sure I already said enough even in my first post (#135). I mentioned “boundary conditions”, “differential equations”, “parameters”, “state variables of a model”, “finite-difference (or spectral) approximation of NSE”. It seems to me that even a student in EE could understand that I am not asking about army cooks or how to feed a squaddie. I was even more explicit when referring you to a pdf in post #150. The pdf contains very accurate formulas. Therefore, I suggest that the “try again” is on your side. Thanks.

    Comment by Alexi Tekhasski — 6 Nov 2008 @ 2:18 PM

  159. Ray Ladbury (138) wrote “My sources had said that the alcohol boom had brought employment if not prosperity to the northeast.” That is my understanding as well. But the majority of the ethanol employment appears to be located further west and south.

    Comment by David B. Benson — 6 Nov 2008 @ 2:26 PM

  160. Read Under a Green Sky, and 600mya we had anoxic ocean with a thin skim of oxygenated water, with sulfur bacteria living the high life. Got that. His point being that that’s the way it was for all time, until 600 mya. And maybe the bacteria have gotten the high hand a couple of times since, don’t know.

    It appears from his chart of co2 that aside from that huge spike 250 mya that Gaia seems to be reducing the point that she will tolerate the co2. Isn’t that just like a woman; wants one thing and then something else!!

    Our new dna acquisition: a gene for microencephalophy back 50,000 ya. Just coincidentally after Toba. And speaking of Toba, could the particulates have held onto water to such an extent that the enveloping atmosphere could hold onto the water and not rain it out?

    Creating a mist so heavy that we had an all-enveloping cloud layer? Would make a nice explanation as to why some —here we go, off into No-No land—as to why at one time there was no Moon? Maybe because we couldn’t see it? And then—whatever it was that broke the camel’s back, and we got the Flood.

    And now, shockingly, some scientists say that the water is draining back into Gaia. Is that naughty girl planning some more deviltry? Dry it out, wait around for a space spack to send it back out?

    Comment by kate sisco — 6 Nov 2008 @ 3:53 PM

  161. Well, Mark these posts of yours in this thread have been a delight to read, regardless of our philosophical differences.

    Comment by jcbmack — 6 Nov 2008 @ 4:29 PM

  162. #2 “What are the major differences between climate models and weather models? Strengths and limitations of both?”

    #2 Gavin wrote: [Response: Conceptually they are very similar, but in practice they are used very differently…. Weather models develop in ways that improve the short term predictions – but aren’t necessarily optimal for long term statistics. – gavin]

    So Gavin, you would say that the “chaos effect” effects (uncertainty principle), is not modeled significantly differently between a climate model versus a weather model?

    Don’t weather models play to the chaos effect (the starting location of each molecule) and climate models have the chaos effect dampened out so that the climate models can follow each other for years because the chaos effect has been stongly diminished?

    Ie. If you have fifteen weather models, they usually diverge significantly after a few days (hours) while climate models don’t?


    [Response: No. They will diverge at very similar rates if run at similar resolutions. The initial condition divergence is a function of the non-linearity in the dynamics (‘weather’) – it has very little to do with differences in the physics or the climatology. Climate models have exactly the same chaotic behaviour as weather models because they are essentially doing the same kinds of calculations. – gavin]

    Comment by Richard Ordway — 6 Nov 2008 @ 5:00 PM

  163. Alexi, the thread here is asking for suggestions for FAQs — I’m not trying to answer your questions here.
    Wrong topic, it’s not meant for discussion; plenty of that in prior threads.

    Comment by Hank Roberts — 6 Nov 2008 @ 5:07 PM

  164. Steven Mosher, 140

    Thanks. Hank also might like to read this as well,

    Comment by Dave Andrews — 6 Nov 2008 @ 5:25 PM

  165. Re Mark Smith @105: “we need to be extremely wary of the law of unintended consequences”

    Absolutely, and the rush to corn-based ethanol is a very good example, but then those who promoted and decided to proceed headlong in that direction were not really doing so to combat rising atmospheric CO2 levels.

    We also need to keep in mind that we know what the world was like with lower CO2 levels, while human civilization has never had to cope with the higher levels we will see in the near future. Yet we do know those levels will create a great many unintended consequences, many of them potentially quite severe indeed.

    Capthcha: waste wholly

    Comment by Jim Eager — 6 Nov 2008 @ 7:18 PM

  166. Re Rod B @124: “Or did someone tell you that none of this stuff is any help to the economy and productivity?”

    It doesn’t when more and more of your tax revenue goes to paying for “this stuff,” yet you still end up borrowing ever more to cover the rest of the bill, and then don’t make any headway paying down that debt.

    I seem to recall a certain European country that used military spending to reduce unemployment essentially to zero, but it didn’t work out very well for them in the end.

    Comment by Jim Eager — 6 Nov 2008 @ 7:41 PM

  167. The edgcm site linked in the initial post by the contributors, describes, in the Setting Up and Analyzing Climate Simulation section,
    how vegetarian boundary conditions can be modified,usimg what they call a “fractional” scheme in which each grid cellis assigned a fraction of each vegetation type(such as desert,rainforest,Woodland, grassland, ………), so that every grid cell in
    the GCM consists of multiple vegetarian types. This partly answers my question above, as to how to treat entities which appear within only a part of a grid cell.

    It describes the flexibility and limitations of this parameter, which can be used in the GCM, as well.

    Comment by Lawrence Brown — 6 Nov 2008 @ 7:45 PM

  168. “Initial Condition Ensemble – a set of simulations using a single GCM but with slight perturbations in the initial conditions. This is an attempt to average over chaotic behaviour in the weather.”

    Gavin, I’m confused. So weather simulations don’t have this feature? Is this a big difference between weather and climate simulations? Can you explain this in much more depth?

    “This is an attempt to average over chaotic behaviour in the weather.”

    … and this is different from weather simulations in what ways?

    So now you can say that climate models have this “averaging over chaotic behaviour” and weather models don’t? This is not clear to me.


    [Response: Weather forecasts use an initial condition ensemble as well. And the forecast is some kind of weighted average of the individual simulations. So there is no big difference in practice. The difference lies in what they are used for – weather models want to know the most likely trajectory of the individual chaotic path over the next few days starting from today’s conditions, while climate models are used to get the long term average of the individual paths over long enough periods so that the initial conditions don’t matter anymore. – gavin]

    Comment by Richard Ordway — 6 Nov 2008 @ 7:46 PM

  169. Suggestions for the list of FAQs:

    These are not questions about the models per se but still about what the models are trying to forecast.

    1) Which part of the planet does “global warming” apply to – ie which parts of the atmosphere (how high), oceans (how deep) and land surface (how deep)? (A subsidiary question would be how the components are weighted, eg does a 1 degree increase in one cubic metre of dry air increase the average by less than a similar rise in the temperature of 1 cubic metre of moist air or ocean?)

    2) What are the main sources for estimates of global temperature and why do they differ?

    Thanks again for the fine site.

    Comment by Garry S-J — 6 Nov 2008 @ 8:43 PM

  170. Richard Ordway,

    perhaps it’s useful to think that climate models are used to get an idea of the statistics of long-term weather conditions, but the weather itself remains chaotic and will never be predictable beyond a week or so. We can’t predict a tornado next year, but we do know when/where tornado season is.

    Comment by Chris Colose — 6 Nov 2008 @ 11:38 PM

  171. Gary:

    1. All of it. :-)

    No, really. Just because the tropopause is getting colder doesn’t mean it is not being affected by global warming. If heat is being retained it isn’t heating up the tropopause.

    2. Science. The main sources don’t.

    Comment by Mark — 7 Nov 2008 @ 3:21 AM

  172. Alexi 158.

    Diffeerential equations.

    The document you linked to was stuffed to the gills with differential equations.

    So it wasn’t “missing”.

    So, just on that one element, what is it you don’t understand.

    Comment by Mark — 7 Nov 2008 @ 3:24 AM

  173. The radiative forcing for CFCs is given as a linear relation for low concentrations see
    Does this hold for the much (ten times or more) larger concentrations we would expect without the Montreal Protocol?
    What is an approximate formula for concentraions large enough that the linear relation is no good approximation?

    Which influence has the oxygen on climate? The concentration in the last 400 million years has probably changed between 15 and 30 percent, changing total atmospheric pressure I assume.
    Inceasing oxygen (for example form 20.9 to 30 percent) in my opinion would:
    Increasing scattering and so albedo, lowering temperature
    Increasing total pressure, broadening of absorption lines, rising temperature
    Increasing adiabate slope, rising SAT directly but decreasing water vapor, total effect??
    Probably increasing ozone, rising temperature?
    Probably decreasing methane, lowering temperature
    Change on clouds, direction of effect?
    Other effects?
    What direction is the total effect and with size has the effects mentioned above?

    Comment by Uli — 7 Nov 2008 @ 3:27 AM

  174. Alexi, a physics based model won’t have a bit labeled “Feedback_from_water” on it because that is what a statistical model would do. The feedbacks are emergent properties of the physics included.

    One reason why you won’t see terms like “feedback” in a physics based model.

    A cheaper statistical model may. Then again, they may not CALL it feedback because, for example, H2O is known to be a feedback mechanism so it would be redundant to call it such.

    But still explain what you’re missing about “differential equation”.

    Comment by Mark — 7 Nov 2008 @ 3:32 AM

  175. Re:153 Thanks Mark, I always underestimate google for that sort of stuff. 260 Million tonnes/yr..or the equivalent of planting 260 million trees. That’s just from soda drinks, then you’ve got the copious amounts of CO2 released from the manufacture and consumption of beer and spirits, aerosol cans etc. Why hasn’t anyone tried to raise that with the media or respective governments. Why cant you find another gas apart from CO2 to make drinks fizzy? Ok! cant be done with beer I know but surely it’s possible with soda..why not use compressed nitrogen or helium..pretty harmless inert gas?

    Comment by Lawrence Coleman — 7 Nov 2008 @ 4:37 AM

  176. Cumfy:>Do GCMs model the 1.4C difference in annual temperature between NH and SH ?

    Mark:>Cumfy, Land.Mostly.
    The NH has lots of land, not a lot of water. SH has not a lot of land which leaves a lot of room for water.

    My principal concern is whether GCMs actually model that difference.

    I was thinking the difference may primarily be due to the difference in polar albedo NH vs SH.

    Comment by Cumfy — 7 Nov 2008 @ 5:18 AM

  177. Uli writes:

    Which influence has the oxygen on climate? The concentration in the last 400 million years has probably changed between 15 and 30 percent, changing total atmospheric pressure I assume.

    Oxygen blocks a little of the ultraviolet light in the stratosphere, at shorter wavelengths than ozone. The amount blocked from reaching the surface would change slightly if the oxygen concentration changed.

    Comment by Barton Paul Levenson — 7 Nov 2008 @ 7:44 AM

  178. > changing total atmospheric pressure I assume

    Why? Is there any information about atmospheric pressure over the long term to go with information about atmospheric chemistry? I found a couple of tidbits:

    Low atmospheric CO2 levels during the Permo- Carboniferous …
    … at a time when total atmospheric pressure was similar or slight higher than now. …

    Pterosaurs couldn’t soar, says expert Oct 1, 2008 … A Japanese researcher has put paleo-biologists in a flap … OR the total atmospheric pressure was MUCH higher. possibly BOTH. …

    Note, I’m offering this as a suggestion for the FAQ collection.
    I’m not soliciting amateur opinions or digression into discussion.
    Raypierre probably knows the answer, I’ll hunt a bit more in his info.

    Comment by Hank Roberts — 7 Nov 2008 @ 10:24 AM

  179. Re: Carbonated drinks

    It seems to me that the appropriate question is: where does the carbon in the CO2 in carbonated drinks come from?

    If it’s from the biosphere, then the biosphere got it from the atmosphere in the first place, so it doesn’t represent an alteration to the carbon cycle which would increase atmospheric CO2 concentration longterm.

    The problem with CO2 buildup is that we’re taking carbon from long-sequestered sources (fossil fuels) and injecting it into the atmosphere is a sudden burst.

    Comment by tamino — 7 Nov 2008 @ 11:32 AM

  180. I am still stuck with the aerosol influence on global temperature (posts 27, 52, 109 and 148). It apparently has had huge compensating effects by negating any rise from CO2 accumulation in the 1940’s to around the 1970’s. We should be able to trace regional effects on a macro and micro basis, showing substantial cooling in the conical wake behind polluting industrial centers – aside from the follow-on wide spread. Besides my earlier query about the recent Chinese rise in aerosol emissions (without apparent local cooling effects) there should be very good traceability of East European changes in emissions. Before the 1989 political and economical changes in East Germany, Poland and Czechoslovakia they had been the foremost industrial suppliers to the Soviet Union, with commensurate horrible pollution.
    We have had detailed infrared satellite survey of the zones behind the iron curtain, i.e. there should be mapping records of before and after 1989. Did discernable warming occur?
    Furthermore, if aerosols did have such a dramatic cancelling effect at the onset of WWII and during the following decades, is aerosol cooling part of the temperature models? They should, shouldn’t they? If so, do they confirm the above mentioned changes in Eastern Europe and China?

    Comment by Dietrich Hoecht — 7 Nov 2008 @ 11:35 AM

  181. … “we’ll say for the record that the late Michael Crichton did a disservice with his denialist potboiler novel State of Fear, which abused climate scientists and environmentalists. President Bush met directly with Crichton while snubbing real scientists. President Obama can begin to set things right by showing that he is instead meeting directly with leading scientists and learning from them.”

    Comment by Pat Neuman — 7 Nov 2008 @ 12:00 PM

  182. Tamino, #179. I answered that in the spirit of showing how MUCH CO2 humans can produce when something as minor as your soft drink can, when multiplied by the number of people on the planet, really DOES add up to a LOT.

    Cumfy, #176. Yes, the models do tell the difference between sea and ice. For one thing, there’s no orography over the ocean and there’s very little water over the land. Ignoring the differences would be silly.

    Comment by Mark — 7 Nov 2008 @ 12:28 PM

  183. Deitrich, #180. Well the amount of aerosols produced were enough to kill large numbers of people annually. That’s how much they affected the atmosphere: they killed people breathing it.

    If something is able to do that, why the disbelief that it is enough to affect the changes seen?

    Comment by Mark — 7 Nov 2008 @ 12:30 PM

  184. RE: #175: CO2 from soda: I think the factor of 52 (well, 50) weeks was already in Mark’s first calculation, so I think 5 million tons was a yearly value already. 260 million tons would be 1% of the yearly ~26 gigatons of CO2 we emit, which would be kind of shocking. 0.02% makes more sense.

    Re: #179: seems to claim that most CO2 used in the beverage industry is a byproduct of the ammonia production process: therefore, even though this CO2 does come from a fossil source, one might argue that it would otherwise be released into the air and therefore is “free” CO2. Now, once there is a _price_ on carbon, soda companies will have to compete with selling credits based on injected CO2 underground.

    Comment by Marcus — 7 Nov 2008 @ 12:43 PM

  185. Well, Mark, you ask: what am I missing in “differential equations”? You already have answered that question: “feedbacks” are missing. There is no “feedbacks” in the original, practical formulation of climate models, thank you for spelling this out. Then why would all climatologists and their skeptics break so many fences over the thing that does not exist? Why would the populist sites like RC spend so much time arguing about the non-existing thing and trying to put “quick definitions” for it? As result of being non-existent, it cannot be properly quantified, measured, and therefore causes nothing but illusion of understanding, which is quite well demonstrated here. Thanks.

    Comment by Alexi Tekhasski — 7 Nov 2008 @ 12:57 PM

  186. Alexi, #185. Well “feedbacks” have nothing to do with differential equations.

    You don’t get “feedback” in electrical amplification differential equations, either. Feedback is what you get when the output leads to the input. It’s not an add-on, it’s the result of the thing itself.

    You don’t model “feedback” your model shows feedback. Otherwise you’re running a statistical model that says something along the lines of “If CO2 plus feedbacks meant an increase in insolation retention equal to 4W/m2, what would the system do”. Which is a statistical model, not a physical one. A physical one has “the water has an effect on temperature of the air”. It also has “the temperature has an effect on the water content of the air”. It doesn’t bother with “water has a feedback effect on anything that increases ore reduces air temperatures” because that isn’t needed: it’s an inherent property of the physics you’ve included in your model.

    So that’s where “feedback” disappears: it isn’t needed in a physics based model because such properties are emergent, not built in.

    Might as well ask “where does the dark come from when you turn the lights off?”.

    Comment by Mark — 7 Nov 2008 @ 1:47 PM

  187. Dietrich Hoecht (180) — I suspect that the East Asian aerosols are having an effect on temperatures and precipitation in North America. I breifly looked at a paper explaining how these aerosols generally move northwest up the coast and then on the westerlies across the Pacific. Locally, the weather and sky have been most unusual for about two years; these aerosols might well explain the effects I am noticing.

    Comment by David B. Benson — 7 Nov 2008 @ 1:51 PM

  188. Who writes code for the models used by professional climate scientists? Do they write requirements for a model to accomplish x,y,z and then turn it over to a programmer to implement? I ask because of the comments about models running on the order of months. Over the years I’ve seen some impressively bad code written by smart people attempting to implement their ideas but with no formal training. Often such code \works\ but is terribly inefficient. Example, years ago I was tasked with updating an application which normally ran for 12-15 hours on a data set. When I was done it ran in 20 seconds. Same machine, same data, different person writing the code. The guy who wrote the original app was stunned, then admitted he had no formal training as a programmer. Just a thought.

    [Response: Unfortunately, it is mostly by scientists (at least in the first instance). As you suggest this is not necessarily optimal, though we do get comp. sci. support. Most efficiency gains at the moment are coming from massively-parallel programming and that is unearthing a number of performance bottlenecks, however, the models do a large number of very separate things, and even if one of those was as badly coded as your example (unlikely, but possible), it would end up reducing the actual run time by only a couple of percent. But you are more than welcome to profile our code and see if you can spot something… – gavin]

    Comment by foodtube — 7 Nov 2008 @ 2:05 PM

  189. Re: #188: My understanding is that while some climate code is fairly ugly (and much of it is written in Fortran which some people think is inherently ugly), the fundamental reason for the time it takes to run a model is the sheer number of calculations.

    You need to run mathematical calculations in every grid cell for every timestep. Every time a model improves its resolution by a factor of 2, it increases computation time by a factor of 16: 2x2x2 physical dimensions, plus you need to perform the calculations twice as many times in order to avoid instabilities (eg, you don’t want a packet of air moving west to move further than 1 grid cell at a time: so if you halve the size of the grid cell you’ll need to halve your timestep).

    And as you add in more processes: chemistry, ecosystems, 3D oceans, etc. you also increase computational demand.

    I know that some models attempt to have dynamic grid cell size, so they only have high resolution where it is needed – this is a nice computational trick that saves time, but is probably limited in applicability.

    Comment by Marcus — 7 Nov 2008 @ 2:29 PM

  190. Might as well ask “where does the dark come from when you turn the lights off?

    Worth noting the discussion of the great natural philosopher de Selby’s views on darkness here.

    As in many other of de Selby’s concepts, it is difficult to get to grips with his process of reasoning or to refute his curious conclusions. The ‘volcanic eruptions’, which we may for convenience compare to the infra-visual activity of such substances as radium, take place usually in the ‘evening’ are stimulated by the smoke and industrial combustions of the ‘day’ and are intensified in certain places which may, for the want of a better term, be called ‘dark places’. One difficulty is precisely this question of terms. A ‘dark place’ is dark merely because it is a place where darkness ‘germinates’ and ‘evening’ is a time of twilight merely because the ‘day’ deteriorates owing to the stimulating effect of smuts on the volcanic processes. De Selby makes no attempt to explain why a ‘dark place’ such as a cellar need be dark and does not define the atmospheric, physical or mineral conditions which must prevail uniformly in all such places if the theory is to stand. The ‘only straw offered’, to use Bassett’s wry phrase, is the statement that ‘black air’ is highly combustible, enormous masses of it being instantly consumed by the smallest flame, even an electrical luminance isolated in a vacuum.

    (The Third Policeman)

    Comment by Gareth — 7 Nov 2008 @ 3:19 PM

  191. Mark (#186): What are you trying to say is that “feedbacks are loose interpretations of statistically post-processed outputs from various fluctuating physical variables generated by a model”, correct?

    I also cannot understand why do you keep the distinction between “physical model” and “statistical model”, which maintains an impression that they are somehow separate and independent. From the initial definitions of this article it follows that there no such thing as a separate “statistical model” but statistically-processed outputs from actual state variables of the running “physical” model. One model, different details.

    This kind of incoherence leads to statements like “If CO2 plus feedbacks meant an increase in insolation retention equal to 4W/m2, what would the system do”. Apparently the system would provide a “feedback”, and the feedback would define another level of “forcing”. Then, the “feedback” to your “CO2+feedbacks” would cause another “feedback”, and another “forcing”, etc. So, what are you trying to state with this fuzzy construction? Would the system settle to a new statistically steady state? Would it run away? Maybe it would oscillate, chaotically? I am just trying to figure out a value of this kind of speculations about undefined “feedbacks” and “forcings” in a spatially-distributed multi-variable system.

    [Response: I will add an Q on this above at the weekend, but Mark’s statements are not incoherent. The 4 W/m2 TOA forcing is the consequence of an imposed change in CO2 – all changes to LW absorption in the atmosphere as a consequence of that initial change (through water vapour, cloud or temperature profile responses) are feedbacks. The total amount of LW atmospheric absorption at the eventual (statistical) steady state will be larger than the 4W/m2 forcing (probably about 10-20 W/m2), hence implying that the eventual temperature rise will be larger than the ‘no-feedback’ response. One could envisage situations such that the feedbacks were large enough to create a runaway condition, but that has very little to do with the current climate system. – gavin]

    Comment by Alexi Tekhasski — 7 Nov 2008 @ 3:20 PM

  192. PS Alexi, how can anyone answer you?

    You started off with: I don’t understand feedback
    Then it was: I don’t understand differential equations
    Now it’s: Wen I say “I don’t understand differential equations”, I mean “feedback in differential equations”.

    Comment by Mark — 7 Nov 2008 @ 3:26 PM

  193. I should like to take this opportunity to offer a small critique of those other models, the simple models.

    Much criticism is given to the projections and of big (AOCGCM) models, at least some of which is based on arguments using simple, some might say simplistic, models.

    As is indicated in the opening presentation, big models have to meet a large and diverse set of criteria and have to do so simultaneously. It seems that simple models are sometimes produced ad hoc to highlight a specific issue meeting only a few, commonly a minimal set of criteria.

    For clarity I should like to classify small models as “climate without weather” models as opposed to the big “climate with (or from) weather models”.

    Ultimately they both need to meet the same set of criteria and they both need to do so simultaneously. I think the requirement for simultaneity is by biggest problem with the use of simple models to argue specific points.

    By way of an example:

    The use of a slab ocean (50m of isothermal water) and a climatic observation to calculate the climatic sensitivity.

    Very interesting, but if one wishes to model the lag of the seasons or the diurnal lag such a model does not work. A 50m slab would (in isolation) would predict much greater lags than are observed.

    Personally I think simple (climate without weather) models are important and ultimately the way forward, but they must meet the all harsh criteria of the observed climate simultaneously or they are simply to simple for purpose.

    Best Wishes

    Alexander Harvey

    Comment by Alexander Harvey — 7 Nov 2008 @ 3:52 PM

  194. No, alexi, feedbacks are emergent properties.

    If rate of accretion depends on the mass of the accreting body, then the rate of the increase in mass of that accreting body increases quickly until all available material is taken. This is feedback. It emerges from the (non feedback) collusion between rate of accretion in a uniform medium and the results OF that accretion.

    With the “Statistical” and “Physics based” model, read the article and the first ~100 comments. They are different in exactly the same way as numerical solution is different from symbolic solution in mathematics.

    That statement describes what a ***statistical*** model would do. The model description you linked to was NOT a statistical model. It was a ***physics-based*** model. This would be why the description of that physics-based model did not include any mention of “feedback” because, and please tell me how else to say this, because you never seem to be able to read it, *** it is an emergent property of the physics, and NOT, repeat NOT, a separate element to model ***.

    The incoherence here is your inability to say what you don’t understand. Any attempt to answer must include that incoherence within itself in any attempt to explain else there is no apparent link between the (incoherent) query and the answer given.

    Comment by Mark — 7 Nov 2008 @ 4:01 PM

  195. Mark,(183), aren’t you the least bit of intellectually curious if a phenomenon appears able to cancel out global warming for 30 years? There is definitely no linkage in bracketing something as atmospheric health hazard and the discussion of the physics of climate change. Is’n this science, with all of its theories, observations, tests and ongoing learning and improving results? I don’t get your kind of argument – it’s like you are afraid of reality.

    Comment by Dietrich Hoecht — 7 Nov 2008 @ 4:23 PM

  196. Dear Mark, you should probably try again to answer my original post (#135). Instead you gave me a lecture on how to cook for army, and what is an eating pattern of a “squaddie”, and decay of nebula. Please take a note that I do perfectly understand what a feedback is (in the normal science and engineering), and how to write and analyze/solve differential equations, both ordinary and partial. I just wanted a clarification of buzzwords you are using. So far you haven’t done a good job as an apprentice at RC. Try harder.
    Gavin: your example does not make it any clearer. One interpretation of what you said is: if 4W/m2 of “initial forcing” causes 20W/m2, then the resulting 20W/m2 would in turn cause 100W/m2 forcing, then 100W/m2 would cause 400W/m2, etc. The formal incoherence arises here because you omitted to discriminate one kind of “forcing” (from CO2) from other (derivative) forcings. In a multi-variable system “forcings” do not add up in a simple algebraic way. Apparently there must be additional qualifications to restore coherency in this loosely-defined “Forcing-Feedback” paradigm.

