A deep freeze holding 90 percent of the world's ice, Antarctica is one of the biggest puzzles in debate on global warming with risks that any thaw could raise sea levels faster than UN projections.

Even if a fraction melted, Antarctica could damage nations from Bangladesh to Tuvalu in the Pacific and cities from Shanghai to New York. It has enough ice to raise sea levels by 57 meters if it melted, over thousands of years.

A year after the UN's Intergovernmental Panel on Climate Change (IPCC) projected sea level rises by 2100 of about 20 to 80 cms, a Reuters poll of 10 of the world's top climatologists showed none think that range is alarmist.