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Musings about models

Filed under: — gavin @ 20 August 2007

With the blogosphere all a-flutter with discussions of hundredths of degrees adjustments to the surface temperature record, you probably missed a couple of actually interesting stories last week.

Tipping points

Oft-discussed and frequently abused, tipping points are very rarely actually defined. Tim Lenton does a good job in this recent article. A tipping ‘element’ for climate purposes is defined as

The parameters controlling the system can be transparently combined into a single control, and there exists a critical value of this control from which a small perturbation leads to a qualitative change in a crucial feature of the system, after some observation time.

and the examples that he thinks have the potential to be large scale tipping elements are: Arctic sea-ice, a reorganisation of the Atlantic thermohaline circulation, melt of the Greenland or West Antarctic Ice Sheets, dieback of the Amazon rainforest, a greening of the Sahara, Indian summer monsoon collapse, boreal forest dieback and ocean methane hydrates.

To that list, we’d probably add any number of ecosystems where small changes can have cascading effects – such as fisheries. It’s interesting to note that most of these elements include physics that modellers are least confident about – hydrology, ice sheets and vegetation dynamics.

Prediction vs. Projections

As we discussed recently in connection with climate ‘forecasting‘, the kinds of simulations used in AR4 are all ‘projections’ i.e. runs that attempt to estimate the forced response of the climate to emission changes, but that don’t attempt to estimate the trajectory of the unforced ‘weather’. As we mentioned briefly, that leads to a ‘sweet spot’ for forecasting of a couple of decades into the future where the initial condition uncertainty dies away, but the uncertainty in the emission scenario is not yet so large as to be dominating. Last week there was a paper by Smith and colleagues in Science that tried to fill in those early years, using a model that initialises the heat content from the upper ocean – with the idea that the structure of those anomalies control the ‘weather’ progression over the next few years.

They find that their initialisation makes a difference for a about a decade, but that at longer timescales the results look like the standard projections (i.e. 0.2 to 0.3ºC per decade warming). One big caveat is that they aren’t able to predict El Niño events, and since they account for a great deal of the interannual global temperature anomaly, that is a limitation. Nonetheless, this is a good step forward and people should be looking out for whether their predictions – for a plateau until 2009 and then a big ramp up – materialise over the next few years.

Model ensembles as probabilities

A rather esoteric point of discussion concerning ‘Bayesian priors’ got a mainstream outing this week in the Economist. The very narrow point in question is to what extent model ensembles are probability distributions. i.e. if only 10% of models show a particular behaviour, does this mean that the likelihood of this happening is 10%?

The answer is no. The other 90% could all be missing some key piece of physics.

However, there has been a bit of confusion generated though through the work of – the multi-thousand member perturbed parameter ensembles that, notoriously, suggested that climate sensitivity could be as high as 11 ºC in a paper a couple of years back. The very specific issue is whether the histograms generated through that process could be considered a probability distribution function or not. (‘Not’ is the correct answer).

The point in the Economist article is that one can demonstrate that very clearly by changing the variables you are perturbing (in the example they use an inverse). If you evenly sample X, or evenly sample 1/X (or any other function of X) you will get a different distribution of results. Then instead of (in one case) getting 10% of models runs to show behaviour X, now maybe 30% of models will. And all this is completely independent of any change to the physics.

My only complaint about the Economist piece is the conclusion that, because of this inherent ambiguity, dealing with it becomes a ‘logistical nightmare’ – that’s is incorrect. What should happen is that people should stop trying to think that counting finite samples of model ensembles can give a probability. Nothing else changes.

167 Responses to “Musings about models”

  1. 51
    Steve Horstmeyer says:

    #8 Neil B.

    Be sure that any GW/AGW skeptics that push the “return to equilibrium” argument realize that it may not be (probably will not be?) the same equilibrium.

    In a number of discussions I have had the term “equilibrium” is treated as it were an unchanging absolute state of a system. There are many equilibria and some may not be much fun for human existence.

    #22 Alistair McDonald

    Your meteorology is not on a sound scientific basis. Yes you can calculate the decrease of density of the lower atmosphere because of an increase in water vapor. However your statement implicitly assumes it will all stay near where it is evaporated, much will be advected (transported quasi-horizontally) away.

    But a greater flaw in your argument is that the static stability of the atmosphere will be fundamentally changed by an expected increase in water vapor.

    To a high degree of accuracy much of the atmosphere is in hydrostatic balannce – the downward gravitational force balances the upward-directed vertical pressure gradient. To get air to rise there must be a mechanism to upset this balance.

    An increase of water vapor cannot do this (and create spontaneous upward motion as you imply) because the water vapor fraction of air is constrained by the amount of kinetic energy available to do the work of evaporation.

    With an Arctic Ocean air/sea interface temperature of 0C the maximum amount of water vapor in the lower atmosphere at equilibrium (i.e. saturation), measured as the partial pressure of total atmospheric pressure would be less than 1% of total atmospheric pressure. At 30C, a tempeature no one expects even in an ice-free Arctic Ocean with a runaway greehouse warming scenario, the fraction of total atmospheric pressure at equilibrium is around 3%. Though the value triples the maximum of 3% is a value much too small to overcome the larger magnitude hydrostatic balance.

    So an increase of water vapor because of increased evaporation created by GW/AGW “will not a tipping point make” by upsetting the hydrostatic balance.

    The greater influence of water vapor increases will be once air is lifted, condensation has occurred and rainfall becomes more plentiful.

    Steve Horstmeyer

  2. 52
    W F Lenihan says:

    Who were the referees that peer reviewed the cited article in the Economist?

  3. 53
    Steve Bloom says:

    Re the Schwartz article: I’m not technically qualified to critique something like this, and there’s very little point in my putting the effort into becoming qualified in that way, but let me describe how I lok at these things (for the benefit of Doug Lowthian in particular): Read the abstract, read the introduction, read the conclusion, and then skim the contents. The purpose of doing this is to not only understnad the basic thrust of the paper but to turn up the caveats, which will indicate how much weight the author thinks ought to be put on the paper.

    In the case of this paper, the next to last paragraph tells the tale: It’s a thought experiment using a simple model that Schwartz does not expect will be correct, although he believes that the approach he takes may have some value. The denialists, it seems, never look for the caveats.

  4. 54
    DocMartyn says:

    “If you evenly sample X, or evenly sample 1/X (or any other function of X) you will get a different distribution of results.”

