Global warming sees polar bears stranded on melting ice

They cling precariously to the top of what is left of the ice floe, their fragile grip the perfect symbol of the tragedy of global warming.

Captured on film by Canadian environmentalists, the pair of polar bears look stranded on chunks of broken ice.

Although the magnificent creatures are well adapted to the water, and can swim scores of miles to solid land, the distance is getting ever greater as the Arctic ice diminishes.

"Swimming 100 miles is not a big deal for a polar bear, especially a fat one," said Dr Ian Stirling of the Canadian Wildlife Service.

"They just kind of float along and kick. But as the ice gets farther out from shore because of warming, it’s a longer swim that costs more energy and makes them more vulnerable."