Tropical tropospheric trends again (again)

Many readers will remember our critique of a paper by Douglass et al on tropical tropospheric temperature trends late last year, and the discussion of the ongoing revisions to the observational datasets. Some will recall that the Douglass et al paper was trumpeted around the blogosphere as the definitive proof that models had it all wrong.

At the time, our criticism was itself criticised because our counterpoints had not been submitted to a peer-reviewed journal. However, this was a little unfair (and possibly a little disingenuous) because a group of us had in fact submitted a much better argued paper making the same principal points. Of course, the peer-review process takes much longer than writing a blog post and so it has taken until today to appear on the journal website.

The new 17-author paper (accessible pdf) (lead by Ben Santer), does a much better job of comparing the various trends in atmospheric datasets with the models and is very careful to take account of systematic uncertainties in all aspects of that comparison (unlike Douglass et al). The bottom line is that while there is remaining uncertainty in the tropical trends over the last 30 years, there is no clear discrepancy between what the models expect and the observations. There is a fact sheet available which explains the result in relatively simple terms.

Additionally, the paper explores the statistical properties of the test used by Douglass et al and finds some very odd results. Namely, that their test should nominally inadvertently reject a match 1 time out 20 (i.e. for a 5% significance), actually rejects valid comparisons 16 times out of 20! And curiously, the more data you have, the worse the test performs (figure 5 in the paper). The other aspect discussed in the paper is the importance of dealing with systematic errors in the data sets. These are essentially the same points that were made in our original blog post, but are now much more comprehensively shown. The data sources are now completely up-to-date and a much wider range of sources is addressed – not only the different satellite products, but also the different analyses of the radiosonde data.

The bottom line is best encapsulated by the summary figure 6 from the paper:

The grey band is the real 2-sigma spread of the models (while the yellow band is the spread allowed for in the flawed Douglass et al test). The other lines are the different estimates from the data. The uncertainties in both preclude any claim of some obvious discrepancy – a result you can only get by cherry-picking what data to use and erroneously downplaying the expected spread in the simulations.

Taking a slightly larger view, I think this example shows quite effectively how blogs can play a constructive role in moving science forward (something that we discussed a while ago). Given the egregiousness of the error in this particular paper (which was obvious to many people at the time), having the initial blog posting up very quickly alerted the community to the problems even if it wasn’t a comprehensive analysis. The time in-between the original paper coming out and this new analysis was almost 10 months. The resulting paper is of course much better than any blog post could have been and in fact moves significantly beyond a simple rebuttal. This clearly demonstrates that there is no conflict between the peer-review process and the blogosphere. A proper paper definitely takes more time and gives generally a better result than a blog post, but the latter can get the essential points out very quickly and can save other people from wasting their time.

284 comments on this post.
  1. Steve Reynolds:

    Martin, Ray, and Mark,

    I asked to see a credible, peer reviewed, analysis about “how relatively minimal the costs of an effective mitigation programme will actually be…”.

    I got an anecdote from Ray, a non-peer reviewed political report (extensively disputed in peer reviewed publications) from Mark, and the IPCC from Martin.

    I checked the IPCC AR4 SPM (last page) again, and it still says:

    Limited and early analytical results from integrated analyses
    of the costs and benefits of mitigation indicate that they
    are broadly comparable in magnitude, but do not as yet permit
    an unambiguous determination of an emissions pathway or
    stabilisation level where benefits exceed costs. {5.7}

    That does not sound very supporting of minimal costs (or even any certainty a positive cost-benefit to mitigation).

  2. Mark:

    Rod #198
    And that’s worse reasoning than you accuse others of.

    Well done.

  3. Martin Vermeer:

    Steve #201, I see you haven’t given up your quote mining habits. Worse, you’re again happy to engage in the lie of conflating uncertainty within an issue with uncertainty on the issue’s reality. Please leave those dirty games to politicians.

    (BTW I take note that you don’t contest that this summarizes peer reviewed science. Of course it is only a SPM; don’t make me dig in the full report.)

    Look at the SPM of WG3 (above link), Tables SPM.4 (page 12) and SPM.6 (page 18). Third column in both tables “Range of GDP reduction”.

