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On the Political Relevance of Scientific Consensus

Senator James Inhofe (R-OK) has released a report in which he has identified some hundreds of scientists who disagree with the IPCC consensus. Yawn. In the comments of Andy Revkin's blog post on the report you can get a sense of why I often claim that arguing about the science of climate change is endlessly entertaining but hardly productive, and confirming Andy's assertion that "A lot of us live in intellectual silos."

In 2005 I had an exchange with Naomi Oreskes in Science on the significance of a scientific consensus in climate politics. Here is what I said then (PDF):

IN HER ESSAY "THE SCIENTIFIC CONSENSUS on climate change" (3 Dec. 2004, p. 1686), N. Oreskes asserts that the consensus reflected in the Intergovernmental Panel on Climate Change (IPCC) appears to reflect, well, a consensus. Although Oreskes found unanimity in the 928 articles with key words "global climate change," we should not be surprised if a broader review were to find conclusions at odds with the IPCC consensus, as "consensus" does not mean uniformity of perspective. In the discussion motivated by Oreskes’ Essay, I have seen one claim made that there are more than 11,000 articles on "climate change" in the ISI database and suggestions that about 10% somehow contradict the IPCC consensus position.

But so what? If that number is 1% or 40%, it does not make any difference whatsoever from the standpoint of policy action. Of course, one has to be careful, because people tend to read into the phrase "policy action" a particular course of action that they themselves advocate. But in the IPCC, one can find statements to use in arguing for or against support of the Kyoto Protocol. The same is true for any other specific course of policy action on climate change. The IPCC maintains that its assessments do not advocate any single course of action.

So in addition to arguing about the science of climate change as a proxy for political debate on climate policy, we now can add arguments about the notion of consensus itself. These proxy debates are both a distraction from progress on climate change and a reflection of the tendency of all involved to politicize climate science.

The actions that we take on climate change should be robust to (i) the diversity of scientific perspectives, and thus also to (ii) the diversity of perspectives of the nature of the consensus. A consensus is a measure of a central tendency and, as such, it necessarily has a distribution of perspectives around that central measure (1). On climate change, almost all of this distribution is well within the bounds of legitimate scientific debate and reflected within the full text of the IPCC reports. Our policies should not be optimized to reflect a single measure of the central tendency or, worse yet, caricatures of that measure, but instead they should be robust enough to accommodate the distribution of perspectives around that
central measure, thus providing a buffer against the possibility that we might learn more in the future (2).

ROGER A. PIELKE JR.
Center for Science and Technology Policy Research,
University of Colorado, UCB 488, Boulder, CO
80309–0488, USA.

References
1 D. Bray,H. von Storch, Bull.Am.Meteorol. Soc. 80, 439 (1999).
2. R. Lempert, M. Schlesinger, Clim. Change 45, 387 (2000).