even in the best of times, half of this century will disappear

Glaciers around the world are melting faster than previously thought. Even if the climate goals of the Paris Agreement are met, almost half will have melted by the end of the century. With current warming, many more glaciers will disappear, researchers conclude after a large study published in the scientific journal Science.

The scientists created a very detailed model based on two decades of satellite data from the 215,000 glaciers. This allows them to develop expectations about the impact of global warming. Never before had so much data been used: previous researchers had only used data from a few hundred glaciers for their models. Small glaciers with an area of ​​one square kilometer or less are particularly vulnerable.

“Previous studies have looked at 100 glaciers and then extrapolated the results, or looked at changes over the past 20 years with satellites,” says Bas Altena, a glaciologist at Utrecht University, who was not involved in the study. the study. “This study merged those two methods, creating a good picture of the possible future.”

According to Altena, the research findings are not surprising. “But the margins of uncertainty in predictions for the future have become much smaller. I am confident that this is an accurate description of what lies ahead: temperature ambitions for the future are now even more closely related to glacier change.”

In the study, the scientists establish that in the most optimistic scenario, that of the Paris Agreement, 49% of the glaciers will have disappeared by 2100. In this scenario, the objective is an increase in temperature not exceeding not 1.5 degrees. .

The current expectation is that the temperature will rise 2.7 degrees above pre-industrial times. This is therefore much more than the objective of the Paris Agreement. If this continues, scientists expect even more than two-thirds (68%) of glaciers to melt. In this scenario, there will be virtually no glaciers in central Europe, the United States, western Canada and New Zealand.

In the least likely and darkest scenario, a warming of 3 to 4 degrees, up to 83% of glaciers could melt.

“On the one hand, you could say that the Paris Climate Agreement has been too positive for high mountain glaciers, but it also shows how important it is to aim for a maximum warming of 1.5 degrees” , says Altena. “The consequences of stronger warming are clear.”

Models predict that the melt will cause sea levels to rise an additional 9 to 15 centimeters, depending on the warming scenario. This is on top of the increase that is already occurring because warming seawater expands and therefore takes up more space.

Such a rise in sea level would affect the living environment of several million people. In addition to sea level rise – which is influenced even more by the melting of ice caps than by the melting of glaciers – the disappearance of glaciers affects the water supply of around two billion people, a large part of world population. The appearance of regions such as the Alps, Alaska and the Himalayas would also change dramatically.

“The melting of glaciers in the high mountains is causing sea levels to rise everywhere, but the consequences are mostly felt locally,” says Altena. “In Central Asia, for example, it has a major impact on agriculture. The meltwater passes through several countries and at a certain point the ice disappeared. It is only in spring that there are the snowmelt water from the mountains, when the growing season is at the onset of fall, there is no longer a natural buffer.”

Partly because glaciers respond slowly to temperature changes – they have a response time of around thirty years – much glacier ice is lost even with successful large-scale climate policy. “No matter what we do, we’re going to lose a lot of the glaciers,” said glaciologist David Rounce of Carnegie Mellon University, who collaborated on the study. “But we are able to make a difference and limit the number of glaciers we are going to lose.”

The scientists write in their research that the findings require setting more ambitious climate goals. “It’s already too late for many small glaciers,” said study co-author and glaciologist Regine Hock of the University of Alaska Fairbanks and the University of Oslo. “But our results show that on a global scale, every degree can make a difference.”

“When we look for solutions, for example in Switzerland, we think of building dams to retain meltwater,” explains Altena. “There are also experiences of applying artificial snow on glaciers. But the most important solution is and remains the fight against global warming. It is easier to turn off the tap than to continue washing with the tap open. “