More experts confirm that IPCC temperature predictions are bunk

by William Yeatman on June 8, 2004

in Science

The careful work of Ian Castles, former chief statistician of Australia, and David Henderson, former chief economist of the OECD, in analyzing the implausibility of the economic projections on which the temperature increases predicted in the UN Intergovernmental Panel on Climate Changes Third Assessment Report critically depend was dismissed intemperately by the IPCC late last year (see Dec. 26, 2003 issue). Now, independent experts have confirmed the validity of Castles and Hendersons analysis and exposed the inadequacy of the IPCCs reply.

The debate centers around the validity of using Market Exchange Rates (MERs), as the IPCC does, or Purchasing Power Parity (PPP) as the basis for predicting future economic output. The responses of the IPCC (also referred to in this context as the SRES Teams) have now been reviewed by an expert in economic statistics, Jacob Ryten, a leading figure in the development, evaluation and implementation of the International Comparisons Programme.

Mr. Ryten comments that he “cannot help being shocked by the contrast between the [IPCC] Teams bold assertions and peremptory dismissal of the arguments advanced by Castles and Henderson, and their manifest ignorance of the conceptual and practical issues involved in developing and using intercountry measures of economic product.” Mr. Ryten concludes (referring to the IPCCs choice of MER over PPP) that, “Worse than rejecting a statistical measure of which one is ignorant even though it appears to answer an intelligible question is accepting one about which one is equally ignorant but answers no intelligible questions whatsoever.” Ryten’s paper is to appear in a forthcoming issue of Energy & Environment.

The criticisms have also been investigated by Professor Warwick McKibbin of the Australian National University and the Brookings Institution and two co-authors (the resulting paper is now available on the Lowy Institute website at ation.asp?pid=129).  Professor McKibbin and his colleagues have also prepared and are considering the publication of a reduced version of the paper which focuses on the SRES aspects. Among its more important conclusions are:

*    The SRES scenarios in their present form are neither transparent nor reproducible. The relationship between the driving force assumptions and projected emissions is “far from clear,” and until this information is made available “it is difficult to assess the usefulness of the SRES projections;”

*    There are various problems with these projections which would arise if the SRES authors had done what they said they had done, but “it may just be that the models did something completely different to what is suggested in the SRES report;”

*    It is crucial to understand the drivers of emissions projections and their sensitivity to changes in key assumptions, but “this understanding cannot be gleaned from the SRES in its current form;” and

*    The broad range of projections produced by the IPCC without any sense of likelihood is “of limited use to policymakers” and is “potentially misleading.”

The current state of the debate was summed up by the Economist (May 27) as follows: “The IPCC claims that measuring at PPP or market exchange rates does not affect the economy any more than a switch from degrees Celsius to Fahrenheit alters the temperature. But the analogy is wrong. PPP and market exchange rates, unlike Celsius and Fahrenheit, are measuring different things. That should not be too hard an idea for scientists to grasp.”

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