    [Response: I disagree (obviously). The 20W/m2 extra LW absorption is not a forcing, it was how the planet has adjusted to the initial change – it is not an imbalance at the TOA. (Just because the units are the same doesn’t make a feedback into a forcing). I do distinguish them – one I call a forcing, the others a result of feedbacks. It’s really not that hard. – gavin]

    Comment by Alexi Tekhasski — 7 Nov 2008 @ 4:26 PM

  197. The Global Climate System: Patterns, Processes, and Teleconnections by Howard Bridgman, John Oliver, and Michael Glantz is an excellent book that will answer most of your questions. Proxy data, ratonal behind the models, how they have improved and some issues on paleoclimate are all covered. If you do not have the money or the time to purchase it, it is available in many libraries. The introduction speaks about the heat budget, important equations and so forth. Oh and I checked, you can get limited access through Google Scholar, so now you can read and learn, then you can ask questions that have an answer. I found the book to be indispensable, and quite frankly it would benefit many of the posters in this thread as well. Also many states have city public library ebooks that one may sign up for and view for about 3 weeks right on the desktop, many technical books can be accessed this way.

    OR (if the book is too advanced to begin with)

    Alexi start with reading relevant articles from Britannica, pick up a general textbook on weather and climate, or physical geography, Richard Christopherson is good, and why don’t you go to,, and physics.web, and make sure you have the appropriate math background. Even non climate modelers with a solid science and math background can get the gist of the models. Some of the references and older posts on this site would really help you understand.

    OR take a few intro courses in meteorology, earth science and take DQ

    Cambridge University Press.

    Comment by jcbmack — 7 Nov 2008 @ 5:26 PM

  198. The six box climate models seem right on and even simpler models, distinguish between solar foercing and greenhouse gases.

    Comment by jcbmack — 7 Nov 2008 @ 5:30 PM

  199. Great article.

    I think it would be great if you guys added a short section explaining the basic way in which clouds are included in the models. A good friend of mine (who’s a scientist in an area far removed from climate) was arguing some time ago that the climate models are useless because they don’t include clouds at all or in such a crude way that their effect is totally meaningless. Apparently, he got this idea from talking to another professor in his university, who seems to specialize in studying clouds.

    After saying this stuff about clouds he went on to mention something similar to the infamous “iris effect” (as the planet warms, more clouds appear, thus reducing insolation and limiting the temperature rise).

    I have seen some models that include clouds, so I’m sure my friend is wrong. But it would be great to have some more info about cloud simulation in your models, to be able to counteract these false ideas.


    [Response: Good Q. Models do include clouds, and do include changes in clouds with climate. There are certainly questions about how realistic those clouds are and whether they have the right sensitivity – but all models do have them! In general, models suggest that they are a positive feedback – i.e. there is a relative increase in high clouds (which warm more than they cool) compared to low clouds (which cool more than they warm) – but this is quite variable among models and not very well constrained from data. – gavin]

    Comment by Rafael — 7 Nov 2008 @ 7:45 PM

  200. Alexi,

    forcing-feedbacks on Earth are a converging series, not a diverging one. It is not necessary for a positive feedback to result in runaway warming.

    Comment by Chris Colose — 7 Nov 2008 @ 7:55 PM

  201. Well put Gavin.

    Comment by jcbmack — 7 Nov 2008 @ 8:33 PM

  202. Read and learn, find the facts, the questions asked say alot…

    Comment by jcbmack — 7 Nov 2008 @ 8:35 PM

  203. Nothing in science is unknowable, if one is discplined, some things are just not known yet; climatology is a branch of science that helps us gain insights into climate. With just 4 years of schooling composed of statistics, physics, calculus, chemistry, Biology, and the obvious related into courses, it should not be difficult to get one’s head around this stuff. Classical and modern physics classes teach a lot, (they are both taight in Community College!) units were stressed the first day of gen chemistry. Engineers should have no big trouble understanding forcing, earth’s wobble and tilt changes, and how math based upon averages is inputed into a complex computer system and we begin to see relevant results. Imagine what might be found based upon larger scale models with randomization. I love this site, obviously I spend time reading the articles and looking at the people’s background who run it. With a masters or phd a high level of mastery and independent thinking is acquired as part of skill sets for internships, professorships, or industry-academic reseacrh, no need to argue moot points.

    Again I applaud the patience and the effort put forth by the site administrators.

    Comment by jcbmack — 7 Nov 2008 @ 8:49 PM

  204. Gavin, you obviously disagree. But I am not saying that I disagree with you either. I am just pointing out to your own words in response to #191: you said that “imposed change in CO2” changes “LW absorption in the atmosphere”. This extra “LW atmospheric absorption” seems to be a driver for other changes. All other changes (from feedbacks), as you say, lead to larger “total amount of LW atmospheric absorption”, which looks like the same object as the one being forced by “that initial change.” So, it is not only the units are the same, but the object is the same, the “amount of LW atmospheric absorption”. So, it looks like the distinction of which part of it comes from “initial forcing”, and which comes from “feedbacks” is lost, it is just a new “amount”. Therefore, a straight logic would dictate that the scheme should continue to iterate, the new “amount of LW absorption” should drive more changes. I am just following your explanation, formally, and the conclusion seems to be an absurd.

    As I said, without additional fuzzy explanations the paragigm of “forcings” and “feedbacks” is incoherent. It does not explain nor predict anything unless you invoke results straight from the model, which, in turn, would be not an explanation but a constantation of the fact. The model just does this, as you would say, right? So, all the buzzwords “forcings” and “feedbacks” serve no purpose.

    Comment by Alexi Tekhasski — 8 Nov 2008 @ 12:12 AM

  205. I have a short (~3000 word) “Layman’s Guide” to climate models that I am trying to refine before adapting it as a narrated slideshow. Any input welcome!

    Comment by cce — 8 Nov 2008 @ 12:33 AM

  206. Re: 179 Tamino. Just been looking up the sources for commercial CO2 and here is a short exerpt from google: “The most common operations from which commercially-produced carbon dioxide is recovered are industrial plants which produce hydrogen or ammonia from natural gas, coal, or other hydrocarbon feedstock, and large-volume fermentation operations in which plant products are made into ethanol for human consumption, automotive fuel or industrial use. Breweries producing beer from various grain products are a traditional source. Corn-to-ethanol plants have been the most rapidly growing source of feed gas for CO2 recovery.” So therefore fossil fuel combustion or refinemet is still the the primary source of industrial CO2 capture. C’mon there has to be another source of gas for soda drink production!! Indeed a hefty carbon tax should be levied on Coca-cola amitil, Pepsico and other such companies..after all soda drinks should be considered a luxury item in my thinking.

    Comment by Lawrence Coleman — 8 Nov 2008 @ 2:04 AM

  207. “Mark Says: 7 November 2008 at 3:21 AM

    “1. All of it.

    No, really. Just because the tropopause is getting colder
    doesn’t mean it is not being affected by global warming. If
    heat is being retained it isn’t heating up the tropopause.”

    That’s my point, Mark – all of what?
    All of the atmophere, OK, but all of the sea, right down to the bottom of the deepest ocean?
    How about the temperature of the land? The top millimetre? The top kilometre? All the way down to the magma? None of it?
    What about lakes and swamps? Is all the water in lakes included? Glaciers – all the way down? Just the top bit?
    Ice sheets? Are they included?
    What about the snow lying around – is water vapour in the air included but ignored when it turns into snow lying around in the fields?
    Presumably someone, somewhere, might know the answer to these questions. It may even be in an obvious place I’ve overlooked, but I think “Which part of the planet does ‘global warming’ apply to?” would be a worthy inclusion in a climate model FAQ.

    “2. Science. The main sources don’t.”

    Well, yes they do, just a little bit. I’d like to know why. I’m sure other non-climate-scientist people would too. Hence my suggestion for “What are the main sources for estimates of global temperature and why do they differ?” to be included in an FAQ. You know, just some basic info about which institutions collect the data, how coverage and estimation methodology varies between them, that sort of thing.

    FAQs obviously can’t go into a lot of complex detail, but to say only that the estimates come from “science” would not be particularly helpful.

    (By the way Mark, your reference to the tropopause appears to argue against a proposition I didn’t, and wouldn’t, make.)

    Comment by Garry S-J — 8 Nov 2008 @ 2:36 AM

  208. Alexi:



    This is a feedback.

    It resides nowhere in the equation as “feedback” because naturally falls out of the equation IF:

    1) you have a nonzero starting a
    2) you iterate

    The “feedback” falls out of the iteration. Without iteration, you have a becoming 1.1a, and then stops.

    Now, what do GCM’s do with their calculations…?


    Comment by Mark — 8 Nov 2008 @ 5:55 AM

  209. OK, Alexi. We’ll go back to your #135 and ignore the waffle since then.

    1: ” What exactly is “forcing”?” Gravitational stress is a forcing. No matter what else is acting on a body in a gravitational field, gravity will consistently have its way. That is a forcing.

    2: “What do you mean under “imposed from the outside”?” In what context?

    3: “Do you “impose” new boundary conditions on the “physics-based” equations?” You can.

    4: “Or do you change a parameter in a differential equations like a gas mix ratio?” You can.

    5: “Is there any “forcing” if the atmosphere mix stays constant, and the Sun shines steady?” If there are more forces that consistently act on the system, yes. If you have a very simple model that only considers those two elements, then no.

    6: “What do you mean under “Feedbacks are changes in the model that occur in response…”?”. It means “feedbacks are changes in the model evolution that occur in response…”.

    7: “Did you mean “changes in the state variables of the physics-based model”?” What do you mean by “state variables”?

    8: “What is “initial forcing”?” Whatever you put in to start the simulation/model.

    9: “The only forcing I am familiar with is a constant flux of SW solar energy.” Ignoring that the solar flux is not constant (and that inconstancy is an input to modern models), That is one. There are others.

    10: “What are the other “forcings”?”. A very few are: water vapour. If your water vapour is out of equilibrium, you will have a forcing that is the systemic response to the water vapour being out of equilibrium.

    11: “What do you mean under “physics-based”?” Based on physical processes simulated in the model. This was explained in the comments earlier. You never did go back and read it, did you. Or if you did, you never said “I get it now” on that point.

    12: “You mentioned F=ma, but for a continuous media, the physical equivalent of the conservation laws would be Navier-Stokes Equations (NSE).”. Only for fluid flow. Heat transfer does not obey NSE. Gravitational mixing doesn’t obey NSE. Cloud formation doesn’t obey NSE…

    13: “Do you mean that GCMs directly emulate NSE by numerically iterating some finite-difference (or spectral) approximation of NSE?” That and more. (See #12)

    14: “What is the definition of “process-level parameterization”?” A process like cloud formation is either an intractable solution or too computationally expensive, so either smaller models modelling what conditions clouds form in and how their form changes are done and the results put into a parameter list. This parameter list then approximates what effect the clouds have under the conditions otherwise simulated in the GCM. This is where tuning comes in.

    Now, notice that several of your questions didn’t get answered because you didn’t explain what your query was about.

    Comment by Mark — 8 Nov 2008 @ 6:10 AM

  210. Alexi 196.

    You say you know about differentiation. This means you know some maths to some level.

    Have you never heard of the Taylor series? An infinite series that sums to less than infinity. In some cases. E.g. the Sin(x) expansion is an infinite sum based on x. And it never goes above 1 or below -1. Even though you are summing an infinite feedback series. Note that Tan(x) has a Taylor expansion and that DOES sum to infinity. It depends on how the numbers are added together.

    Rather like GW feedback processes on Earth.

    On Venus, the feedback was of a different magnitude and there is, if not a catastrophic runaway, a feedback that has expanded beyond the ability of life as we know it to exist.

    In any case, any real physical process cannot sum to infinity, else Venus may be outshining the rest of the galaxy from its infinite runaway greenhouse effect giving it infinite temperature. Which is obviously silly.

    Comment by Mark — 8 Nov 2008 @ 6:15 AM

  211. > please focus on real questions that have real answers

    From the initial post.

    Any thread can be derailed by anyone sufficiently persistent — if you keep typing in response.

    Alternative: Google for the same question. Often it’s been asked and answered, or asked and unanswerable, elsewhere — often by the same person.

    “Why?” can be asked as long as the kid can stay awake, til they outgrow it.

    Comment by Hank Roberts — 8 Nov 2008 @ 10:45 AM

  212. #180 Dietrich Hoecht: yes the anthropogenic aerosol effect is impressive isn’t it? But do place it into perspective. We can describe the increasing greenhouse forcing as an exponential growth process with a doubling time of 30 years. This means that in 1978 it was half of what it is now, and in 1948, one quarter. The difference between those two, one quarter of today’s, is what was compensated… well, partly. Volcanic aerosol variations also played a role.

    I tried to find references for you on regional aerosol effects, and my hat tip is: google the INDOEX project. The Indian Ocean is perfectly located for this. One caveat I should make is, don’t expect to find any regional temperature effects. I may be too pessimistic, but the problem with regional temps is that the background noise, natural variability (“weather”), is so much larger than for the global case. And even worse for short time periods. This may be the reason why the reported results are in terms of forcing effects, not temperatures (and quite spectacular).

    I didn’t search for more references but I am sure there are. I am not a climatologist so you can do this as well as I :-)

    Comment by Martin Vermeer — 8 Nov 2008 @ 11:24 AM

  213. Hank’s caution is well-taken, but I am going to make a stab at this anyway. Alexi’s post, #206, had this:

    “This extra “LW atmospheric absorption” seems to be a driver for other changes. All other changes (from feedbacks), as you say, lead to larger “total amount of LW atmospheric absorption”, which looks like the same object as the one being forced by “that initial change.” So, it is not only the units are the same, but the object is the same, the “amount of LW atmospheric absorption”. So, it looks like the distinction of which part of it comes from “initial forcing”, and which comes from “feedbacks” is lost, it is just a new “amount”. Therefore, a straight logic would dictate that the scheme should continue to iterate, the new “amount of LW absorption” should drive more changes.”

    Alexi, I think you are conflating a brief description with the process itself. Just because one term, “LW atmospheric absorption,” is affected by multiple processes (feedbacks) does not mean that all distinction between these inputs is lost–for one thing, they will all have different constraints, response curves, etc., and will be taking effect concurrently, though interactively, over differing time frames.

    Additionally, the real quantity we are trying to derive isn’t LW absorption, it is temperature.

    Comment by Kevin McKinney — 8 Nov 2008 @ 12:21 PM

  214. It seems right that clouds are a positive global warming feedback, on the average. Although more clouds in summer favor cooler daytime temperatures, more clouds in summer favor warmer overnight temperatures. And, more clouds in winter in mid-high latitudes favor higher surface dewpoints with higher melt rates.

    Comment by Pat Neuman — 8 Nov 2008 @ 12:37 PM

  215. If my math and physiology is correct, breathing puts out way more, about 200 times, CO2 than Mark’s 4 cans of soda per week — and it is a net add from long sequestered carbon (though most not near as long as fossil fuel).

    Comment by Rod B — 8 Nov 2008 @ 1:48 PM

  216. Marcus (184), bankrupting the coal industry and 75% of the power generation industry is bad enough. But when you blast the soda industry, that’s going too far :-P ….

    reCAPTA = some protest

    Comment by Rod B — 8 Nov 2008 @ 1:57 PM

  217. Samson wrote:
    when I am discussing with climate skeptics, they often refer to the third report of the IPCC (page 774): “In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”

    Gavin responded:
    There are at least two aspects to this question. First, how well do we know the forcing into the future? We can’t do a very good job at estimating the future trajectory of technology for instance, or economic development, and so regardless of how well we understand climate, our ability to predict exactly what will happen is limited. Secondly, we don’t have full information about the current conditions, and so, like for weather forecasts, if there are aspects of climate change that are chaotic, we can’t predict those over the long term. However, it is worth pointing out that the statement does not imply that we can’t know anything about the climate system in the future. We know that if there is a big volcano, the climate will cool – and many aspects of the resulting changes will have been predictable. The same is true for increasing GHGs – the climate will warm. Models can’t tell you exactly what will happen where, but there is a lot they can say. – gavin

    A lot which is of interest to academics, but not enough to be relevant for real world application. A prediction of the spread of possible future outcomes is far too wooly for real world application. So what if you can say that the future will be a bit warmer and maybe a lot warmer? You knew this before you ran the simulations. In the real world of growth and development, the choice of the course of action hinges on knowing the severity of the problem. Can we make it if we continue with this infrastructure, or must we change the infrastructure to something different? Will the beam carry the load? Will the fuel in the tank be enough to reach that airstrip? Well, we have somewhere between a little and a lot, but we can tell you with great confidence that the further you fly the more fuel you will use!


    Yours, a very disappointed former AGW believer.

    [Response: Your mistake was thinking this is a matter of ‘belief’. – gavin]

    Comment by Stefano — 8 Nov 2008 @ 2:00 PM

  218. Mark (209), a question: Aren’t solar insolation and atmospheric gas mixture the ONLY two things that can be forcing? What else might there be, at least long term (excluding volcanoes and such)? Or are you referring to the different inputs that effect either of the two forcing sources?

    [Response: Forcings can be a much larger class of things that effect any aspect of the boundary conditions for a specific model. For instance, closing the Isthmus of Panama (4.5 millions years ago) was obviously a forcing that likely had profound effects on the climate – it wouldn’t be easy to characterise in radiative terms though. Similarly, orbital forcing has a very small global mean radiative effect, but dramatic consequences due to how the seasonality of the changes impacts ice sheets etc. The ones that are most relevant today though are those that affect atmospheric absorption and reflection of radiation, and surface impacts on either radiative or hydrologic fluxes. – gavin]

    Comment by Rod B — 8 Nov 2008 @ 2:52 PM

  219. I mean I formerly believed the scientific community.

    It is a strange thing to criticize my “mistake” for that.

    Comment by Stefano — 8 Nov 2008 @ 2:56 PM

  220. Re #215

    Just in case you’re not being droll!:

    Breathing isn’t a net add at all, and the CO2 has only been “sequestered” for a rather short time (in plants and the poor animals that we eat).

    All of the carbon in the biosphere is just continuously recycled in a relatively closed system that involves firstly the drawing of CO2 out of the atmosphere by photosynthesis:

    6CO2 + 6H2O —- (CHOH)6 + 6O2

    [where (CHOH)6 is generic carbohydrate]

    …and then we eat the plants or the animals that eat the plants, and return the CO2 to the atmosphere by respiration (aka “breathing”):

    (CHOH)6 + 6O2 —- 6CO2 + 6H20

    I expect that the contribution of this specific form of the cycle “breathing” is small in fact in relation to the bacterial decomposition of dead plant matter as observed in the very large cyclic variation of atmospheric CO2 that results from the Northern hemisphere plant growth and decay cycles.

    So breathing isn’t a net add. The only net adds are from tectonic activity, deforestation and other land clearance activities, and the rather humungous amounts of carbon currently being added to the short term carbon cycle through the massive burning of long-sequestered fossil fuel…

    Comment by Chris — 8 Nov 2008 @ 3:02 PM

  221. FAQs on “what don’t we know and how do researchers approach this” would be good, on a whole variety of questions.

    One would be — can we get a “whole planet” measurement if we are far enough away? Can we do that for Mars or Venus for example? Could an instrument like ‘Triana’ do it for Earth?

    One that keeps coming back is solar influence. “Flux tubes” were in the news recently. Any evidence of excess transfer of energy there, or is this just a better description of what happens?

    Could any amount of solar energy can transfer but be stored chemically in reaction products that don’t return the energy til time elapses after they’ve spread widely through the atmosphere, for another example — part of a whole group of “what can we imagine that wouldn’t be easy to find even if we started looking” questions.
    Possible example, I’m not sure:

    Comment by Hank Roberts — 8 Nov 2008 @ 3:39 PM

  222. Isthmus of Panama about 4 +- 1 million years old:

    Comment by David B. Benson — 8 Nov 2008 @ 4:50 PM

  223. #217. Stefano said:

    “A prediction of the spread of possible future outcomes is far too wooly for real world application. (…) In the real world of growth and development, the choice of the course of action hinges on knowing the severity of the problem.”

    But in the real world of growth and development, we rarely do, certainly if you are talking globally and over multi-decadal time scales. How much will the population grow by mid-century? How much oil and gas is out there waiting to be found? What technological advances will happen? The answer to any of those questions will be a spread of projections based on questionable assumptions. A “best estimate” is sometimes just a middle projection cited in a confident tone of voice.

    With the partial exception of infrastructure, the “real-world” examples you cite are simple engineering problems, not global strategic issues for the 21st century. The question is not like “will the fuel in the tank be enough to reach that airstrip”. What we are talking about is more like, How much fuel will be burned by how many airplanes reaching their airstrips over the next half-century, given various projections for population growth and economic development, imponderables about changing patterns of mobility and technological breakthroughs, and market reactions to unpredictable events like terrorist hijackings? (And, lest we forget, what will the carbon from that fuel do to a complex climate system?)

    Those with a “real-world” need to know if the infrastructure will hold (will there be enough of those air strips?) presumably have to model travel demand. And they don’t even have the luxury of being able to base their models on well-known physics.

    Stefano, did you become disappointed with AGW because it turned out to be more complex than a textbook engineering problem? Surely you knew that before they ran the simulations.

    Comment by CM — 8 Nov 2008 @ 4:51 PM

  224. OT I know. But regarding the saturation I was previously asking about.

    Comment by Richard C — 8 Nov 2008 @ 4:57 PM

  225. Re 215 & 220:

    You know, breathing *is* a net add, systematically speaking, because our food production involves massive amounts of fossil fuel consumption.

    Comment by Kevin McKinney — 8 Nov 2008 @ 5:18 PM

  226. The following question might be useful for the FAQ, though I dunno if it’s frequently asked: what are the “main types” of GCMs? I.e. I’m asking for taxonomy(s). Since my contact to date with GCMs has been limited, I can only guess at some candidate classifications, but some things that come to me are

    * algorithmic, e.g. Lagrangian vs Eulerian.

    * lineage. Given how models are created by research groups which propagate over time, I’m guessing that some models begat other models in Biblical fashion.

    Comment by Tom Roche — 8 Nov 2008 @ 5:29 PM

  227. Re 157
    Mark, your land-ocean heat capacity argument appears to suggest that the SH would be warmer than the NH, because of more efficient energy capture by the oceans.

    Is that what you intended ?
    It just that(NH=14.6,SH=13.4)

    Comment by Cumfy — 8 Nov 2008 @ 5:32 PM

  228. Now that I think about it, prior to the previous question should be one that probably *is* frequently asked: what are some of the major/leading GCMs? Apologies if this was discussed in the voluminous comments, but I searched for “major” and “leading” and didn’t find a match for this question.

    Comment by Tom Roche — 8 Nov 2008 @ 5:35 PM

  229. On the CO2 from a can of soda: Marks says:

    “Lawrence, look it up. From a quick google:
    CO2 per can of soda 6g CO2.
    22 cans a week is a lot, so say 4 cans average.
    4Billion people.
    4×10^9×4×50×6g = 5×10^12g = 5×10^9kg = 5×106T = 5Million tons.”

    That’s the local frame – and we are concerned with the global frame. Imagine you are measuring the flow rate of a river – but where does the water come from? Is it from rainfall, from snowmelt, from glacier melt, or is someone mining hundred thousand year old groundwater up in the mountains?

    With the can of soda, you could measure the ratio of 14-C to 13-C in the CO2 coming out of the soda, and if it was identical to the atmospheric ratio, you would know that the CO2 last saw the atmosphere very recently. If there was no 14-C, you would know the opposite. If you measure the 14C content of CO2 coming out of a gasoline engine, you’ll see none – unless the engine is running on biofuels.

    So, let’s take this approach. 100 g of pure water can hold 0.34 g of CO2 at O Celsius. So, where does your soda company get their CO2 from? They pressurize the soda using pure CO2, from atmospheric sources. Thus, the actual answer is zero, if we look only at the carbonated water – but if we look at the entire process of producing and drinking a can of soda, we get a different number.

    The actual atmospheric cost of drinking a soda is not the release of dissolved gases, but rather the fossil fuels used in mining and processing the aluminum needed to make the can, to power the factory that converted the corn syrup, benzoic acid and other ingredients into a tasty beverage, and to grow and process the corn in the first place. Then there’s transportation, distribution, etc. This could all be done with renewable solar and wind, or with coal power – so that number is highly variable – there is no one right answer.

    The conclusion is that the solution there is not to feel guilty about drinking a soda, but rather to push for a large-scale solution that will make our agricultural and industrial systems free of the need for fossil fuel inputs. Wind, solar, biofuels, geothermal and nuclear are all low-carbon energy solutions that directly address the problem.

