Climate models had so far underestimated their contribution to future sea level rise.
Ice caps, whose melting would raise the oceans by several meters, could well collapse with half a degree of additional warming of the climate. This is shown by recent studies which shed light on their hitherto unsuspected weaknesses.
The Greenland and Antarctic ice caps have lost more than 500 billion tonnes per year since the year 2000, or six Olympic swimming pools every second. But climate models had so far underestimated their contribution to future sea level rise, taking into account only the effect of rising air temperatures on the ice, and neglecting the interactions complexes between the atmosphere, the oceans, the ice caps and certain glaciers.
Up to an elevation of 1.4m
Researchers based in South Korea and the United States have established what the sea level rise will be by 2050 according to the different scenarios of the experts of the Intergovernmental Panel on Climate Change (IPCC). If current climate policies continue, melting in Antarctica and Greenland would result in a rise of about half a meter in sea levels. This figure would rise to 1.4 meters in a worst-case scenario, in the event of a significant increase in greenhouse gas emissions, linked to human activities and the use of fossil fuels (such as oil, gas and coal ).
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The study by these scientists, published on February 14 in the journal Nature Communicationalso specifies when runaway melting and runaway disintegration of these ice sheets could occur. “Our model has thresholds between 1.5°C and 2°C of warming – 1.8°C being our best guess – for accelerating ice loss and sea level rise”, explained Fabian Schloesser, of the University of Hawaii, co-author of the study. Temperatures have already risen by almost 1.2°C in the world since the pre-industrial era (+1.7°C for France).
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Scientists have long known that the West Antarctic and Greenland ice sheets, which could raise sea levels by 13 meters in the long term, had “tipping points”. Beyond these thresholds, their disintegration would be inevitable. But the temperatures associated with this phenomenon had never been precisely identified.