The Global Warming Challenge

Evidence-based forecasting for climate change

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Professor Armstrong's letter to Senator Boxer on the forthcoming publication of Polar Bear Population Forecasts: A Public-Policy Forecasting Audit

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April 9, 2008

The Honorable Barbara Boxer
Chairman, Committee on Environment and Public Works
United States Senate
Washington, D.C. 20510

Dear Senator Boxer,

Since presenting the presentation of my testimony on the validity of the government polar bear forecasts at your U.S. Senate Environment and Public Works Committee hearing on January 30 of this year, I along with my co-authors Kesten Green of the University of South Australia and Willie Soon of the Harvard-Smithsonian Center for Astrophysics, have continued to work on our research paper on the methods that were used to make the forecasts. Thanks to extensive peer review, we have made many improvements. I enclose a copy of the paper. The current version of the paper is always available at

I am pleased to inform you that it has now been accepted (subject to further revisions) by Interfaces. Thus, it stands as the only peer-reviewed study on polar bear forecasting that has been accepted for journal publication.

We found the forecasts of declining polar bear numbers contained in the government’s administrative reports were not the product of scientific forecasting methods. Given the large current population of bears and the upward trend in the population, our findings lead to the conclusion that there is no scientific basis for listing polar bears. Indeed, a reliance on evidence-based forecasting suggests that it is more likely that the polar bear population will increase rather than decrease.

I would be happy to discuss the details of our paper with you.


Professor J. Scott Armstrong, The Wharton School

Written by climatebet

April 10th, 2008 at 3:39 pm

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