    Most of the cap-and-trade solutions, however, don’t take the carbon cycle into account. Under those solutions, the acceleration of CO2 emissions (seen clearly in the 50-year record from Hawaii, linked below), will continue. Take a look at the graph, and note that if CO2 emissions had stayed constant at 1960-1965 levels, we’d now be at around 340 ppm, not 380 ppm. Look for yourself:

    Thus, we are on track for the BAU scenarios in the IPCC. Petroleum supplies are not increasing, but there is a lot of coal. Since dirtier source of oil (Canadian tar sands) are now being promoted, the accelerating trend is expected to continue.

    So far, the only thing that has lead any country to reduce fossil fuel use is an economic collapse (Russia, 1990s). The problem is that economics relies, eventually, on ecological and climatic stability, and fossil fuel use tends to undermine both. This is something that most economists have not been taking into account.

    That’s part of the reason that “econometric models” routinely produce nonsense – their predictions are no better than blind guesses, and are probably worse due to their biases. Electricity demand forecasting is one particularly notorious area, as it was widely used to justify very unrealistic programs. Another is NAFTA – the econometric models claimed the accord would result in wage increases for both U.S. and Mexican workers, which was not at all true. Econometric modeling is mostly nonsense, and no sane government should ever use it as the basis of policy decisions.

    Climate models, on the other hand, have a successful track record – look at the melting Arctic, warming around Antarctica, the surface temperature, the water feedback effect, the reduction in mountain glaciers… etc.

    Comment by Ike Solem — 8 Nov 2008 @ 5:50 PM

  230. Found great stuff through unlimited a cutting edge internet information site:

    The issues with the IPCC report are discusses, reanalyzed and the applications of the models are re explored.

    Comment by jcbmack — 8 Nov 2008 @ 7:52 PM

  231. Just a thought for the FAQ, specifically on difference between physics-based models and statistics-based models. In an old post here I summarized some different kinds of models.

    Some people are used to models that either give *exact* answers that must be *right*, or are simply useless, and if so, are inclined to be cynical about results of climate models. Some are actually physics models, i.e., like some of the protein-folding mentioned in the above post, and which has the awful property that an error early in a sequential chain causes wild divergence in the final result.

    It might be worth a few words to note the difference between models that must be accurate/perfect at every step to be useful, and those that are constrained approximations that are still quite useful without needing to be perfect. MCAD fluid dynamic codes and petroleum reservoir models, as well as climate codes, seem to fit the latter category.

    Comment by John Mashey — 8 Nov 2008 @ 8:15 PM

  232. Chris 220 keep in mind, carrying capacity. With over six billion people on the planet and the bacteria and deforestation you mentioned, all the CO2 from us does not offer zero net effect.

    Comment by jcbmack — 8 Nov 2008 @ 10:31 PM

  233. Hank 221 all kind of technology do exist which could potentially hold and harvest solar energy….I do believe that bacteria in properly engineered system could also capture and convert CO2.

    Comment by jcbmack — 8 Nov 2008 @ 10:34 PM

  234. Re:220 Chris, you forgot to include in your calcualtions that the number of cattle, sheep, pigs and poultry etc have been growing close to exponentially with the rate of human expansion- their waste products mean a nett increase in the amount of CO2 being puffed into the air over time but also the increase in other gasses such as methane and nitrous oxide. All this is happening when tropical rainforests are being wiped out wholesale across the world that are designed to take in the CO2 in the air and sequester it as wood- typically hardwood long term. The CO2 taken in by rainforests per hectare is massively greater than a hectare field of sorgom for pigfood. This is a grossely unsustainable system whichever way you want to cut it.

    Comment by Lawrence Coleman — 8 Nov 2008 @ 11:25 PM

  235. Re: Ike Solem, in that case I would guess there is very little 14C in soda cans/bottles due to the fact that the majority of industial CO2 is still captured from fossil fuel sources. I would still still feel guilty about drinking it becasue a sizable percentage is not immediately tranformed and recycled in the biospherical carbon cycle but makes it’s way over the decades into the upper atmosphere. I agree that the entire production process from the manufacture of the aluminuim or the moulding of the glass or the fabrication of the plastic bottles uses huge amounts of CO2 and produces plenty of fine particulate carbon emissions. This must also be tackled vigorously by governments and the appropriate carbontax applied on those factories. As I mentioned to Chris the ‘biospherical’ carbon cycle is out of balance. Not enough and rapidly vanishing carbon sinks and too much livestock and people pumping CO2 into the air which a part will make it’s way into the upper atmosphere over the coming decades.

    Comment by Lawrence Coleman — 9 Nov 2008 @ 12:49 AM

  236. Mark (#209 &#210). I praise your effort. It is quite telling. You got 1, 5, 10, 11, 12 and 13 wrong. To learn what a “state variable” is, read carefully section 2.1 of this assessment report (thanks to jcbmack for link):
    first paragraph. About NSE, see the second paragraph, and please remember that “fluid dynamics of an ideal gas” is not NSE. Also, be aware that the water vapor is canonized here as a classic “feedback”, although I could concur with your heretic view that it is a forcing as well, just as any other “state variable” under appropriate time scale.

    Comment by Alexi Tekhasski — 9 Nov 2008 @ 1:17 AM

  237. Rod B (#218): It looks like you can call anything as “forcing”. For a normal people, closing of Panama isthmus constitutes a new BOUNDARY CONDITION while starting from initial conditions that resulted from old boundary. The orbital variations are astronomically parameterized as part of insolation, which is again the main boundary condition imposed on the system. Atmospheric absorption and reflection is mostly determined by the instant state of cloud cover, which is usually presented as “feedback”. The more I read this thread, the more conflicting messages appear.

    Comment by Alexi Tekhasski — 9 Nov 2008 @ 1:38 AM

  238. Very arresting article in ScienceDaily… That shows that the present level of CO2 @ 386ppm is already in the dangerzone that will cause catastrophic climate change if not reduced to well below 350ppm in the coming few decades. The group of 10 scientists include Prof.James Hansen, 2 other leading academics from Nasa Goddard, a scientist from Yale, the UK and France. They propose replacing coal as a fuel source by 2030. They say geo engineering is a waste of time since to reduce CO2 by even 50ppm would require a global expenditure of US$20 trillion. What do you think?

    Comment by Lawrence Coleman — 9 Nov 2008 @ 3:22 AM

  239. The article is a good example of global warming. I noticed another similar one that talks about reaching the danger zone due to global warming

    Comment by Rita — 9 Nov 2008 @ 5:11 AM

  240. Ike,

    Now add that you have to pressurise the CO2.
    Using a machine.

    Which runs of HC fuels.

    In any case, read a later response I gave to Tamino. The answer to your point is contained within.


    Comment by Mark — 9 Nov 2008 @ 5:42 AM

  241. Cumfy 227.

    How to you get that?

    The small surface penetration means that there is little thermal inertia. Land heats up quicker in response.

    So if there’s WARMING, you would see a lag in the SH because the water has a lot of thermal inertia whereas the NH land has responded quickly.

    If there’s cooling, the inertial would hold the SH warmer for longer.

    Comment by Mark — 9 Nov 2008 @ 5:44 AM

  242. As Gavin said, RodB (#218), they are not the only forcings. I even gave one that WASN’T one of those two in the message. Pity you didn’t read that far.

    ANYTHING that feeds back its output into its input is a feedback. If it feeds more, then it is a positive feedback, if it feeds it as a reduction, it’s a negative feedback.

    How come when it comes to “feedback in climate” no bugger knows what it means, but when it comes to “feedback in the rabits/foxes cycle” or “feedback as in my mic is next to the loudspeaker for the mic”, everyone knows it?

    How about this: temperature changes ice cover. Ice cover changes albedo. Albedo changes temperature. Temperature chances ice cover. Ice cover changes albedo. Albedo chances temperature. Temperature…

    If the models didn’t have ice cover feedback, you’d be complaining that this proves them useless. When it does, you complain that it shouldn’t be considering them because they aren’t feedbacks (because that is the direct meaning of your listing of the “ONLY TWO feedbacks”).

    Comment by Mark — 9 Nov 2008 @ 5:52 AM

  243. Stefano, #217. Gravity (based on a model showing it as a curve in spacetime) will continue to make you fall even if I believe it is right.

    So calling it a belief (which is incorrect in the first place) doesn’t make AGW wrong.

    Comment by Mark — 9 Nov 2008 @ 5:53 AM

  244. RodB, #215.

    So you now agree 100% that human actions can have a MASSIVE effect on the climate?

    Please educate those people and correct them when they say “But the planet is huge, there’s no way man can mange that. If you think so, it merely shows your arrogance that we can have an effect on this world”.


    Comment by Mark — 9 Nov 2008 @ 5:55 AM

  245. Gary, #207 All of the globe. Since the query was “what part of the globe is affected by GW” I didn’t see the need of specifying it.

    If you are unable to remember your questions, how will you remember the answers?

    All of the globe is affected by GW. Tautologically. But in reality too.

    All of the atmosphere is affected by GW.

    All of the ocean. All the way down, all the way up.

    All of it. “It” being defined by your question.

    Your “issue” seems to be you didn’t mean “affected” but “warmed”. But in that case, why do you want to know? Are you going to move house to where the various effects cancel out and no net change found? And then move again when the variables change (because they could change, for example, by people moving all to the same area, creating a heat island effect, thereby being a self-defeating prediction).

    What do you mean by “the main sources of estimates”? The estimates are in the IPCC report. The sources are noted in there. The differ because they aren’t measuring temperature but something that varies with temperature (and, one would hope, nothing else). However, that doesn’t work too well. Try measuring a temperature of 400C with a mercury thermometer. Even if you measure a temperature it COULD manage, you need a different instrument to measure temperatures in a range. Read up on metrology.

    But even if you have a thermometer that is effectively 100% accurate, you haven’t measured the global temperature, you’ve just read one very small segment of the global atmosphere. The bit that has brushed past the thermometer.

    So that’s one error. Sampling error.

    Radiosondes have a similar problem, since they hold a thermometer in them.

    Radar measurements sum up the radiation over a beam whose apeture and sampling are settled (under ideal conditions) by the diffraction limit of the sensor. However, two problems:

    1) That isn’t a nice simple square, but working with the diffraction pattern is computationally expensive and cannot be used in a satellite where it can’t plug into the mains.
    2) This is most definitely NOT temperature.
    a) You have the effect of all other “visible” layers doing its thing to your data. E.g. if you shine an IR torch up at it, it can’t tell it’s a torch, it just looks “too hot”
    b) The effect you see from one layer is affected by all the other layers above it (absorbtion, dispersion, etc)
    c) The layer itself is messing with your data (pressure broadening, mixed atmosphere, etc)

    And with satellites, you have to work out where all these measurements are for. If you have the satellite 5 seconds of arc out, you are pointing at a different place than when you last calibrated where it was pointing.

    I don’t think that question really helps anyone decide what’s going on. You have to get REALLY deep into a lot of other things to understand WHY there are uncertainties and they require knowledge of many different disciplines of physics, maths and engineering.

    None of which you can do anything other than “OK, the error in temperature is X they say and I will believe them”. Or, if you’re a denialist “I won’t believe them” or “This PROVES they are wrong!!!”. Then again, a denialist won’t bother to do any work if they can just jump STRAIGHT to a conclusion, so adding that info doesn’t actually help.

    Errors are stated.

    Believe them or don’t.

    Anything else requires more work than just an FAQ.

    Comment by Mark — 9 Nov 2008 @ 6:17 AM

  246. CM wrote:
    The answer to any of those questions will be a spread of projections based on questionable assumptions. A “best estimate” is sometimes just a middle projection cited in a confident tone of voice.
    Stefano, did you become disappointed with AGW because it turned out to be more complex than a textbook engineering problem? Surely you knew that before they ran the simulations.

    CM, recall Samson’s question, what do you say to skeptics who quote the IPCC and say the future climate state is “not predictable” ?

    If we take your point in that context, part of the answer becomes, “A ‘best estimate’ is sometimes just a middle projection cited in a confident tone of voice.”

    I think you just made a skeptic’s day.

    I’m not trying to be facetious. Bear in mind that the public are hearing very confident assertions from spokespeople on the climate change issue who appear to all intents and purposes to be representing the scientific community.

    So a problem arises, how do you answer members of the public who subsequently read a little and found that, “AGW turned out to be more complex” ?

    That might even be one for the FAQ.

    Comment by Stefano — 9 Nov 2008 @ 7:35 AM

  247. Re 106: can the remaining wiggles be compared to the Gibbs phenomenon observed in generating for instance a square wave by a Fourier series… The amplitude of the initial wiggles does not decrease using more and more Fourier terms… Or is discontinuity not a feature occurring in climate models?

    Comment by Francis Massen — 9 Nov 2008 @ 8:03 AM

  248. Stefano: “what do you say to skeptics who quote the IPCC and say the future climate state is “not predictable” ?”

    I would say it is as predictable as anything else can be in this uncertain world.

    “So a problem arises, how do you answer members of the public who subsequently read a little and found that, “AGW turned out to be more complex” ?”

    I would quote: “The best laid schemes of mice and men go oft astray”. I would say that it is a know issue that the best tactical position never survives contact with the enemy. I would say that if they have ever tried to fix stuff themselves, they have found out that there’s a lot more to their solution than they expected.

    And in none of these cases have we then turned around and said “OK, we can’t be certain, so let’s not do it”. We’ve still schemed, still assume our generals make tactical decisions in war and people STILL try to fix their plumbing when it seems a simple problem.

    So why not here?

    Comment by Mark — 9 Nov 2008 @ 9:03 AM

  249. So Alexi, #236. In order to know your question we must read other threads and other elements.

    Please do the same here.

    Read up elsewhere and leave.

    I notice you didn’t even say why some were “wrong”.

    You seem to require, nay DEMAND, more rigour from others than you deign to supply yourself.

    On #237. Yes, you can call anything a forcing. Sun forces air to rise. Work forces you out of bed. So you must ask what you want to know. Do you want to know what climatological forcings are? They are forces that last climatological timescales.

    Also, have you considered that your question seems to you to be “anything” is because it was a stupid question?

    Comment by Mark — 9 Nov 2008 @ 9:09 AM

  250. PS re #237. How can I answer a question “wrong” when you say that you don’t know the answers? Either you know the answer and so know it wrong or you don’t know it is wrong.

    Comment by Mark — 9 Nov 2008 @ 9:11 AM

  251. Stefano, #219.

    So what made you not believe the scientific community?

    Given we have no evidence of you ever believing them in the first place, how do we know you are telling the truth? See, we are acting skeptically. Just like you.

    Comment by Mark — 9 Nov 2008 @ 9:13 AM

  252. Detrich, #198. Yes, but not if the theory supposed is “Well, it COULD happen”. I could transubstatiate and become a demi-god and no longer care what happens to mortals.

    No idea how, nor even if it’s possible.

    So I don’t bother to entertain the idea.

    Now, do you have a theory that puts in stasis the GW for thirty years that isn’t “well, there could be one”? If you do, let us all know. Expect skepticism over it.

    And make sure you explain what you’re doing properly.

    Comment by Mark — 9 Nov 2008 @ 9:53 AM

  253. Stefano (217), I agree with you that most of what scientists focus on is of interest to academics, but not necessarily relevant for policy. What is relevant for policy is the main thrust of the expected changes and their expected consequences; the details are in the realm of academics, not policy making.

    You write “So what if you can say that the future will be a bit warmer and maybe a lot warmer?” If we take “the spread of possible future outcomes” in a business as usual scenario, then it’s fair to say that if it’s bad, it’s really bad, and if it’s good, it’s still pretty bad. In other words, the scientific details are not going to radically alter the needed policy response. As Herman Daly noted in a recent speech ( “If you jump out of an airplane you need a crude parachute more than an accurate altimeter”. I commented on his speech on my blog (as did Michael Tobis on “init”).

    Comment by Bart Verheggen — 9 Nov 2008 @ 10:11 AM

  254. Mark, please, let people post questions. They may not please you, they may have poor assumptions — but they’re not atypical of questions people ask. The thread here is dedicated to _collect_questions_.

    Just smile and let them post their questions. Some will be useful here.

    There are plenty of threads in which someone is wrong on the Internet.

    Comment by Hank Roberts — 9 Nov 2008 @ 10:51 AM

  255. How many components do the models have? How many different physical (or statistical) parameters are there?

    Some of those parameters are probably known quite precisely. But others must be less precise. Are the models rerun with various plausible values for all these parameters?

    Comment by Harvey Motulsky — 9 Nov 2008 @ 10:53 AM

  256. re: #231, by John Mashey

    many thanks for the link to your “old post”…IMHO, it should
    be on the required reading list for all of us participating in
    discussions of climate models

    Comment by Larry Lidar — 9 Nov 2008 @ 11:49 AM

  257. re #255

    I think the answer to your question is yes; see here

    Comment by Larry Lidar — 9 Nov 2008 @ 1:02 PM

  258. Mark (#249, #250): Please note that I did not say I don’t know the answers. I said I am confused with your definitions, so I wanted to hear yours. So far you did a good job in representing incoherence in the jargon.

    Regarding the question about “forcings” to be stupid: so, in your opinion it is clever to “explain” workings of climate in terms of “forcings” and “feedbacks” that you cannot even explain what they are, but it is stupid to ask questions about them?

    The reason for all this confusion is that the climate is a system with tightly-coupled spatio-temporal state variables, each one affecting the other in a circular self-feeding way. What is stupid (as you phrased it) is to attempt to “explain” its behavior by slicing it into “forcings”, “amplifiers”, and “feedbacks”. These are all concepts from essentially one-dimensional electro-mechanical control theory, where these building blocks and signals are separated by design. This partitioning does not apply to dynamics of fluid. If you will attempt to justify the partitioning by invoking a difference in time scales, it will be still goofy because the system is strongly turbulent, and turbulent systems have CONTINUOUS spectrum of time “wiggles”, and there is no considerable time interval where you can “draw a line” and separate “statistical averaging” from “large scale dynamics”.

    I hope that my comments would lead to more coherent answers to the FAQ, such that people would not hold their smiles (as compared to Hank’s sentiment in #254). Now I will follow your suggestion and leave. Thanks.

    Comment by Alexi Tekhasski — 9 Nov 2008 @ 2:36 PM

  259. Re #225/#232/#234

    Yes, each of those is a salutory reminder of the added burden of industrial human existence.

    Respiration (“breathing”) is inherently net-neutral with respect to CO2, and if one considered the pre-industrial age, the planet could support a large fauna (including pre-industrial/pre-agricultural humankind) whose breathing merely returned CO2 into the atmosphere, previously ingested (as metabolites of carbohydrate) from plants which pulled this CO2 out of the atmosphere in the first place. The planet could in principle support a very large fauna, including humans, while maintaining net-neutrality with respect to CO2 production.

    It’s only when deforestation and other land use changes made a net shift of carbon in the short term carbon cycle from plants back into the atmosphere, that humans began to make a net positive return of CO2 into the atmosphere (although deforestation is essentially reversible in principle), and it’s very true to point out that industrial scale animal husbandry with its high cost in fossil-fuel-derived energy does mean that what might otherwise be a relatively closed system of cycling CO2 from the atmosphere through plants and then animals and back to the atmosphere, does become net positive with respect to CO2 emissions.

    But if one were able to maintain the large numbers of domesticated/food animals without using fossil fuels to power the farming systems, and didn’t make any further land use changes, then there would be no net positive CO2 emissions (there might still be net CH4 emissions, but presumably every CH4 would be released at the expense of CO2, since there’s nowhere else for the carbon to come from).

    There is a very relevant point that respiration (“breathing”) is inherently net neutral and it’s only the added fossil fuel energy inputs that make a “naturally” net-neutral process “unnaturally” net-positive. So large numbers of humans needn’t necessarily be a net-burden on the planets resources….in fact the long term future of mankind requires that we deal with this issue of developing societies based on sustainable agricultural and industrial practices powered by renewable energy sources… such a system of societies, humans (and their animals) could breathe to their hearts content knowing that their respiration makes no net contribution to CO2 emissions….an interesting question, though is what sort of a world human population might be supportable within net-carbon-neutral societies….

    …but that’s not a question that relates to General Circulation Models I suspect!

    Comment by Chris — 9 Nov 2008 @ 2:39 PM

  260. OK, Hank, tell me how to answer your request without posting another reply!


    The threads I have answered have fallen under three cases:

    1) I can at least answer this one. The majority.
    2) I’ve been asked a question. A large fraction.
    3) Smartarsery. After a while when the brain cells of the poster seem not to be firing, this one may kick the thinking into gear. At least to the extent of returning the favour.

    PS I would point you back to #211 for perusal. You post on a #3 tenant too.

    PPS Does a thread only take one post every five minutes? No? Then how is this posting stopping others?

    Comment by Mark — 9 Nov 2008 @ 3:32 PM

  261. Stefano (#246) — I appreciate the warning that my remarks might be twisted to make a climate skeptic’s day.

    But the point was: It is wrong to suggest that real-world development-related policy decisions are routinely based on very precise predictions of future problems, and that we cannot act on climate change because the models do not meet these alleged standards.

    And this is not to defensively whine that climate projections are no worse than many predictions in other fields. On the contrary, global warming is a problem for which the world is rather well equipped to make informed policy, thanks to the IPCC reviewing the best available scientific knowledge, and thanks to ensembles of hindcasting-capable models constrained by (real-world!) physics.

    The observation that experts sometimes make “best estimates” for hand-waving reasons clearly has nothing to do with e. g. the range and most likely value for climate sensitivity in the IPCC 4AR, where pains have been taken to work out the probabilities from independent lines of evidence.

    It has been very eloquently pointed out in this thread why one can and should act on these probabilities (especially, #34 Garry S-J and #253 Bart). But sure, the outcome could lie towards the less bad end of the range. Should skeptics therefore say with Dirty Harry, “Go ahead, make my day”? Well — “Ask yourself: Do you feel lucky?”

    Comment by CM — 9 Nov 2008 @ 6:29 PM

  262. Bart wrote:
    You write “So what if you can say that the future will be a bit warmer and maybe a lot warmer?” If we take “the spread of possible future outcomes” in a business as usual scenario, then it’s fair to say that if it’s bad, it’s really bad, and if it’s good, it’s still pretty bad. …. “If you jump out of an airplane you need a crude parachute more than an accurate altimeter”. I commented on his speech on my blog (as did Michael Tobis on “init”).

    Well, earlier I was criticized for comparing climate change to a simple textbook problem, like how much fuel is needed to reach the airstrip. It was said that the reality of climate is much more complex. However, you’re now comparing the future scenarios to an equally simple textbook problem, that of needing a parachute to slow my descent from a plane. You refer to a simple scenario to reinforce the view that the decision to act is simple and obvious. Now either this whole business is simple or it is complex. Or am I missing something? (That’s not rhetorical, really, what am I missing?)

    It is this disconnect between the public message about the simple need to take action on climate change, and in contrast what is understood by academics/professionals in the field regarding the complexity of the problem, that could turn into a major headache. Going back to our plane analogy, say I ask you whether we have enough fuel to reach the airstrip, and you reply that based on your projections, yes we do (even though you have poor data available re. our heading and position and fuel consumption and there is a slow leak somewhere that you’ve had to parametrize). So we carry on flying and crash short of the runway. How do you think I will feel when I turn to you and say, “but you said we would make it?”, and you come back with a reply similar to what Mark said, “well, the best laid schemes of mice and men go oft astray”. How will I feel? What will I think of you?

    The public isn’t hearing “we project a spread of scenarios”, what the public is hearing is a confident unequivocal assertion. And that is what I’ve realised I have to stop believing. Had the public message been accurate and properly representative from the beginning, then this mess of time wasting arguments between “skeptics” and the science community would not have occurred, methinks.

    Sorry that’s a bit long, but that’s pretty much all I wanted to say.

    Comment by Stefano — 9 Nov 2008 @ 6:53 PM

  263. Alexi Tekhassi writes:

    straight logic would dictate that the scheme should continue to iterate, the new “amount of LW absorption” should drive more changes.

    It’s a converging series, not a diverging series. 20 W/m^2 of feedback is all you get from 4 W/m^2 of forcing.

    Comment by Barton Paul Levenson — 9 Nov 2008 @ 7:02 PM

  264. Rod B writes:

    If my math and physiology is correct, breathing puts out way more, about 200 times, CO2 than Mark’s 4 cans of soda per week — and it is a net add from long sequestered carbon (though most not near as long as fossil fuel).

    Rod, CO2 from breathing comes from carbon which has been eaten, which is from the biosphere, not from fossil fuels.

    Comment by Barton Paul Levenson — 9 Nov 2008 @ 7:07 PM

  265. The above, “Carbon Capturing Rock”, was published in MIT’s Technology Review. Any thoughts?

    Comment by lainev — 9 Nov 2008 @ 8:03 PM

  266. Stefano, if a system is sufficiently complicated, you cannot expect a model to be a crystal ball. In fact we do not need a crystal ball to see the effects of climate change. They are occurring even now, with loss of many species (e.g. frogs and other animals in the cloud forests of Central America) and threats to many others (polar bears, seals…). So, we know that there will be threats. What we do not know is how all those threats will manifest–which are credible and which are not.
    We do not look to models to predict the future, but rather to elucidate the physics–and the physics tells us what we need to avoid, what we need to mitigate and what we may be able to safely accommodate. Right now, you are saying that because the models (in your opinion) are not reliable, you reject the conclusions of the overwhelming majority of climate scientists. Yet, the models do not establish risk. The risks is inherent when we make serious changes that affect the infrastructure of human civilization. Rather the models are essential in limiting risk. So you might want to think twice before adopting too sanguine an attitude.