    Absolutely true, fits are forced to the end of decay components as data is normally taken on a timebase so you have very few data pints at the beginning, where change is the greatest, and very few at the end, where change is the smallest. There are ways around it. Typically, fits are done by comparing the data set to a model, and fit to get the smallest sum of squares Sum of (model-real)^2.
    However, you can multiply the squares at time = t, with an exponential function so that the amount of information is reflected in the fit.
    This is only a rough and ready solution, but it is possible to get good fits in enzyme kinetics using this methodology (using the M-M equation instead of an exponential).
    Indeed, what should be fitted is the “information” in the system, but you need to do the fit before you know where the information is.
    There is a lot of work in this area in information theory, but to be honest, I really do not understand it.

  5. 55
    Jim Eager says:

    Re 24 Dean: “What is the source for more Cat 5 hurricanes? the Hurricane center has denied any such claim and frankly, they’d know.”

    Georgia Institute of Technology and the National Center for Atmospheric Research for starters:

  6. 56
    Marcus says:

    On Bayesian priors and probability distribution generation: doesn’t the work of Forest et al. (GRL 2006) and Webster et al. (Climatic Change 2003) address some of these issues? In the former paper input distributions are not generated arbitrarily but rather derived from historical data, and in the latter these distributions are used to generated pdfs of future climate in a consistent fashion. Of course, these generated pdfs don’t address issues like the probability of poorly understood tipping points, but they are certainly a step up from using or model ensembles to define pdfs (note that I think that both model ensembles and the .net experiment are very useful, just not for pdf definition). (Disclaimer: I work with the authors I’m citing)

    [Response: Indeed. The problem discussed in the Economist is not related to the use of priors per se, but to the assumption that an appropriate choice of priors allows you to sample model parameter space in a probabilistic way. Mind you, some of the discussion on the influence of priors in the Forest et al papers is a little overblown, since their importance reduces every time you add in new information (as Annan and Hargreaves 2006 showed). I too agree that the CPDN ensembles are interesting though. – gavin]

  7. 57
    steven mosher says:

    gavin, stupid question time.

    I know somewhere here abouts you have explained “climate sensitivity ” Could you give a quick
    definition. And then an explaination of how one estimates the varience of the metric

    [Response: – gavin]

  8. 58
    Lynn Vincentnathan says:

    RE #39 & #35, and “the Venus effect.”

    Well, a lot of people have trouble understanding analogies (and poetry, for that matter). But then again many people don’t have such trouble. I would guess most people grasp them. That’s why they’re in such heavy use.

  9. 59
    John Mashey says:

    re: #52 & The Economist
    The Economist is not a peer-reviewed scientific journal.

    However, from multiple firsthand experiences, IF you send a pleasant note (which doesn’t have to be intended as a letter to editor to be printed) to them that basically says:
    1) “This is in error, facts…”

    2) “OK article, but you need to know about XXX, see URL, a good source on this topic.”


    a) Sometimes later articles show they go do more homework.
    b) Sometimes you even get a person-generated email in reply.
    c) and some.times they even invite you to stop by next time you’re in London.

    I already took action 2) on this topic yesterday.

  10. 60
    Daniel C. Goodwin says:

    Re message 48 where Chuck Booth points out the playful allusion to Watson and Crick’s

    It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.

    What fun! Patriotism is dangerous medicine to fiddle about with, however, particularly in the current atmosphere where the percentage of American exceptionalism is increasing in toxicity, when calculations more fully account for biogeophysical feedbacks.

  11. 61

    Re #38

    Ref. #41

    Re #46

    Dear Richard,

    I agree with you. It is an unscientific assessment. But I travel around the world quite a bit and I am hearing this type of comment more and more. I did not wish to infer that it was scientific assessment, merely an observation that has a modicum of relevance to the discussion.

    Besides the certain places that are getting cooler are fewer than the places that are getting warmer :)

    Beyond that, the physical evidence in the melting of the glaciers is pretty much the smoking gun. Combine that with the observed increase in SST and stronger storms, et cetera…

    By the way, I am not submitting the comments for peer review.

    Thanks for the input,

  12. 62
    Ike Solem says:

    Eric (skeptic) says: “What they forget is there are negative feedbacks elsewhere, particularly in the weather in a wetter world. Tim pointed one out in the Sahara.”

    I think you’re entirely missing the point – there is significant uncertainty in the regional predictions, and much less uncertainty in the global predictions. Look at the observations and forget about the models for a second:

    There, they look at the tropospheric and stratospheric temperature trends for 1979-2005 and find that there is a poleward shift of the tropospheric jet streams and their associated subtropical dry zones.

    Other measurements show the increasing trends in Indian, Atlantic and Pacific seas-surface temperatures. The notion that higher sea-surface temps means more evaporation means more precipitation over Africa is just too simplistic.

    As yet another contributing factor, the deforestation in West Africa means less evapotranspiration over land surfaces and a possible related decrease in precipitation.

    Any honest person would include all these factors – the anthropogenic CO2 forcing, the intrinsic natural climate variability, and the effects of deforestation. What the denialists are doing is just picking those factors that support the notion of ‘beneficial natural global warming uninfluenced by humans’ and ignoring all the others.

    If you really want to understand what’s going on, you can’t leave anything out. If you want to promote a certain position, than you only include evidence that supports that position – which is the difference between scientific work and public relations work.

    Note – people are just now starting to come up with physical models that explain the formation of jets in the atmosphere. One concept here is ‘jumping jets’ – a possible example of a planetary-scale transition or tipping point. It refers to the tendency of some jets to reposition themselves (and their associated climates) suddenly when the climate forcing reaches some threshold level. The change in jet stream positions over the US and the Atlantic during El Nino / La Nina is an example of this phenomenon. This helps explain the apparent contradiction between high sea surface temperatures and expanding dry regions. The drying American Southwest is another example of this effect.

  13. 63
    Mark Hadfield says:

    Re 30: “His work depends on (among other things) the assumption that there’s only *one* characteristic timescale for global climate. Physically this would seem to be impossible; each component of the climate system (atmosphere, ocean, cryosphere) will necessarily have a different characteristic timescale.”

