PARIS | Each degree of increase in the temperature of the planet will accelerate the disintegration of the Antarctic ice sheet, eventually causing an inevitable and increasingly rapid rise in ocean levels, according to a study published this week.
The planet has already gained more than 1 ° C compared to the pre-industrial era, and 1 ° C more (i.e. + 2 ° C, the minimum target of the Paris climate agreement) would inexorably cause an increase in the level of the sea of 2.5 meters just because of the collapse of Antarctica. Another 3 ° C additional would bring this increase to 6.5 meters, warn the authors of this study published in Nature.
This dramatic rise in the oceans, devastating for coastal metropolises like Bombay or Miami, would occur over several hundred or even several thousand years. But this gloomy future is playing out today: it is the greenhouse gas emissions of the next decades that could set in motion this then inevitable process.
According to the results of this study, the disintegration of the gigantic Antarctic ice cap (which contains enough water to cause 58 meters of sea level rise) will be faster and faster with each additional degree of warming.
For example, for each of the first two degrees above pre-industrial temperature levels, the oceans will rise about 1.3 meters. But between + 2 ° C and + 6 ° C, this increase would double to 2.4 meters per degree of warming. And beyond that, each degree would cause an additional 10 meters of rise, pushing the cap beyond its point of no return.
“It is our use of coal and oil that determines if and when critical temperature thresholds are exceeded in Antarctica,” one of the authors, Anders Levermann, climatologist at the Potsdam Institute for Climate Impact Research, said in a statement ( PIK). “And even if the loss of ice occurs over a long period of time, the corresponding levels of CO2 can be achieved in the near future,” he added.
The part of the ice cap covering West Antarctica is expected to collapse first, eroded first by the warming sea and creeping under the coastal glaciers.
“Glaciers the size of Florida could fall into the ocean,” noted Torsten Albrecht, also a PIK researcher.
This study “makes clear the urgent need to stabilize global warming, in accordance with the objectives of the Paris Agreement” (+2 ° C or even +1.5 ° C), commented Matt Palmer, of the UK Met Office. , the British weather organization, which did not participate in the study.
While state commitments place the planet on a + 3 ° C trajectory, even a + 2 ° C world “poses an existential risk to entire nations,” added Jonathan Bamber, glaciologist at the University of Bristol, cited by Science Media Center.