"The American Enterprise Institute is launching a major project to produce a review and policy critique of the forthcoming Fourth Assessment Report (FAR)." Thus begins a letter recently sent to my colleagues Jerry North and Steve Schroeder. This letter invites them to write a "well-supported but accessible discussion of which elements of climate modeling have demonstrated predictive value that might make them policy-relevant and which elements of climate modeling have less levels of predictive untility, and hence, less utility in developing climate policy."
I fully support the idea that people should dive into the AR/4 (that's what everyone else calls the Fourth Assessment Report) and take a look at the science themselves. While one might be skeptical that the AEI will give the AR/4 a fair hearing, the fact that they have solicited input from a credible and mainstream scientist like Jerry North suggests to me that I should not prejudge their effort.
That said, I think they've set themselves up to fail by their choice of question. "What's the policy value of climate models?" can be split into two parts:
(1) What are the scientific uncertainties in the models?
(2) Given this level of uncertainty, can model predictions then be used as a basis for action?
Question 1 is a scientific one, which fills thousands of journal pages every year. This could indeed be a valid subject for a scientific review paper. Quesiton 2, however, is not a scientific one. Two people can agree on the level of uncertainty in the model but disagree on whether that level of uncertainty precludes or demands action --- it just depends on a value judgment about how risk averse we should be.
For example: one person can say, "if there's a 1% chance that climate change might lead to catastrophic impacts, then we need to act now." Clearly the models provide that level of certainty. Another person might say, "I think we should be 99% certain that climate change is a significant risk before we take action." The models do not provide that level of certainty, so to that person the models are too uncertain. The choice of 1% vs. 99% is a moral judgment, not a scientific one.
This type of tangling between positive (scientific) and normative (moral) questions is one of the major reasons that the climate change debate can be so confusing to the general public. We discuss this in chapter 2 of our book.
Also note: they're willing to pay $10,000 to the authors. That's A LOT of money for this type of activity. It was enough that it made me think, "maybe I should get involved with this." Then I snapped back to reality.
[note added 7/31: My wife read this blog, saw the figure of $10,000, and asked me sweetly, "Are you SURE that climate change is real? We could really use the money."]