    Comment by Ray Ladbury — 9 Nov 2008 @ 8:55 PM

  267. CM wrote:
    But the point was: It is wrong to suggest that real-world development-related policy decisions are routinely based on very precise predictions of future problems, and that we cannot act on climate change because the models do not meet these alleged standards.

    Well you can act, but which of the range of scenarios should you focus on? Do you focus more on adaption, or more towards prevention? If you can’t give the policy-makers a clear target, then action will be based more on political leanings. The less precise your forecasts, the more they will use their gut instincts, and their innate political view. You have a range of scenarios? Well, some politicians lean left and feel the government is there to protect people. Some politicians lean right and feel the individual should be unencumbered by legislation. Some people are very cautious, while others are heavy risk takers. Sometimes one group does better than the other, and sometimes it is the reverse. Adaption or prevention? Does one believe that tomorrow new technology will come along? Or that no new technology is forthcoming and we must cut cut cut and conserve? This is why I commented, rather harshly to be sure, that these projections don’t have real world application, at least in the sense of actually specifying clearly to governments what action they should take. Some people take the view that we shouldn’t do anything at all, and it can be quite hard to argue convincingly that they are wrong.

    Comment by Stefano — 9 Nov 2008 @ 9:18 PM

  268. Sorry to be off topic but isn’t this;

    a solution to our problems?

    Comment by ziff house — 9 Nov 2008 @ 10:08 PM

  269. Alex Tekhasski,

    If you double CO2 with no other changes, then radiative forcing increases by about 4 W/m^2.

    But there will be other changes, due to the consequent temperature increase: increased water vapor, reduced snow and ice cover, etc. So in the real world, if you double CO2 the net radiative forcing increases by about 20 W/m^2. The “extra” 16 W/m^2 is therefore called “feedback.”

    How hard is that to understand?

    Not hard at all. Unless of course you work very hard deliberately to confuse the issue. Your departure will not be mourned.

    [Response: Sorry to be pedantic, but the 20 W/m2 extra LW absorption you end up with is not a ‘radiative forcing’. The radiative forcing is defined as the initial TOA imbalance – as the planet reacts, that imbalance decreases (close to exponentially) until (at equilibrium) it is zero. However, that equilibrium state – given the changes in water vapour, clouds and increases in surface temperature happens to absorb more LW than you started with. – gavin]

    Comment by tamino — 9 Nov 2008 @ 10:10 PM

  270. Gavin, I am sorry, but you have to be more pedantic. The “equilibrium state” cannot absorb more LW since, by the definition of equilibrium, the net absorption is zero, and insolation (corrected for albedo) is still the same. You must mean something else.

    [Response: No I do not. Consider the amount of LW coming from the surface which is partially absorbed by the atmosphere (if there was no absorption, there would be no greenhouse effect). An immediate increase in CO2 increases that absorption and creates a TOA radiative imbalance by the same amount (4 W/m2 for 2xCO2). As you equilibriate, the planet warms (reducing the TOA imbalance) and water vapour increases, increasing the amount of surface LW absorbed in the atmosphere, but not adding to the TOA imbalance (though it does slow the equilibration). By the time you get to the end, there is more LW from the surface absorbed in the atmosphere (~20 W/m2) while the TOA imbalance ~ 0. In the absence of SW feedbacks, the outgoing LW at the TOA is the same as before, but that LW is coming from higher in the atmosphere. – gavin]

    Comment by Alexi Tekhasski — 10 Nov 2008 @ 12:42 AM

  271. So Gavin where are you trying to take the models now? Being that great improvement has been made, what are you working on now?

    Also, where do you think climate is going to take us in the next 50 years or so based upon the best analysis of the trends? I am curious to hear directly from a reliable source what we may need to better work on in regards to slowing down very much, potentially, catastrophic consequences. When one conisders the combination of fossil fuels, deforestation, 6.6 billion people breathing, plat life limits, (in some cases increased adaptation of course) some bad energy policy decisions in light of sophisticated applications of data, math etc… what do you propose humanity might want to do, in order to reverse or atleast slow down current trends related to AGW in conjunction with natural processes?

    We are so quick as scientists, non experts, the lay public, some ill informed undergrads, ad infinitum, to argue in this blog, however, you as a first hand expert modeling paleoclimate and modern climate trends and obviously with a handle on chemistry and physics, also have a vested interest in our planet and though you do the modeling for a living, I do not doubt it has helped you gain inisghts and opened up your eyes to the complexity and current to future detriments and potentialities we all face as humanity.

    I pose this question to Gavin as I see him reply to a wide variety and large number of posts, but any moderators of this site, feel free to comment, as I read your backgrounds, published works and books, it has been both a joy and educational journey.

    Comment by jcbmack — 10 Nov 2008 @ 12:47 AM

  272. Stefano,(in general to your various posts) first of all no one can predict the future with absolute clarity, this is akin to the crystal ball mentioned by another poster, relying upon Nostradamous like predictions or looking to the constellations for truths in and of themselves. What is interesting, first of all is the rigors of science are so poorly misunderstood by most people, even the very educated, and completely put into God like perspective by the ignorant. If I were to tell you that the last bathroom stall is the cleanest of all stalls statistically, that might change people’s reactions, most going to the last stall, which would change the outcomesm would it not? The same can be said about how we do not know precisely how warm the globe will get in 25, 50, 100, or 150 years, dynamics do change; the 1990’s was the height of recent population explosion, and even though the global population is rising steadily, the incline has decreases a bit; China, India, japan have issues with pollution, overcrowding, exponential GDP growth or decline, respectively. We do know the warming since the industrial revolution has occured and that isn due atleast in part to human activity and we know that the planet cannot withstand continual additional CO2 to the atmosphere; the math used, the data collected, the training involved in doing thism is enormous. Some scientists disagree on the magnitude of the AGW threat, but the threat is very real; Pink Flamingos become pink, cheifly in Africa, by eating plankton in a toxic water body; in Arsenic filled lakes aquatic life thrives; some plants adapt to CO2 and grow beyond other plants; some die, release CO2, and more burning adds to this issue; breathing by itself is well tolerated by the planet, but add all the positve feedbacks and we soone realize even in light of negative feedbacks overwhelms the system and we see a slow, but positive heat increase, if it were faster we would be in trouble now and if it were slower perhaps we would miss the seriousness of the situation; but we live in the here and now and what are we to do now and the immediate future to slow down AGW trends for the not so, and even more distant future?

    Comment by jcbmack — 10 Nov 2008 @ 1:12 AM

  273. Mark makes a lot of solid points Alexi. I do suggest continued reading of the data, I provided some of best (and longest) data published that can be found anywhere on the internet. Even if Mark did (and I am not suggesting he did) make minor errors, he has been extremely accurate all through this thread. No scientist has a hold on all data, and only a few have a hold on all the concepts, and we all grow tired at times and forget. The point that Mark hits home on is simple: AGW is a reality and clear and present danger. No one here or anywhere offers an argument, logic or solid data to indicate otherwise, you should keep that in mind; Anthony Watts needs a lecture on galvanized steel, material chemistry, and thermal expansion:) I am glad, however, you are reading the sites I pasted, I suggest you get a hold of the Global Climate Systems book as well, if you read every word, look at all the diagrams and can do all the math and do not misunderstand any of it, well, that will really get you on your way; I have read it over three dozen times and it is an excellent reference for us to get old and forget at times how to state something.

    Comment by jcbmack — 10 Nov 2008 @ 1:17 AM

  274. Rod B didn’t you hear about the thousands of US soldiers wh did no get paid during their occupation of Ira, came home and either were still not paid at all or only minimally and were refused tuition reimbursemen for college? Also, the clinical setting in the military was so underfunded since Vietnam that many shell shocked (PTSD) and otherwise mentall ill or traumatized soldiers are not getting the professional help they need.

    The underfunding for proper body armor, helmets and other supplies is also well documented and reported on in addition suits being brought against the military and government.

    Now we certainly need the military in all its facets, and the war economy does fund many workers, however, not since WWII have we seen such a post war economic and baby boom in this country; also with the pull backs in the Korean action, at the Peking river, we more than sealed our fate, needing to pull out of a country we did know eneough about geographically and we were flanked much like many of our wars and occupations; WWII was our last real success.

    Giving money to the top, trickle down theory has far too many failings to be still considered a viable socio-politcal-economic solution.

    Comment by jcbmack — 10 Nov 2008 @ 2:06 AM

  275. Stefano, #267 you are correct. Yet this is ABSOLUTELY 100% the same with any other legislation. The only way around this is

    a) lie. Tell people we’re certain when we aren’t to get the politicians to do the right thing. This is WRONG. And no scientist who wants to keep their reputation intact will consider it

    b) sack politicians and let the scientists decide. This is wrong too because this is a democracy. If the balance of all those leaning MPs is an action that isn’t sufficient then people will suffer but this will be at the hands of those MP’s who operated on dogma rather than reason.

    Any why should all this overt and explicit uncertainty be a skeptic’s dream? The error in the temperature rise could be 5DegC +/- 6DegC and a *denialist* would be over the moon, saying “see, it could be COOLING”. Because they aren’t sceptical, they WANT it not to be warming and so forget the other side: it could be 11DegC warmer. Trout die in water warmer than what?

    A true skeptic is HAPPY to see +/-6 error not because it proves one point but it proves that there is still a lot to learn. But that doesn’t make a *skeptic* think there is nothing wrong and nothing to do. It makes a *denialist* do it because they want to be able to do nothing or at least the same stuff as they did before. ‘cos change is scary. If you’re currently well off, a change is likely to make you less well off. And when it comes to THEIR wealth, the worst case scenario is ALWAYS the one trotted out (“You’re going to have us all living in the stone age!!!!” ring any bells, people?).

    Comment by Mark — 10 Nov 2008 @ 3:57 AM

  276. Alexi #258.

    Make the sun hotter. What happens on Earth? Temperature goes up. Permanently (unless the sun gets cooler, earth moves away, etc).

    It FORCES a change in temperature on climatological timescales.

    It is a climatological FORCING.

    Pump CO2 up there? Warmer because the residence time is decades to millenia, a climatologically forced change.


    In both cases the system CANNOT decide to do otherwise. The climate is forced to change in a simple way. It gets hotter if you increase, cooler if you decrease.


    Now, pump water vapour into the air. What happens? It rains out. But that doesn’t take a climatological period to happen. So there is no forcing of the climate to change, the process itself is self-regulating on a climatological scale. NOT a forcing.

    But, lets look at the sun getting hotter again. Say it gets 1degree hotter. A hotter atmosphere will hold more water, so any water that evaporates will be able to stay there (if it is small enough change to fit in the warmer air’s ability to hold it). But this causes it to be a little warmer again. Let’s say 1/2 a degree for each degree of change. So it makes it WARMER than just the one change you put in with the sun. It feeds back more warming than the simple system. A FEEDBACK.

    Now, this extra water warms the air by 1/2 a degree. Doesn’t change the sun’s output. But this warmer air can hold another bit of water vapour. And so another 1/4 degree is added to the warming of the atmosphere. But that holds more water… etc. So it is a POSITIVE FEEDBACK (remember, we already have seen that absent sun warming, there’s no change in water content so water is not a forcing). So what is the eventual change? A sum of the infinite series 1/2+1/4+1/8+…1/inf. Which doesn’t total infinity, but +1.

    So the Sun warmed the earth by its climatlologial FORCING 1 degree. The water vapour FEEDBACK increased the effect of the sun’s change to 2 degrees. The sun didn’t get hotter, but the positive feedback of water vapour in the atmosphere doubled it.

    So now do you get it?

    Probably not, but others not deliberately trying to “not get it” will.

    Comment by Mark — 10 Nov 2008 @ 4:10 AM

  277. Stefano (#262, 267), I can understand your irritation with people who oversimplify the science and downplay uncertainties in an unsound way. Their motives can be pure — effective, pedagogic communication of a serious public issue — and the balance is hard to strike. But it can boomerang badly if people conclude — wrongly — that the quality of the PR reflects on the quality of the underlying science. Still, the science is out there for skeptics to access if they are interested in knowledge, not point-scoring. The last IPPC WG1 report is nearly a thousand freely downloadable pages with spreads, uncertainties, and qualifications.

    In any case, science does not determine policy. Politicians and the public legitimately differ over how to deal with the facts in the light of differing ideologies, values, and attitudes to risk. Even precise and unequivocal knowledge of future temperatures, if available, would not by itself dictate a precise and unequivocal course of action to governments — not even on basic strategic choices of prevention or adaptation. Narrowing down the uncertainties might help cut through excuses for inaction, but I think you are granting those excuses far more than the present state of knowledge warrants, too.

    Comment by CM — 10 Nov 2008 @ 4:25 AM

  278. Stefano writes:

    Some people take the view that we shouldn’t do anything at all, and it can be quite hard to argue convincingly that they are wrong.

    Yeah, the oil people, the coal people, the automobile people…

    Comment by Barton Paul Levenson — 10 Nov 2008 @ 6:50 AM

  279. You should add a definition of “parameterization.” You use the term a lot but do not explain it.

    Comment by David Wojick — 10 Nov 2008 @ 8:49 AM

  280. Re posts #275 et seq.,

    The willful ignorance–whether motivated by (short-term) self-interest, cupidity, or sheer crankery can be quite breathtaking (not to mention provocative.)

    Reactions to the NSIDC “guest spot” on Watt’s Up? included, I swear to God, the argument that though alternate explanations for observed warming might lack evidentiary support, there could still exist evidence for “unspecified causes!” (“We don’t know what it is, but it is fully supported by the evidence!?”)

    Worse (or better?) this was received by several posters as a telling point. . . to me, sheerest psychopathology. Overall, the thread was characterized by a really extreme refusal to confront facts–but I’ve seen this in online debates before, as I suppose many of us have; you point out several lines of well-accepted research only to be told, once again, “there is no evidence.” Well–no evidence that the denialist likes. That’s why there is a discernible fashion to dismiss all surface records in favor of the UAH satellite data. (One debater told me it was “the only true way to measure the temperature.” I told him I live rather closer to sea level than to the tropopause.)

    Comment by Kevin McKinney — 10 Nov 2008 @ 10:25 AM

  281. Stefano wrote: “Well you can act, but which of the range of scenarios should you focus on? Do you focus more on adaption, or more towards prevention?”

    Actually, if you studied risk analysis, you would already know the answers to your questions. We are often asked to make policy or design products in the face of significant uncertainties. The constraints on the solution are engineering constraints: they have to work and they have to be economical.
    If adaptation is the most effective and economical strategy, we adapt. If avoidance is the most effective and economical strategy, that’s our option. If our risk estimate cannot be bounded by the models (and here you have to take a “worst case” or WC at 90% confidence), then you have to adopt a two-pronged strategy: Do what you can to avoid the threat or to mitigate its consequences with reasonable effort and work to improve your models. Under no circumstances can you ignore a threat whose risk cannot be bounded. That’s where we are with climate.

    Comment by Ray Ladbury — 10 Nov 2008 @ 10:31 AM

  282. The FAQ entitled “Are the models complete? That is, do they contain all the processes we know about?” needs to be either rectified or clarified. It does not mention large scale processes which are (1) under active study, (2) might explain 20th century warming and (3) are not included in the models. Indirect solar forcing and abrupt changes are two examples among many. If it be argued that we do not “know about” these processes enough to include them in the models then that should be explained. The distinction is that between computable knowledge and non-computable knowledge. The models are confined to the former, but climate science is presently awash with the latter. These are processes that are being investigated that we do not understand well enough to write computable equations for. There are many hypotheses and large scale change phenomena under investigation which are not reflected in the models. The models and the science are not co-extensive, for the science is much larger. The FAQ should make this clear.

    Comment by David Wojick — 10 Nov 2008 @ 10:36 AM

  283. David, check the definition — you can do this online; it’s clear. Try
    You don’t need more than a pointer to a dictionary except when a field has its own peculiar and different definition for commonly used words.
    Just as your “climatechangedebate” site uses familiar words undefined.

    Comment by Hank Roberts — 10 Nov 2008 @ 11:34 AM

  284. Mark Says:
    10 November 2008 at 4:10 AM

    Make the sun hotter. What happens on Earth? Temperature goes up. Permanently (unless the sun gets cooler, earth moves away, etc).

    Theory says that the sun over the last 55 million years has gotten hotter. Despite the fact that the Earth hasn’t moved enough farther away to offset this, the earth is now cooler. Must be that pesky “etc”.

    Ok, the largest reason is probably less water vapor in the air now. What? That’s a feedback, and I can’t count it? Then I might say it’s due to less carbon dioxide in the air, but that’s at least partially a feedback, too. Well, then maybe it’s continental drift, since at least I don’t see any way that could be a feedback.

    This climate stuff is sure complicated, especially the “etc” part.

    [Response: Since water vapour is largely a function of the planetary temperature it doesn’t drive that temperature in any real sense. Solutions to the ‘faint young sun’ paradox almost always involve the longer term changes in CO2 and CH4. But the relevance of this to the last century where we have a much better understanding of the relevant terms is very low. Climate is indeed complicated, and you don’t need to resort to a ‘gotcha’ style of blog commenting to have that acknowledged. – gavin]

    Comment by Greg Simpson — 10 Nov 2008 @ 1:22 PM

  285. the moeny denialists make will not matter if we keep going at the rate we are going; then when they concede they want to do dangerous things; carbon capture in the ground… forget about reducing actual emissions and alternative energy sources, let us just bury everything… sickening really. Also reading one paragraph of a climate report does not constitute reading and learning.

    Comment by jcbmack — 10 Nov 2008 @ 1:38 PM

  286. A nagging concern I have is that fossil fuels are effectively permanent CO2 draw down. I can’t see how any sizable part of these reserves would have naturally been reintroduced back in to the atmosphere.

    We have now effectively put back a huge amount of carbon that would not have found its way back over the inter-glacial cycles. This is completely bucking the natural progression.

    This probably means that we are in for big time warming no matter what we do.

    On top of the GW effect the small addition of heat energy from using these fossil fuels probably stacks the equilibrium even more, although it’s only is a fraction of the equation.

    Comment by paulm — 10 Nov 2008 @ 1:49 PM

  287. Mark #275 “It makes a *denialist* do it because they want to be able to do nothing or at least the same stuff as they did before.”

    There are many legit positions (pro and con) to take on any one of the concerns brought up by climate change. To take the most ridiculous comments out there and paint a stereotype is interesting and fun, but intellectually lazy.

    And everyone (even the most responsible) wants to ‘do the same stuff they did before’ – do they not? If I were to take the position that mitigation money would be better spent elsewhere, I may not be totally correct, but it sure doesn’t make me a total ephing idiot. It doesn’t make me irresponsible. It doesn’t make me selfish, ignorant, or bought.
    It may just mean my priorities are ever so slightly different than yours.

    Comment by Michael — 10 Nov 2008 @ 2:17 PM

  288. David Wojick, Maybe we should posit that warming could be caused by Keebler elves working overtime on their bake ovens in their hollow tree as well? ;-) If you can’t model how it works, it ain’t physics. If it ain’t physics, it doesn’t belong in the models. If it’s needed in the models, then the models would fail to reproduce observed trends. Since the models do reproduce trends pretty well, I don’t thinki we should be terribly concerned with missing physics.

    Occams razor: I will not multiply causes.

    [Response: … unnecessarily! If there are identified physics that the models are missing, people will endeavour to insert it. The problem is when the ‘physics’ is some uncertain correlation in noisy data. If Wojick is thinking about GCR-cloud connections, this is being done (it requires a full aerosol model including all the different modes of formation, accumulation, growth and impacts on clouds), but all estimates so far are that changes in ionisation makes only a negligible difference. This is of course completely independent of critiques of the statistical work put forward by some, and the plain fact that with no trends in GCR, it can’t be related to recent warming. – gavin]

    Comment by Ray Ladbury — 10 Nov 2008 @ 2:21 PM

  289. What do you do when your model shows results that don’t match real world measurements, ie. the cooling of the planet rather than the predicted heating over the past 10 years?

    Do you assume that the model is wrong?
    Do you assume that the real world data are wrong and that the model is correct?

    [Response: What the models show is discussed here. RIght now there is no clear discrepancy. If that changes then there are three things that would need to be examined – the models, the data, and how the comparison is being made (i.e. the relevance of the particular model experiment, and what variables are actually being compared). I can think of dozens of cases where the each of those factors ended up being at fault – and so presupposing that one must be the cause of all mis-matches is foolish. You just have to see. – gavin]

    Comment by Shoshin — 10 Nov 2008 @ 2:27 PM

  290. Michael, reread again. And don’t be so one sided: someone who is skeptical will look at 5+/-6 and go “That’s a big error bar”.

    Only a denialist will go “See! It could be cooling!!!”.


    A skeptic doesn’t believe the anti side either. A denialist wants any excuse to justify their presuppostion.

    If you feel this is an unworthy stereotype, how about YOU explaining why that happens? NOTE: This HAS HAPPENED BEFORE.

    Comment by Mark — 10 Nov 2008 @ 2:49 PM

  291. Greg #284

    “Theory says that the sun over the last 55 million years has gotten hotter. Despite the fact that the Earth hasn’t moved enough farther away to offset this, the earth is now cooler. Must be that pesky “etc”.”


    The denialist camp keep coming up with new ones. Well, we know it was warmer back when the sun was cooler. But higher CO2. So the “It used to be 400ppm and things were a-ok!!” is thereby nullified, barring any information from you.

    And please tell me how much cooler it is when the peak was 2005 and last year was second..?

    Now, how MUCH warmer is the sun over, say, the last 150 years? Is that enough? You just seem to want to say “The sun got hotter and that explains it”.

    Well it doesn’t.

    Please tell us how much hotter the sun got and how much that should heat the earth.

    Dare ya.

    PS Michael, see how someone is willing to take as gospel any fragment that may support the “It’s all a scam!” denialist dogma. Please explain why else that moonbat said what they did.


    Comment by Mark — 10 Nov 2008 @ 2:55 PM

  292. re 287: “And everyone (even the most responsible) wants to ‘do the same stuff they did before’ – do they not? If I were to take the position that mitigation money would be better spent elsewhere, I may not be totally correct, but it sure doesn’t make me a total ephing idiot. It doesn’t make me irresponsible. It doesn’t make me selfish, ignorant, or bought.
    It may just mean my priorities are ever so slightly different than yours.”

    It depends upon the consideration you give to actual evidence. The context of the thread for #275 is consideration of those who *refuse* to consider it in a reasonably objective manner, of whom there are sadly many examples.

    Comment by Kevin McKinney — 10 Nov 2008 @ 3:14 PM

  293. Stefano (262): The details of the science are complex, but the (policy-relevant) main thrust is relatively simple in comparison. Based on this main thrust the decision to act should indeed be simple and obvious. In my view there’s an inverse relationship between the degree of scientific detail and its policy relevance.

    You seem to claim that the public message should have paid more attention to the details and the uncertainties; I think that the media (and many scientists when engaging in public communication) actually pay too much attention to those, at the cost of laying out the big picture of what we know. Moreover, the issue is more usefully framed in terms of risk rather than in terms of uncertainty. These two things could have gone a long way in preventing the “time wasting arguments between “skeptics” and the science community”. Canadian science writer Lydia Dotto has some good thoughts on this: I discussed the role of the media on my blog,

    Your plane analogy argues in favor of the precautionary principle: Better be safe than sorry when we risk missing the runway. I agree, both on your analogy and on the real-world example of dealing with the risk of dangerous climate change.

    Comment by Bart Verheggen — 10 Nov 2008 @ 3:26 PM

  294. Ray Ladbury (288) Says:
    10 November 2008 at 2:21 PM

    “David Wojick, Maybe we should posit that warming could be caused by Keebler elves working overtime on their bake ovens in their hollow tree as well? If you can’t model how it works, it ain’t physics. If it ain’t physics, it doesn’t belong in the models. If it’s needed in the models, then the models would fail to reproduce observed trends.”

    Both your claims are false, Ray. For example, we know that abrupt events occur, so they are physics. They are large enough to explain the observed warming. But we do not know the mechanism so we can’t model them. The fact that the models can be made to reproduce historical trends, to the extent they can which is not well, merely shows that the hypotheses embedded in the models are physically capable of explaining the trends, not that they do explain them. It is also necessary to rule out the competing hypotheses, and this has not been done. We are not talking about elves here, we are talking about phenomena and hypotheses that are being actively investigated within climate science.

    Comment by David Wojick — 10 Nov 2008 @ 4:23 PM

  295. David Wojick wrote: “There are many hypotheses and large scale change phenomena under investigation which are not reflected in the models.”

    Such as, specifically, what?

    Keep in mind that anthropogenic global warming is not a “hypothesis”. It is an empirically observed fact: human activities, principally the burning of fossil fuels, are in fact releasing large quantities of CO2 into the atmosphere. That anthropogenic increase of atmospheric CO2 is in fact causing the Earth system to retain more of the Sun’s heat. The Earth system is in fact getting warmer as a result. These are facts, not hypotheses. They are not derived from models. They are derived from actual empirical observations.

    Whatever other unspecified “many hypotheses and large scale change phenomena” you may wish to “investigate” — or speculate about or hand-wave at — you have to deal with those facts.

    Comment by SecularAnimist — 10 Nov 2008 @ 5:04 PM

  296. What software programs are usually used in developing climate change models?

    Have any of this models taken data from the 1900 and come up with the weather we are having today?

