Jonah,
Charismatic megafauna strike again! If you look at the Alaskan temperature record, you can see that there was a big shift in temperatures in 1976 and that temperatures have remained roughly steady since then. When the Pacific Decadal Oscillation shifts back, Alaska will probably cool down again. This has probably happened many times in the past. Moreover, over in Canada, the chief Polar Bear Biologist for the government of Nunavut has said, “Of the 13 populations of polar bears in Canada, 11 are stable or increasing in number. They are not going extinct, or even appear to be affected at present.”