    You’re understating the wrongness of Schwarz’s assumption, Tamino. Each of these components on the climate system has a whole range of time scales. Specifically the ocean (which is the component that is most relevant here) has a time scale for absorbing heat in its top metre or so, a longer time scale for mixing this heat down to the maximum seasonal mixed layer depth, a longer time scale again for subducting heat into the permanent thermocline and a very long time scale for warming up the whole thing. Thus between 1961 and 2003, global average SSTs increased by about 0.45 degC (AR4 WG1 Fig 3.4a), the average temperature of the layer to 700 m increased by about 0.1 degC (AR4 WG1 chap5 Sec & Exec Summary) and the average temperature of the entire ocean increased by 0.037 degC (AR4 WG1 chap5 Sec

    Sorry this is a bit off-topic :-)

  14. 64
    Alex N says:

    I understand that permafrost thawing has sometimes been presented as a “tipping point”, even though it’s one of several contributing feedbacks. But the question is whether we have a good idea of the maximum likely carbon release (both existing methane and organics decay). With significant outgassing, perhaps it could become a stronger feedback despite being “globally well-mixed”? Along with oceanic methane spurts and other effects, we presumably still have the possibility of acceleration events tipping other elements in the system. Since we can’t determine how everything will play out, this is all quite an experiment.

  15. 65
    Eric (skeptic) says:

    Ike (#62), it’s a very good point to take into account all evidence. I believe Alistair (#22) does not. There are many potential warming and cooling effects as Steve (#51) points out. They all have to be taken into account and that’s when the tipping point tends to disappear. I agree with Ike, Nick (#23), Ray (#26), and Lawrence (#29) that the effects of the local tipping points will be global in many cases and difficult for life. But that does not make them global tipping points, just global effects. In a world with lots of local tipping points the global balance will certainly start to be affected, plus the effects may be messy enough that nobody will care what the global average is anymore. But the negative feedbacks, negative tipping points and numerous positive global side effects will be just as real.

  16. 66

    Re #11: “The problem is genetic. The average human is just not good enough in math to survive the next 200 years.” Not true.

    While we’re discussing Bayes Theorem and other areas of probability and statistics, others
    out there are working on developing and improving alternatives to fossil fuels, such as fuel cells, solar panels, wind turbines, plug in hybrids and the like. Models are important much as Paul Revere was important in telling us what’s coming. The next step is to react. People in other developed countries have already made important changes.

    Here in the U.S., we’re coming around to realize that energy efficiency is critical and that conservation is not just a “personal virtue” in the words of a very influential political figure. A penny saved is a lot more than a penny earned,especially when environmental effects are considered. You don’t have to look much farther than the record profits of oil companies and oil exploration companies in the past few years to see the cynicism in those words.
    We don’t need to know tensor calculus or matrix or probabitiy theory to put a halt to what’s becoming more and more obvious with each passing year.

  17. 67
    Andrew says:

    The way to handle the problem of parameterzation dependence of sampled estimates in statistics is pretty much along the same lines as Jeffreys’ prior; oddly enough Harold Jeffreys was a geophysicist.

  18. 68
    Blaine says:

    If you evenly sample X, or evenly sample 1/X (or any other function of X) you will get a different distribution of results. Then instead of (in one case) getting 10% of models runs to show behaviour X, now maybe 30% of models will. And all this is completely independent of any change to the physics.

    The point of the butterfly effect in chaotic systems is that the resulting probability distribution IS independent of the distribution with which you started. Provided that you allow enough time to elapse in the model, the results from neighboring samples will be entirely independent. Both you and the Economist appear to be assuming that model output will vary smoothly with the input parameters, which is generally not the case for chaotic systems.

    It is important not to confuse the probabilites that something will happen in a model with the probability that it will happen in real life. When X% of the ensamble elements of a model predict that something that means that that is the chance that it would happen providing that the initial starting condition is correct, that the model accurately captures the physics, and so forth. The chance that it will actually happen in real life must take into account these errors as well, which is sufficiently complicated that estimates of real life chances are not usually published.

  19. 69
    Mitch Golden says:

    I guess I don’t understand something at the end of this article. If the probability of any particular path in the simulation is not proportional to the probability of this path actually occurring, then why is it valid to average the ensemble of paths and claim that the average value of the (say) temperature increase is the same as the likely value of the actual temperature increase? What does the distribution of paths actually mean?

    [Response: Fair point. The reason why the multi-model mean is used is because it empirically shown that it works the best at getting other observables correct. That implies that at least some of the errors are random and not systematic. But it doesn’t imply that there are no systematic errors remaining. – gavin]

  20. 70
    Alex N says:

    Eric (skeptic): Seems like the “numerous” positive (“global”?) side-effects discussed by “skeptics” are often rather dubious or leave out caveats, and don’t appear to outweigh the negatives associated with the situation getting out of hand. And I’ve yet to see any successfully reviewed study suggesting negative feedbacks or “negative tipping points”(?) are strong enough to prevent that from happening. Seems that on timescales important to humanity, amplifying feedbacks are likely to rule.

  21. 71
    John Monro says:

    I don’t know, I am only an old, near retiring age, bumbling general practitioner. I have no more qualifications to discuss AGW, tipping points or GIS melting than the next person, though I have studied these issues extensively on this site and others, I have John Houghton’s book, even read Fred Pearce’s book in 1989, but regrettably put that information in the back of my mind for the next decade. But having said that, I think my age, and my experience of life, and in particular, my experience of other people’s lives, and the normal course of physiology and the abnormal course of pathology, has gained me some insight into the how living systems do function and how they go wrong. Although James Lovelock doesn’t possess a clinical medical degree, he has worked in many medical fields and has a PhD in medicine. He certainly knows his physiology, and has applied that breadth of view in his theories about Gaia. I would suggest that this view point is of inestimable value when examining complicated issues like AGW.

    My comments both about tipping points and Bayesian projections, and so much about AGW would be the same. I think we need, like a good physician, at the times you have something wrong with you and you don’t quite know what’s going on, to stand back a bit and look at the whole organism and the totality of its functioning. If the world was my patient, I would be very apprehensive about the prognosis, and the patient should be justifiably frightened.