    Comment by ed — 10 Nov 2008 @ 5:36 PM

  297. David you are in grave error. We know quite well most of the mechanisms.

    Comment by jcbmack — 10 Nov 2008 @ 5:43 PM

  298. It takes a long time for industry, organizations, institutions to change due to the vast complexity, but AGW and green house gases and their roles are known.

    Comment by jcbmack — 10 Nov 2008 @ 5:44 PM

  299. #292 ‘It depends upon the consideration you give to actual evidence. The context of the thread for #275 is consideration of those who *refuse* to consider it in a reasonably objective manner, of whom there are sadly many examples.’

    Unfortunately Kevin, those who *refuse* are the group I am talking about. The vast majority – those who are voting on policy issues, talking to friends, arguing with thier kids’ elementary school teachers – do not grasp the science behind GCM’s, for instance. Most have to make life decisions based on non-scientific reasons.

    There is a good reason we elect politicions and not scientists.

    Comment by Michael — 10 Nov 2008 @ 5:48 PM

  300. Green house gases do militate climate trends, not in dispute at all.

    Comment by jcbmack — 10 Nov 2008 @ 5:48 PM

  301. Read:

    Comment by jcbmack — 10 Nov 2008 @ 5:57 PM

  302. “Have any of this models taken data from the 1900 and come up with the weather we are having today? …” – Ed at 296

    Ed, in 1908 Arrhenius basically came up with a prediction of our weather – with just his noggin. No computer, maybe not even an adding machine.

    He didn’t know we would burn a significant percentage of the earth’s extractable hydrocarbons by 2008, but I think he would have had a fairly accurate notion of what that would mean for the 2008 climate.

    Comment by JCH — 10 Nov 2008 @ 6:36 PM

  303. David Wojick, was that you named with Inhofe’s lawsuit?

    Comment by Hank Roberts — 10 Nov 2008 @ 6:42 PM

  304. # 299 That may be true… th election o politicians, but what are the advantages when these politicians are the exact same demographic that does not understand the GCM’s either? Sara Palin thought she was an ingineer and an energy expert! She thought she knew better not only in a political, sense, which we all have a right to agree or disagree, but she was telling scientists how to doi things; she complained about Drosophila reseacrh; do you realize it is because of Drosophila we understand things like neuraxins and pproperties of neurogenesis etc… I am not expecting the general public to understand forcings and trends in exquisite detail, however, if the educational system were better equipped the US would not be last in educations, specifically science and math. Politicians need atleast a broad view and some understanding above the generak public as they serve in the best interest of the public; or atleast they are supposed to.

    Comment by jcbmack — 10 Nov 2008 @ 6:55 PM

  305. “Unfortunately Kevin, those who *refuse* are the group I am talking about. The vast majority – those who are voting on policy issues, talking to friends, arguing with thier kids’ elementary school teachers – do not grasp the science behind GCM’s, for instance. Most have to make life decisions based on non-scientific reasons.

    There is a good reason we elect politicions and not scientists.”

    Not all politicians have been willing to listen to scientists for information needed for policy decisions. We have a quite clear change on that account recently in the US.

    Comment by t_p_hamilton — 10 Nov 2008 @ 6:57 PM

  306. Read the new issue of Earth or go to The October issue highlights issues of climate and agriculture issues and the need to revamp the current practices; also the October issue of Nature covers the need or the overhaul of economics as a discipline and politics as usual.

    Comment by jcbmack — 10 Nov 2008 @ 6:58 PM

  307. “Economics in crisis,” a scientiic solution,” ‘Nature, October 30, 2008:

    ‘Economics needs a scientific solution,’Financial engineers have put too much faith in untested axioms and faulty models, says Jean-Philippe Bouchard. To prevent economic havoc, that needs to change.’

    “Compared with physics, it seems fair to say that the quantitative success of the economic sciences has been disappointing. Rockets fly to the moon; energy is extracted from minute changes in of atomic mass. What is the flagship achievnent of econoomics? Only its recurrent inability to predict and avert crises, including the current worldide credit crunch?’ Excerpted rom Nature Opinion, p. 1181.

    Ok here is a question should we take on more of a utilitarian approach to these issues or prioritarianism approach?

    Comment by jcbmack — 10 Nov 2008 @ 7:07 PM

  308. Also if anyone reads the Economist on a regular basis they tend to report things down the middle and global warming is a serious issue among most of the economic experts there as well.

    Comment by jcbmack — 10 Nov 2008 @ 7:08 PM

  309. Well, David, investigate away. In the mean time, we’ll go ahead and explain things with the climate models we have–which despite your unsubstantiated allegation do work remarkably well. Perhaps you’d care to give us an example of physics currently missing from the models and an estimate of its impact? I do better with concrete examples that dramatic declarations.

    Comment by Ray Ladbury — 10 Nov 2008 @ 7:39 PM

  310. This David Wojick?

    Comment by Joseph O'Sullivan — 10 Nov 2008 @ 7:51 PM

  311. Bart wrote:
    Narrowing down the uncertainties might help cut through excuses for inaction, but I think you are granting those excuses far more than the present state of knowledge warrants, too.

    Bart, Mark, CM, Ray, thank you for your thoughtful replies. I have asked about the spread of scenarios and a common point in your replies is that it is normal in the real world for there to be uncertainty about the risks, and nonetheless we must act.

    Let me go back to the analogy of the plane low on fuel, because this is the issue. Landing on a runway is safe. Choosing an alternative improvised place to land is likely to cause injury. But an unpowered descent that crashes short of the runway could kill everyone, whilst a powered descent in a field that you have time to choose and prepare for, may result in far fewer fatalities. Or consider a medical procedure. You could cut out a small tumor and the patient will live 5 years. But if the cancer is more advanced, cutting it out could leave the patient dead on the table. In the public debate on climate change we often seem to talk about this implicit “failsafe” of action. But the Precautionary Principle, if you truly wish to abide by it, demands that you demonstrate that the cure is not worse than the disease. Skeptics and denialists resist change, sure, but they do so with some justification–change is scary, because you don’t really know what will happen. Just as changes to climate cannot be known exactly in advance, so the effects of changes to the economy cannot be known exactly and there may be unforeseen consequences, just as the climate may warm in a very unlikely but absolutely worst scenario.

    We have the difficulty of trying to solve what is essentially a new problem. When a person tries to tackle a fire for the first time, using their best judgement and care, they typically make numerous and costly mistakes, and may likely die, for tacking a fire is counterintuitive. Experienced firefighters on the other hand know what to do and can make the situation safe. What I am suggesting is that there is a threshold of knowledge, and that unless we have enough understanding, it is probably safer to not try to fix things, as is the case for a small child trying to get the bread out of the live toaster. Now we may know enough already… or maybe the spread of projections is too wide and we are left wondering whether the patient will live longer if we operate or if we don’t. I just wouldn’t assume that we have a failsafe plan. That really needs to be thought about.

    Comment by Stefano — 10 Nov 2008 @ 8:06 PM

  312. Mark (242), if you are referring to water vapor, I was including that in atmospheric gases. I think your and Gavin’s point is that while one could probably put all forcings into two groups (except major one-off things like volcanoes and plate tectonics…), it is academic and not particularly helpful; one is better off looking at the other individual forcings as separate entities (gives better insight), and there is no benefit (maybe even a detriment) in putting them in nice neat families. I can buy that. I was just curious, not trying to make a point.

    Comment by Rod B — 10 Nov 2008 @ 8:09 PM

  313. Mark Says:
    10 November 2008 at 2:55 PM


    The denialist camp keep coming up with new ones. Well, we know it was warmer back when the sun was cooler. But higher CO2. So the “It used to be 400ppm and things were a-ok!!” is thereby nullified, barring any information from you.

    PS Michael, see how someone is willing to take as gospel any fragment that may support the “It’s all a scam!” denialist dogma. Please explain why else that moonbat said what they did.

    Me, a “denialist”? Not at all, and I don’t think anything I wrote actually implied that we’re not causing dangerous warming. I liked the post of yours that I responded to, but I thought you were being a bit snippy with the “unless” … “the earth moves away”, so I poked a little fun at you.

    Anyhow, I’m sorry for contributing to the noise on the forum unnecessarily. I’ll restrain myself in the future.

    Comment by Greg Simpson — 10 Nov 2008 @ 8:42 PM

  314. Stefano, It seems to me that the precuationary principle applies to the scientific side of the argument–we know human civilization, with all its complicated infrastructure functions with CO2 in the 280-350 ppmv range. If you are going to move outside of that range, you damned well better show that it will not affect infrastructure catastrophically.
    What is more, we know for an absolute fact that energy infrastructure MUST change due to peak oil. We are merely saying that we need to fund sustainable energy sources rather than spewing yet more CO2 into the atmosphere.
    In engineering, I cannot predict exactly what weight will cause a bridge to collapse. I can do a calculation and bound the safe range of weights. This is no different. The science of CO2 is settled. We’re now trying to come up with an engineering analysis of what is stable.

    Comment by Ray Ladbury — 10 Nov 2008 @ 8:55 PM

  315. Stefano writes in #311, “Skeptics and denialists resist change, sure, but they do so with some justification–change is scary, because you don’t really know what will happen. Just as changes to climate cannot be known exactly in advance, so the effects of changes to the economy cannot be known exactly and there may be unforeseen consequences, just as the climate may warm in a very unlikely but absolutely worst scenario.”

    Three points:

    1) economic disaster will not negatively affect the ability of the planet to support human life; climate change can.

    2) We now have several nations that have in fact met or exceeded their Kyoto targets (and had done so pre-credit crunch), notably the UK, Germany and Sweden–and did so with no major economic trauma. So significant mitigation can be accomplished, and there is now a body of experience indicating how to do it–or at least, how to begin.

    3) “Climate *may* warm?” It HAS and IS.

    Comment by Kevin McKinney — 10 Nov 2008 @ 9:02 PM

  316. > 215, 220, what we exhale

    There’s some merit to Rod’s argument — and some numbers are available on how much of the food people are eating ccomes from energy-intensive, fossil-fuel-dependent farming.


    Corn-fed animals fuel America
    * 22:00 10 November 2008 by Catherine Brahic

    Biofuel demand is not the only market pressure being felt by US corn farmers. Much of the fast food that powers Americans – a $100 billion annual market – is indirectly made from corn as well, according to researchers in Hawaii.

    Hope Jahren and Rebecca Kraft of the University of Hawaii purchased 486 servings of hamburgers, fries and chicken sandwiches from McDonald’s, Burger King and Wendy’s in Los Angeles, San Francisco, Denver, Detroit, Boston and Baltimore.

    Back in the lab, they analysed the carbon isotope content of each serving. Previous research has shown that it is possible to determine whether an animal ate predominantly corn feed or grass from the ratio of C13 to C12 in its body tissue.

    The pair found that 100% of the chicken in these three fast-food chains had been reared on corn alone. Some 93% of the beef came from cows that had been fed a corn-only diet. Just 12 burgers – all from west-coast Burger Kings – came from beef that had eaten something else….

    —–end excerpt——-

    So, there’s actually a useful, educational response to the claim that “exhaling CO2” affects climate. To the extent you’re exhaling carbon identifiably from fossil fuel, higher than the atmospheric background, anyhow.

    You are what you eat. So is the atmosphere.

    “Rewards less” says ReCaptcha

    Comment by Hank Roberts — 10 Nov 2008 @ 9:13 PM

  317. 315, Kevin, Contrarians will always have fun with temperature variations. It’s time for switching tactics
    and use Density Weighted Temperatures of the entire atmosphere.

    Comment by wayne davidson — 10 Nov 2008 @ 10:52 PM

  318. So do we value the current generation more, the future or try to be equal in light o environmental and economic concerns?

    Comment by jcbmack — 10 Nov 2008 @ 11:52 PM

  319. # 315 Kevin; I get your point, but an economic collapse would most certainly negatively impact the globe, and the ability of millions, if not hundreds of millions of people to support themselves; eat, have a roof over their head, compete in a non-existent or greatly shattered market.

    The environment is certainly something to care about and for and the long term effects of rising fossil fuels emissions will both increase cancer cases, inflation, and economic despair in general. The two are related. Big business is everywhere; those supercomputers are not cheap and these computers we chat on come from old military advancements, as do HD screens and so forth, and yet as the carbon footprints go up in the places like China, well, people are also eating better and living more comortable.

    Comment by jcbmack — 11 Nov 2008 @ 12:02 AM

  320. As climatologists attempt to create and improve upon exisitng models,this does not mean that the 3 and six box, STELLA etc… are to be discarded, rather the sensitivity of models, better if not perect modeling o clouds and ocean atmosphere interfaces, there always seems to be something that is lost in translation which is improved upon by input of former models. The boundary conditions, the variance and variables get more easily modeled as more time is utilized and of course various scenarios from empirical observations are inputed; the sites I pasted and the book I recommended explain a lot about the weather and climate models, similarities and differences.

    Comment by jcbmack — 11 Nov 2008 @ 12:06 AM

  321. Stefano # 311, excellent points, here is where I question and have asked Gavin and Realclimate on their thoughts, both here and in email. SO2 in the stratosphere is not a good idea, neither is playing around with the system without better predictive qualities of how certain drastic efforts might present with their effects. Many innovative ideas that would work and would ar safer are being ignored at this time. We do need to reduce CO2 emissions, but we also do not want high levels of aerosol sulfates or low altitude ozone everywhere either. Here we must use some caution and discretion. When we speak of hotter periods in the paleoclimate record or more absorption of radiation and other historical-pre-historical climate conditions, keep in mind that 6.6 billion people were not here and that the conditions needed to sustain such a global population (with advent of agriculture, and urbanization) both in way of climate and economics has changed dramatically. I honestly cannot believe any scientist, let alone a climatologist would seriously consider extreme measures that could be even worse to the state of the global climare system. It is true that what to do precisely and in what regards and to what degree in light of reality and human condition is difficult to say the least.

    Comment by jcbmack — 11 Nov 2008 @ 12:14 AM

  322. Gavin, I am sorry, I have to ask you again. You said between the lines in #270: “as you equilibrate”, “by the time you get there”, all sounds like now you are talking about a transient process, while in #269 you said “that equilibrium state … happens to absorb more LW than you started with” (which I read as an absorption process related to the state of equilibrium). One might think that if a thermally insulated physical object continues to absorb more than it emits, it would eventually overheat with no limit … A really accurate formulations would be very helpful here.

    [Response: The planet is not thermally insulated. If you want equations, this was all worked out in a simple toy model a while back. – gavin]

    Comment by Alexi Tekhasski — 11 Nov 2008 @ 12:33 AM

  323. Then again there is no question I cannot answer for myself… getting through all their published work I can find…any publications you can suggest?

    Comment by jcbmack — 11 Nov 2008 @ 1:01 AM

  324. More esoteric and involved?

    Comment by jcbmack — 11 Nov 2008 @ 1:06 AM

  325. David B. Benson #118, forgot to get back to you sooner; you are on the right track with SO2 emissions. Clouds do not always form in the manner we might think of them as forming, in relation to our own regional bias. Precipitation does decrease soil moisture goes up; winds change, so depending upon the location, wind effect will influence shading…partially.

    Comment by jcbmack — 11 Nov 2008 @ 2:01 AM

  326. Alexi 322, 4W in Feedback isn’t *instantaneous* so the equilibrium state of the system is delayed until you get to whatever the feedback makes that 4W change when the feedbacks are in a stable state.

    Comment by Mark — 11 Nov 2008 @ 3:23 AM

  327. RodB #312. Water vapour is one. So is ice albedo. So is circulatory change if the change lasts long enough. Lots. You say you included it in your description but you didn’t, did you. You just said “atmosphere”. As David asked, what did you leave out? State specifically. What did you include. State specifically.

    They are feedbacks not forcings because they will not change without a force to keep them out of the previous state. Once that happens, they feed back into the system to change the original change either more (positive) or less (negative) feedback processes.

    Now how come you don’t understand this when it comes to climate but are absolutely a-ok with it in other places?

    Comment by Mark — 11 Nov 2008 @ 3:29 AM

  328. Greg, no need to constrain yourself if I can explain why I call you a denialist.

    You come across as one because, without ANY working out to see if it’s enough, you just say “The sun is getting hotter, so that could be it” and then use the standard denialist mantra that has been incorrect for the last two years: “The earth is actually cooling now”. Which is a denialist rather than skeptic statement because when it was moving up, ten years wasn’t long enough. When it is going down, it seems 10 years is abolutely fine and definitive.

    It isn’t skepticism because a skeptic would be thinking of your statements, Greg, “Has the sun gotten warmer? How much, or is it just in the noise? And has the earth gotten cooler or is it a measurement error?”.

    You see, they’d be skeptical of the “no AGW” side too. That is what a skeptic DOES.

    But when you pick up threads and only show them as proving no AGW and have not done anything like as much checking of those facts as you demand from the pro AGW proofs, you aren’t being skeptical, you’re denying AGW.

    Now if you really are skeptical, use it on both sides of the argument.

    If you are a denialist, then trying to hide it will require you to moderate yourself here where the inference proof is written down here in this post.

    Comment by Mark — 11 Nov 2008 @ 3:35 AM

  329. Stefano, 311: Not as costly a mistake as standing there saying “Well, there’s a 10% chance the wind will blow it away from me”.

    Comment by Mark — 11 Nov 2008 @ 3:37 AM

  330. Michael, the reason why we vote for politicians rather than scientists is twofold:

    1) Only politicians go into politics
    2) If scientists go into politics they become politicians

    It isn’t their career but the lobbying that causes them not to listen. Either cupidity or the fact that they keep being told a lie and as Goering(?) said, if you repeat a big lie often enough, it will be believed.

    And lobbying is done in private.

    FOIA on all meetings with lobbyists and no meetings outside of work may solve it, but they employ expensive solicitors and so will find a way around any reasonable law and no unreasonable one should be passed.

    Comment by Mark — 11 Nov 2008 @ 3:42 AM

  331. David #294. OK, so how do we model when these abrupt events happen? Could the Black Death be modelled? No. There was no way to say WHEN it would spread, even if the contagion and its virulence could be.

    So you don’t put them in models because you can’t model WHEN they happen and so can’t model their happening in your model.

    Now, when you go and try to scrag Ray, reread your past posts. You’ve been WRONG on more than two occasions. Yet you have never said “oops” or changed your tune.

    Now, what events are large enough to change the CLIMATE? Go on, tell us some.

    Five. Five that have a reasonable chance of happening in the next 50 years.

    And then wait as we tell you how you’re wrong FIVE TIMES. And we’ll not be making it up, you really WILL be wrong five times. Because the only things that can change are already included in the IPCC reports as risk. And you can’t reuse them because you are claiming things not reported on. And you’ll probably not like ones that make GW worse.

    Go on.


    Comment by Mark — 11 Nov 2008 @ 3:49 AM

  332. Alexi, I’m not sure I understand the difficulty you are having. Of course the system absorbs more IR when it returns to equilibrium–because it is at a higher temperature, it is also emitting more IR (and with a slightly shifted spectrum). Yes feedbacks amplify the effect, but the series is convergent, and therefore the warming finite.

    Comment by Ray Ladbury — 11 Nov 2008 @ 6:36 AM

  333. Apart from Co2 positive forcing I hear that other other positive forcings are cancalled out by the negative forcings to about 2.7 w/m^2 and hence the models do not represent them due to this cancellation and hence only Co2 forcings is represented. Is this the case ?

    Comment by pete best — 11 Nov 2008 @ 6:52 AM

  334. David Wojick writes:

    It does not mention large scale processes which are (1) under active study, (2) might explain 20th century warming and (3) are not included in the models. Indirect solar forcing and abrupt changes are two examples among many

    The sun hasn’t changed its luminosity noticeably in 50 years. We’ve been measuring it from satellites since the 1960s and have good proxies for long before that. And what are “abrupt changes?” What kind of abrupt changes? Changes in what?

    Comment by Barton Paul Levenson — 11 Nov 2008 @ 7:42 AM

  335. Mark #326. The 4W forcing isn’t instantaneous either, so the feedback is happening while the forcing is still in progress, so how do you distinguish which is which?

    [Response: The forcing is caused by the change in an external parameter – something that isn’t a prognostic variable in the model. It’s very easy to define. That forcing will cause the prognostic variables to change (like the surface temperature) and which in turn will change other aspects (like water vapour) which add to the surface temperature changes. The mechanisms of feedbacks are built into the model, the forcing comes from outside. -gavin]

    Comment by simon abingdon — 11 Nov 2008 @ 9:05 AM

  336. Mark – Go back and read what Greg originally wrote, particularly the timeframe to which he was referring. His whole point was that it is not as simple as “Make the sun hotter. What happens on Earth? Temperature goes up. Permanently (unless the sun gets cooler, earth moves away, etc).” All temperature reconstructions suggest that the earth is considerably cooler than it was 55 Million years ago despite the current understanding that the sun is hotter and the earth isn’t any farther from the sun. Therefore, the change must be in the “etc.” Your jumping all over him for no good reason.

    Comment by Bob North — 11 Nov 2008 @ 10:17 AM

  337. wayne davidson, #317:

    It’s time for switching tactics and use Density Weighted Temperatures of the entire atmosphere.

    A major source of the variance in GMST is ENSO. ENSO’s redistribution of heat involves the ocean. In the West Pacific and Indian Ocean there is a huge pool of very warm water known as the West Pacific (or Indo-Pacific) warm pool. It’s not just warmer in temperature – it also has a higher sea level. Large, persistent high-pressure cells in the North East Pacific and South East Pacific drive winds which push warm surface waters west, and pile them up in the West Pacific. From time to time – these high pressure cells weaken, which allows the West Pacific Warm pool to expand. The immense heat content of the West Pacific Warm pool spreads out over a much larger area. This is an El Nino event. It causes GMST to rise – but all the heat comes from the ocean. There is also an opposite event – La Nina, which casues GMST to drop. Together the oscillation is referred to as ENSO. One of the strongest El Ninos on record occurred in 1997-1998. It is a major reason why 1998 – tied with 2005 – is the warmest year on record. The claim that the earth hasn’t warmed since 1998 relies on the El Nino driven warmth of 1998 (as well as other misunderstandings). So density weighted temperatures of the entire atmosphere would be a step in the right direction (provided good long-term records for the rest of the atmosphere – which only go back to the 1970s), but strong El Ninos would continue to drive substantial variations in global density weighted atmospheric temperatures. 1998 would very likely still be tied with 2005.

    Comment by llewelly — 11 Nov 2008 @ 10:33 AM

  338. Mark, when you make a flat statement of fact, like this:

    > Could the Black Death be modelled? No.

    Would you please back it up with a cite or some basis for your belief?

    You are being very certain about what you believe. Cites would help those of us who’d rather rely on sources than on trust.

    You can look up the work done on that question in Medline; you will also find the public health work done by the military during both WWI and WWII helpful, as well as much recent work since computers came along. Seriously.

    Comment by Hank Roberts — 11 Nov 2008 @ 10:52 AM

  339. about your response 270.

    Maybe is it possible to consider that a 4 W/m2 forcing with a 16W/m2 feedback is equivalent, to get an idea of resultant surface temperature, to a 20 W/m2 forcing without feedback?

    Comment by Pascal — 11 Nov 2008 @ 11:06 AM

  340. Gavin, I’d welcome a sanity check on

    Seems to me David’s mistake is not noticing that the rapid events are internal to the climate system, not external; they may cause fast changes in albedo for example for a while; and they are modeled, see Dr. Bitz’s work on Arctic sea ice, or any model including volcanos or Atlantic deep water currents etc.

    [Response: David is one of the people who won’t accept any attribution study because they can’t include the ‘unknown unknowns’ – he’d be great jury member for the defence; no matter how strong the evidence there is always some doubt. He won’t even accept the attribution of climate changes 1991-1993 to Pinatubo – because, how do you know something else didn’t come along and give the same response at the same time canceling out the effects of the aerosols? Conversations with him on this topic tend to be short and unproductive. – gavin]

    Comment by Hank Roberts — 11 Nov 2008 @ 11:13 AM

  341. 337 llewelly, I cant agree more. But I dont know what El-Nino does to DWT measurements.
    I have an idea what La-Nina does to a DWT at a distant from the South Pacific Arctic station….
    Nothing significant! DWT of Feb Mar 07 vs Feb Mar 08 were very similar, in fact 08 Was warmer by 1 K by radiosonde DWT’s as per graph on my website. La-NIna also likely triggers a cooling effect
    over Arctic surface temperatures, as has happened in February March 08, especially has happenned in the 70’s… Even if Arctic surface got cooler, the whole Upper Air remained just as warm or warmer. I think its because during La-Nina
    there is less Anvil seeds in the stratosphere, effectively rendering a greater part of the Arctic cloud free, cooling its surface significantly, but not the entire Arctic atmosphere. I would estimate EL-Nino events do the opposite, triggering more thunderstorms world wide, as per evidence in this nice piece of lightning research for North America… :

    31.1 million lightning strikes for North America in 1998 significantly less for 1999 and 2000….

    DWT’s vary a whole lot less than surface temperature averages, reflecting the true nature
    of the state of heat in the entire atmosphere. Hence the reason to switch to a stronger
    more compelling proof of Global Warming would suck away the last breaths of doubts
    spun by mischievous contrarians knowing full well that surface temperature trends are long term,
    but count on the ignorance of the lay, and jump up and down very excited by any short term surface temperature drop.