    All ranges quoted are within the ball park of a few percent of GDP that I stated, and that I stand by: below 3 percent up to 2030, and below 5.5 percent up to 2050, even for the most aggressive scenario. Less, and based on more studies, for the others.

    Sure, lots of uncertainty, just as there is in the science. But this is what the odds look like. Policy making under uncertainty is the norm; those refusing to do so don’t deserve to survive.

    BTW this SPM also discusses at some length the “low hanging fruit” that would actually save money mentioned by Ray, and that you dismiss as anecdotal; those are the negative numbers figuring in the above mentioned table columns, mostly at the top. Serious researchers say so based on real-life experience.

    I rest my case. Thank you for wasting my time, perhaps someone else finds this info useful.

  4. Ray Ladbury:

    Steve Reynolds, I still have yet to see a convincing study that limits risk as well, so if risks of climate change are unlimited, we have to mitigate regardless.
    Are you seriously contending that we couldn’t do anything more. Anything we do buys time, and time is key to both mitigation and adaptation. Really, I have to say that I am very disappointed with magic-of-the-marketplace economists in this regard. All I’ve seen from them is handwringing and dire warnings of how any effort to address climate change will bring the end of prosperity. In the end, we HAVE TO address this problem, and if markets and corporations don’t provide answers, people will look to other places for them.

  5. Mark:

    Steve 201 You have one.

    Unless being looked at by parliament bodies for whether it should be given to the public as ‘not peer reviewd’.

    Which would be odd considering they include real peers…

  6. Walt Bennett:

    With regard to mitigation, in case any of you missed it: that was and remains my point. We aren’t seriously addressing mitigation; we aren’t seriously discussing removing CO2 from the atmosphere. We aren’t even, as far as I know, discussing such basics as how big is the pot of money, and how best to apportion it.

    We are talking, so far as I know, about two things: (1) reducing CO2 emissions and (2) saving forest.

    Anybody who believes that either of those two efforts will generate a net savings in the next decade, is drinking Kool-Aid, in my not-so-humble opinion.

    I want lots more research and development of real mitigation strategies; you know, the kind that have a chance to succeed.

  7. Steve Reynolds:

    Ray: “Are you seriously contending that we couldn’t do anything more. Anything we do buys time, and time is key to both mitigation and adaptation.”

    I agree with that and what you said in 200.

    Ray: “I have to say that I am very disappointed with magic-of-the-marketplace economists in this regard. All I’ve seen from them is handwringing and dire warnings of how any effort to address climate change will bring the end of prosperity.”

    Some have also advised revenue neutral carbon taxes. But those things are most of what the _economists_ can do (advise against inhibiting action of the market).

    The market will respond by the efforts of millions of investors, managers, engineers, and workers actually solving the problems. It is going on right now in response to higher oil prices.


    I find it unnecessary to respond to argument by insult.

  8. Rod B:

    Marcus (199), I think that is a fairly accurate assessment.

    I would have some minor disagreement around the edges — for the record: It’s true that the EPA implementation might not be onerous; but it also could just as easily be terribly burdensome. They do have to look at cost/benefit analyses, but if they decide that the CO2 impact could conceivably destroy a majority of the planet’s population within a few decades, they are not going to give me and others much consideration for the electricity we’ll have to forego. If they are inclined, it is certainly not beyond their capability to stretch the science to their liking. Would calmer heads prevail and restrict their foray? Probably, but they still could get us started down the road to ruin. Then again, as you say, maybe not.

    Secondly, a picayune but significant point. The Court ruled that the EPA had to look at it. They did not rule that the EPA had to find CO2 a pollutant under the CAA, though it would be easy to (wrongly) infer bias toward that in Justice Stevens’ words.

  9. Rod B:

    Ray, setting aside my skepticism for the moment, I agree with what you say. Actually, even given my skepticism, I’m all in favor in doing relatively easy stuff (and “easy” could still be large-scale) as some insurance while we continue the debate and development, and to get a jump on peak oil, and for other secondary benefits. However, what scares me is taking the debate away from learned policy makers (on both sides) and, to a large degree anyway, even from the professional scientists, and dumping this “you bet your world” in the hands of a few bureaucrats. This is what’s behind my “be careful what you wish for” comment.

