The polar ice sheets are more vulnerable to moderate global warming than had been thought, says a new study published inNature.
An additional 2 degrees of warming could lead to large-scale melting in Greenland and Antarctica and a global sea level rise of more than six metres, according to an analysis of sea levels during the last warm interglacial period, which took place about 125,000 years ago.
American researchers said that unless greenhouse gas emissions were cut, the planet could be committed by 2100 to this long-term outcome, which would leave much of Bangladesh and the Netherlands submerged and hundreds of millions of people displaced.
Michael Oppenheimer, a professor of geosciences at Princeton University, said:
"These findings should send a strong message to the governments negotiating in Copenhagen that the time to avoid disastrous outcomes may run out sooner than expected."
The period about 125,000 years ago provides an indication of what the planet could be like with moderate warming because the poles then were at temperatures expected to be reached with a further global warming of 1 to 2 degrees.