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J. Scott Armstrong, Kesten C. Green, and Willie Soon (2008)
"Polar Bear Population Forecasts: A Public-Policy Forecasting Audit." Interfaces (with commentary), 38, 382-404.



Polar bear fears groundless (31 March 2008)

The U. S. government commissioned studies to support the listing of polar bears as a threatened or endangered species. Polar bear numbers are currently high and the population has been increasing rapidly in recent decades. Everyone likes polar bears, so this is good news. A decision to list would require forecasts that the current upward population trend will reverse. The government studies concluded that polar bear populations would decrease substantially.

Decision makers and the public should expect people who make forecasts to be familiar with the scientific principles of forecasting just as a patient expects his physician to be familiar with the procedures dictated by medical science. Three scientists, J. Scott Armstrong of the University of Pennsylvania, Kesten Green of Monash University, and Willie Soon of The Harvard-Smithsonian Center for Astrophysics, audited the government studies to assess whether they were consistent with forecasting principles. Their paper, “Polar Bear Population Forecasts: A Public-Policy Forecasting Audit,” has been accepted for publication in the management science journal Interfaces. It is the only peer-reviewed paper on polar bear population forecasting that has been accepted for publication in an academic journal.

They concluded that the government forecasts were based on false assumptions and their polar bear population forecasts contravened many principles for scientific forecasting. Indeed, the reports followed fewer than one-sixth of the relevant principles. Given the importance of the forecasts, all principles should be properly applied. In short, the government reports do not provide relevant information for this decision.

Research shows that for issues such as the population of polar bears—situations that are complex and where there is much uncertainty—the best forecast is that things will follow a “random walk;” in effect, this model states that the most recent value is the best forecast for all periods in the future. Because the polar bear population has been increasing over recent decades, however, a continuation of that trend over the short term is possible.

Polar bears listed as threatened under the Endangered Species Act in defiance of scientific evidence (14 May, 2008)

“Secretary of the Interior Dirk Kempthorne announced on May 14, 2008 that he is accepting the recommendation of U.S. Fish and Wildlife Service Director Dale Hall to list the polar bear as a threatened species under the Endangered Species Act (ESA). The listing is based on the best available science, which shows that loss of sea ice threatens and will likely continue to threaten polar bear habitat. This loss of habitat puts polar bears at risk of becoming endangered in the foreseeable future…”. See the U.S. Department of the Interior website for the full announcement.

This extraordinary announcement is at odds with evidence that the polar bear population is currently thriving, and is based on false assumptions and unscientific forecasting procedures. The forthcoming Interfaces paper by Armstrong, Green, and Soon, provides evidence that the “best available science” does not support a listing.

BBC “Five live” Interview with Scott Armstrong during the International Conference on Climate Change (9 March, 2009)

Host: The New York conference “Global Warming: Was It Ever Really A Crisis?” has been described as the world’s largest ever gathering of global warming skeptics. Professor Scott Armstrong from Wharton School of Management at the University of Pennsylvania and a world renowned forecaster has turned his attention to the global polar bear population. Professor Armstrong, hello, welcome to Five Live. more... Audio.

No change in polar bear population (May, 2011)

The Polar Bear Specialist Group of the International Union for the Conservation of Nature (IUCN) has reported that there was no change in the polar bear population in the most recent four-year period studied.

The finding is consistent with the conclusion of a 2008 paper by Scott Armstrong, Kesten Green, and Willie Soon (“Polar Bear Population Forecasts: A Public-Policy Forecasting Audit”) that “the inconsistent long-term trends in the polar bear population suggest that it is best to assume no trend in the long-term.”

The polar bear population finding contrasts with Senator Boxer’s hearings in January 2008 in which she expressed the view that the number of polar bears would decline rapidly. Professor Armstrong offered to bet her that the number of polar bears would not decline, but she did not respond to the challenge.

The Polar Bear group’s report can be found here.

The Armstrong, Green, and Soon paper on polar bear population forecasts can be found here.