  10. Rod B:

    Martin V, you imply that making policy decisions in uncertainty always comes out great. I beg to differ.

  11. Kevin McKinney:

    re Martin (#203)–

    Thanks, I do think that will be quite useful information, actually!

  12. Martin Vermeer:

    Rod B #210: on the contrary. I didn’t mean to imply, nor do I believe so. Only that using knowledge you have, even uncertain knowledge, gives you invariably better odds than ignoring it. (Well, the same odds as an edge case.) How it actually turns out… you win some, you lose some. Ask any military commander.

    Steve R #207: how convenient.

    Kevin #211: (blush)

  13. Ray Ladbury:

    Steve, the market tends to respond to events in real time. It’s got a piss poor record of responding to long-term threats–for instance it is responding to high oil prices even though we’ve known peak oil is coming for a generation. It also does a poor job of factoring in marginal costs when it determines the true cost of a commodity. The usual mitigation against this shortcoming has been regulation–which you and many other classical economists oppose. So here is the challenge:
    1)We have a threat that is known to pose significant economic risk.
    2)It is possible, even probable, that the threat will pose a mortal risk to economic prosperity if not human civilization.
    3)The consequences of the threat remain uncertain and will likely not be immediately evident until it is too late to do anything about them.
    4)How does the market come up with effective mitigation of this threat?

    So far, all we have is either denial or downplaying the risks. Think of this as market capitalism’s final exam question. The advocates of controlled economies, etc. are already hard at work on it. Market capitalism has a blank page so far.

  14. Joseph O'Sullivan:

    I’ll reply one last time then I’ll claim res judicata.

    What the Supreme Court ruled in Massachusetts v EPA from the official decision:
    “Petitioners have standing to challenge the EPA’s denial of their rulemaking petition. Pp. 12–23.”

    A much shorter and non-technical summary from the Pew Center:

    For procedural reasons unique to the legal system the Court did not tell the EPA to regulate CO2, but for all intent and purpose that is what the ruling means. Even The Wall Street Journal agreed in an editorial this week.

  15. Rod B:

    Martin (212), agreed

  16. Rod B:

    Joseph, I agree with your #214, which doesn’t contradict anything I said.

    The “all intent and purposes” stuff though is an indication, not a legality. The EPA could in fact technically conclude that CO2 need not be regulated and be in full compliance with the Court order. General inferences of what the Court meant, even if valid, does not trump what the Court explicitly said.

  17. Mark:

    Walt, 206

    Your original point was to ask for help with spurious pseudo-scientific nonsense (139).

    Turns out you were a believer like him.

  18. Mark:

    Steve 207:

    ‘The market will respond by the efforts of millions of investors, managers, engineers, and workers actually solving the problems. It is going on right now in response to higher oil prices.’

    Not when these investers are the last ones to be affected by the problem and the first to pay to solve it.

  19. Hank Roberts:

    > last ones to be affected

    You imagine no one beyond your own lifespan will be affected?

  20. Steve Reynolds:

    Ray: “It’s [market] got a piss poor record of responding to long-term threats–for instance it is responding to high oil prices even though we’ve known peak oil is coming for a generation.”

    I disagree. Some companies have a poor record of responding, and may go bankrupt as a result. Others that respond better (such as Toyota) will do well. That is the market at work, eliminating organizations making poor use of resources. I wish it worked that way for government organizations.

    As for your question (which I think is a good one, even if I doubt point #2, let’s assume it for now):

    I agree the market cannot solve this by itself, since no one owns the atmosphere (the much discussed ‘tragedy of the commons’). So given our current world system, governments must set a cost for emitting GHGs. As most economists advise, this should be done with revenue neutral carbon taxes (and not cap and trade or other easily corrupted schemes).

    If the situation is as dire as you propose, the taxes will be sufficiently high for the market to direct vast resources away from fossil fuels to the most viable alternatives. The last thing we want is for these resources to be directed by politicians with a shorter term outlook than nearly anyone else.

