Bummer: CO2 causes polar bear population to "dwindle" from as few as 5,000 45 years ago to only 20,000 to 25,000 now

Mother of all polar bears from Ireland: study - ABC News (Australian Broadcasting Corporation)

The Arctic's dwindling population of polar bears all descend from a single mama brown bear which lived 20,000 to 50,000 years ago in present-day Ireland, according to a new study.
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The analysis of genetic material inherited only through females also showed that brown and polar bears mated periodically over the last 100,000 years.
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There are currently 20,000 to 25,000 polar bears left in the wild, according to the International Union for the Conservation of Nature.

Bear Hunting Caught in Global Warming Debate - New York Times

[2006] They note that there are more than 20,000 polar bears roaming the Arctic, compared to as few as 5,000 40 years ago, before Canada, Denmark, Norway, the Soviet Union and the United States agreed to strong restrictions on trophy hunting in the 1970's.