Polar bears could be extinct by the end of this century, scientists predict, if nothing is done to halt global climate change. Already, the Arctic ice sheet is half the thickness of 30 years ago and 10 per cent less extensive, according to the Arctic Climate Impact Assessment, the work of more than 250 scientists over four years. They blame global warming, caused by the burning of fossil fuels, and warn of consequences all over the world if ice covering solid ground melts and sea levels rise.

Warnings such as these and fears that the heat waves, floods and hurricanes of last year could have been early consequences of global warming have prompted Tony Blair, the British prime minister, to make tackling climate change a priority for world leaders in the coming year.