    For instance, take the comments about tipping points, are they local, are they global? This is not the issue. The loss of the Indian monsoon might not affect me here in New Zealand, but there are a billion people on the planet that it would. The loss of ice in the Arctic, (and this year surely brings us to the realisation that the tipping point in the Arctic is almost upon us – what chance no summer ice within ten years, or five years?) again might be remote to me, but to the Inuit and to those living in northern climes in Europe, who number many millions, it could be very troublesome. Increasing heat and dryness in the south-western USA would again adversely affect tens of millions directly and in the “breadbaskets” of the world, affect hundreds of millions in their food supplies. One thing we must understand is that the whole planet is local, we are all co-dependent on one small globe whizzing through the ether. We are several orders of magnitude larger than Easter Island, but we are just as isolated and just as vulnerable. I very much doubt there is such a thing as a “local” or “regional” tipping point. We are all in this together and too many such arguments seems to me the sort of thing that Rana temporia might have croaked on about in the heating pan of water.

    Similar also are my comments on Bayesian predictions. This is all so esoteric, and seems almost to come down to the same sort of arguments that once exercised the best brains in Christendom as to how many angels can dance on the head of a pin.

    So let’s stand back, and things become so much clearer.

    There is, as far as we know, only one planet in the universe that can support life, and it is the one that supports us, and if something goes wrong with this planet, we cannot escape anywhere else.

    We are called Homo sapiens sapiens, which supposedly should mean that we have the intelligence, properly directed, to deal with the sort of problem that besets us.

    We have now almost all of us accepted the reality of AGW.

    We are ourselves the direct cause of these problems. We know the world’s climate can change due to other factors not involving human agency, but for the moment, the threat of the heating world arises from our own actions.

    It is, even with present technology and the power of many thousands of expert people’s minds, impossible to precisely predict the future but whatever the future, it is definitely going to be very different from today, perhaps as different as the ice-age planet was ten thousand years ago. We haven’t yet reached a one degree C rise in global temperature, but this year brings warning of the complete loss of arctic summer ice and the imminent collapse of the normal arctic climate. If less than one degree can do this, what will 2 degrees or even more accomplish?

    Humanity has thrived in its present environment, which includes a relatively constant climate in the Holocene, hardly varying at all for ten thousand years. Humanity has come to occupy every ecological and climatic niche over this time. It is almost certain, because we have prospered in a relatively constant climate, that any change in that climate will bring many more problems than benefits. All our infrastructure, our housing, where we live, whether by rivers, lakes or coasts, our water supplies, our farms and farming practices, our industry, our fishing, our forests, are adapted to those niches and, almost by definition, any change in prevailing climatic conditions will mean that this infrastructure will not be best suited for the new climate.

    We are now so numerous, and have already occupied all the most favourable areas of the Earth’s surface, that we won’t be able to move to avoid these climate difficulties, but will have to adapt our present investment and infrastructure to cope. The expense and the difficulty of this obviously is going to be massive, and has the capacity to severely reduce our wealth. It is likely that there will be some areas that this will in fact be impossible, e.g., the Ganges delta, Florida, flood plains, dry areas dependent on aquifers or glacial water feeds etc. It is likely that many areas, already full to the brim with humanity, will need to cope with tens of millions of climate refugees. Imagine New Orleans magnified a hundred-fold or more, even in a best-case scenario. .

    We talk about 2 deg C of warming with some equanimity, as if this is not really going to be an issue, and of course we are already committed to at least 1.5 deg C of warming. Yet even this amount of warming could prove quite disastrous to some areas of the world, and there may be major climatic changes that we haven’t even envisaged. It is likely that the melting of the summer ice in the Arctic will be the first example of major climate change to cope with. Will the jet stream move south, north or stay where it is? Will increasing atmospheric moisture cause major increases in summer rainfall in northern latitudes, including North America and most of Europe. Will the floods the UK has seen this year become the norm and how could we cope if it did? We shall shortly find out.

    Is anything that I have written under any serious dispute? Yet this last few weeks have seen Russia planting small flags on the Arctic Ocean floor, Denmark asserting territorial claims off the Greenland coast, and Canada promising to station hundreds of soldiers in its Arctic Territories, all with the object of securing sovereignty over the possible resources of the Arctic. These resources include of course, oil and gas; the Arctic is one un-explored region where large amounts of such fossil fuels could be found.

    There is some sort of supreme cosmic joke here, though I don’t find it particularly humorous. That humanity should so poison our atmosphere as to permanently damage one of the Earth’s major climatic control mechanisms, then take advantage of this damage to damage our climate even more, is just so absurd, so stupid, so cosmically cretinous, as to beggar belief. It is the positive feedback mechanism to beat them all.

    And yet, looked at from our present perspectives, it is hardly surprising. The vast majority of humanity hasn’t even noticed or commented. Here in New Zealand we are proposing to spend over a billion dollars in oil and gas exploration in the oceans to our south. Our commitment to continued economic expansion is almost total, and even threats to the health of our planet doesn’t cause us to waver in this.

    I think we solve this quandary by looking at AGW in an entirely different way. To go back to my introduction, when I introduced myself as a physician, standing back, and taking the overview, not only has the physician a professional obligation to you and your welfare, and your family and children, but he has a moral obligation, which actually transcends this professional obligation. Furthermore, and this is the important point, this moral obligation is in fact no different in kind or degree to the moral obligations that we all have to each other in any case. It would be my contention that AGW is, as much as anything, a moral issue, the supreme moral issue of our times. Our moral obligation to our planet arises from our moral obligation to each other. Whilst we can certainly examine AGW from a scientific, political, economic, environmental or societal viewpoint, I don’t think we are going to get very far until we admit this moral perspective.

    And this is why I believe that we should be looking at the morality of what we are doing. It brings everything back into focus. We continue to make the most appalling errors by treating this issue as one of pure logic. It would be nice to think that humanity could be guided by logic but, generally, this doesn’t happen. It is not logical to damage our planet any further, but it is not entirely illogical to try and sustain our present standard of living either, it has brought humanity many undoubted benefits. But by simplifying all these discussions and arguments to a simple moral perspective we avoid these pointless and irresolvable arguments. What we are doing to the planet and ourselves is immoral, here are some reasons why.

    It is immoral to be fouling our own nest.
    It is immoral to fail to take action to deal with global warming.
    It is immoral to undertake actions that will make global warming worse.
    It is immoral not to care for others as we would wish to be cared for ourselves.
    It is immoral for rich nations to cause damage to poor ones who are not responsible.
    It is immoral not to care for our children.
    It is immoral not to care for their children
    It is immoral not to care for the planet that sustains us.
    It is immoral to diminish the lives of others for our own benefit.
    It is immoral to require others to deal with problems that we have created.
    It is immoral to try to get others to ignore the problem.
    It is immoral to care more for our present wealth than any of these other things.

