Previous estimates on temperature thresholds might be too high
By Summit Voice
SUMMIT COUNTY — A global temperature increase of 1.6 degrees Celsius could be enough to trigger an irreversible meltdown of the Greenland ice sheet, according to a team of European researchers.
Previous research suggested a temperature increase between 1.9 to 5.1 degrees Celsius would lead to a Greenland meltdown. The new study estimates that a temperature increase of half as much could lead to the point of no return.
The scientists with the Potsdam Institute for Climate Impact Research and the Universidad Complutense de Madrid used a new climate model incorporating regional climate data and climate feedback associated with changes in snowfall and melt.
The simulation proved able to correctly calculate both the observed ice-sheet of today and its evolution over previous glacial cycles, thus increasing the confidence that it can properly assess the future. All this makes the new estimate of Greenland temperature threshold more reliable than previous ones.
Logically, the researchers said that, the warmer it gets, the faster the ice will melt. A business-as-usual scenario, with no significant reductions in greenhouse gases, could result in up to 8 degrees of warming, with up to 20 percent of the Greenland ice sheet melting with 500 years and complete meltdown in 2000 years. Climate science skeptics will be quick to point out that sea ice around Greenland has grown to a greater extent than in the past few winters, but that doesn’t obviate the long-term trend of ice loss from the Greenland ice sheet. Substantial melting of land ice could contribute to long-term sea-level rise of several meters and therefore it potentially affects the lives of many millions of people.
“This is not what one would call a rapid collapse,” said Alexander Robinson, lead-author of the study published in Nature Climate Change. “However, compared to what has happened in our planet’s history, it is fast. And we might already be approaching the critical threshold.”
if global warming is limited to 2 degrees Celsius, complete melting would take about 50.000 years. Still, even within this temperature range, often considered a global guardrail, 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,” said team-leader Andrey Ganopolski of the Potsdam Institute for Climate Impact Research. “If the global temperature significantly overshoots the threshold for a long time, the ice will continue melting and not regrow, even if the climate … returns to its pre-industrial state,” Ganopolski said.
Ganopolski explained some of the feedback loops that could affect the rate of melting:
The ice sheet is over 3000 meters thick and thus elevated into cooler altitudes. When it melts its surface comes down to lower altitudes with higher temperatures, which accelerates the melting. Also, the ice reflects a large part of solar radiation back into space. When the area covered by ice decreases, more radiation is absorbed and this adds to regional warming.