Climate Change Cloud War


Fighting words over clouds.

Climate change scientific politics can be really vicious. The latest outbreak of nastiness is over a recent paper [PDF] published by University of Alabama climatologists Roy Spencer and William Braswell in the journal Remote Sensing. In general, computer climate models find that increases in temperature drive changes in cloud cover which drive further increases in temperature. Simplifying considerably, Spencer and Braswell find that changes in clouds can actually drive temperatures. In other words, casuality can work both ways. The upshot is that if Spencer and Braswell are correct then the computer computer models are likley projecting higher global temperatures than may actually occur as a result of adding greenhouse gases to the atmosphere. (Go to Spencer's blog for a "primer" on the paper's findings. Scroll down.) 

In addition, Massachusetts Institute of Technology climatologist Richard Lindzen and Yong-Sang Choi of Ewha Womans University in South Korea also published a new paper [PDF] in the Asia-Pacific Journal of Atmospheric Sciences analyzing the feedback effects of sea surface temperature changes and clouds. What they are trying to get at is climate sensitivity which is defined as "how much the average global surface temperature will increase if there is a doubling of greenhouse gases (expressed as carbon dioxide equivalents)." Lindzen and Choi found "that all current models seem to exaggerate climate sensitivity (some greatly)." 

Now these results are quite at variance with the "consensus" of "mainstream" climate scientists. To trot out Carl Sagan's old (but good) slogan: Extraordinary claims require extraordinary evidence. In any case, the two papers apparently provoked considerable angst (even backlash) from mainstream researchers.

Earlier this week, Texas A&M atmospheric scientist Andrew Dessler published a paper in Geophysical Research Letters that aims at directly refuting the findings of Spencer and Braswell. Dessler's energy budget analysis argues that the two papers are, among other things, confusing changes in the El Nino Southern Oscillation system in the Pacific Ocean with changes in cloud feedback dynamics. In addition, Dessler accuses Spencer and Braswell of cherrypicking data. Dessler reports that Spencer and Braswell ran 14 climate models with their specifications, but reported the results of only the six that supported their claims. Dessler published the figure below which he asserts shows all the model runs that together tend to support the notion that rising temperatures produce positive cloud feedbacks.

Climate model runs

Thus Dessler concludes: 

…the observations presented by [Lindzen & Choi] and [Spencer & Braswell] are not in fundamental disagreement with mainstream climate models, nor do they provide evidence that clouds are causing climate change. Suggestions that significant revisions to mainstream climate science are required are therefore not supported." 

Now this is how the process of science is supposed to work: a researcher makes a claim and other researchers look at the claim and try to refute it. This back-and-forth eventually yields something close to reality. And I still have confidence that it will here. But passions run high when it comes to climate change. After all, both sides make apocalyptic claims: the end of the world vs. the end of the economy.

One of the odder features of the current battle over clouds is that the editor of the journal that published the Spencer and Braswell paper, Remote Sensing, has resigned. The editor, Wolfgang Wagner declared…

…the problem I see with the paper by Spencer and Braswell is not that it declared a minority view (which was later unfortunately much exaggerated by the public media) but that it essentially ignored the scientific arguments of its opponents. This latter point was missed in the review process, explaining why I perceive this paper to be fundamentally flawed and therefore wrongly accepted by the journal. This regrettably brought me to the decision to resign as Editor-in-Chief…

For their part, Spencer and Braswell assert that they did not "ignore the scientific arguments of its opponents," but, in fact, that was the whole point of their article. In any case, if the claims made by Wagner are true, then the proper thing to do is to retract the paper, something which Wagner did not do, nor has he even suggested it. 

The explosion of comment caused by this contretemps in the blogosphere can be found on the more "skeptical" side of climate science at Spencer's blog, Wattsupwiththat, ClimateAudit, and Roger Pielke, Sr.'s Climate Science. For the more "alarmist" take go to RealClimate, DailyClimate, ClimateProgress, and Deltoid.