  21. Ray Ladbury:

    Toyota did well because the Japanese domestic car market demands small, efficient cars, and that demand has expanded as we approach Peak Oil. Japan’s domestic market demands small, efficient cars because Japan tases the bejesus out of gasoline. For the US market, Toyota (Honda, too) has been producing much larger vehicles. So it would appear to me that the Japanese government’s policies of artificially increasing the price of fuel deserves most of the credit, not necessarily farsightedness of corporate management. My point still stands. We’ve known Peak Oil was coming for a generation, and yet we are still poised for an economic shock because markets did not favor development of alternative energy sources as long as Oil was cheap.
    Now here’s something I really don’t understand. Why would you favor carbon taxes over cap and trade? Surely, cap and trade is closer to a market system. Yes, it can be corrupted or otherwise screwed up, but that is also true of taxation. And by opting for a tax you are leaving the policy in the hands of the same short-sighted politicians you so deplore.

  22. Hank Roberts:

    Market theory? Agonizing reappraisal.

  23. William Astley:

    B. Santer et al’s Fact Sheet.

    The following is a link to B. Santer et al.’s fact sheet. (Santer et al. in their paper assert they have refuted the conclusions of Douglass et al. 2007.)

    Looking at the Santer et al’s data, there are some unanswered questions.

    Look at the graph in the fact sheet which shows the tropical surface temperature & tropical mid-troposphere temperature Vs year, 1980 to 2005.

    There is an obvious holistic change pre 1992 vs post 1992, in surface temperature Vs mid-tropospheric temperature.…-factsheet.pdf

    There is almost no warming 1980 to 1992 of the mid-troposphere. As Douglass et al. state for that period the tropical mid-troposphere and tropical surface temperatures, track each other and there is no relative increase in the mid-troposphere temperatures. (i.e. The mid-troposphere does not warm 1980 to 1992.)

    After 1992 there is a sharp warming of both surface and troposphere. From 1992 to 2005 the mid-troposphere does warm more than the surface.

    There is however no explanation as to why starting in 1992 the mid-troposphere warming suddenly occurs. i.e. There is a mechanism change pre-1992 vs post-1992.

  24. Mark:

    Hank, #219. No, they could be affected before they die. However, anyone with enough money to be called “an investor” will be the last to be hit.

    E.g. Will someone with two houses be affected before someone who can only afford cheap housing (on a flood plain)?

    GW will affect the third world poor, then the third world rich, then the first world poor then the first world rich. By the time it gets to putting Bill Gates on his uppers or risking his life, it will likely be his children or grand children. Maybe not even then.

  25. pft:

    I try to keep an open mind, but when I read the paper whose sole purpose was to validate the models with observations since 1979, and saw that it stopped at 1999, it was obvious the reason why must have been that observations past 1999 were not predicted by the models. Despite increasing CO2 levels, temperatures are now at 1980 levels. The models can not account for this drop in temperature.

    [Response: Try to make sure that when you open your mind that your brain doesn’t drop out. The period 1979-1999 was chosen because that was what Douglass et al used, and which is the maximum period of overlap between the AR4 model simulations and the observations. See our previous post on the range of model simulations for the recent period – which include a significant number that have similar trends to observed, even while they have the same long term trends. – gavin]

  26. Hank Roberts:

    “… gradually … gradually ….”

    Yep, there’s a problem with their public position paragraph; the repetition of the word is a bit spooky.

  27. dagobert:

    Mark #223
    This is true not only for possible impacts of GW but also for the impacts of mitigation strategies like carbon taxes. If you can barely afford a small second hand car for your daily commute, you’ll be hit hard by more expensive fuel, while the typical driver of a Porsche Cayenne probably won’t even notice a difference.
    With cap and trade programs it comes down to the same thing. In the short run, it leads to higher prices for practically everything which effects the poor before the rich even notice. In order for the markets to swing to carbon mitigating technologies, something like an external ‘forcing’ is probably required, but it has to be applied very carefully and slowly. The car markets in Japan and Europe had decades to adjust to high fuel prices. Trying to apply the same sort of pressure too quickly to the US market could end in economical and social disaster.

