The five countries that ring the Arctic on Thursday declared climate change the single greatest threat to polar bears, calling for urgent action to curb global warming. Months ahead of a crucial global climate conference, the five countries -- Canada, Denmark (with Greenland), Norway, Russia and the United States -- expressed their "deep concern" at the end of a three-day meeting in the northern Norwegian town of Tromsoe. "The parties agreed that long-term conservation of polar bears depends upon successful mitigation of climate change," they wrote in a joint statement following discussion on threats to the white bear that have...