    I could go on, I often do. But I will end with observing that there is now something distinctly Darwinian in what we are doing – in fact I think Darwin would have a good chuckle at our expense, if, as a humane man, he wasn’t weeping. We are the universe’s first species, as far as we know, intelligent enough to have discovered the theory of evolution, the principle of natural selection and survival of the fittest. What is now so ironic is that we seem determined also to be the universe’s first species to deliberately set out to prove it.

  22. 72
    Dominic says:

    I know this is off topic, however Philip Stott wrote a letter into the Telegraph today which included this line:

    ‘First, new research indicates that our climate may be only one third as sensitive to C02 as has been assumed.’

    What research is he talking about??

    link to the letter –


  23. 73
    Ed says:

    So the distribution of model results isnt a pdf of the climate system.

    Then what does it tell us?

    Should values, like the 11 degrees simulated by, be considered ‘possible’?

    Or is even the range meaningless?

    [Response: Personally, I don’t consider 11 deg C possible. It’s interesting to see that a model can generate something like that, but whether it matches with the real world is key. Many of the subsequent analyses of the CPDN runs show that even modest requirements of TOA radiation balance for instance, none of the high end numbers survive the cut. – gavin]

  24. 74
    Ed says:

    “The way to handle the problem of parameterzation dependence of sampled estimates in statistics is pretty much along the same lines as Jeffreys’ prior; oddly enough Harold Jeffreys was a geophysicist.”

    The problem is how to find the Jeffrey’s prior when the likelihood function isnt available analytically as a function of the parameters.

  25. 75

    [[The really odd thing, for me, is that mathematically, the data themselves contradict his hypothesis of a single timescale for climate response. I believe I can show, beyond doubt, that the data he presents *reject* the idea of such a simple behavior, but Schwartz presents an argument (which I regard as invalid) that they confirm it.

    I’m considering writing it up for JGR, and also considering doing a blog post on the subject.]]

    I wish you would do the former (the latter would also be good). I’d love to see a paper in JGR from a regular poster here (other than the professional climatologists, that is).

  26. 76


    “Why is the albedo of Venus important? When the albedo is at 0.80, the Global Warming Theory falls apart. . .]]

    I looked at your reference. I’ve never seen a clearer example of pseudoscience. The paper starts getting things wrong right at the start, by saying global warming theory was invented “a few decades ago” — try 1896. It then goes on to say that airborne carbon dioxide “reflects thermal energy” — no it doesn’t, it absorbs it. And so on and so on. The author of your reference is a crackpot, clear and simple.

  27. 77
    Walt Bennett says:

    Re: #71


    Very interesting post, well stated. I approach the problem slightly differently. The problem with the morality argument is that there are those who will argue the immorality of needlessly disrupting societies and economies to chase a ‘solution’ to a ‘non-existent problem’, or to a problem about which not enough is known to wisely choose a credible solution. There is a point to be made there.

    The problem with the Darwinian argument is that many people do ‘get it’. Those who argue in favor of a BAU approach are not necessarily oblivious to the self-detructiveness of that stance; they simply understand that it will be others, not themselves, who will face those consequences. At its base, this approach can be defended as practical and rational, at least as far as it serves the near-term interests of those who hold it.

    My approach is this: man has greatly accelerated his ability to alter his environment (Gore’s “bigger shovel” example in AIT). Man has not necessarily accelerated his ability to understand the consequences of these alterations. To some extent this blindness is useful, because we don’t know enough about future conditions and capabilities to choose too far in advance.

    AGW is clearly a new paradigm. Each of us contributes the tiniest increments to the overall problem, but the comnbined, sustained contribution is a real problem. We don’t feel that, though: it’s a mighty chilly August here in Pennsylvania, for example. We don’t see it: CO2 is invisible and mostly odorless. We can’t always take specific measures to reduce our contribution, and when we do, we don’t always understand the consequences of THOSE choices.

    Complex stuff.

    Much too soon to judge our ability to learn from this experience. We are still in the bubbling cauldron of competing ideas.

    I do not necessarily disagree with your views vis-a-vis morality and Darwinism, but I do not believe they are the root issues which confront us. I believe that the root issue is simply, man learning how to sort through myriad sources of information in order to make perceptive judgements. It’s almost impossible to imagine this process as something that can be done with any degree of rapidity, or as something with any sort of definable end-point.

  28. 78
    Alex Nichols says:

    re Dominic #72
    Just to avoid any confusion, the Stott who wrote to the Telegraph is not the same person as Peter Stott, the climatologist at the Hadley Centre, who wrote the recent paper linking changing patterns of rainfall to Global Warming.

    (I am also not the same person as # 70!)

  29. 79
    steven mosher says:

    RE 57.

    Thanks Gavin.

  30. 80
    John L. McCormick says:

    RE # 45

    Nigel, you said, [I dont think the Amber Waves comment is an error of judgement, It is a genuine image of how good ot could be if only we did what we know we shuld.]

    The American diet relies upon that Amber grain (and the amber lager we love so well)and exports the surplus stock of those Amber Waves of grain.

    Here is where I disagree with Dr. Hansen and all the ethanol advocates.

    It is self-destructive to use the global grain basket to fuel our vacation trip to the beach. And, the ethanol industry is betting the farm on predictable climate conditions during the growing season in a world of record Arctic sea ice meltback and its conseguences for Western North American temp and precip.

  31. 81
    Daniel C. Goodwin says:

    Re John L. McCormick in post 80

    I doubt that McCormick’s characterization of Hansen as an “ethanol advocate” is accurate, though I can understand how the footnote I quoted might lead one to that impression.

    Regarding not what Hansen personally advocates anyhow, but what Hansen et al advocate in “Climate Change and Trace Gases:” their conclusion is: (1) That some means must be found to draw down atmospheric co2 concentrations. (2) If emissions from combustion of biofuels are sequestered (and sequestering looks like a tractable engineering problem), the result of such activity on a large scale would be to draw down atmospheric co2.

    There are many interesting things about this proposal. One of them is that, where co2 extraction technologies are concerned, Hansen et al found none more efficient or promising than those which life has already developed: photosynthesis and respiration. Another interesting thing is this proposal’s implicit blithe dismissal of problems like the price of tortillas in Mexico.