  28. Rod B:

    Hank, I really appreciated your referenced article (222). I think it explains, indirectly at least, why capitalism and market driven systems need not be destroyed (as some here have maintained) because they are insufficient it some areas, but rather should be supplemented in those areas that capitalism or free private enterprise (a major part of individual freedoms) is not designed for or hasn’t the wherewithal to handle (ala tragedy of the commons) by appropriate government intervention, rule making, or regulation.. Subject to those requirements, then let capitalism and markets free to do what they do better than anything else.

    One caveat: some take that necessity to control and remove freedoms in certain circumstances, not as a restrained and strongly constrained action but as a rationalization to control and take liberties with total abandon to satisfy other “hidden” agendas. Got to be careful of and watch out for them.

    I don’t know if this is how you intended, but it’s how I took it.

  29. Mark:

    Dagobert #227 I have no clue as to what you’re trying to say.

    What does that have to do with #223? That was solely about how the mitigation cost is an immediate cost the wealthy pay now that won’t affect them for a long time. Point being that ‘the market’ won’t want to solve it: the capitalist system gives the ones with the most money the biggest say, whether they deserve that say or not.

  30. William Astley:

    This comment is in follow up to my comment 223. (The link to Santer et al’s fact sheet did not work in my comment 223 and it is necessary to see the graph from Santer et al’s paper to understand my comment and question.)

    From the above link.

    “Figure Caption: Estimates of observed temperature changes in the tropics (30°N-30°S). Changes are expressed as departures from average conditions over 1979 to 2006.”

    Look at the graph showing the temperature anomalies tropical surface and tropical mid-troposphere Vs time 1979 to 2006. Prior to 1992 is no mid-troposphere warming. From 1992 to 2006 the mid-troposphere does warm more than the surface.

    There is however no explanation as to why starting in 1992 the mid-troposphere warming suddenly occurs. i.e. There is a mechanism change pre-1992 vs post-1992.

    Douglass et al. 2007 note the same observation but reached a different conclusion than Santer et al.

    It seems it is not possible to determine which paper is correct without an explanation of the pre and post 1992 change.

  31. Lauri:

    RE 227
    With cap and trade programs it comes down to the same thing. In the short run, it leads to higher prices for practically everything which effects the poor before the rich even notice.

    Well, this is true only if you increase the amount taxed. The fiscal system can be adjusted so that environmental taxes do not increase the overall tax rate, or tax rate by income class. If you have international cap and trade, then, yes, the money that flows to another country has to be net collected in a way or another.

    This brings up the of question how big of a tax are we talking about. A typical CO2 price in computations is 20 $/ton CO2. That would mean (I hope I got the numbers right) 16 cents per gallon. Would the daily commuter notice this difference in the middle of the gas price ups and downs recently?

  32. Fred Staples:

    My occasional attempts to challenge the (90%) certainty about AGW expressed on this site seems to have received shorter shrift than usual.

    If you doubt (136) that current data shows little warming since the seventies, have a look at Tamino’s chart (first “this”, comment 29). Pay particular attention to the temperature scale on the left hand side – 1cm is equivalent to 0.2 degrees centigrade – and think about what we are trying to measure – the global average temperature, all of it, oceans, atmosphere and continents. Better still, take a few temperature readings during the course of a few days in your own environment, and see how they vary.

    As for the underlying climate science, here is a simple experiment. Turn off the bedroom radiator and go to bed on a cold night without bedcovers. When you feel cold, wrap yourself in a thick duvet and think about what happens.

    Are you warming the duvet, or is it warming you?

    What physical characteristic is responsible for the temperature drop across the duvet, inside to outside?

    Has radiation anything to do with the warmth that you experience?

    As for “explanations”, Hank, (138) I am trying to locate one of Gavin’s where I think he said that “in this context”, presumably atmospheric radiation, “heat and energy are equivalent”. Can you help?

  33. Hank Roberts:

    pft, seriously, read the thread Gavin points to.
    Once you understand basic statistics you see the world more clearly — and realize how easily a short run of numbers gets mistaken for a trend. If you don’t have the math, at least read the words and think hard about what they’re trying to teach.

  34. Peter Williams:

    Any idea why the models don’t show the negative temperature trend at 500hPa that the sonds do? That’s pretty interesting. What’s the tropopause – 250?

