Climate Change.

AuthorVan Doren, Peter

Climate Change

* "What We Know and Don't Know About Climate Change, and Implications for Policy," by Robert Pindyck. June 2020. SSRN #3614104.

The author who has most informed my thinking about climate change is Robert Pindyck, professor of economics at MIT's Sloan School of Management. In this paper, he explains clearly how little we know, why we know so little, and how that lack of knowledge matters for policy.

He first looks at the science of climate change and projections of the likely effect of carbon emissions on future temperatures. He reviews the 140 studies that have been published since 1970 on "climate sensitivity"--the increase in the global average temperature that would result from a doubling of atmospheric carbon concentration. Most of the studies (115 of the 131) have "best estimates" of this increase that range from 1.5[degrees] to 4.5 [degrees]C. That is a wide range, and if we include the outlier 16 studies' "best estimates," that range expands to between 0.5[degrees] and 8[degrees]C. The uncertainty in the estimates is increasing slightly over time: the standard deviation in post-2010 studies is 1.13 as compared to 1.03 in pre-2010 studies.

Why is there such uncertainty? The short answer is feedback loops: changes in the underlying physical processes arising from initial temperature increases created by increases in carbon concentration. We do not know if feedback is normally distributed nor do we know its mean and standard deviation. An important article in Science in 2007 ("Call Off the Quest," by Myles R. Allen and David J. Frame, 318[5850]: 582-583) argued uncertainty about climate sensitivity is in the realm of the "unknowable" and that the uncertainty will remain for decades.

What economic damages result from temperature increases? We have some sense of how higher temperatures might affect...

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