    Comment by wayne davidson — 11 Nov 2008 @ 11:15 AM

  342. David: What do you mean by “indirect effects”?

    If you mean the hypothetical modulation of cosmic radiation by the sun, there is a new study out:

    Based on this experimental result, it appears that the impacts are very marginal, if anything at all. Seems to settle the case pretty well.

    Comment by Pekka Kostamo — 11 Nov 2008 @ 11:53 AM

  343. #337, llewelly

    “From time to time – these high pressure cells weaken, which allows the West Pacific Warm pool to expand”
    I’ll bet the weakening of these cells around 1977, causing the great climate shift and most of the global warming (and all the warming of Siberia and Alaska) the following 30 years is not found in the model runs.

    Comment by lgl — 11 Nov 2008 @ 12:29 PM

  344. gavin #335 The mechanisms of feedbacks are built into the model, the forcing comes from outside. -gavin

    What system is the model modelling? What does “outside” mean?

    [Response: It depends on the model. Whatever it is modelling, there are internal prognostic variables and then fixed elements that provide external boundary conditions. For a standard AGCM, the amount of CO2 is a fixed input, as is the sea surface temperature, the shape of the mountains etc. Changes in those external parameters are a forcing. For a coupled ocean-atmosphere model, the sea surface temperature is a prognostic variable and so no longer acts as a forcing. In climate-speak, people often talk about ‘forcings’ as a shorthand for the forcings in a standard coupled ocean-atmosphere model and refer mainly to their TOA radiative effect which is useful for comparing their effects. – gavin]

    Comment by simon abingdon — 11 Nov 2008 @ 12:30 PM

  345. Mark Says:
    11 November 2008 at 3:35 AM

    Greg, no need to constrain yourself if I can explain why I call you a denialist.

    You come across as one because, without ANY working out to see if it’s enough, you just say “The sun is getting hotter, so that could be it” and then use the standard denialist mantra that has been incorrect for the last two years: “The earth is actually cooling now”. Which is a denialist rather than skeptic statement because when it was moving up, ten years wasn’t long enough. When it is going down, it seems 10 years is absolutely fine and definitive.

    Wow, right back at you. I was pointing out that your statement was known to be false, not addressing AGW theory. If you had said “A warmer Sun means the Earth will be warmer than it otherwise would be” you would have been close to correct. Perhaps that’s what you meant, but it’s not what you said.

    I didn’t see any need to justify my points, because I think they are reasonably in accord with scientific consensus, but let’s look at them now.

    Theory says that the sun over the last 55 million years has gotten hotter.

    Were you unaware of this? Google and some interpolation gives me a figure for the solar constant of about 6 watts per square meter less than today. That’s not a huge amount, but it’s not trivial, either.

    the earth is now cooler.

    Since I’m comparing today with the late Paleocene, when Antarctica was largely ice free, I don’t think this is controversial.

    the largest reason is probably less water vapor in the air now.

    I’m on shakier ground here, so I qualified it. Water vapor is the most important greenhouse gas, but it’s an educated guess that the change in water vapor has been more important than the change in carbon dioxide, but since, as I wrote, “That’s a feedback, and I can’t count it”, it doesn’t really matter.

    I might say it’s due to less carbon dioxide in the air, but that’s at least partially a feedback, too.

    As the Earth warms carbon dioxide is driven from the ocean, when it cools it goes back in. That makes it a feedback, but I didn’t say it was only a feedback. Our current burning of fossil fuels is clearly a forcing.

    maybe it’s continental drift

    One suggestion for the long term cooling is that the arctic ocean has become partially land locked, leading to an ice cap and increasing the Earth’s albedo. Another is that the rise of the Himalayas has sucked carbon dioxide out of the air. A related possibility is that there was increased vulcanism as India approaches Asia, and a reduction since then, has allowed the level to decrease. All of these are related to “continental drift”, to use the old term for it.

    The only thing I’m really skeptical about is how soon some say the dire consequences of global warming will manifest, but I don’t see that as a reason not to drastically lower our greenhouse gas emissions now. We should have started twenty years ago.

    Comment by Greg Simpson — 11 Nov 2008 @ 1:07 PM

  346. Bob 336 read what Greg was “replying” to. In the context of “what is forcing” how does that relate? The heat of the sun was still a forcing.

    Greg 345. Same thing.

    Either of you want to answer?

    And yes, I’m aware (as are climatologists who do this for a living. They are aware of this “Daystar” the hot burny thing up in the sky). Now do you think that isn’t taken into account?

    So either of you, how does your return change the sun being a forcing?

    Hopefully Greg you will understand why I called you a denialist.

    Hank, #338. How would it have been modelled? The *effects* could be now, because they are based on measurements we can make and predict. E.g. human population density, virulence, contagiousness and incubation of the plague. Mobility of the people. But it then depends on multiple factors that are not up for measurement (in the same way as we can say “If we had another pinatubo, over here, it would have $this effect” but cannot say WHEN we have it). Such as the vector (we thought it was satan so killed cats. Then rats. Now it is thought something else). Where the pool was and whether it was mutating into something worse. Etc.

    Or, alternatively, you could see if you can find a model of the Black Death that would have predicted its occurrence on the date/time it did. I couldn’t.

    Could find lots of models on how such a plague WOULD spread. One was used in the Bird Flu scare to see what effect it would have. Another use was for the Foot and Mouth in the UK to see what needed to be done to stop its spread.

    Which, incidentally, would have been a lot easier if farmers hadn’t lied about it or moved stock illegally so they could make short term profit. Sound familiar?

    Comment by Mark — 11 Nov 2008 @ 1:20 PM

  347. gavin #344 “the shape of the mountains etc. Changes in those external parameters are a forcing”

    Please explain how changes in the shape of the mountains are an issue.

    [Response: They are an external parameter that could change, leading to a response in the climate. Bit of a longer timescale than the 20th C, but the principle is the same. I think you are overthinking this – it really isn’t that difficult. – gavin]

    Comment by simon abingdon — 11 Nov 2008 @ 1:28 PM

  348. Further to Gavin’s #335 reply. It’s something that isn’t modelled in the model itself.

    The Sun is the prime example because no earth atmosphere model includes the Sun simulation within.

    Another would be anthropological CO2. Because that can’t be predicted. E.g. the crash recently has caused oil demand to drop dramatically. A climate model doesn’t include economic models too. And if it had, it would have got it as wrong as the economists did.

    Although a guess could be used to see what would happen if… Which is what the IPCC did. “if we double 1980 CO2 what would happen?” etc.

    IMO though the easiest way to tell the difference is if the process causes a change to remain. Water squirted in the air won’t. It rains too quickly for the trapped heat to keep the air that moist.

    A feedback causes more change based on the change in *forcing* levels but won’t cause a change in itself with no forcing changes.

    So a change in geography could do that. If Antartica weren’t stuck over the south pole, it would not be so cold there. Or so dry. And continents move on a scale that makes climatology seem quick.

    If you’re looking for a list of what is a forcing and what is not, you’ll have to answer the question “for what model?”. Either that or accept the ones that are in all of the IPCC models included. David won’t like it because they don’t include models with the unknowns in it, but it’s either that or answer “which model do you mean”. And in that case, you’re better off talking to whoever wrote the model.

    Whichever the latest Met Office (UK) model is, ask the Met Office.

    Meteo France’s model? Ask Meteo France.

    Someone here may know the answer, but there are a lot of models out there, so you may get a lot of different answers. This doesn’t mean the models are wrong, it means they work differently when you look to the detail.

    And that, really, is what “what is forcing” that seems to be the current meme is. A detail. The “not a detail” answer is “read a book” (Apologies to One Ton Tony/Handy). A dictionary will tell you.

    Comment by Mark — 11 Nov 2008 @ 1:34 PM

  349. > Hank, #338. How would it have been modelled?

    Of course at the time of the Black Death, modeling wasn’t being done.

    Abrupt events do occur, and are modeled. FAQ.

    See Gavin’s inline comment earlier. We aren’t likely to convince David; we’re here to suggest questions for the FAQ. Let’s dance.

    Comment by Hank Roberts — 11 Nov 2008 @ 2:00 PM

  350. 349. The result IF one happens is modeled. When they happen is not effective at doing so. See earthquake predictions (if you haven’t seeded it LIBERALLY with sensors, and even with them you only have a few weeks if that of advance warning).

    PS They were $700 glasses you s.o.b.!

    Comment by Mark — 11 Nov 2008 @ 2:10 PM

  351. further on 351. The events CAN be subsituted on a statistical model.

    Have we turned it back to the thread topic now, Hank?

    Comment by Mark — 11 Nov 2008 @ 2:12 PM

  352. I noticed the Hansen et al article today about the 350 ppm being already a danger zone scenario. What do you guys from real climate say about it and what are the differences to other models/articles saying that 450ppm is the critical threshold and what are the implications for stabilization efforts of the EU, (possibly) the US and other countries in your opinion?


    [Response: We discussed this a while back. – gavin]

    Comment by Nico — 11 Nov 2008 @ 2:18 PM

  353. — A FAQ about the importance of rate of change (and rate of change OF rate of change, and the need to at least understand what calculus can explain if not how to do it).

    — A FAQ item for ocean acidification/ph change.
    Relevant to the need for cross-disciplinary work, too.

    This may help:

    “… expect to see changes in pH that are three times greater and 100 times faster than those experienced during the transitions from glacial to interglacial periods. Such large changes in ocean pH have probably not been experienced on the planet for the past 21 million years.”

    “In May 2004, SCOR and UNESCO-IOC co-hosted an international symposium to address these issues …. the two organizations agreed to make this symposium a regular event to be held every 4 years.

    “… joined by two new international organizations: the International Atomic Energy Agency’s Marine Environmental Laboratory and the International Geosphere-Biosphere Programme, enhancing links to the UN system and to interdisciplinary Earth science.

    “This web-site is a follow-up of the first symposium and is meant to provide a central source of information for ocean scientists on research activities in this area.”

    Comment by Hank Roberts — 11 Nov 2008 @ 3:06 PM

  354. Regarding the FAQ “How have models changed over the years?” Saying that “model simulations have become demonstrably more realistic” and citing Reichler and Kim 2008 to prove it is overstating the case, to say the least.

    The Reichler paper is a study in strange statistics. They combine a large number of climate related state variables into a single number, like the Dow index. Then they show that one of the latest ensembles comes marginally closer to matching this number, for a single observed state of the climate, than did some previous generation ensembles. This index number bears no relation to the climate parameters of actual interest, other than containing them. Nor is there any consideration of trend matching.

    The reason they did not look at matching important model values with observation is because there has been no improvement. Same for trends. As for forecasts, the models are still all over the map. The fact that the range of temperature forecasts has not converged is actually a major research area. Many people think the unrealistic, high end forecasts are due to runaway positive feedbacks, in the models not in reality. But of course it is just these feedbacks that yield the forecasts of dangerous warming. All things considered the claim that the models have become “demonstrably more realistic” is unrealistic. Ironically, the Reichler paper begins by citing some papers to this effect.

    Comment by David Wojick — 11 Nov 2008 @ 3:39 PM

  355. The discussion of chaotic “wiggles” in the FAQ is puzzling and probably wrong. The FAQ begins with a correct observation, namely that “there are wiggles at almost all timescales – daily, monthly, yearly, decadally and longer…” But it then goes on to talk as though these wiggles are something to ignore, or to average out using ensembles. Neither is true.

    Climate is a chaotic system and the actual climate is not an ensemble. Decadal and longer internal oscillations could explain the temperature record of the last 100 years. The oscillations were relatively uniform — temps rose for the first third of the last century, then fell of the second third, then rose again for the third third. Now they are falling again. Chaotic systems are notoriously immune to forcing and the climate is one. These wiggles are something the modelers should be studying, not brushing aside.

    [Response: It just ain’t so. How does that chaotic system respond to the seasonal forcing? Or is that just a figment of our imagination as well? Or orbital cycles? or volcanoes? There are loads of examples demonstrating that that there is a predictable forced response of the climate to forcings. That isn’t to say that the wiggles aren’t worth looking at – of course they are, but your implication that the presence of chaos implies that there can’t be a predictable forced component is simply fallacious. – gavin]

    Comment by David Wojick — 11 Nov 2008 @ 4:10 PM

  356. Final recommended readings: Global Warming and Global Politics by Matthew Paterson and Climate Change in Prehistory by William James Burroughs.

    Comment by jcbmack — 11 Nov 2008 @ 4:35 PM

  357. Ray Ladbury wrote:

    It seems to me that the precuationary principle applies to the scientific side of the argument–we know human civilization, with all its complicated infrastructure functions with CO2 in the 280-350 ppmv range. If you are going to move outside of that range, you damned well better show that it will not affect infrastructure catastrophically.
    What is more, we know for an absolute fact that energy infrastructure MUST change due to peak oil.

    Ray, CO2 is just one variable. On the subject of catastrophes, what about overpopulation? This is the mother of all problems. What if we need to quickly stop population growth? People in the most developed countries have the fewest children. It follows that to stop population growth we need the developing world to grow their standard of living as fast as possible–in as few generations as possible. You don’t want four kids having four kids having four kids. You want four kids to have two, and them to have just one. In the meantime to fuel that growth, CO2 levels may go up quite a bit, as coal and oil are quick to obtain, but you’ll have done something arguably far more important, which is to urgently and rapidly reach the point where we can reduce our numbers. Then everything starts returning to balance.

    Can we focus on emissions cuts and rapid development at the same time? Many governments seem to think not. Many think they should use their coal. There is a Japanese saying; “chase two rabbits, catch none”.

    Comment by Stefano — 11 Nov 2008 @ 7:19 PM

  358. Seismologists are trying to gain a a second or two warning of the S wave from earthquakes to assist people in getting under the table. Japan has better warning systems as most of their earthquakes start offshore. Early detection is a tricky thing, regarding earthquakes.

    Comment by jcbmack — 11 Nov 2008 @ 7:52 PM

  359. Mark (327), ice albedo (change) and ocean currents strike me as more feedback stuff than forcings. Though I suppose a modeler can define any forcing he chooses and still be correct within his context and algorithms. Nor do I see that it matters given my question re grouping all forcings into two neat families which was pretty much answered as unhelpful, likely wrong, and probably silly. I do understand feedback vs. forcing. What led you to believe I didn’t. And what on earth is the contention here; I’m totally missing our “disagreement”…

    Comment by Rod B — 11 Nov 2008 @ 8:23 PM

  360. How about a bibliographic FAQ?–people always want sources, and while the bibliography is doubtless out there, the layperson has a tough time finding the really crucial ones amidst the merely workmanlike. Maybe top 25 (or 40? 100?) historical climatological papers? It could certainly help demonstrate the historical depth of the science.

    (Captcha seems to think it’s a hot idea: “Combustion waves.”)

    [Response: The AIP: Discovery of global warming site has a good bibliogrphy (linked on the sidebar). But there might be something to this… I’ll think about it. – gavin]

    Comment by Kevin McKinney — 11 Nov 2008 @ 9:20 PM

  361. Stefano – if you dont cut CO2, then the climate change is going to deliver a number of unpleasant ways to bring population down. If you want to give developing countries time to breath, then developed world is the place that needs to bring down CO2 emissions, fast and low.

    Comment by Phil Scadden — 11 Nov 2008 @ 10:54 PM

  362. Can someone please answer the following questions about extreme climate events?
    Do you know if anyone has performed rough calculations of the effect on Earth’s average temperature of the following?

    1. Direct effect on Earth’s average temperature of complete permanent loss of Arctic ice-cap for half the year.

    2. Release of all CH4 and CO2 stored in permafrost both on land and under the Arctic Ocean bed (order of magnitude).

    3. I understand that there is not a linear relationship between CO2 concentration and Earth’s average temperature; that as CO2 concentration increases, the marginal effect on temperature decreases due to saturation of spectral lines. Does this mean that, under positive feedback processes that release very large quantities of CO2 into the atmosphere, there is a limit to the increase in the average temperature of Earth? If so, is this limit of the order of 10, 100 or 1000 degrees C? If the limit is of the order of 10 degrees C, then how is it possible that Venus has such high temperatures, much higher tan its distance from the Sun would explain?

    Comment by Dr Mark Diesendorf — 11 Nov 2008 @ 11:14 PM

  363. I just heard on the news yesterday that latest oceanographic research (I didn’t catch the source unfortunately- my 3y/o son was having a tantrum) says global crustation stocks will collapse by 2030 if the acidicfication and warming of the oceans continue to rise. That’s 50 years ahead of the IPCC forcasts.
    If that was to occur in my understanding then global fisheries will also collapse leading to world wide famine expecially of the asian countries. Is this so?

    [Response: Famine might be a little strong, but the health of many fisheries is certainly in a parlous state. – gavin]

    Comment by Lawrence Coleman — 11 Nov 2008 @ 11:37 PM

  364. Dr. D., try these for the answers to your third question.
    (found with Google, searching: runaway climate realclimate )

    Lessons from Venus:

    Recall Earth was apparently whacked hard by something about the size of Mars early on; that changed a primordial near twin of Venus, with a more typical amount of CO2 in its planetary atmosphere, to what we live on (Earth) and under (the Moon). Quite different.

    Comment by Hank Roberts — 12 Nov 2008 @ 12:50 AM

  365. Oh, more for Dr. D on #3, on ‘saturated spectral lines’ — covered here:

    Comment by Hank Roberts — 12 Nov 2008 @ 12:52 AM

  366. Dr. Mark Diesendorf

    I can only answer bits of 2 and 3

    Regarding #2, this paper has 1.6 Trillion metric tons of Carbon locked up in NH permafrost, but that is one area (deep soils in northeastern Siberia). They also say, “global soil C stocks from 0 to 3m depth (peatlands not included) have been estimated to be 2300 Pg (Jobbágy and Jackson 2000).” A “Pg” to represent billion metric ton.

    On #3, After very large concentrations of CO2 (such as when most of the atmosphere is CO2 enriched) the logarithmic behavior no longer holds and sensitivity is increased; the logarithmic rule is mainly applicable to conditions relevant on Earth. What’s more, after very high pressures, collision-induced broadening becomes a relevant factor which is different than the normal absoprtion associated with the spectral lines. Adding more greenhouse gases (even on Venus) will always produce some extra warming insofar as the temperature continues to decrease in the vertical (the lapse rate).

    In any case– The Kombayashi-Ingersoll limit gives a quantiative outlook on the runaway greenhouse which depends on acceleration due to gravity at the surface, how much sunlight you’re getting, etc. The thing is that when you put sufficient greenhouse gases in the atmosphere, the saturation vapor pressure puts a limit on how much stays there before it condenses out. On Earth, water vapor cannot accumulate anymore since it will just form a cloud and precipitate as snow or rain. Increasing temperature from extra CO2 does raise the saturation pressure and thus you get a bit of extra water vapor (a positive feedback), but it’s small compared to the Venus situation. Unlike Earth where most of the water is liquid (the ocean), on Venus, any input of extra CO2 or water vapor stays in the atmosphere (or goes to space). This kind of situation where the ocean boils away cannot happen here until the sun brigtens sufficiently which would take a billion years or longer, and the CO2 reservoir will be released until its supply is diminished. And it will be very much like Venus….

    Comment by Chris Colose — 12 Nov 2008 @ 3:08 AM

  367. RodB, 359. I thought it strange. You normally pick something less silly to be contrarian about.

    If you meant your (and others question about “what is forcings” was unhelpful, wrong and probably silly, you’ve hit the problem right on its head.

    You’re right as well that a model without sea ice modelled within has to be a forcing. It’s why the Sun is taken as one. The forcing is purely one way. A warmer earth doesn’t heat the Sun. I know there are newer models that model sea ice and likely land ice too.

    Hope that clears it up.

    The disagreement was over the idea that “what is a forcing” is an unhelfpul question. It cannot be answered except in the specific where it isn’t a question whose answer you can take out of that model usefully.

    NB: My goodness, the oracle does seem to be strange today: Household Nostrils?

    Comment by Mark — 12 Nov 2008 @ 3:31 AM

  368. Stefano, 357, which is why CO2 equivalent is the “450 maximum” limit. Includes the climatological effects of other gasses.

    As to overpopulation, only a command government like china can tell people to stop boffing. NO government will start a cull.

    So how do you suggest we get people to die off?

    Heck, economically that is stupid. Who is going to pay for the pensions? That only comes from a higher GDP being paid off to people who no longer work. If you don’t have more people, that means inflationary economy is mandatory unless we kill people off on retirement.

    Worse, the West is more densely populated in general and definitely more of a stress on the capabilities of the region they live in to support them (water aquifers being drained and not replenished is more common in the modernised west so indicating that they are exceeding the resources available). So the cull MUST take place here in the West rather than in the more populous (but less stressful on resources) poorer nations.

    Fancy shuffling off this mortal coil for the sake of the planet?

    Didn’t think so. Population control is for “other people” not you. Problem is, everyone thinks that.

    Comment by Mark — 12 Nov 2008 @ 3:38 AM

  369. Glen, regarding the past colder sun, read comment #31 in “Adapting to Amsterdam”.


    Comment by Mark — 12 Nov 2008 @ 3:50 AM

  370. A simple question – apologies if it has already been asked.

    On what timescales and scenarios are the models typically tested? For example, some interesting scenarios I could think of are:

    – simulating the events from 1900 up to now
    – simulating the events from 100.000 years ago up to the start of the industrial revolution
    – simulating the climate over a timescale of several hundred million years

    Have model runs so far been mainly concerned with one type of scenario?

    [Response: Transient runs from the 19th Century are common. From 1000AD to the present is becoming more so. For earlier periods (last ice age etc), models generally use time-slice experiments – these have been done for many different periods. – gavin]

    Comment by Vincent van der Goes — 12 Nov 2008 @ 4:34 AM

  371. Hank Roberts writes:

    Recall Earth was apparently whacked hard by something about the size of Mars early on; that changed a primordial near twin of Venus, with a more typical amount of CO2 in its planetary atmosphere, to what we live on (Earth) and under (the Moon). Quite different.

    I think the runaway greenhouse on Venus is generally attributed to its proximity to the sun. Narrow models of the sun’s continuously habitable zone (CHZ) put the inner boundary at 0.95 AUs. Kasting’s most generous estimate puts it at 0.85 AUs. Venus’s semimajor axis is 0.72333 AUs.

    Comment by Barton Paul Levenson — 12 Nov 2008 @ 7:45 AM

  372. Stefano #357: Saying we have to address EITHER climate or development is a false dichotomy. Both are facets of the same underlying issue–sustainability. If we address climate in the industrial (or post-industrial?) world, but ignore developing countries, they will burn whatever they can get their hands on to meet their needs and the climate will warm anyway. If we address development at the expense of climate, agricultural production will likely collapse and with it any economic gains from our efforts.
    The fact of Peak Oil means that things have to change. The only question is whether things change so that we address all the threats that confront us, or do we screw it up and do a half-assed job by ignoring development, climate change, water quality, soil depletion, or any of a number of threats that confront us.

    Comment by Ray Ladbury — 12 Nov 2008 @ 9:21 AM

  373. gavin #347 “I think you are overthinking” Which do you recommend?

    [Response: I get it now. This is a obviously a Turing test…. – gavin]

    Comment by simon abingdon — 12 Nov 2008 @ 9:58 AM

  374. Ray, peak oil means things eventually have to change, but it does not mean that mankind will not burn most of the rest of it in a big hurry. Oil is easy to use. Oil, even at 147 a barrel, is cheap.

    Straws in the ground; suck that milkshake.

    At 60 a barrel, expect oil consumption behaviors to expand rapidly. Local GM plant is on full overtime. What do they build? Big pickups and SUVs.

    Comment by JCH — 12 Nov 2008 @ 10:23 AM

  375. JCH, Yeah, I know. I really don’t think humanity is smart enough to avoid the “empirical” approach to answering the question of how climate change will affect civilization. Still, there’s a far cry from using up the rest of the oil to using all the oil + coal + tar sands + oil shale….The latter 3 are less easy to use, and require significant changes in infrastructure. The intelligent thing to do would be invest in new infrastructure that also addresses climate concerns, but then, it probably ought to tell us something that alien civilizations have given our planet wide berth in their search for intelligent life in the cosmos.

    Comment by Ray Ladbury — 12 Nov 2008 @ 10:52 AM

  376. Vincent van der Goes (370) — There is a paper by Abe et al. describing a GCM run from the Eemian interglacial (125,000 ya) to the peak of the Holocene (about 7000 ya).

    I found this most impressive.

    Comment by David B. Benson — 12 Nov 2008 @ 3:18 PM

  377. The mantra of getting off foreign oil means tar sands in Canada and Venezuela are going to be exploited with gusto. Venezuela and Canada already ships significant quantities, and Venezuela is offering new partnerships at this very moment. So the straws in the tar sands already exist and lots of new ones are about to be plunged. It just an extra-thick milkshake.

    ExxonMobil and Venezuela are embroiled in a nasty legal battle. And every so often a ship full of Venezuelan tar shows up at a remote, well-hidden ExxonMobil refinery, built especially for that extra-thick milkshake, and the two enemies put down their motions and subpoenas and refine money.

