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Are IPCC climate-forecasting methods too complex?

Authors:
Kesten Green at University of South Australia
Kesten Green
J. Scott Armstrong at University of Pennsylvania
J. Scott Armstrong
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Abstract and Figures

The United Nations Intergovernmental Panel on Climate Change’s (IPCC’s) forecast of dangerous manmade global warming is an important influence on public policy decisions in many countries. Rational policies require that policy makers obtain forecasts from evidence-based methods. A review of comparative studies found that sophisticatedly simple methods, which can be readily understood by decision makers, provide forecasts that are substantially more accurate than those from more complex methods. Using a checklist of nine items, we assessed the simplicity of the IPCC’s forecasting procedures. The checklist items cover the understandability of the forecasting process and models, and the clarity of the relationships between the model outputs, forecasts, and decisions. Our checklist responses gave the IPCC procedures a “simplicity rating” of 1.7 or 19%. In contrast, a “no-trend forecast,” obtained a simplicity rating of 8.4 or 93%. We suggest that making policy decisions on the basis of forecasts from poorly understood procedures could be characterized as “faith-based policy making.”
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