2023-10-22 21:32:28
Good and bad news from the polar front of climate change: First the good: “The Greenland ice sheet is probably more resistant to global warming than previously thought.” The Potsdam Institute for Climate Impact Research (PIK), which begins a press release with this sentence , immediately follows up with the bad one: “But even a temporary exceedance of the critical temperature threshold can still lead to a sea level rise of more than one meter in our simulations.” Niklas Boers, who works at PIK and the Technical University of Munich, is quoted here researches.
Joachim Müller-Jung
Editor in the features section, responsible for the “Nature and Science” department.
Two messages, a study: Boers and Nils Bochow from the Arctic University of Norway in Tromso have, for the first time, virtually virtually measured the huge ice sheet on Greenland using current glacier models – well into the next millennia. The Greenland ice cannot be overestimated as one of the most important climate-changing elements. Greenland is currently warming four times faster than the global average.
In every single year since the end of the 1990s, the ice on Greenland has decreased; most recently, there have been years with several hundred billion tons of ice lost annually. This meltwater alone drops the water level by a little less than a millimeter – per year! – increase.
The question is: Is global warming bringing this massive ice sheet, which is several kilometers thick inland, to the brink of collapse? Until now, due to a lack of meaningful simulations and based on paleoclimatic findings, it was assumed that the system would eventually tip over as the planet continued to warm. Irretrievable. However, it was always clear that this melting process takes a long time – not a few decades, as is expected for the drying out of the Amazon rainforest or the thawing of large parts of the Nordic permafrost, but many millennia.
Boers and Bochow have now tried to determine the critical threshold more precisely with their two ice models. Your result, that in “Nature“ has been published: Between 1.7 to 2.3 degrees above the pre-industrial global warming level – and thus roughly in the area of the Paris climate target corridor – “abrupt” ice loss occurs. But even if the planet continues to warm up afterwards, quickly and radically (up to theoretically six degrees), complete collapse could be prevented. Under one condition: Global warming must be brought back below the aforementioned critical threshold of 1.7 degrees as quickly as possible – the researchers speak somewhat cryptically of “sufficiently quickly”, i.e. in decades to centuries.
Less risk through CCS techniques?
How could that work? At some point the greenhouse gases are specifically removed from the atmosphere, for example using the CCS processes for carbon extraction and storage, which are still inefficient on a large scale today. Or with gigantic reforestation projects worldwide.
In any case, hardly anyone expected the temperature tolerance of the icy Greenland reservoir. If what the simulation models show, which are still roughly resolved spatially and, according to the researchers, are subject to numerous uncertainties, is true, then there is something like a lower-risk climate policy scope – as long as you only look at the Greenland ice cream and the possibilities that lie very far into the future want. The researchers call this scope the “safe operating space”.
A thoroughly misleading, or at least unclear, term, as reading the Nature study makes clear. Because he excludes a lot of things that are definitely addressed in the publication. Humanity will not be able to feel safe in the near future because the melted Greenland ice sheet is part of a larger whole in the Arctic and global climate system, which may react much more sensitively and quickly than the Greenland ice sheet itself.
Domino effect caused by meltwater
The huge amounts of fresh water flowing out of Greenland could trigger a climate domino effect: the global circulation pump AMOC, which is constantly pumping thousands of liters of seawater into the deep sea near Greenland and is thus one of the main drivers of global ocean circulation with its inflows from the North Atlantic and from the warm Gulf Stream further south could dry up due to the inflow of fresh water.
Pia Heinemann Published/Updated: , Recommendations: 6 Tim Kalvelage Published/Updated: , Recommendations: 9 Oliver Becht Published/Updated: , Recommendations: 12
A slowdown in the AMOC circulation has been measured for years. If this main marine artery of the planet stops, this is likely to have global effects, because AMOC, like the Greenland ice sheet, is one of the more than a dozen central tipping elements of the world climate system.
In other words: Even before the fate of the Greenland ice sheet is sealed, it could have initiated a perhaps even greater catastrophe. And even if the critical temperature threshold of 1.7 degrees is exceeded for a short time – the “overshoot” – so much ice from Greenland will have melted that, according to researchers, sea level alone will rise by “more than a meter”. This does not take into account the huge amounts of meltwater that are now pouring into the oceans worldwide from the polar ice cap around the South Pole and from the glacial reservoirs in the Alpine mountain regions.
#reprieve #Greenland #ice