    Comment by JCH — 12 Nov 2008 @ 4:11 PM

  378. Regarding the FAQ “What is robust in a climate projection and how can I tell?” Given that the results differ a lot from model to model, it follows from this FAQ that none of these results is robust. That the planet will warm some with large GHG increases may be relatively robust, but whether such warming will be significant is not, because the models disagree. Moreover the paleo record is ambiguous here, given that temperature seems to lead GHG rise. Nor is theory unequivocal because there is reason to believe that the models lack negative feedbacks found in nature. And of course if one or more of the alternative hypotheses currently under investigation turns out to be true then the model results are just wrong, robust or not.

    Comment by David Wojick — 13 Nov 2008 @ 10:31 AM

  379. That doesn’t make sense, David.

    What definition of “robust” are you using?

    I don’t see a definition on your “debate” blog but you’re not using the standard meaning (that one of a group of different data sources can be removed without changing the result from the study).

    Comment by Hank Roberts — 13 Nov 2008 @ 2:00 PM

  380. David, #378.

    There are robust outcomes:

    GW is mostly Anthropogenically caused.
    It is getting warmer.

    Oddly enough, through all the denailosphere, there are not robust projections or even causes that meet standards of being workable. I guess this means that you’ll be ignoring the denialists until they turn up with some concrete and robust outcomes themselves.

    Comment by Mark — 13 Nov 2008 @ 2:07 PM

  381. Interesting tracking. Watch for it at your local …

    Comment by Hank Roberts — 13 Nov 2008 @ 2:33 PM

  382. This could well go under “Start Here”

    John Mashey on how to learn about science

    Category: Global Warming
    Posted on: August 21, 2008 3:03 PM, by Tim Lambert

    Another post on John Mashey’s virtual blog. Everything that follows is from comments posted here by Mashey, lightly edited.

    This long essay grew from a dialog in this thread into something that may be a more general resource than just some answers to Mr Manny.

    I’m sure it’s mentioned, but not sure where.
    Excellent. Should be an e-book or something.

    Comment by Hank Roberts — 13 Nov 2008 @ 2:54 PM

  383. In case those of you living in the USA have not noticed, your computers and laptops are powered by coal. Your homes are heated by gas and your electric is powered by the same. There’s a slim chance that if our nation pulled in one direction that we could get a decent portion of our electric generation out of new nuke plants 6-10 years from now if we start building like crazy now. There is no “alternative” power source that will have any impact on providing the juice for your HD TV for 20 years. China commissions a new coal plant every week and you are not going to over-rule the denialists in China to change that. Let’s all just chill and accept that we’re going to pump out CO2 for the next 25-50 years until our economies are ready to transition away from petro as a power source.

    Comment by Mary — 14 Nov 2008 @ 5:18 PM

  384. Unfortunately Mark, that is tue in light of the current economic scheme of thingsl the technology exists and the ability to apply as well, but it takes money, time, and some companies losing out in the process and quirks in a newly applied system. Atleast pickens is doing something.

    Comment by jcbmack — 15 Nov 2008 @ 1:46 AM

  385. Oops I meant Mary, but keep in mind the technology and the ability to engineer it, already does exist and has for quite a few years now.

    Comment by jcbmack — 15 Nov 2008 @ 2:07 AM

  386. Mary, conservation is the biggest, fastest approach. You’re paraphrasing very pessimistic sources — where are you getting your numbers?

    Most ‘knowledgeable’ sources were shown to have grossly underestimated people’s willingness and readiness to conserve when called on for help.

    This isn’t hard and it saves rather than costs money:

    In related news:

    Governor Schwarzenegger today issued an executive order (S-13-08) requiring state agencies to assess and plan for rising sea levels caused by climate change….

    The nation’s oldest continuously operating sea level gauge, located at Fort Point in San Francisco, logged a seven-inch rise during the last century…. with a lax response to climate change, the Pacific could rise three times that much this century.

    The order goes out three days before Schwarzenegger hosts a Governors’ Climate Summit in Beverly Hills.

    Comment by Hank Roberts — 15 Nov 2008 @ 12:01 PM

  387. Re David Wojick @378: “Moreover the paleo record is ambiguous here, given that temperature seems to lead GHG rise.”

    The paleo record is not at all ambiguous: as temperature rose in response to natural increases in insolation more GHGs were released into the atmosphere (mainly CO2, CH4, and H2O), and then those GHGs induced yet more warming, which released yet more GHGs, etc., until equilibrium–and a warmer climate–was reached.

    Today we’re just skipping that first natural warming step by injecting GHGs directly into the atmosphere, which is already inducing warming, which will result in yet more GHGs being released naturally, etc., until equilibrium–and a warmer climate–is reached.

    In fact, we’re already starting to see rising natural emissions of GHGs from natural sources in the form of CO2 and CH4 from thawing permafrost and methane clathrates, and a reduction in the ability of the ocean to absorb CO2. No ambiguity what so ever.

    “Nor is theory unequivocal because there is reason to believe that the models lack negative feedbacks found in nature.”

    On the contrary, the known negative feedbacks (clouds, aerosols) are in fact included in the models, although some are not yet modeled as well as they should be. In any case, the theory does not in any way rest on the models.

    “And of course if one or more of the alternative hypotheses currently under investigation turns out to be true then the model results are just wrong, robust or not.”

    And you are sure of this how? If one of the hypotheses currently under investigation should prove to have merit there is no way to predict in advance how much a factor it might be, and in any case, it would not alter the property of GHGs to absorb and emit LWR one iota.

    Inconvenient, that.

    Comment by Jim Eager — 15 Nov 2008 @ 1:40 PM

  388. > sure of this how?

    ReCaptcha: 3/4 pocketbook

    Comment by Hank Roberts — 15 Nov 2008 @ 2:43 PM

  389. Just as an example of the information currently available:

    50 percent reduction scenarios:

    found here:

    Environ. Res. Lett. 3 (October-December 2008) 044002

    What do recent advances in quantifying climate and carbon cycle uncertainties mean for climate policy?

    Comment by Hank Roberts — 15 Nov 2008 @ 7:00 PM

  390. re: #386 Hank
    re: Schwarzenegger & sea level

    This, of course has been going on for a while.
    1-day conference earlier this year brought together representatives of local SF Bay Area governments on the topic, to hear about the science, discuss current and near-term plans, and run through longer-term planning exercises. The latter offered useful experiences in the political difficulties that will be encountered, given the amount of infrastructure at sea level, and the unsurprising wish of anyone that *their* property be behind any dikes that get built.

    Comment by John Mashey — 16 Nov 2008 @ 5:36 AM

  391. David, #378.

    Any how did the paleo creatures burn a trillion tons of carbon sequestered in fossil fuels? Because WE have done that, so if you want to use past data to refute current situations, you have to account for any differences.

    Also, the lag there is 600 years. So where is that 600-year-old change in temperature that is “causing” this increase in CO2 concentrations?

    I wonder where that “skeptic” RodB and his pals are, to unload their skepticism on your poor science?

    Comment by Mark — 16 Nov 2008 @ 6:42 AM

  392. Thank you John. I’ve been watching the landfill in the Bay west of Berkeley and Albany grow and thinking, whether intentional or not, the dikes are already being developed.


    Comment by Hank Roberts — 16 Nov 2008 @ 1:59 PM

  393. Mark, I could probably ask David some probing questions, but your shots are doing just fine…

    Do the quotes imply I’m just a pseudo-skeptic? And what pals???

    Comment by Rod B — 16 Nov 2008 @ 2:37 PM

  394. Can I use a climate model myself? Not so far as I know, though I would like to, because I use a Mac. If you know of any that run on OS X, please include them.
    The Climate Institute has a model for calculating the effects of emission reductions, which may also be of interest:
    – but it also is Windows-only.

    [Response: Macs run on a Unix background, and so ModelE will run. You may need to find/purchase an appropriate F90 compiler. – gavin]

    Comment by Malcolm Tattersall — 16 Nov 2008 @ 5:07 PM

  395. There was an invitation given to us to ask questions which might be relevant to add to this FAQ.

    I have seen numerous questions offered.

    Is there a time frame for an updated FAQ?

    [Response: Soon! I am collating the questions that I think are interesting (along with some of the responses already offered, and will have a part II post up soon. Real world priorities have taken precedence on getting to this. Thanks for your patience! – gavin]

    Comment by Jim Cross — 16 Nov 2008 @ 5:25 PM

  396. Malcolm, I haven’t tried this but you might look into it:
    EdGCM, or the Educational Global Climate Model

    (Google turned up a thread complaining it worked fine on the Macs but wasn’t behaving on Windows, for this one user; maybe info in there):

    Comment by Hank Roberts — 16 Nov 2008 @ 8:28 PM

  397. This presentation may suggest a way other than a posting_plus_comments format to present FAQ items.

    This one is read-only — a similar layout could link to old and new comment threads as well as to references and sources:

    Comment by Hank Roberts — 16 Nov 2008 @ 8:52 PM

  398. Mark, I find it almost humerous that you describe the efforts of the highly qualified climate scientists on this site as “poor science.” Would you care to explain specifically what you mean by that? Otherwise, please understand that you have just made yourself look very foolish. Hint: what you have said in your post #391 does not even come close.

    Comment by Ron Taylor — 16 Nov 2008 @ 9:50 PM

  399. Malcolm, if you want to run a climate model at home on your Mac, you will see from ClimatePrediction’s (CPDN’s) application’s page that three of the four model types currently on offer should run on it. You’d first need to download the BOINC platform that the models run on from here: Models typically run for between a couple of weeks and three or four months if the computer processes them 24/7.

    Comment by Maureen Vilar — 16 Nov 2008 @ 10:10 PM

  400. Ron Taylor, the “poor science” is from people like David and others. “It’s the cosmic rays I tells ya!”. Or “It’s been cooling these past eight years!”.

    Please explain how the paleoclimate that didn’t have fossil fuels burnt and had a 600 year lag from temperature rises to CO2 rises applies to this day where we can measure there are fossil fuel CO2 in the atmosphere and there is no 600 year old temperature rise that explains the CO2 in this size of change.

    This, was what my post was about.

    That’s the poor science.

    Now, did you read or did your knee get in the way?

    Comment by Mark — 17 Nov 2008 @ 3:41 AM

  401. RodB, 393. You ALWAYS wait for someone else to knock the obvious denialist. Ever thought of getting in there first?

    And your “pals” are because whenever you’re talking about being a skeptic, you always talk in the plural. Either you know them or you’re using a verbal technique to spread any blame (“There are others, are you going to call them on this???”) that I’ve been on the receiving end before. There are two ways to deal with it:

    a) Ignore the plurality and make it individual (this is also, oddly, the way to win a fight when you’re one against many: make it one to one)
    b) Ask who else they are

    Hey, be thankful I’m using b!!!


    Comment by Mark — 17 Nov 2008 @ 3:45 AM

  402. Oops. Sorry Mark, it must have been the knee. I somehow totally reversed your meaning.

    Comment by Ron Taylor — 17 Nov 2008 @ 10:28 AM

  403. Mark, skeptics covers a broad populace. I don’t know them all; I don’t agree totally with all; I might not even like some; I can still refer to skeptics as a collective group (2nd or 3rd person — doesn’t matter). Seems neither complicated nor nefarious to me. What’s your beef?

    Comment by Rod B — 17 Nov 2008 @ 11:13 AM

  404. RodB #403. Look in the other thread.

    The ranges that explain your postings:

    1) You’re a misaligned skeptic.
    2) You’re in denial
    3) You’re a denialist

    Now, even in #3 you’re better than the very vast majority of denialists.

    Your misalignment is that you don’t approach ALL the data with skepticism. You’re denial is that you “still want to be convinced” which will end when you want it to, not when you’ve been convinced. And your denial is if you’re appropriating the cloak of skepticism (which is so often done: you NEVER hear someone say “Well, I’m a denialist”, do you?).

    My beef is that you should show the same level of skepticism (which at least has a reason of some sort toward it) to the posts trying to show something wrong with AGW.

    Do that and the beef is gone.

    PS you can refer to skeptics as a collective. Just don’t do that in the same sentence that you call yourself one. Separate the two out and then people can argue with *your* skepticism and not have to deal with “hypothetical skeptics” or with denialists who will use (abuse, if you’re not one of them) your posts as extra attack vectors.

    I don’t talk of myself any ANY other group. I talk about me and I talk about other groups. I don’t “borrow” the weight of others in my beliefs.

    Because when I’m wrong, it is *me* that got it wrong. “But that other guy did it” was a common defense tactic at university when the professor marking got a “where did you get that from?” from the student. That’s a BIG part of the reason why more than one “marks” the papers. Of course, they don’t, or maybe only a couple, they just lend their weight to the marking of the one who did it so you can’t complain.

    Needless to say, it didn’t work with me. I told the individual what I thought and said “I’ll talk with them too”.

    Comment by Mark — 17 Nov 2008 @ 1:41 PM

  405. As a scientist and as a world citizen, I fully support RealClimate and I am very grateful to my colleagues for the energy they put in persuading people of the reality of climate change and of the care that most scientists take when interpreting their results. Nonetheless, I would have provided a more balanced answer to some of the FAQs, in particular about the tuning and validation of our GCMs. We do know for example that different GCMs capture the late 20th century observed warming despite the use and/or the computation of different radiative forcings. This is the reason why I am sometimes less enthusiastic than my colleagues about the way we build and evaluate our models. I also feel that climate change is progressing faster than the accuracy of our 21st century climate projections and that recent observations have done at least as much as our modelling activities in convincing people (including many scientists) of the human influence on climate.
    I know how dangerous such remarks are (especially in this blog) and my idea is not to provide new arguments to those who do not trust climate models. On the contrary, I wonder if it’s not time for RealClimate in particular and climate scientists in general to consider a new target: instead of trying to convince the blind or dishonest players, we could take action to make governments aware of their duties. We already know enough about climate change to inform important and necessary decisions for adaptation and long-term mitigation. We know enough about models’ strengths and limitations not to challenge their global and long-term (late 21st century) projections on the one hand, while on the other, to be very modest about our ability to rapidly improve the regional details and decadal evolution of our climate scenarios.
    This leads me to a surprising conclusion: I wonder if the most useful decision that climate modelers should make after the IPCC got the Nobel prize is not simply to postpone the next IPCC report (AR5), but to inform our governements that no report will be delivered until more ambitious and resolute decisions are made about the reduction of GHG emissions (yes we can !).
    Such a break would be also very valuable for the climate modeling community. It would give us time to fully draw on the lessons of the AR4 simulations (which are still being analysed) and to discuss new priorities. As an example, do we really all agree with the idea of seamless prediction (see RealClimate article of October 9th) and how can we reconcile the fact that seasonal predictions show more skill in the Tropics where climate scenarios show more spread ? Do we all agree that the development of more complex Earth System Models, including new couplings and feedbacks, is the best solution for issuing more reliable projections and, if so, on which timescales ?
    In my opinion, IPCC simulations should never become a routine activity (as weather prediction has) because every 5 years we basically achieve the same “prediction”, but with a shorter lead-time. Once again, it is not out of question that climate is evolving faster than our dynamical understanding of regional climate change. While the window for global decisive action is rapidly closing, climate scientists should not make careless promises about their ability to reduce uncertainties in climate scenarios over the next few years, and thereby provide our governments with excuses to shun their responsabilities until they know more detail about how fast and adverse their regional impacts of global warming will be (compared to those in other countries).
    Hoping that my colleagues of RealClimate will find real questions and no rhetorical excess in my proposition and looking forward to reading your comments.

    Comment by Hervé — 17 Nov 2008 @ 4:01 PM

  406. Mark (404), Man! All this convoluted analysis is making my head hurt. 1) As said before, I have in specific circumstances directly criticized and corrected other skeptics. I don’t know if this counts in your book of my being skeptical of other skeptics or not. (Nor do I particularly care.) 2) I defend my own science assertions, and now and then the assertions of other skeptics if they have the same scientific thought. 3) I occasionally take the side of skeptics as a collective group when they are pigeon-holed and attacked with ad hominem or collective derogatory accusations — which is quite often. 4) I do not even play with “denialist” lest the term gets some credence beyond the egregious flagitious nefarious playground smear and guilt by association of its origin.

    If I’m skeptical with one specific aspect of AGW science, I have to be skeptical of ALL of the science??!!? That’s nonsense.

    Skeptics are not a monolithic homogenous group.

    It is neither my job, responsibility, nor interest to challenge other skeptics (even though I do from time to time). My interest, and hence onus, is only on the science, understanding as best I can and questioning aspects that don’t seem right — almost all of which has to be directed to AGW scientists and proponents. I pay attention to both proponents and skeptics if they are credible; to neither if they are simply strident. (I’m ignoring the AGW tenet that “skeptic” and “credible” are never to appear in the same sentence…)

    Comment by Rod B — 17 Nov 2008 @ 4:35 PM

  407. Herve (405) writes: “I wonder if the most useful decision that climate modelers should make after the IPCC got the Nobel prize is not simply to postpone the next IPCC report (AR5), but to inform our governements that no report will be delivered until more ambitious and resolute decisions are made about the reduction of GHG emissions (yes we can !).”

    Dear Herve -and I know how the French treasure their Nobels, the real ones like de Gennes, Charpak or my dear professor Fert-, you surely must be aware that the Nobel Peace Prize is an award given by members of parliaments, not by scientists.

    Your candid comment sounds like a tacit acknowledgement that in spite of this Nobel public relation boost, this worldwide “coup” and the infinite mileage the media was willing to borrow against this asset, the fortune of your paradigm still remains in Nature’s hands more than in governments’…

    Herve (405) writes then: “In my opinion, IPCC simulations should never become a routine activity (as weather prediction has)…”

    As for the routine of weather predictions, the Monday referendum at the Cafe du Commerce would suggest this activity is still fraught with high risks… “yes, we can!”, hopefully for all of us, one day you may!

    A galactic citizen, taxpayer and scientist.

    Comment by Antonio San — 17 Nov 2008 @ 7:01 PM

  408. Global radiation/heat budget maps

    I find these to be one of the most informative representations of current climate.


    Is there:

    1. Any equivalent outputs for GCMs ?
    2. Comparisons between GCMs and satellite-data heat budgets ?

    Comment by Cumfy — 17 Nov 2008 @ 7:31 PM

  409. Herve, Your points are well taken. We will certainly never convince everyone–not even every honest man–of the reality of climate change. However, I do think we need to remain aware of the potential for “swiftboating” from anti-science types. We need to remain vigilant and counter disinformation.
    There is also the fact that while the evidence for anthropogenic climate change is cogent and unambiguous, we still do not fully understand all of the implications thereof. For this reason, improvements in climate models are crucial to mitigation efforts–if we can’t model the risk, we can’t bound it. So, in my opinion, we must advance on both fronts–confront decision makers with the necessity to address climate change now so we can buy time for the future while at the same time advancing our understanding of the implications of climate change. It is really a problem of mitigation in the face of uncertain and unbounded risk.

    Comment by Ray Ladbury — 17 Nov 2008 @ 9:02 PM

  410. > ambitious and resolute decisions are made about the
    > reduction of GHG emissions

    Given that the world seems to be meeting the Kyoto emission reduction levels so far, one approach would be to _replace_ the idled capacity with clean energy, rather than restarting the old dirty technology whenever the economy begins to revive.

    That would mean using the “stimulus” money (borrowed from the grandchildren) for building the new clean tech needed.

    I could see bailing out Detroit — with money committed to getting the supply chain recreated for new lightweight efficient best-available vehicles, for a decade, to take the dirty tech off the highway, for example.

    Bailing out the electric power industry — with money for distributed solar, even knowing solar’s getting better and cheaper as fast as computers, because investing in the _distributed_ part, a smart network, would be the big cost to pay in advance of better installations. It would need a lot of programmers and a lot of electronics.

    Bailing out the cities and the housing industry — with money spent on insulation, even for renters, putting people to work doing what’s needed to make the current housing stock last another 50 years while replacements are being figured out, but at much greater efficiency.

    Bailing out the fisheries industry because people need to eat — on the assumption we’re not going to destroy the breeding stock.

    Bailing out agribusiness — because continuing to put fossil fuel products (toxic waste, melamine, and the like) onto fields and call it “fertilizer” (per today’s NYT) is a dead end, and must stop.

    Could work. Couldn’t hurt, given where we are now.

    “Gridley dred” says ReCaptcha. Hmmm …

    Comment by Hank Roberts — 17 Nov 2008 @ 10:50 PM

  411. Cumfy, could you give a short description of what the heat flux map (407) shows? Second, does it say that the terra firma has no/little surface (?) heat flux, or that it just doesn’t measure it?

    Comment by Rod B — 17 Nov 2008 @ 11:55 PM

  412. Rodb, 406: “If I’m skeptical with one specific aspect of AGW science, I have to be skeptical of ALL of the science??!!? That’s nonsense.”

    Well, see, that’s where your bias or blinkered view manifests itself.

    Pro AGW debate and Anti AGW debate ARE THE SAME SCIENCE.

    Be skeptical of the “proofs” of it being wrong as well as the “proofs” of it being right.

    Reflect on why you think they are different sciences.

    Comment by Mark — 18 Nov 2008 @ 3:31 AM

  413. #376 David, could you give a link/reference please.

    Doesn’t yield anything obvious.

    Comment by Cumfy — 18 Nov 2008 @ 6:40 AM

  414. Antonio San, I’m sorry. Did you have a point? If so, I missed it among all the elliptical references.

    Comment by Ray Ladbury — 18 Nov 2008 @ 8:38 AM

  415. #411 Rod,
    Its a set of maps of (monthly/annual) plotting all heat components (solar,sensible,latent,long wave (thermal)and net (all summed))

    Since these heat components are so fundamental and must be central variables in all GCMs, I would anticipate that most modellers would have similar such GCM output plots as key diagnostic utilities in their model “toolkits”. I am just not aware of any being published/made available; hence my original question #408.

    The map (out of ~130 total), that seems to display as default is(net, annual) flux; which I guess is the one you perhaps are referring, and gives the “biggest picture” so to speak:

    Yes, net land flux is (measured not assumed)near zero, land having little thermal capacity.

    What I find most intriguing is the South:North distribution, with broadly speaking, the Southern oceans appearing to act as a heat sink and North Atlantic/Pacific as dispersers of heat.

    I was wondering whether this contributed to the North/South global mean temperature difference of 1.2C (earlier question), and how effectively GCMs model that.

    Comment by Cumfy — 18 Nov 2008 @ 12:15 PM

  416. Cumfy (413) —

    A. Abe-Ouchi, T. Segawa, F. Saito Clim. Past Discuss., 3, 301-336, 2007

    Comment by David B. Benson — 18 Nov 2008 @ 1:34 PM

  417. Cumfy, thanks. I find this very interesting. I’m a bit confused…, or reading it wrongly. It says positive flux is net downward which I would take as energy/power entering the surface, which shows a bunch of power entering the S. Pacific and a lot leaving the Arctic — seems backwards from what everyone says. Can you clear this up?

    So for all practical purposes the net net flux entering/leaving solid terra firma, including Antarctica, is zero with only minor exceptions. I find that fascinating as I would have never guessed. Since there is virtually no latent or sensible heat involved here, this means the sum of incoming solar (not including albedo), outgoing longwave, and incoming (returning) longwave is zero. True?

    My next question of wonderment: how on earth (pun intended) are these measurements made with such accuracy and granularity??

    Comment by Rod B — 18 Nov 2008 @ 9:22 PM

  418. This probably merits some FAQ attention, at least to explain the acronyms, more likely for what they’re doing:
    “CMIP5 – The Federation
    Next week there is a meeting which I hope will finalise the data requirements to participate in CMIP5….

    PCMDI is leading the development of a global data archive federation to support CMIP5. It needs to be global: conservative estimates of the volumes of data to be produced for CMIP5 are that there will be PB produced in the many modelling centres involved in producing conforming simulations….”

    Comment by Hank Roberts — 18 Nov 2008 @ 11:31 PM

  419. Gavin, it might be worth a mention in the FAQ of how climate models overlap with ocean chemistry models. Maybe with a pointer to those doing that kind of modeling; I really don’t know how much overlap there is.

    Notes from a recent conference here. Of course there’s much else out there. Just curious where these overlap.

    Given the rate and apparent irreversibility of ocean pH change in only a few decades, will that change assumptions used in some climate models that include ocean plankton species, like LeQuere’s work?

    Comment by Hank Roberts — 18 Nov 2008 @ 11:50 PM

  420. Regarding #405 by Hervé. The proposal that the IPCC withhold its valuable services until the world does something serious about the supposed threat of climate change is amusing. But the post does raise an important point, one that the FAQ do not address. This is the distinction between basic and applied modeling. Doing weather and climate forecasting for practical purposes is applied science, it is not scientific research. Weather and climate forecasters are not scientists, they are like engineers, using science.

    In science, forecasting is only done to test hypotheses, or at least to play what-if with exploratory hypotheses. What I do not see happening is climate models being used to test or play with hypotheses, that is, for basic climate science. There don’t seem to be any exploratory models, just applied models. This is a serious gap in the climate research program.

    David Wojick, Ph.D.