  35. Hank Roberts:

    > negative temperature trend at 500hPa …
    > What’s the tropopause – 250?

    What latitude are you asking about, Peter? Pointer please?

  36. Marcus:

    Fred Staples (#232): Obviously, the answer you are looking for in terms of the duvet is that it reduces heat loss by reducing convective heat losses. Of course, it also reduces radiative heat losses too. The mechanism being that the outside of the duvet is cooler than the inside of the duvet, and therefore the temperature differential with the heat sink is less, and therefore loss of heat is less. The duvet’s effectiveness depends on its conductivity, and on the conductivity of the air trapped between the duvet and the body.

    Of course, in the Earth system, we are surrounded by vacuum, and therefore there is _no_ convection (or conduction) loss. Therefore, for the Earth climate system, radiation is the ONLY heat loss mechanism, and therefore radiative absorption is key.

    But I seem to recall having a previous argument with you about how a vacuum flask works, and if you haven’t figured out how one works yet, you aren’t going to understand heat transfer in the climate system either. You might note that space blankets are popular because in addition to reducing convection, they are effective at reducing heat loss through evaporation and radiation as well. And the reason that cloudless nights are cooler than cloudy ones is because radiation loss is much higher.

  37. Hank Roberts:

    Sorry, Fred

  38. Hank Roberts:

    Typo; same result though, Fred:“heat+and+energy+are+equivalent”
    You’re looking for the first law of thermodynamics there.

  39. Peter Williams:

    Re 235: Hank, sorry – I’m not an atmospheric scientist. My background is hydrodynamics and turbulent transport. I’m just saying the sonds clearly show wider swings to the negative and positive than the models do. They’re more “S”-shaped, which is kinda interesting, because it tells you (I think) that there’s some interesting transport going on where the models have some room for improvement. What fraction of that is convective and what fraction is radiative I haven’t a clue, since it’s not my field.

  40. Peter Williams:

    PS … and so where the tropopause is, is important for figuring out that transport. I don’t really know the atmosphere so I’m not sure where that is in hPa, but it’s interesting to note that the sonds clearly show that the atmospheric lapse rate in the lowest part of the troposphere, from surface to 500 hPa, is becoming larger in magnitude. This region of the atmosphere is becoming more convectively unstable. In contrast, the region between 500 and 200 hPa is becoming less convectively unstable. Any deviation from a purely adiabatic lapse rate should be telling you something about vertical transport. What, I don’t know.

  41. Kevin McKinney:

    Returning to an earlier topic on this thread, I came across a report on EU Kyoto compliance today:

    “In 2006, four EU-15 countries (France, Greece, Sweden and Britain) had already reached a level below their Kyoto target.

    “Eight further EU-15 member states (Austria, Belgium, Finland, Germany, Ireland, Luxembourg, the Netherlands and Portugal) project that they will achieve their targets, but projections from three member states (Denmark, Italy and Spain) indicate that they will not meet their emission reduction goals. Of the eight percent target, 2.7% has already been achieved and should rise to a 3.6% cut through existing policies and measures by 2010. Buying carbon credits will account for another 3% and reforestation for carbon sink purposes another 1.4%.

    “The report also gives a long-term estimate of the emissions situation in Europe. Although emissions are projected to continue decreasing until 2020 in all 27 members of the EU, the 20% reduction target compared with 1990, endorsed by European leaders in 2007, will remain out of reach without the implementation of additional measures, such as the EU energy and climate change package proposed by the European Commission in January 2008, the agency said.”


    (Captcha: “policy produced”)

  42. Hank Roberts:

    Peter, when you write
    > the sonds clearly show …

    Are you saying this based on something besides looking at the picture at the top of this page? Are you referring to an article or a post on another weblog?

  43. Fred Staples:

    No Marcus, (236), it is not the convective effect. It is the insulating effect – the TOG value, or to be more precise the thermal conductivity of the duvet, which is responsible for most of the warming. If you doubt this, try replacing the duvet with a thin sheet, which will inhibit the convection.

