Glaciers are melting faster and faster all over the world, but what this means for the future could only be roughly predicted with previous models. An international research team has now developed a new glacier model that, based on the latest data and knowledge of glacier dynamics, allows for the first time an individual forecast for all 215,000 glaciers worldwide. The simulations show that on the current course of 2.7 degrees warming by 2100, almost two-thirds of all glaciers could disappear. Mountain ranges in Europe and other mid-latitudes would be largely ice-free as a result. However, the new projections also show that it is not too late: every tenth of a degree less counts to curb melting.
Whether in Greenland, in the Antarctic or in the high mountains: almost everywhere in the world, glaciers are melting, and climate change is making their ice masses disappear faster and faster. Even the long-stable glaciers of East Antarctica and the Himalayas are rapidly losing thickness and volume, scientists have found. In some regions of Greenland and West Antarctica, the ice melt could even have become a matter of course - it will continue for decades to centuries even if warming is stopped immediately. In the most recent report by the Intergovernmental Panel on Climate Change (IPCC) from 2021, scientists also pointed out the dramatic and ongoing consequences of global glacier melt: Due to the disappearance of the ice caps, the sea level could continue to rise for centuries to millennia and then remain high for thousands of years, according to the IPCC -Authors. In addition, the mountain glaciers are important water resources for millions of people.
First individual forecast for all glaciers
It is therefore important to be able to predict the development of glacier melt as precisely as possible. So far, however, most of the models used for this have been based on relatively standardized and simplified parameters for glacier dynamics, which did not reflect the individual conditions and processes of each glacier - and were therefore inevitably inaccurate. An international team led by David Rounce from Carnegie Mellon University in Pittsburgh has now developed a new, more accurate model that reflects the glacial dynamics and the processes that are important for the ice balance in a more comprehensive and detailed way. "In principle, we have improved the methodology in this study because we have combined satellite observations and models and can therefore also take regional characteristics and dynamic development into account," explains co-author Fabien Maussion from the University of Innsbruck.
The simulation, combined from two earlier models, now provides forecasts for each of the more than 215,000 glaciers worldwide and their development in the period from 2015 to 2100. For their study, the researchers used this model to calculate the future glacier development for four climate scenarios. These scenarios include best-case global warming of 1.5 degrees above pre-industrial levels, as targeted by the Paris Agreement, and two, three and four degrees of warming by 2100. “We are because of the current Levels of emissions are unfortunately on track for a 2.7 degree temperature increase,” says Maussion. He and his colleagues have now determined what this will mean for mountain glaciers and polar ice masses.
Europe ice-free from as little as 2.7 degrees of warming
The results confirm the continuing retreat of glaciers worldwide: Even if global warming were limited to 1.5 degrees, the ice streams would lose around a quarter of their ice mass by the year 2100. A good 100,000 glaciers - almost half of the existing stock - would have completely melted and disappeared by then. With each additional warming, the loss of ice increases: If there is a warming of 2.7 degrees, as is to be expected given the current course of climate protection efforts, then two thirds of all glaciers could be affected, as the scientists report. As a result, the high mountains of the temperate latitudes, such as in Central Europe, western Canada, the USA and New Zealand, could lose almost all of their ice. With a warming of three to four degrees, 83 percent of all glaciers worldwide would disappear, the total mass loss would be 41 percent.
"Thus, temperature evolution has a significant impact on mass loss, in some cases determining whether a region will become completely ice-free by the end of the 21st century," Rounce and colleagues write. At the same time, the melting glaciers also have a significant impact on sea level - and the new model now provides more accurate figures for this as well. According to this, with a warming of 1.5 degrees, the level will rise by 90 millimeters by the year 2100 due to the melting of the glaciers alone. If the previous climate course of 2.7 degrees is maintained, it would be 115 millimeters and with a warming of four degrees the sea level would rise by 154 millimeters. However, the simulations also show that it is still possible to avert the worst scenarios. "Unfortunately, it's already too late for a lot of glaciers, but that doesn't mean we can't do anything more," says Maussion. "Any reduction in greenhouse gas emissions and thus the move away from fossil fuels helps to save existing ice sheets and limit sea level rise."
Source: David Rounce (Carnegie Mellon University, Pittsburgh) et al., Science, doi: 10.1126/science.abo1324