    Please remember, the point here isn’t “look how full of crap Hansen is,” the point is that even the most thoughtful people around (Hansen, for his courage through the decades, really is a personal hero of mine) make some intellectual blunders occasionally. I’ve even been known to stumble myself, believe it or don’t.

  32. 82
    John L. McCormick says:

    RE # 81, Daniel, I share your respect for, and appreciation of, Dr. Hansen and his contribution to our understanding AGW.

  33. 83
    Ron Taylor says:

    Re 71- I fully agree with this posting by John Monro.

    I would add a growing concern that the stance of some denialists may include a hidden agenda. That agenda is basically this: “When things really begin to hit the fan and hundreds of millions or billions are in great distress, we will have to be strong enough to fend them off and let them die. Otherwise, they will overwhelm us and we will all go down together. So we have to push for continuing development and ward off any any action that might compromise our hegemonic position, even if that means accelerating the crisis.”

    A note to denialists – I know this does not represent most of you, but please take care that this sort of idea does not creep into your thinking.

  34. 84
    Lynn Vincentnathan says:

    RE the “reticent scientists” thread (#7, 9, 19, 37, 44), I did my thesis on “Environmental Victimology,” and came to realize there are several perspectives:

    (1) THE NAYSAYERS (often industrialists), who would prefer not to accept that a problem is happening, and would require more than 95% confidence it is (99, or even 101% :) ).

    (2) THE SCIENTIFIC MODEL: Scientists usually require 95% or greater confidence to make a claim. They need to protect their reputations, so that people will go on believing them — so making false claims (alpha error) is much worst for them as professionals, than failing to make true claims (beta error). They cannot be the boy crying wolf. If they are, they get cut out of the loop.

    (3) THE MEDICAL MODEL: Victims and potential victims of environmental harm, and environmentalists, and the general public (you’d think), would like to avoid environmental harm in the first place. They would be reticent to continue a practice that MIGHT be harmful to them or others. They would be greatly averse to failing to avoid a true harm (beta error). As are doctors and their patients when viewing test results — the doctor will not tell his patient he/she is are only 94% confident the lump is cancerous, so they won’t operate, and to come back next year to see if it’s made the 95% confidence interval.

    So it’s usually potential/actual victims, environmentalists, and the public who are well in front of the false-claim-avoiding, reticent scientists in clammering for ameliorative action.

    But this time it’s different (as scientists have themselves pointed out…and are scratching their head over); the scientists are the ones out in front clammering, while the public switches the dial to some entertainment channel.

    I’ve been thinking for over 17 years (since I became active on the GW issue), that we’d reach some societal “tipping point,” and go into a very different state, a revitalization (or social) movement to address this issue (e.g., the 60s anti-war, civil rights, and feminist movements). I’ve been waiting…..

    Of course, there is industry/government/media complex obstructionism, and a social movement’s need for many to perceive future/current harm to themselves, and the issue of GW being a bit slow-moving.

    But now I’m thinking that there are these other socio-cultural-psychological negative feedbacks that are stalling this flip into action. For one thing, it’s a lot easier if there are single, identifiable perpetrators against which to rail. But it is we ourselves who are the perpetrators, though on the whole the greater perps will suffer the least, and the least (or non-perps) will suffer the greatest. The very poor, who are and will be suffering the most, tend to lack social mobilization resources….though the movement might come alive with them — or become a big world clash.

    I’m thinking what this issue of mitigating global warming will take (at least on the part of the higher end perps, like us Americans) is very difficult, introspective work, self-examination, and humility. You’d think religions would be in the forefront, since that’s their province….but some of the greatest resistance I’ve seen is from the “religious,” and it seems religions (in addition to many good things they do) have this dsyfunction of helping people become self-righteous and impervious to acknowledging they might be doing something wrong. The religious do join social movements……against other people’s sins.

    This is a tough nut to crack. But a great opportunity for some deep and true improvement in the (inner and outer) human condition. Like a real conversion to goodness and caring.

  35. 85

    Re: #81

    I have been thinking about the biofuels as sequestration idea for a while (not very deeply I admit!) but here is my noodling.

    Suppose we come up with a scheme like that proposed by some UNH researchers to use green algae in closed tanks to produce biodiesel fuel stock. One could apply this technology in a number of ways.

    One would be to hook it up to municipal waste water systems and have localities produce fuel stock that they could sell to refineries. This would be great for a number of US policy problems like improving balance of trade, removing the funding sources for unstable/repressive/hostile regimes, funding local government (imagine if your city ran at a profit like the State of Alaska) and so on.

    But suppose for a moment that one could make the technology very simple and cheap. Tanks built from discarded plastic beverage bottles, feed stock from seaweed or other local biomass (think tropics where there is much poverty). storage in discarded steel drums or even the bottles themselves, a cottage industry of picking up the produce with circling trucks. This would become (for a while) an easy way to make money and if the technology is simple/viral enough, we get sequestration out of the deal too. Once we have reached break-even on energy generation, we could continue to buy the fixed carbon for sequestration, energy supply buffering (think strategic petroleum reserve) or even maufacturing (plastics). If it gets too out of control, the market will drop the price too low for even poor Indonesian farmers and they will be left with a system that simply makes them self-sufficient in energy.

    Anyway, just an idea.

  36. 86
    Lynn Vincentnathan says:

    I’m also thinking there’s probably a difference among different types of scientists. A geologist won’t be losing his/her focus of scientific interest for billions of years, but biologists may be losing their species of scientific focus, and might be more vocal in their speaking out against GW.

    The death of an organism (a person, animal, or plant) is not only a tipping point, but a tipping point of no return (as opposed to climate “hysteresis” (#35), which is more like an extreme fever that eventually goes back down).

    So is extinction of species.

  37. 87

    Re #71 Where Doc Munro ended:

    We are the universe’s first species, as far as we know, intelligent enough to have discovered the theory of evolution, the principle of natural selection and survival of the fittest. What is now so ironic is that we seem determined also to be the universe’s first species to deliberately set out to prove it.

    It is highly unlikely that we are the Universe’s first species, which leads to Enrico Fermi’s Paradox – Where are they? See:

    The paradox is easily resolved if we assume that any species that developed intelligence would inevitably be aggressive, since it would have developed through the process of the survival of the fittest. Like us, they too would burn their planet’s fossil fuels as if there was no tomorrow. They too would not only cause the end of their civilisaton, but also the end the prospect of any new civilisation because the natural resources needed to advance beyond the stone age had already been squandered.