    For the heat to be removed from your body you have to establish a substantial temperature differential across the duvet, which is why the inside of the duvet (and you) will feel 20 degrees centigrade warmer than the outside temperature if the duvet is thick enough. Radiative effects must be present, but they are negligible in comparison.

    Something similar is true of greenhouses. Everyone quotes the elimination of convection as the reason why the interior is warm. But you can still find radiative explanations of greenhouse warming (W in, 2W radiated from the interior, W back from the glass, W out, Page 18 of Global Warming by John Houghton, for example). To some extent this must be true – the point is that the radiative effect on the inside temperature is negligible.

    If the atmosphere consisted of Oxygen/Nitrogen only, its thermal conductivity would be very low, solar heating would be much the same, and the insulation effect (and the gravitational lapse rate) would produce a substantial temperature differential from the surface to the top of the atmosphere without any radiative absorption. Both the earth and the atmosphere would radiate directly to space. Add absorptive molecules and you will slow the radiation from the earth and add a radiative effect to the temperature differential – mainly from water vapour but also from CO2.

    I do not know how much the radiative effect will add to the surface temperature, but it is certainly not responsible for the whole 33 degrees differential attributed to the presence of the atmosphere. It is only this radiative effect which will be perturbed by additional CO2.

    If we think that the perturbation is significant, as the modellers do and many knowledgeable people do not, we must look to the data for confirmation. As Houghton and Hansen have both pointed out, we are looking for a small differential in an ill-defined temperature which is very difficult to measure accurately anywhere and which varies naturally over time, both randomly and systematically.

    The statistics of trend lines can help. A trend line will be significant if, and only if, the variance of the data about the trend line is sufficiently less than the variance of the data about its own mean. Relatively few data points can produce a significant trend if they are all close to the trend line; many data points may not produce a significant trend if they are widely dispersed.

    The F test in Excel does the maths, (Hank, 233) and has the additional bonus of calculating the range of trend lines within which the true trend probably falls. Sadly, the data points must be independent, and the variations about the trend lines must be normally distributed, which means that we cannot use the monthly data (where the downward trend since 2001 is significant) because the values appear to be serially correlated.

    It is obviously easier to establish significance (and be more confident) if we have a long time period and many data points. The downward trend in the annual data since 2001 is not significant now, but if the current 1978 temperatures persist it will be.

    My point, however, is that neither the trend data, nor the underlying theory give any support for the (90%) certainty that most of the warming during the last century was anthropogenic.

    As Sir John Houghton said, in 2001:

    “The fact that the global mean temperature has increased since the late 19th century and that other trends have been observed does not necessarily mean that an anthropogenic effect on the climate has been identified. Climate has always varied on all time-scales, so the observed change may be natural.”

    Since 2001 his doubts must have been reinforced.

    [Response: Hardly – gavin]

  44. Hank Roberts:


    That short snippet from Houghton (IPCC, 2001) is being blogflogged like crazy recently by people who don’t know how to look these things up. At least they make it easy to identify them by doing so.
    Hoist on their own petards.

    Global Warming – The Complete Briefing 3rd Edition, John Houghton
    New ISBN: 9780521528740

  45. Ike Solem:

    Re Fred Staples:
    “My point, however, is that neither the trend data, nor the underlying theory give any support for the (90%) certainty that most of the warming during the last century was anthropogenic.”

    Wrong. By your argument, if no one had collected any data, then there would be no possibility of global warming. What if there was no instrumental record whatsoever from the 20th century? What if all the data was erased (by aliens, say)? Could one then say anything with certainty?

    Of course one could! We can use physical theory to predict tides, planetary orbits, trajectories, even the effects of heating of a fluid (like our atmosphere). We are not at all reliant on statistical analysis of data to predict the future.

    It’s worth reminding readers that there are two general approaches to modeling – one is the statistical method, and the other is the dynamical method (sometimes called first principles), and there are all manner of blends.

    To review the dynamical method, we start with the atmosphere and we pretend that none of the air molecules can move – they are fixed in place. This allows us to create a “radiative balance” model, which calculates how energy from sunlight and from the earth’s surface is absorbed and emitted. This gives you an exaggerated temperature profile: too warm at the surface, too cold aloft.

