Carbon emissions within the next 50 years could lead to a tipping point where large parts of the Greenland ice sheet melt over the next 10,000 years.
A large portion of the Greenland ice sheet could melt over the next 10,000 years if cumulative carbon emissions reach 1000 gigatonnes, roughly double what has already been emitted.
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| The ice sheet near Pituffik, Greenland Kerem Yucel/AFP via Getty |
Global warming driven by emissions of carbon dioxide and other greenhouse gases is already causing substantial melting on the Greenland ice sheet. By 2100, meltwater from Greenland alone is expected to contribute several centimetres of sea level rise.
But 2100 is hardly the end of the story. “The lifetime of CO2 in the atmosphere is thousands of years,” says Dennis Höning at the Potsdam Institute for Climate Impact Research in Germany.
Höning and his colleagues modelled how different levels of carbon emissions in this century would affect the Greenland ice sheet over the next 10,000 years.
Where previous models assumed the atmospheric concentration of carbon remained constant after a pulse of emissions caused by human activity, the model developed by Höning and his colleagues accounted for natural sources and sinks of carbon, such as wetlands and oceans.
The researchers identified two separate “tipping points” beyond which melting accelerates as the ice recedes to lower altitudes, where temperatures are even higher.
They found the first tipping point would occur with cumulative carbon emissions of 1000 gigatonnes, causing the southern portion of the ice sheet to melt over 10,000 years, resulting in 1.8 metres of sea level rise. If the initial pulse of emissions were to reach 2500 gigatonnes of carbon, the model found most of the ice sheet would melt over that period, causing 6.9 metres of sea level rise.
Emissions scenarios vary widely, but if CO2 emissions were to continue at current levels, it would take around 45 years to reach 1000 gigatonnes of carbon.
“What this and previous work make clear is that Greenland is very likely entering dangerous territory,” says Alexander Robinson at the Complutense University of Madrid in Spain. “Curbing carbon emissions sooner rather than later will help ensure that the Greenland ice sheet remains stable in the future.”
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