    Comment by David Wojick — 19 Nov 2008 @ 4:22 PM

  421. David Wojick — On the contrary, one was used here:

    Tziperman, Raymo, Huybers, and Wunsch, Consequences of pacing the Pleistocene 100 kyr ice ages by nonlinear phase locking to Milankovitch forcing, Paleoceanography, 2006.

    and more recently another by Thomas Crowley and William Hyde:

    Comment by David B. Benson — 19 Nov 2008 @ 4:58 PM

  422. David Wojick,
    Wow, you actually raised a relevant point. Once a threat has been demonstrated credible, the role of the model is to bound (from above) the risk it poses. This is quite difficult at this point, since some potential risks posed by climate change (e.g. Ocean acidification/anoxia, etc., global failure of agriculture,…) in effect spell the end of human civilization. In effect, we have unbounded risk. Under such circumstances, the proper risk mitigation strategy is to do whatever is possible without bankrupting the system to limit/avoid the risk while work continues to improve models/understand and pose more stringent upper bounds.
    David, your point argues far more for rapid action than it does for delay!

    Comment by Ray Ladbury — 19 Nov 2008 @ 6:10 PM

  423. Did you try Scholar?“+test++hypotheses”


    On the existence of multiple climate regimes – ► [PDF]
    … To test hypotheses about the existence of regimes, it is … 3. P ROBABILITY MODELS (HYPOTHESES … density appropriate for describing continuous climate variables in …
    Cited by 35

    Implications of global change and climate variability for vector-borne diseases: generic approaches …
    RW Sutherst – International Journal for Parasitology, 1998 – Elsevier
    … Models are tools with which to develop and test hypotheses. … geographical distribution
    and seasonal phenology of target organisms in relation to climate. …

    Cited by 63

    Comment by Hank Roberts — 19 Nov 2008 @ 6:32 PM

  424. Rod
    I’m reading the maps the same way. (Hope we’re right!)
    The Kuroshio and Gulf Cuurents are notorious exporters of heat to the Northern Hemisphere (peaking at 1000 Wm-2).

    More generally, I claim no real expertise as such, but can only recommend (highly) some stuff from a doyen of heat-budgetry:

    Excellent Overview

    Meridional Heat Transport (Detailled+)

    Detailled Critique of JRA (the maps I originally referenced)

    (Seems all these types of analyses (inc JRA) are subject to methodological, sytematic, and measurement biases. )

    (Preprint)Gives important update on the classic global mean heat budget diagram including increased effect of GHG and apparent decrease in global dimming since original diagram.

    Comment by Cumfy — 20 Nov 2008 @ 3:02 PM

  425. David Thanks for the link

    Comment by Cumfy — 20 Nov 2008 @ 3:03 PM

  426. The discussion of feedbacks and fallouts is interesting in that it reveals some of the misunderstandings people have. One in particular I have encountered contends that, yes, CO2 is a greenhouse gas, but that the feedbacks have been inflated to produce a high CO2 sensitivity. People do not seem to understand that CO2 does not have its own set of feedbacks. Rather most feedbacks tend to be driven by temperature, and the system doesn’t care whether the extra watts are coming from greenhouse gasses or increased insolation. If you change the feedbacks significantly, you wind up with a model that fails dramatically–not just with respect to CO2 forcing.

    reCaptca reveals its politics: fault Laborite

    Comment by Ray Ladbury — 23 Nov 2008 @ 8:05 AM

  427. Re:#177/178
    Barton Paul Levenson, I know but I think that the faktors I wrote above are more important.

    Hank Roberts, I assume that the total amount of nitrogen is almost constant over the last billion years. So change in oxygen means change in total pressure.
    I doubt that pterosaurs or other flying animals can used to estimate the total atmospheric pressure directly. Because drag and lift is changed by total pressure in the same way, the direct effect of oxygen for respiration is more important I think. Note that birds can currently fly in high altitude.

    I hope still for an at least particular answer to my questions in #173. Is there really no publication on these subjects yet? Please look on my question again. Thanks.

    Comment by Uli — 27 Nov 2008 @ 4:04 AM

  428. Uli, what have you done since you asked, to try to look these questions up? Where have you looked, what did you read to establish the lack of publications? Whose help did you ask?

    I doubt we could have reached 10x CFCs before losing the ozone layer; look up Paul Crutzen’s Nobel Prize speech, it’s online.

    If you haven’t found anything in the journals on linearity of the effect of those molecules at 10x concentration — assuming you’ve asked a good reference librarian for help and she’s not been able to find anything to answer you — I’d speculate that nobody’s published on that narrow question because all the other feedbacks at that point would be so complex as to muddy the waters, so to speak. If you haven’t asked a reference librarian, try that approach.

    As to your assumption about nitrogen and total pressure, I’d check that first. Same advice on how to check, if you haven’t asked for help beyond us amateur readers on blogs.

    How much gas is dissolved in the oceans, for example, and would also have to be eliminated somehow before atmospheric levels change? Remember even a massive CO2 change would be handled by natural biogeochemical cycling over a long time span, its only our 100x natural rate of increase that’s changing ocean pH. I’d bet the same is true for any other gas — the ocean’s a far greater buffer over long time spans than it can be over the short time span of human change.

    Comment by Hank Roberts — 27 Nov 2008 @ 9:19 AM

  429. My question to this distinguished discussion group is whether anyone has ever modeled building a dam across the Strait of Gibraltar to combat rising sea levels in the Mediterranean?

    The Strait is only 14.2km across and such a dam is technically feasible. In a previous Ice Age an ice wall across the Strait dammed the Mediterranean.

    I’m sure such a dam would have many unfavourable environmental consequences. However, I wondered whether blocking the hotter Mediterranean sea away from the rest of the World’s oceans would have any favourable effect on world ocean temperatures or would the result be negligible?

    Comment by Brian — 28 Nov 2008 @ 3:14 AM

  430. Pielke, Sr. has posted a direct response to ‘FAQ’ for folks interested in the conflict of ideas. My apologies if someone has already noted the link:

    Comment by wmanny — 30 Nov 2008 @ 2:53 PM

  431. Slightly off-topic, but have you considered an ongoing topic listing summaries (abstracts) for current significant publications and discussing their significance? Two recent ones come to mind:

    Water vapour warming

    Carbon is forever

    [Response: Actually, we did think about an online journal club which could be hosted by different people each week and discuss interesting or controversial papers outside of the simply the ones that get a lot of press. Comments anyone? – gavin]

    Comment by Al S. — 30 Nov 2008 @ 5:19 PM

  432. > online journal club
    Yes please. I’d like to watch and learn.
    Serious filters for folly, please.

    Comment by Hank Roberts — 30 Nov 2008 @ 6:58 PM

  433. Brian:
    First hit is:
    [HTML] ►Climate Control Requires a Dam at the Strait of Gibraltar
    RG Johnson, MIA Initiation – Eos, 1997 – Vol. 78
    Fig.3. a) Location of the proposed dam on the sill across the Strait …

    Comment by Hank Roberts — 30 Nov 2008 @ 7:03 PM

  434. gavin,

    Some of the most interesting posts at RC are ones (especially on ice) that involve discussion on “the latest stuff” which are not well known. This would be a good aside to tutorials on stuff which are well known or on spending too much time addressing nonsensical talking points.

    Comment by Chris Colose — 30 Nov 2008 @ 7:09 PM

  435. [Response: Actually, we did think about an online journal club which could be hosted by different people each week and discuss interesting or controversial papers outside of the simply the ones that get a lot of press. Comments anyone? – gavin]

    I would definitely like to see something like that. One of RC’s great contributions is opening science literature to the public outside the normal scientific circles.

    Maybe writing something like the editor’s choice section in the Journal Science where the findings of interesting papers are summarized and then adding some commentary about the paper. This would be very interesting and useful. The commentary could discuss the merits of the paper or how it changes what is known in the area discussed.

    Comment by Joseph O'Sullivan — 1 Dec 2008 @ 1:41 AM

  436. Hank – thanks for the response. I did a google search on damming the Strait of Gibraltar and found a few hits. However, I couldn’t get a sense of whether it is a seriously accepted idea or one on the fringes of science (and whether it has ever been studied / funded seriously)??

    My question was prompted as last week I attended Dr James Hansen’s evidence session to the UK Environmental Audit Committee. A friend had told me that Hansen was ‘a legend’ and the meeting was open to the public. It was not well attended (circa 20 people) (or well reported in the media). The general public and politicans’ attention is elsewhere on the recession… I was frustrated in the meeting at how all the politican’s questions related to measuring CO2 emissions and whether the IPCC process could be improved. Very few questions were on solutions.

    People have now generally accepted scientific theories on global warming, and I, for one, would like to see more research/studies on solutions and less research on measuring the problem in greater and greater detail and on IPCC reports. Simply measuring the problem and then proposing increasingly unrealistic targets for globally co-ordinated CO2 reduction doesn’t seem to be enough. Is there a plan B? Perhaps should seek open a sub group on fringe theories to give some small air time to the other theories/solutions being considered (such as ocean mirrors etc.).

    Comment by Brian — 2 Dec 2008 @ 4:42 AM

  437. Journal club is an excellent idea

    Possibly get authors involved ?

    Comment by Cumfy — 2 Dec 2008 @ 6:57 PM

  438. > damming the Strait of Gibraltar

    It’d probably be easier to empty out the Great Lakes, you’d only have to convince two nations to allow it. The Mediterranean involves a lot more.

    But going carbon-neutral and accelerating the rate at which CO2 comes out of the atmosphere will be enough, and far more directly related to what we know about the problem.

    This may help when considering any huge geoengineering idea with dubious effects:

    Comment by Hank Roberts — 2 Dec 2008 @ 7:21 PM

  439. Thanks I found that link hilarious! :-) What verse do you think that the the world is currently up to?

    I agree that draining the Great Lakes would be easier than damming the Strait of Gibraltar (as you say, less countries are involved). I would put them in the following order of difficulty:

    1. draining the Great Lakes
    2. convincing the nations bordering the Mediterranean to build a dam in the Strait of Gibraltar
    3. achieving a scenario where all the countries in the world go carbon neutral.

    Comment by Brian — 2 Dec 2008 @ 8:11 PM

  440. The correct lyric is
    “… wiggled and jiggled and _tickled_” …

    There’s good science recommending controlling CO2 (even ignoring atmospheric physics, considering only ocean chemistry). Geoengineering won’t help the oceans. Look up Peter Ward for the worst case scenarios.

    Comment by Hank Roberts — 2 Dec 2008 @ 8:48 PM

  441. Speaking of Peter Ward

    Hydrogen Sulfide Extinction
    EARTH SCIENCE Impact from the Deep
    … heat and gases emanating from the earth and sea, not asteroids, most likely caused several ancient mass extinctions…. By Peter D. Ward
    June 09, 2007

    available in RTF form:

    how would we do if the atmosphere dropped to 15 percent oxygen instead of 20 percent? Here’s a model worth a look:

    Berner R.A.
    GEOCARBSULF: A combined model for Phanerozoic atmospheric O2 and CO2
    (2006) Geochimica et Cosmochimica Acta, 70 (23 SPEC. ISS.), pp. 5653-5664.

    “Atmospheric oxygen shows a major broad late Paleozoic peak with a maximum value of about 30% O2 in the Permian, a secondary less-broad peak centered near the Silurian/Devonian boundary, variation between 15% and 20% O2 during the Cambrian and Ordovician, a very sharp drop from 30% to 15% O2 at the Permo-Triassic boundary, and a more-or less continuous rise in O2 from the late Triassic to the present.”

    Comment by Hank Roberts — 2 Dec 2008 @ 8:54 PM

  442. Thanks, I can see why they haven’t made movie out of Peter Ward’s theories – too depressing!

    I’m still not convinced that geo-engineering, in conjunction with doing everything else achievable, won’t help the climate.

    For example, it might well be that the results of properly funded study that climate models suggest that the dam only needs to stay closed for 5 years to have a positive effect on ocean temperatures. After that you just open it. That’s the beauty of modern dams – they can be open or closed at the press of a button. If at any time climate scientists dislike the results the dam is having they just press the open button. How many disruptive theories can be switched off that easily?

    Comment by Brian — 3 Dec 2008 @ 5:03 AM

  443. Dear All,

    A quick question,

    the models account for the temperature anomalies in a largely convincing way (within 0.1C or so), and as stated above they are not tuned to achieve this. Yet they can have very different implied climatic sensitivities.

    The question is do they give the absolute temperatures to the same accuracy?

    This a bit of a tricky question as it is possible to be confident of the temperature record anomalies, HadCRUT3, etc., but not be certain of the precise absolute global average baseline temperature to the same accuracy.

    Best Wishes

    Alexander Harvey

    Comment by Alexander Harvey — 5 Dec 2008 @ 11:39 AM

  444. Brian, did you find anywhere anyone actually suggesting blocking Gibraltar would have some predictable effect on climate? Where’s the idea coming from that you think it might be useful?

    Comment by Hank Roberts — 5 Dec 2008 @ 12:00 PM

  445. Thanks for this FAQ, very useful & informative. One naive question I have: How is a “global average temperature” measured/calculated/estimated? Is it a theoretical temp. that the atmosphere would have for a given heat content, assuming thermodynamic equilibrium? A time-integrated statistical mean of weather station measurements? Or … ??

    Comment by Scott M. — 6 Dec 2008 @ 1:14 PM

  446. Scott M. (445) — AFAIK the surface temperature products use monthly weather reports from ground stations and something similar from ship reports of SSTs. These are then weighted by area and then averaged.

    Determining troposhere temperatures from satellite data is much more complex.

    Comment by David B. Benson — 6 Dec 2008 @ 3:54 PM

  447. Hank – the 1997 Johnson paper you referred to earlier, Climate control requires a dam at the Strait of Gibraltar, was the main source I could find, where an effect on the climate was predicted.

    I wondered whether it had been studied or dismissed as an idea since using more up to date climate models (or different types of dams). Looking at it very simplistically, you would think that insulating the rest of the world’s oceans from the hotter Mediterrean sea should have some helpful cooling effect on ocean temperature. However, I have no idea what the follow on consequences might be for ocean currents, salt levels, rainfall etc.

    Comment by Brian — 8 Dec 2008 @ 5:14 AM

  448. A very simple “climate model” is to divide up the atmosphere per person and look at the effect that burning a ton of carbon has on one share of atmosphere. The atmosphere weighs about 6 million gigatons (billion tons) so that is a million tons per person. If I burn a ton of carbon (MW = 12) I increase the concentration of CO2 in my hypothetical sealed share of air (MW = 29) by 2.4 ppm (by volume), correct?

    I think this simplified “climate model” is essential. It illustrates the possibility that all the other factors, like carbon sinks (oceans, algae and plants), are being overwhelmed by our burning of fossil fuels.

    Comment by Davidha a citizen — 8 Dec 2008 @ 10:55 AM

  449. Brian, here’s now to find out:

    Click under the paper, where it states the number of later papers citing it (don’t take that as the absolute number, various citation tracking services exist and criteria vary, but it’s a good start — a reference librarian can give you a far better answer than I can).

    Comment by Hank Roberts — 8 Dec 2008 @ 1:52 PM

  450. (PS, for going beyond this one example, on how to find subsequent cites generally — I tried various search strings in Scholar before hitting on the one that pulled up the paper; if you are trying to find a paper in Scholar and your first search doesn’t work, usually some fragment of its title, authors, or journal reference will locate it — just experiment.)

    Comment by Hank Roberts — 8 Dec 2008 @ 1:55 PM

  451. I just want to add that Piaget is considered the progenitor of constructvism and he was Biologically oriented, however, the resurgence of his ideas in light of modern brain scans and cognitive psychology really changed the paradigm in the 1970’s and 1980’s.

    Comment by jcbmack — 8 Dec 2008 @ 2:37 PM

  452. Dear All,

    Re: my 443,

    I can now answer part of my own question:

    The NCDC havew provided us with the absolute temperatures underlying their 1901-2000 baseline at:

    one can clearly see one of the reasons that we commonly use anomalies.

    Whereas the global mean is 13.9C the seasonal variation is +/-1.9C (July/January), clearly showing the asymmetry between the Northern and Southern hemispheres, I think.

    Given those figures can any one tell me the following:

    How well do any of the models match these figures?


    How does one get access to CMIP3 data? (When I try to access the registration page:

    I get an error 403 (Forbidden)

    Any help will be very gratefully received.

    Best Wishes

    Alexander Harvey

    Comment by Alexander Harvey — 10 Dec 2008 @ 2:02 PM

  453. Dear All,

    Re: my 452,

    I have found this page:

    Which in Section 2. Present Day Climate: Subsection a: Global and annual means

    gives a brief statement regarding CMIP2 control runs:

    I quote:

    “Taking into consideration all of the observational uncertainties, it appears that the actual value of surface air temperature was between 13.5°C and 14.0°C during the second half of the 20th Century and roughly 0.5°C less in the late 19th Century. It therefore seems that several of the models (which simulate values from less than 12°C to over 16°C) are in significant disagreement with the observations of this fundamental quantity.”

    It should be noted that the models assume somewhat differing levels for CO2 and the solar constant.

    In all I am not surprised by the spread of around +/- 2.5C, one would have to get a lot of things right to get this close.

    There is much more to read on their web page and many figures worth having a look at.

    Best Wishes

    Alexander Harvey

    Comment by Alexander Harvey — 11 Dec 2008 @ 9:12 AM

  454. The EdGCM files are no longer available for download. Are there any other Windows models available? Are there any open source model projects underway?

    [Response: Oh dear. I’ll look into this and see what the story is. – gavin]

    Comment by Richard C — 12 Dec 2008 @ 8:00 AM

  455. Re#428:
    Hank Roberts,
    sorry for the late answer. I have searched some journals, and used google and google scholar but maybe I have not the right keywords.
    The best I have found
    Myhre “Infrared absorption cross section, radiative forcing, and GWP of four hydrofluoro(poly)ethers”
    I cite “In both models the calculations are performed with 0.1 ppbv of the gases to ensure that the weak limit approximation is valid,…”
    An upper limit from the absorption cross sections in the pictures are about 10 to 20 ppbv depending on the gases. But this maybe too high if the resolution is too low.
    So maybe a linear increase in radiative forcing do not overestmate it too much.

    The N2 and O2 dissolved in the ocean are only 1 or 2 percent of the amount in the atmosphere. CO2 is the only main gas of the atmosphere which has higher solubility.
    In #441 you cite Berners ‘GEOCARBSULF’, as a source for possible large change in oxygen, and so total pressure, I asked about the consequences for the total radiation budget.
    I does not expect that amateur readers can (easyly) answer this questions. But I hoped that a few of the scientists working in this field read this and maybe know a relevant paper or other answer.

    Comment by Uli — 12 Dec 2008 @ 12:03 PM

  456. Thanks Uli. I can’t help further as an amateur, but you’re right, perhaps as this thread is reviewed for material for use in a FAQ someone knowledgeable can answer your question.

    Also for possible FAQ use, this might be an area of change worth noting in a discussion of ocean circulation:

    Comment by Hank Roberts — 14 Dec 2008 @ 12:23 PM

  457. Apologies if this is covered elsewhere on this excellent site but one of the points made by skeptics concerns the warming footprint or greenhouse signature (I think in the tropics 10KM up?) which the IPCC models predict. The argument is that it has not been found and therefore either the model is wrong or CO2 is not causing the warming. Any links/advice appreciated.

    [Response: Part i,Part ii, Part iii. – gavin]

    Comment by Chris — 19 Dec 2008 @ 12:23 AM

  458. Your description at the start of this thread of how climate models use observed data is along the lines (forgive the oversimplification) of
    i) build the best mechanistic model we can
    ii) start from some observed initial point
    iii) ‘forecast’ the results from thr IP to now
    iv) assess the fit of the predictions to the observations

    Presumably poor fits motivate you to change model components – indeed it seems likely than one trigger for publication is that you have a substantially better fit than the previous published model.

    Question – how do you prevent over-fitting to the observed data with this algorithm 0 indeed don’t you almost guarantee it, since you likely don’t publish models with a poorer fit?

    [Response: You separate the observations used to develop the model from those used to evaluate it. Specifically, we use the climatology of temperature, water vapour etc. to test the algorithms and their response to climate change (such as Pinatubo, or the 20th C) to evaluate the model. We don’t tweak the algorithms to get a better sensitivity and it would be next to impossible to do in any case. We do add in effects that are demonstrated to be important – such as more complex oceans, more detail in the stratosphere etc. but only things that have an a priori reason to be there. We don’t tune individual parameterisations to get better trends over the 20th C. – gavin]

    Comment by Ian — 4 Jan 2009 @ 2:01 PM

  459. Thanks

    To be clear, I wasn’t assuming that you were ‘tuning to to fit’ current data.

    But, I’m not completely sure you wouldn’t get some over-fitting without any parameter tweaking/tuning – the public record might act essentially as a GA. I guess you end up relying on the constraints of doing the physics accurately, so it’s probably not as bad as the awful problems we sometimes have with complex non-mechanistic models.

    Comment by Ian — 4 Jan 2009 @ 5:48 PM

  460. # 42 In response to Craig Allen

    “Can you provide an example of any economic model that has been anywhere near as successful?”

    Actually I can. Just as in climatology, economic models have to explain known facts before they are widely accepted. The Solow (1956) model, for example, attempts to mimic some long-term stylized facts of advanced economies, and it is indeed able to replicate them. For instance, the Solow model conforms to the following empirical facts: 1) per capita output growth is approximately constant over long periods of time; 2) the share of income that comes out of labor is approximately constant over time; 3) the capital to output ratio is approximately constant over time; 4) the real hourly wage rate grows approximately at the same rate of output per capita; 5) the capital rental rate is approximately constant over time.

    More recent models are able to replicate these facts but also replicate other, more complex empirical facts. The basic Real Business Cycle model, for example, explains roughly 70% of economic fluctuations of the post-war US economy using only technological shocks, that is, labor-augmenting productivity shocks. Other models explain the long-run rate of growth of economies, the labor market behavior of agents, etc.

    These models have been used to study extreme episodes or interesting topics like the Great Depression, the Industrial Revolution, and the size of the informal economy.

    Of course, numerous other models have been proposed that failed to mimic reality on several accounts and have therefore been abandoned. But some basic models and their extensions have stood the test of time and are widely used and trusted upon.

    I can give you detailed bibliographic references on all these claims but I believe that is unnecessary here.

    In the 70s, Robert Lucas, a brilliant economist and Nobel prize winner, warned economists about the risks of using historic statistical correlations alone to predict or simulate economic systems. Doing so assumes that expectations of agents are fixed. But since they can change due to policy changes, the use of the previous estimations, based solely on correlations, must be abandoned if we are to study the impact of policies. In order to unearth the true economic parameters that govern the agents’ actions, one needs a sound theoretical foundation, and then estimate those parameters conditional on the model that we use.

    Now I think this criticism applies to climatology, so you guys have to be careful. In your case, assuming that human activity changed the climate, past correlations should be invalid or at least incomplete. So using them in your models might be inaccurate or wrong. And the fact is that, like economic models, a GCM may conform very well to past experiences but be terribly wrong in predictions or simulations of policy changes.

    Comment by Antunes — 8 Jan 2009 @ 11:21 AM

  461. Antunes says: “In your case, assuming that human activity changed the climate, past correlations should be invalid or at least incomplete.”

    That is why global climate models are not statistical models, but rather dynamical. Past experience is important only in terms of identifying forcints, etc. and validating the models. Uniformitarianism is a well established principle in Earth sciences–the basic physics doesn’t change

    Comment by Ray Ladbury — 8 Jan 2009 @ 12:48 PM

  462. Antunes (460) — The early anthropocene hypothesis has been well studied by W.F. Ruddiman and others. Ruddiman has written the popular “Plows, Plagues and Petroleum” and papers on his web site are readily accessible. In addition, he has a guest thread here on RealClimate.

    While others have recently aided in the verification of the central theme of early AGW, Ruddiman’s popular book is a good place to start. While reading this, note that no actors changed their motivations, AFAIK.

    Comment by David B. Benson — 8 Jan 2009 @ 4:33 PM

  463. Re:Antunes(#460),

    this sounds interesting. I have a few questions.
    Does these models like the Solow (1956) model or the basic Real Business Cycle model, also applicable for other economies as the US?

    And the long time behaviour of these models.
    Can for example the economy of the UK from year 1000 to 2000 successfull simulated, provided someone makes some usefull assumptions on the unknown needed data of the past?

    “In your case, assuming that human activity changed the climate, past correlations should be invalid or at least incomplete. So using them in your models might be inaccurate or wrong.”
    Yes, of cource. Therefore physically based (climate) models like GCMs do not use past correlations at all.
    Physical models are intended to make predictions of what happens if some parameters change.

    Do some economic models use past correlations (of time series)?

    Comment by Uli — 9 Jan 2009 @ 12:04 PM

  464. As a fairly well educated non-scientist, the comment in #21 about satellite measurements resonates — if there’s more heat coming in than going out it must be staying here. Pretty convincing argument that eliminates all the FUD.

    Is there good science behind the satellite observation concept?

    Another (cross discipline) question regarding climate: The Vikings expansion ca 1000 AD is typically explained as the result of a warming trend the fueled population growth in Northern areas. Do climate models explain this?

    Regarding economic models — they actually are based on physics. Unfortunately they are based on physics as it stood before the discover of the 2nd law of thermodynamics, which is part of the reason why they don’t work. The book, “The Origin of Wealth” does a really good job of explaining it in detail, but another thing they don’t take into account is that economic outcomes are based on individual decisions made by vast numbers of people. Economic systems are not random, but neither can they be predicted with any accuracy very far into the future. Pretty much like the weather.

    Suggestion for the FAQ: In the definitions section you may wish to define “climate.”

    Comment by Pyper — 9 Jan 2009 @ 12:13 PM

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