    Then, we add in fluid dynamics and convection (warm air rises, right). Then, we have a radiative-convective model of the atmosphere, which allows us to calculate how changing the composition of the atmosphere changes the radiative effect.

    The so-called greenhouse gases are of interest here, in that they are mostly transparent to sunlight, but opaque to infrared. The earth’s radiative spectrum is all in the infrared, so if you increase the concentration of those gases, you should see some warming. How much? That’s what models are for.

    Now, if we want to move further into the future, we have to include the oceans, which are also absorbing heat from the atmosphere – so if we warm the atmosphere, we warm the oceans (as well as the land surface). Our planet’s surface is 70% water. This is an area of great complexity. Ocean circulation models are complex, and the exchange between the atmosphere and the ocean is even more so. Are the models reliable? Well, so far they’ve been conservative, haven’t they? The rate of Arctic melting, in reality, has exceeded the model predictions, leaving one to conclude that the models appear to be underestimating the response.

    Furthermore, the models do not predict future changes in atmospheric composition, do they? To do that, they would have to include the entire biosphere, as well as the main uncertainty, future human behavior.

    Can you produce a model that predicts future human behavior? Economists have tried, and all their results have ended in dismal failure. Will rational long-term self-interest outweigh short-term greed? Good luck predicting that one.

    Regardless, the fundamental flaw in your reasoning is your lack of knowledge about the difference between statistics and dynamics, which you appear to not to understand at all.

  46. Ray Ladbury:

    Oh, Fred, you poor man, you are so confused!

  47. Marcus:

    Fred: What is the thermal conductivity of a vacuum? It is ZERO. So adding a low thermal conductivity atmosphere on top of the planet doesn’t do much if it is transparent to radiation. Basically, in the absence of any longwave trapping gases, the sun will heat the surface to 255 degrees Kelvin. The atmosphere, in equilibrium with the surface, will cool at the dry lapse rate (and be really really cold at high altitudes). But because it is completely transparent to radiation, the surface will continue to loss heat as a 255 K blackbody straight out to space through _radiation_. Insulation only works if it blocks a relevant heat loss mechanism.

    Again, why is a clear night colder than a cloudy night? Why does a vacuum flask work? Why does a duvet with big holes or a greenhouse with lots of open windows not work very well? Why do space suits have heat exchangers to cool the astronauts? (hint: because vacuum insulates perfectly for everything except radiative heat loss)

  48. Steve Carson:

    Sorry to be off-topic, can anyone recommend 2 or 3 good introductory climatology books. I’ve read the IPCC TAR “Overview of the Climate System” – section explaining the basics of climate. I’ve got an engineering degree. I’m motivated to learn. Recommendations appreciated. Thanks.

    And apologies for making some of you angry, but..

    There must be many thousands (tens of thousands?) visiting this site because they aren’t sure what the truth is about human-induced climate change. Systematically characterizing people with opposing viewpoints as deceitful/bad/evil or stupid is not helping your cause. Even if you can see clearly into the hearts and minds of others, keep it to yourselves and just explain climate theories as clearly as you can.

  49. Mark:

    Fred #243, no the TOG doesn’t do ANY heating. Your body does the heating and the duvet slows it getting away from your skin.


    Now add that the earth/atmosphere/space isn’t you/duvet/atmosphere and you have nothing to state.

    The TOG/Duvet is only illustrative of how adding even more insulation can still cause a lot of extra insulation, so the “CO2 is 100% saturated” is not valid as why there’s going to be no more GW.

    Oh, and what happens to you if you are sleeping in a summer night at 20C? Will your body be at 40C? No? Then your “duvet keeps you 20C warmer” is a load too.

  50. Barton Paul Levenson:

    Fred Staples writes:

    If the atmosphere consisted of Oxygen/Nitrogen only, its thermal conductivity would be very low, solar heating would be much the same, and the insulation effect (and the gravitational lapse rate) would produce a substantial temperature differential from the surface to the top of the atmosphere without any radiative absorption.

    No, it would not. With no clouds, the albedo would be about 0.13 and the Earth and atmosphere would both be at abougy 277 K. You’d have no lapse rate at all.