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Andrew Dessler's New Paper Debunks Both Roy Spencer And Richard Lindzen

Posted on 6 September 2011 by Rob Painting, dana1981

Andrew Dessler, a climate scientist at Texas A&M University, has released a scientific paper (Dessler 2011) that looks at the claims made by two of a small group of "skeptic" climate scientists who regular SkS readers will be familiar with: Roy Spencer and Richard Lindzen.  Both were co-authors on peer-reviewed papers released this year (Spencer & Braswell [2011] & Lindzen & Choi [2011]) which, once again, sought to overturn the orthodox view of climate.  Dessler (2011) finds that the conclusions of these two papers are unsupported by observational data. 

Spencer & Lindzen: Tipping reality on its head

The Spencer/Braswell and Lindzen/Choi papers have an unusual take on global warming: rather than warming causing a change in cloud cover (i.e. acting as a feedback to either increase or reduce warming), both papers claim that it's the other way around - changes in cloud cover cause changes in the surface temperature (in the present case, warming).

Spencer/Braswell and Lindzen/Choi look at the relationship between changes in ocean heat, cloud cover (directly affecting the amount of heat lost to space), and global surface temperature over recent decades. The idea is, if the change in surface temperature over that period is affected by changes in cloud cover, but changes of the surface temperature associated with the ocean warming are small, then changes in cloud cover must be driving the present global warming.

Dessler: Putting reality back on its feet  

Putting aside the problems with their energy budget equation, Dessler looks at the values Spencer/Braswell and Lindzen/Choi use for their calculations.  Rather than examine the data for two of the terms in their equation (heating of the climate by the ocean & change in cloud cover allowing heat to escape to space), Lindzen and Spencer approximate them from other observations, and their results rely heavily on assumptions about the size of these values.

Rather than rely on assumptions, Dessler uses other observational data (such as surface temperature measurements and ARGO ocean temperature) to estimate and corroborate these values.  Dessler finds that, in contrast to Spencer/Braswell and Lindzen/Choi, the change in cloud cover is far too small to explain the short-term changes in surface temperature, explaining only a few percent of surface temperature change.  In fact, the heating of the climate system through ocean heat transport is approximately 20 times larger than the change in top of the atmosphere (TOA) energy flux due to cloud cover changes.  Lindzen and Choi assumed the ratio was close to 2, while Spencer and Braswell assumed it was close to 0.5.

Dessler finds that the short-term changes in surface temperature are related to exchanges of heat to and from the ocean - which tallies well with what we know about El Niño and La Niña, and their atmospheric warming/cooling cycles.

Spencer & Braswell: A classic example of cherrypicking

In order to claim that the climate models differ from observations when comparing the surface temperature and energy leaving the Earth at TOA with the lead-lag between them, Spencer/Braswell cherrypick  observational data and model results that show the greatest mismatch (Figure 1).

Figure 1: Dessler (2011) reconstruction of Spencer & Braswell's figure 3, showing relationship between top-of-atmosphere (TOA) net flux and surface temperature, as a function of lag between them.  The blue line is the observational data chosen by Spencer and Braswell.  The red lines show other available observational data.  The shading represents the two-sigma uncertainty of two of the data sets.  The black lines show climate model results.  The black lines with crosses show the climate model runs chosen by Spencer and Braswell in their paper.

The blue line in Figure 1 is the TOA and Hadley Centre surface temperature data chosen by Spencer/Braswell, and the red includes other datasets of the surface temperature. The black lines are the 13 climate model runs, with the 'crosses' indicating 5 of the 6 models analysed by Spencer/Braswell.  Although Spencer/Braswell analyzed 14 models, they only plotted the 3 with highest and 3 with lowest equilibrium climate sensitivities.

In the process, Spencer and Braswell excluded the three climate model runs which best matched the observational data.  Dessler found that these three model runs were also the ones which are among the best at simulating El Niño and La Niña, which is not surprising, given that much of the temperature change over 2000-2010 was due to the El Niño Southern Oscillation (ENSO).  Thus Dessler concludes that

"since most of the climate variations over this period were due to ENSO, this suggests that the ability to reproduce ENSO is what's being tested here, not anything directly related to equilibrium climate sensitivity."

Violating the Laws of Thermodynamics

Dessler also examines the mathematical formula that both studies use to calculate the Earth's energy budget, and finds that it may violate the laws of thermodynamics - allowing for the impossible situation where ocean warming is able to cause ocean warming.

Much ado about nothing   

The short-term change in surface temperature over the 2000-2010 period is a result of ocean heat being exchanged with the atmosphere (via ENSO). This in turn alters atmospheric circulation, which alters cloud cover, but the impact of cloud cover on surface temperature only explains a small percentage of the surface temperature change.  Thus the lead-lag relationship between heat leaving the Earth at TOA and surface temperature reveals nothing about what is driving the short-term surface temperature change. 

In short, the "skeptic" hypothesis that changes in cloud cover due to internal variability are driving global warming does not hold up when compared to the observational data.  Once again we have two heavily-hyped "skeptic" papers that have failed to live up to their billing.

