If Al Gore wasn't impetus enough, now there's yet another reason to start worrying about global warming: It's forcing polar bears to eat each other. Sayeth the Discovery Channel:

Polar bears in the southern Beaufort Sea may be turning to cannibalism because longer seasons without ice keep them from getting to their natural food, a new study by American and Canadian scientists has found. ... Researchers discovered the first kill in January 2004. A male bear had pounced on a den, killed a female and dragged it 245 feet away, where it ate part of the carcass. Females are about half the size of males. "In the face of the den's outer wall were deep impressions of where the predatory bear had pounded its forepaws to collapse the den roof, just as polar bears collapse the snow over ringed seal lairs," the paper said. "From the tracks, it appeared that the predatory bear broke through the roof of the den, held the female in place while inflicting multiple bites to the head and neck. When the den collapsed, two cubs were buried, and suffocated, in the snow rubble."

This is heartbreaking, especially if you've seen the amazing footage of polar bears (including a newborn) in the documentary La Planete Blanche. At this rate, the only polar bear your grandchildren will ever see is the one in the Musee d'Orsay.