  38. 88
    Lynn Vincentnathan says:

    Here’s something re what to expect from 2100 temps — no ice cap (I guess this is another nail in the denialist arguments):

    Study casts doubt on earlier ice cap research

    Source: Copyright 2007, Reuters, see:
    Date: August 22, 2007
    Byline: Michael Kahn

    Pinhead-sized fossils buried deep under the ocean show that glaciers did not coat the poles 41 million years ago, a new study shows, disputing earlier research that suggested huge ice sheets covered the Earth’s extremities.

    Any glaciers then — a time when the planet was much warmer — would only have been in small areas in Antarctica’s interior and not in the Northern hemisphere, said Paul Wilson, from Britain’s National Oceanography Centre, who led the study…..

  39. 89
    Hank Roberts says:

    Lynn, that’s apparently referring to something now in Nature.

    I followed their link back as far as Reuters.

    “… In the period his team studied, the earth had about as much carbon dioxide in the atmosphere as scientists predict may be present in 100 years, so the findings also offer clues as to how rising greenhouse gas levels may affect the planet, Wilson said.”

  40. 90
    Heigi Blume says:

    I think the world is naive if they continue to blind themselves towards our environmental issues. It’s time we open our eyes and see all of the symptoms that occur every day. The symptoms for the “tipping point” are happening as we speak.
    Whether or not there is a tipping point, we need to act as if we are drawing near the tipping point. Politicians twiddle their thumbs at the mercy of corporations. We have no time to wait, our world is in a dire state and something needs to get done, now.

  41. 91
    Ike Solem says:

    Eric says:”But the negative feedbacks, negative tipping points and numerous positive global side effects will be just as real.”

    That statement would be more believable if you were to attempt to give some (any) examples of such “positive global side effects” or “negative tipping points”.

    A number of comments above point to the need to ‘do something’, but let’s just spell it out – we need to end the use of fossil fuels on a global scale, and we need to put an end to deforestation, particularly in the tropics.

    Doing this creates a big problem – what source of energy will humans use in the future? Solar and wind are huge energy sources that are largely untapped. If we start with replacing all fossil fuels used in agriculture with solar / wind power (coupled to efficient energy storage systems, of course), than you can get agriculture off fossil fuels. Once that is done, you can examine the issue of sustainable biofuel production.

    The basic point is that a blend of renewable energy sources will be required. A lot can be learned from traditional energy sources – i.e. synergy matters. For example, you can use solar thermal heating to provide a good deal of the energy needed for ethanol distillation. As many have pointed out, one acre of biofuel crops provides enough fuel to work that field for decades. Put all these energy sources and storage mechanisms together – sunlight, wind, photosynthesis and improved technology – and you have enough energy for all, with no need for nuclear power or coal carbon sequestration.

    If one includes human activity within the ‘Earth system’, then a rapid transition to a renewable economy would be an example of a ‘negative tipping point that counters the projected long-term effects of global warming’.

  42. 92
    Folbec says:

    I’m pretty much convinced now that the climate is changing due to CO2 polution.

    I’d like to be pointed a reasonable site discutting prospective :
    – what could be done
    – what will likelly be done (my personnal bet is : too little too late, starting in 10 to 20 years when politicians feel the anger of Joe Sixpack the voter who finally got flooded or desertified)
    – who will loose
    – who will win

    anyone can point to such a site ?

    [Response: Try or – gavin]

  43. 93
    Rod B says:

    re 83: “a growing concern that the stance of some denialists may include a hidden agenda… ”

    I’m positive this is true, as it is for many proponents of the AGW theory. Might be best to just leave the factions of both camps alone, though I have to admit their cacophony sometimes just can’t be ignored.

  44. 94
    Rod B says:

    Actually there has been a set of environmentalists that for some time now have the survival and enhancement of the human species way way down on the priority list. Granted they’re the fringe, but they’re fun to talk about…

  45. 95
    catman306 says:

    “Politicians twiddle their thumbs at the mercy of corporations. We have no time to wait, our world is in a dire state and something needs to get done, now.
    Comment by Heigi Blume ”

    I have in my hands a photocopy from Science 10 February 1989 pp 771-781. “The Greenhouse Effect: Science and Policy” Stephen H. Schneider.

    “Within the past year (1988) cover stories of both time and Newsweek have featured global warming from the green house effect and ozone depletion from industrial chemicals. The intense heat, forest fires, and drought of the summer of 1988 and the observation that the 1980s are the warmest decade on record have ignited an explosion of media, public, and governmental concern that the long debated global warming has arrived-and prompted some urgent calls for actions to deal with it. For example, the National Energy Policy Act of 1988 to control carbon dioxide emissions was introduced by Senator Wirth in August 1988, and hearing were held on 11 August. At that hearing,, there were sharply conflicting views about whether policy actions are premature given the many remaining scientific uncertainties. Whether some amount of scientific uncertainty is ‘enough’ to justify action or delay it is not a scientific judgment testable by any standard scientific method. Rather, it is a person value choice that depends upon whether one fears more investing present resources as a hedge against potential future change or, alternatively, fears rapid future change descending without some attempt to slow it down or work actively to make adaptation to that change easier.”

    So although the science has improved during the past 18 years, the politicians and corporations haven’t. They and the media are not guilty so much of lying in what they say, they are guilty of lying by NOT saying things to the general public.
    Business as usual.

    I wish our resident skeptics and denialists could see this article and research what is contained in the footnotes. Then they’d begin to understand the science behind climatology and that very little of Realclimate is ‘new’. And that delay of action was ALWAYS the game plan. (And I wish archived issues of Science were available online to non-subscribers.)

  46. 96
    Eric (skeptic) says:

    Hi Ike, my own small example would be my $32/month electric bill from mid-June to mid-August in hot Virginia (2000 sf house). I am not worried about warming around me, if it happens it will help me save money in the winter with minimal effect in the summer. Planting even more shade trees might be my very minor negative tipping point. I agree with your sentiments though because if we are going to heavily subsidize farmers then we should subsidize them to become sustainable in the long run.

  47. 97
    Aaron Lewis says:

    Re 84
    People need to feel that damage will occur within their planning horizon before they express any real outrage. (Cite personal experience running an environmental canvassing operation.)

