By Dr David Whitehouse
BBC News Online science editor
Greenland's ice sheet could disappear within the next 1,000 years if global warming continues at its present rate, a report in Nature magazine suggests.
It could all go, say researchers
Jonathan Gregory and colleagues from the University of Reading, UK, say their studies forecast an 8C increase in Greenland's temperature by 2350.
They believe that if the ice cap melts, global average sea level will rise by about 7m (23ft).
Even if global warming was halted the rise could be irreversible, they say.
The researchers estimated that Greenland was likely to pass a threshold of warming beyond which the ice sheet - second in size to Antarctica - could not be sustained unless much greater reductions were made in emissions of greenhouse gases.
They found that over the next 350 years global warming was likely to pass the critical threshold in 34 out of 35 model calculations.
Greenland's average temperature only needs to increase by 3C to melt its ice sheet, but some of the modelling studies forecast a much higher rise by the year 2350.
"Without the ice sheet, the climate of Greenland would be greatly altered," says Dr Gregory.
If the ice sheet was removed, Greenland would be a lot warmer because the land surface would be at a lower altitude and reflect less sunlight.
"Unlike the ice on the Arctic Ocean, much of which melts and reforms each year, the Greenland ice sheet might not re-grow even if the global climate were returned to pre-industrial conditions," he says.
Tentative evidence suggests the ice sheet has already to started to melt.
"It's quite possible that Greenland is already making a slight contribution to global sea levels," says Dr Gregory.
A broad consensus of mainstream scientific opinion holds that human-produced greenhouse gases, such as carbon dioxide (CO2), are driving an unnatural rise in global temperatures.
Before industrialisation, the atmosphere contained 280 parts per million (ppm) of CO2. At present, it stands at 370 ppm.
The study in the journal Nature considered scenarios in which the CO2 was stabilised at 450, 550, 650, 750 and 1,000 ppm.
The only international agreement on cutting greenhouse gases is the UN's Kyoto Protocol, which requires industrial countries to make a small cut in global emissions by a timeframe of 2008-12.
But the pact is in limbo. It still needs to be ratified by Russia to take effect and in any case has been abandoned by the United States, the world's biggest CO2 contributor.