 


 

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Comments 51 to 64 out of 64:

  1. Forgive me, if this comment is off track. Apropos of "accuracy of climate models", a letter in my local paper suggested that current research by Dr Craig Woodward at School of Geography, Planning and Environmental Management, Uni of Queensland "may have significant impacts on climate models used for predicting global warming". Head of school (I think) Prof James Shulmeister is purported to have said: "All our current climate models may be way off base." Research involved looking at fossilized chitinous head capsules of larvae in mud layers in lake beds for info about climate at the time they lived. Anyone know how that impacts on accuracy of models? Been following weekly blogs and commentary with fascination. But bit new to this form of communication. Hope I haven't broken the thread.
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  2. Dave123: You have hit it on the head. You can't make a case with present evidence for clouds doing much. Neither Dessler nor Spencer have shown with any certainty anything. It is good that they are looking at this issue, but as of today, nothing conclusive is derived from either authors papers.
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    Response:

    [DB] Camburn, the inescapable conclusion one draws from Dessler's paper and your comments on it is that you simply do not understand what it is you are reading.

  3. You mistake my meaning Camburn. The central tendency of the data points to a small effect, not something that overturns the 2-4.5 sensitivity range of the IPPC that centers on 3. The denialist position magnifies this uncertainty to an unworldly extent.
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  4. Philip Armit, unless the research can change the absorption and emission spectra of CO2, CH4, and H20, change measurements of albedo, change cloud and aerosol feedbacks, and change other elements of "current climate models," I doubt if such a paleo study can do much with a "current climate model." Now, if you actually meant "change our understanding of past climate change," then, yes, that's more possible. Further discussion should move to one of the paleo posts/arguments. Don't worry about your comments getting lost on an old thread, as many regulars here watch the "recent comments" page.
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  5. The funny part about McIntyre "auditing" Dessler 10 is that, Dessler's is the conservative look at the subject and draws wide conclusions based on the error bars. The ones making the outlandish claims about cloud effect on the climate are Spencer and Lindzen! He says he has all the data. He has all the papers. This should surely put the idea that McIntyre is an independent "auditor" into serious dispute.
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  6. 51, Philip Amit, Dr. Shulmeister's quote doesn't at all mean what it implies when considered out of context. It is very clear from the article (here) that what they are discussing is only a new method of measuring, by proxy, precipitation levels in Australia. He is talking about an opportunity to better evaluate the actual versus modeled precipitation levels specifically predicted for Australia. This is very, very different from the implied idea that all climate models are way off base in every way. Also note that a better place for your comment would have been Models are Unreliable. In the future, if you have a question that seems off-topic, please use the search button in the upper left corner to find an appropriate thread and post your comment or question there.
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  7. 53, Dave123, If you don't mind my putting words (back) into your mouth (meaning you did say this in your comment #50), what you mean to say is that "the central tendency of the data points to a small short term effect." This work says nothing whatsoever about the long term changes in clouds, and their ultimate feedback resulting from increased temperatures resulting from increased CO2 levels. Camburn's attempt seems clearly aimed at somehow twisting these studies to imply that we know nothing at all about clouds and so can't fairly estimate climate sensitivity, when the only commonality in the two ideas is that the word "clouds" appears in both.
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  8. 57, Sphaerica- Absolutely correct! Dave
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  9. The first sentence of the article contains one too many "the"'s.
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  10. Roy Spencer posted on WUWT defending his work re: Dessler, albeit not too well in my opinion. I asked why he didn't show the other 8 models he ran (the ones that, you know, didn't disagree with the temperature data as much as the 6 he did show), and whether or not he had some physical mechanism postulated that could cause cloud coverage to vary consistently and over a climate relevant (>10 years) period +/- from the temperature driven water vapor cycle. I noted that he really did not do himself any favors by selecting only the strongest evidence for his hypothesis, despite running multiple models. Waiting to see if he actually responds to my questions...
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  11. KR @60 The fact that Spencer is using an anti-science web site to try and defend his scientific integrity is incredibly ironic, and desperate to boot. It also shows that Spencer is interested in influencing as many misguided, uninformed and gullible minds as possible-- he is engaging in propaganda.
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  12. Spencer's WUWT post is just a re-post of the poor defense of his paper on his own blog. In it he fails to explain why he omitted 8 of the climate model runs (including the ones which best matched the data), why he chose the observational data set which maximized the model-data discrepancy, why he failed to include error bars, etc. Basically the only of Dessler's points against his paper he addressed was the ocean heat transport to cloud TOA flux change ratio (Dessler's 20:1). Spencer claims it's closer to 2:1, but commenters on his blog have already identified some errors in Spencer's calculation. It's also ironic that Spencer criticizes Dessler for supposedly not using the "best" data, when Spencer didn't even attempt the calculation in his own paper.
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  13. Joshua Hill over at PlanetSave included a brief You Tube video by Dressler in his post of yesterday (Sep 6) “Clouds Do Not Cause Climate Change.” Perhaps one of the moderators with more technical expertise than I could import that video onto this comment thread -- or perhaps incorporate it into the article itself.
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    Moderator Response:

    [DB] Embedded video in the OP at the end.

  14. Dr. Dessler's paper is available here: http://geotest.tamu.edu/userfiles/216/Dessler2011.pdf The link at the top of this page is obsolete.
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