Greenland’s icy mountains and the island’s entire ice cap could disappear in the next 1 000 years because of global warming, European scientists warn on Thursday.
If that occurs sea levels will rise by seven metres, drowning low-level coastlines around the world.
Greenland is covered by the biggest ice sheet in the northern hemisphere: almost 1 235 200 square kilometres of ice which is up to 3 kilomtres thick, the base of which is below sea level.
But Jonathan Gregory, of the Hadley Centre for climate prediction at the University of Reading, and colleagues from Brussels and Bremerhaven, report in the journal Nature that an average annual warming in the region of 2,7C would mean that the rate of melting would outpace the annual snowfall.
The greater the warming, the faster the snow melts. The worst-case predictions for Greenland, made by an intergovernmental panel of scientists, involve an average warming of 8C. At those temperatures oceans that have risen by 2,5mm a year will start to rise by a steady 7mm a year.
There are already signs of consistent melting in Greenland. Researchers reported in 1999 that the ice sheet was thinning by about a metre a year.
The latest research confirms the picture of an increasingly mild polar world. Alaskan glaciers are in retreat. The Arctic Ocean icepack has thinned by more than 30% in the past three decades and has been shrinking by an area equivalent to the Netherlands each year during the same period. If warming continues by the end of the century the Arctic could be free of ice altogether during summer months, British scientists predict.
Dr Gregory and his colleagues looked at computer models of climate change and the complicated links between ocean and atmosphere in a world warmed by greenhouse gases such as carbon dioxide and oxides of nitrogen. Of 35 combinations of warming and changes in the circulation of ocean currents and winds, 34 involved Greenland heating up by at least 2,7C. In many cases the predicted warming exceeded 8C.
The scientists also warn that once the ice sheet has melted it might not return. Icy regions stay cold because ice reflects light and heat, whereas rock and blue water absorb warmth.
Dr Gregory said: ”If you get to a level of carbon dioxide which implies a certain warming that is going to be sustained. If of course you did manage by some means to return the carbon dioxide to its current concentration, the climate might cool down a bit and the melting might stop. But there may be a point of no return.
”The reason why it would be irreversible is because the sea and rocks are much less reflective than ice, and because [ground level] is much lower if you remove the ice sheet – the topography of Greenland is mostly ice sheet and the base of it is below sea level, so if you remove the ice sheet you have a low-lying piece of land and that makes it warmer anyway.” – Guardian Unlimited Â