Tuesday, February 27, 2007

Posner on Global Warming Skeptics
Mike Rappaport

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.


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Mike Rappaport


Maybe what Posner is trying to say is that when one discusses scientific issues, one should appeal to scientific arguments rather than Ad Hominem attacks.

Posted by: USD Law Student | Feb 27, 2007 7:31:32 PM

I am not making an ad hominem attack. Calling people who didn't serve but favor war "chicken hawks" is an ad hominem attack. My point is that there are biases and other circumstances that make it more likely for people to adopt mistaken positions. I am pointing these biases and circumstances out.

Posted by: Michael Rappaport | Feb 27, 2007 9:57:20 PM

Perhaps this is an obvious point, but I think that the credibility that scientists' command comes from experimental sciences where a hypothesis can be rigorously tested through controlled experiments. With experimental sciences no one is particularly concerned about the ideology of the scientist, only with the results of his experiments, which can be repeated by other scientists. The double-blind controls of experimental sciences are there precisely because scientists recognize how the prejudgments of the scientists can effect the results in unintended and subtle ways.

Climate modeling is far removed from experimental science. It is based on complex computer models that would be difficult for anyone to analyze who did not play a role in their creation. The models although complex and far less complex then the climate that they are modeling and contain many assumptions about processes that are not fully understood. Moreover, the models are based on limited historical data that has shown limited variation in the past two hundred years. There is a great deal of room for the prejudgments of the scientists to effect the results.

In my view, climate models have more in common with the "science" of ecomomics than, say, physics. Although for many years people who made their living creating macro-economic models touted the value of their work, I think most economists have come to understand that macro-economic models are at this stage of their development pretty much worthless. Many of the consensus views of economists that were once based on these macro-economic models have been discredited. I don't have sufficient knowledge of climate models to critique their validity, and they may very well turn out to be accurate models. But I certainly will not be surprised if they go the way of macro-econmetric models.

Posted by: PaulD | Mar 1, 2007 4:00:21 AM

I am suprised to see Posner become lost in the Warming "debate". The Warming crowd is Chicken Little wearing the Kings Cloths. There is no compromise to be found between correct and incorrect, and the right to be heard does not include the right to be taken seriously. But the consequences of accepting this as legitimate are very serious, if you actually believe the stated goals of the Warmists. They have constructed their house of cards, and cannot tolerate the slightest wind. Posner's ignorance on the subjest is not shared by those who have taken to scorn after being subjected to years of weekly falderal.

Posted by: james Wilson | Mar 7, 2007 7:10:32 PM