Under emissions scenarios leading to 2°C of global warming and above, significant and rapid mass loss from the Greenland Ice Sheet would lock in several meters of unstoppable and irreversible global sea-level rise, persisting at least tens of thousands of years. The threshold of irreversibility could be reached in as little as 600 years if high levels of CO2 emissions (equal to emissions today) continue through 2100, even if all emissions go to zero immediately in 2101 (RCP8.5). The process slows, but still occurs if temperatures exceed 2°C for any sustained period of time. With high emissions through 2100 however, the altitude of Greenland’s ice sheet will have been lowered so much by about 2600 (with a contribution of 2 meters to global sea levels) that its melt will continue, even if temperatures subsequently go down. To avoid Greenland’s entering this stage of irreversible mass loss, global temperatures must be lowered to near pre-industrial levels before this threshold is reached. This new modeling work did not include recent observations of ice sheet dynamics such as the acceleration and retreat of outlet glaciers (see Nov. 27 capsules), which may well mean an underestimation of the potential rate of ice sheet loss and time to this threshold of irreversibility.
https://tc.copernicus.org/articles/14/4299/2020/tc-14-4299-2020.pdf
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