By PETER DYKSTRA
When Interior Secretary Dirk Kempthorne announced the listing of the polar bear as a threatened species in May, the political trench warfare over global warming flared up anew. Environmental groups professed surprise that a reluctant Bush Administration acted at all. Global warming deniers said the decision was ludicrous. They cited a polar bear population — a five-fold increase since the 1970s, a doubling since the 1950s, a quadrupling since the 1960s.