The Greenland ice sheet will suffer steep losses from melting if global warming exceeds 2°C above pre-industrial levels. This is indicated by a modeling study published in 'Nature'. However, this work adds that subsequent cooling below 1.5 °C can mitigate ice loss.
The Greenland Ice Sheet is estimated to have contributed more than 20% to the sea level rise observed since 2002 as a result of ice melting due to rising temperatures. The shrinking ice is a consequence of human-caused global warming and “poses a serious threat in terms of global sea level rise,” the study recalls.
However, it is unclear how the ice sheet will respond to future temperature increases.
Models and evidence from climate history indicate that feedback mechanisms can be triggered for the Greenland ice sheet, leading to more or less sustained melting. But at the same time the ice sheet can stabilize in multiple different configurations along warming or cooling trajectories.
And why this study?
The reason is that ice of land origin is expected to contribute to sea level rise by several centimeters this century and that the Greenland ice sheet is one of its main contributors.
With further global warming, a partial or complete loss of the ice sheet is expected, implying a rise in global sea level of up to 7 meters in the next tens of thousands of years.
“We found a global mean temperature threshold of between 1.7°C and 2.3°C above pre-industrial levels for abrupt ice sheet loss,” the study states.
The scientists used two independent modeling systems to determine the behavior of the ice sheets and investigate the impact that would occur in different scenarios. And the results show that factors such as the maximum temperature reached and the period of time in which the objectives of that global average temperature are exceeded are critical in determining the stability of the ice sheet.
“The study shows that, even if we exceed these thresholds, if we turn back quickly enough, a massive loss of ice could be avoided,” Marisa Montoya, co-author of the study, professor of Earth Physics and Astrophysics, tells this newspaper. from the Complutente University of Madrid, who clarifies that when he talks about “sufficiently fast” he refers to a scale of a few hundred years.
Analyzes indicate that this ice loss can be mitigated (even for maximum warming of up to 6°C or more above pre-industrial levels) if global mean temperatures are subsequently reduced to 1.5°C within a few centuries. However, time is crucial: if the return to colder temperatures after a threshold breach takes more than a few centuries, then the ice sheet is likely to contribute several meters to sea level rise.
According to one of the models used, with a global increase of more than 1.7 degrees, without strong measures to stop climate change, Greenland would lose its ice over the centuries.
The other model, developed by the paleoclimatic modeling and analysis group of the Complutense University of Madrid (UCM), sets the threshold for total ice loss at 2.3 degrees of global temperature increase.
"When we talk about 1.7ºC and 2.3ºC, they are the thresholds of each of the models. We have used two models, one of them Spanish, because the reviewers of our work wanted to see that the same effect is produced," says Marisa Montoya. "The relevant thing is that we see that there are thresholds and that they must be around those values," he adds.
In a scenario, in which warming occurs that remains constant but in which this threshold is not exceeded, the rise in sea level would be "a few meters on a very long time scale."
But “if the (temperature) threshold is exceeded then the rise in sea level can be about 7 meters, which is the potential of Greenland; That is its ability to contribute to the rise in sea level, and that means the complete disappearance of its ice,” says Montoya.
The researcher specifies that this rise of more than six meters would occur “in a future scenario of tens of thousands of years.”
“The objective of the article is to show that even if we exceed certain thresholds, if we return quickly enough we can avoid a very large loss of ice,” insists the researcher. “But if we do nothing and exceed 1.5ºC, as established by the Paris Agreement, we will exceed the elevation of 6 meters in the long term.” A matter of between tens and thousands of years, she adds.
