Given the historical facts about polar bears, then, we were surprised when we learned that a team of experts commissioned by the U.S. Geological Survey had predicted that the population of bears would fall by two-thirds by the year 2050. These predictions were made "...to Support U.S. Fish and Wildlife Service Polar Bear Listing Decision," under the federal Endangered Species Act. We wondered whether the bear experts' forecasting methods could be trusted.

Fortunately, the trustworthiness of the bear experts' forecasting methods is not just a question of opinion. Scientific research on forecasting has been conducted since the 1930s and has led to a set of evidence-based principles (rules or guidelines) that dictate which procedures are appropriate for the conditions. The forecasting principles have been published, and are easily available at forecastingprinciple.com.

Using an Internet search, we found roughly a thousand published papers that addressed the problem of forecasting polar bear numbers. None of them made reference to the scientific literature on forecasting. Most importantly, neither did the nine government reports prepared in support of the listing decision.

We judged two of the reports (Steven Amstrup was the lead author of one and Christine Hunter was the lead author of the other) to be the most relevant forecasting documents. Both Amstrup's and Hunter's forecasting procedures started with the assumption that the sea ice predictions from the General Circulation Models (GCM) that are favored by some climate researchers are valid. They are not. The Models do not constitute scientific forecasting methods and do not deal correctly with what is known about the physics of ice. Since the underlying assumption that the GCM sea ice forecasts are valid is false, the polar bear forecasts are of no value.

We nevertheless used forecasting principles to audit the forecasting procedures used by Amstrup and by Hunter in order to determine whether their procedures would be useful for making conditional forecasts of bear numbers. That is, what would be the bear population in 2050 if low ice conditions prevailed over the intervening decades?

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