Tuesday, February 27, 2007
Responding to the kind of arguments I have quoted concerning global warming skepticism, Judge Posner writes:
The global warming skeptics point out that there are natural climate fluctuations [and] that anticapitalists are enthusiastic beaters of the drum for action against global warming . . . . These points are correct, but do not support the skeptical position. The existence of natural climate fluctuations increases the risk from human-caused global warming, because increased atmospheric concentrations of carbon dioxide increase the amplitude of the fluctuations. The fact that the motives of some of the people who are worried about global warming are political is irrelevant to the scientific issues, not only because scientists use apolitical methods of testing their hypotheses, but also because there are politics on both sides of the global warming debate: if leftwingers exaggerate the danger of global warming, rightwingers belittle them excessively.
Let me respond to these points. Posner has made a great deal of the first one: that natural fluctuations might combine with human caused global warming to cause a truly catastrophic increase in temperatures. I have no reason to question Posner's claim, but he fails to draw a distinction here. If there are natural fluctuations, then the global warming we have observed so far might not be due to human causes. So the natural fluctuations increases the possibility of a worst case scenario, but also decreases the possibility that the observed fluctuations are actually the result of human activities. He should acknowledge this. How one should respond to these fluctations is a more difficult matter than Posner acknowledges in his post.
Posner also claims that "scientists use apolitical methods of testing their hypotheses." Well, yes, except when they don't. Or put differently, there is a long history of "scientists" reaching scientific results with practical conclusions that turned out to be wrong. And this is most likely to be the case when the practical conclusions are a matter of political debate. Whether it is being in favor of eugenics, advocating that women not breast feed, predicting population explosions, or recommending that people eat low fat/high carb diets, the supposed "apolitical methods" are problematic. They are subject to biases of overconfidence and also the problem of extremism, which occurs when a "consensus" is used to keep people quiet. (See, e.g. some of Cass Sunstein's work on deliberation.) And these problems seem especially apt in a "science" like climate change where the models are so complicated and where, as I understand it, there is not much opportunity for real testing of whether the models can predict.
My sense is that Judge Posner prides himself on being a conservative who is not ideological -- who can fairly take science into account when it cuts against his ideology. His hostility to libertarians and Hayek falls under this category. But ideological mistakes are not the only mistakes. Failing to recognize the limits of science and experts is an important one and I believe Posner falls prey to it here and generally.