    Now we have rather short planning horizons. Tell people that there will be sea level change in 80 years, and they do not care because it is beyond their planning horizon. They assume that as the seas rise, people will move somewhere else and technical problems will be solved as they arise.

    Tell people that there will be real problems in 5 or 10 years and you will get a response. Better yet, show them that there is a problem NOW! Show people pictures of drowned polar bears and you will get a response NOW! Show people what is happening to the penguin colonies and you will get a response.

    I have read about drowned polar bears and dead penguins, Why have I not I seen any pictures? Talk about scientific reticence! We have a duty to tell people what we see.

    Somebody needs to confront Rush Limbaugh with a very dead polar bear and a very dead penguin. That will get you some news headlines. Then do it on PBS, ABC, & CBS.

  48. 98
    John Monro says:

    Re # 77,

    Walt, thank you for your comments. As I stated at the start of my posting, I am a pretty average human being and possess no blinding intellectual insights into our present predicament. We do discuss here the problem of AGW, but as you will be aware, there are many other major issues pressing on humanity, due to our own actions, these include nuclear warfare, oil depletion, overpopulation, environmental damage, deforestation, the rape of the oceans; basically the imminent collision of humanity’s perceived and ever-increasing requirement for the planet’s resources and the inability of a finite planet to provide them, or a finite atmosphere to hold the pollutants. I am not a technophobe or alternative life-styler (though I certainly don’t criticise such people, generally I admire them), I appreciate how technology and science has liberated much of humanity from drudgery and disease and ignorance, and that life for many of us is no longer a constant battle for survival.

    But it seems to me that despite all the arguments for and against economic expansionism, Business as Usual, as you put it, we are in danger of arguing ourselves to oblivion. Take the Iraq war for instance, would we have got ourselves into such a predicament if we had taken on board a simple moral stance, war is immoral, and nothing other than a dire, credible, immediate and sufficiently damaging threat of enemy action should make it anything other? Doesn’t the vast majority of humanity shun war, abhor it; yet here was the world’s most advanced nation, and some of its friends, proceeding to a frightful war, and all wars are frightful, on some vague intellectual pretext.

    In a sense, isn’t what we are doing to the planet, akin to a war against nature, and isn’t dealing with the massive problems that face us all, also a war, against our own nature? In other words, aren’t so many of the problems we face basically just moral ones?

    I am not at all religious; I have become increasingly atheistic for a couple of decades, and much more definitively in the last few years. But as a humanist, I do still believe very strongly indeed in the ethical and spiritual dimension of humanity, and that most people, whatever religion or culture, will understand this. I think we have forgotten our ethical and moral duties to ourselves and our environment, we no longer bother considering the ethical dimensions of so much of what we plan and achieve, and in fact we are derided when we do. It is this lack of moral capacity in ourselves and our institutions, I believe, that has, mainly, brought us to the pass we are now in. For example, large corporations are often charged, and rightly, for their amorality in dealing with many of these matters – deforestation, human rights, workers’ health, bribery and corruption, the worsening of third world impoverishment, pollution etc. – and yet we are told that a corporation only has a duty to its shareholders, to maximise the return on their capital and that legally no other considerations are allowed. To which I would say, what sort of world is this that moral and ethical considerations are legally barred in some of the most important endeavours that mankind undertakes?

    Walt, you say “Those who argue in favor of a BAU approach are not necessarily oblivious to the self-destructiveness of that stance; they simply understand that it will be others, not themselves, who will face those consequences. At its base, this approach can be defended as practical and rational, at least as far as it serves the near-term interests of those who hold it.” Isn’t this the problem, something that may be practical and rational, for those that stand to benefit, isn’t practical or rational at all for many others. This argument is simply not defendable. Isn’t it just simpler to say, this attitude, this action, it is immoral, which it undoubtedly is, stop it now. It may have seemed, at the time, rational to the leadership and population of Germany for that country to invade Poland, and it was certainly practical, after all they did it, but by a long way, it wasn’t moral. Ditto Iraq.

    You go on to say My approach is this: man has greatly accelerated his ability to alter his environment (Gore’s “bigger shovel” example in AIT). Man has not necessarily accelerated his ability to understand the consequences of these alterations. To some extent this blindness is useful, because we don’t know enough about future conditions and capabilities to choose too far in advance. Apart from the obvious rejoinder that if we don’t know the consequences of our actions, we shouldn’t be doing them (if Germans knew what the consequences of invading Poland would be, would they have proceeded?), isn’t the contentious point the “bigger shovel”? I would suggest that the “bigger shovel” is in fact the “greedy shovel”. Do we need a bloody shovel in any case; wouldn’t “intelligent spadework”, in our present precarious position, be rather more appropriate? This is the moral argument; isn’t so much of what passes for desirable economic activity nowadays merely greed, pure and simple?

    I think many people would now agree that AGW is not merely the accidental or unavoidable by-product of a progressive civilisation, but is in fact the ignorant and heedless poisoning of our environment by greed, and is directly the result of the hubris of humanity, that we live in some parallel universe, where the normal laws of nature no longer apply. Our inability to see ourselves any longer as creatures of biology, just as dependent on the processes and rules of nature, as much as any tiger, eagle, dolphin or any other form of life, is the basic cause of so many of our present trials and tribulations. I still contend therefore that AGW is above all a moral question, of our relationships to each other, to all other living things and to the planet that sustains us.

    This all seems rather a long way from the remit of Real Climate in presenting the science of AGW, but, and I am sure I speak for most other contributors and readers, we have long since accepted the reality of the problem, most of us are becoming increasingly alarmed about the obvious urgency and severity of the AGW, and increasingly frustrated by humanity’s present inability to agree an effective strategy in dealing with it. Hopefully this discussion will help.

  49. 99
    Ron Taylor says:

    Re 93 – Rlod B says: “Actually there has been a set of environmentalists that for some time now have the survival and enhancement of the human species way way down on the priority list. Granted they’re the fringe, but they’re fun to talk about…”

    I have no idea who you might be talking about. They would not be people that I, or anyone I know, would relate to. Care to say a little more about who they are and what their influence might be?

  50. 100
    steven mosher says:

    RE 97… PSSST Aaron.

    you forgot to RTFM and

    ” Cite personal experience running an environmental canvassing operation.”

    THAT, is some rich and creamy Irony.

    Recently Dr. Hansen discussed the concept of Ursafuct
    in an email from columbia. That would make a great thread here