Berlin, March 12: The Greenland ice sheet seems to be the most vulnerable to global warming at this stage than previously estimated.
The temperature threshold for melting the ice sheet completely is in the range of 0.8 to 3.2 degrees Celsius of global warming, with a best estimate of 1.6 degrees above pre-industrial levels.
These are the latest findings by the Potsdam Institute for Climate Impact Research (PIK), Germany and the Universidad Complutense de Madrid, the journal Nature Climate Change reports.
Today, already 0.8 degrees global warming has been observed. Substantial melting of land ice could contribute to long-term sea-level rise of several metres and therefore it potentially affects the lives of many millions of people, according to a Potsdam statement.
The time it takes before most of the ice in Greenland is lost strongly depends on the level of warming. “The more we exceed the threshold, the faster it melts,” says Alexander Robinson, who led the study.
In a business-as-usual scenario of greenhouse-gas emissions, in the long run humanity might be reaching 8 degrees Celsius of global warming.
This would result in one-fifth of the ice sheet melting within 500 years and a complete loss in 2000 years, according to the study.
“This is not what one would call a rapid collapse,” says Robinson. “However, compared to what has happened in our planet’s history, it is fast. And we might already be approaching the critical threshold.”
Conversely, if global warming would be limited to two degrees Celsius, complete melting would happen on a time-scale of 50,000 years. Still, even within this temperature range often considered a global guard-rail, the Greenland ice sheet is not secure.
“Our study shows that under certain conditions the melting of the Greenland ice sheet becomes irreversible. This supports the notion that the ice sheet is a tipping element in the Earth system,” says team-leader Andrey Ganopolski of PIK.