Every Tenth of a Degree Helps

The substantial loss of mass in glaciers worldwide is something that, aside from glaciologists, tends to be observed only by a few dedicated mountaineers or skiers. Yet millions of people are feeling the devastating effects of the melting glaciers – in the form of rising sea levels, flooding and drinking water shortages.

“What happens on the glacier does not stay on the glacier,” says Michael Zemp, Director of the World Glacier Monitoring Service (WGMS) at the University of Zurich (UZH), cutting right to the chase. “Glacier melt threatens everyone who lives on coastlines; everyone who lives below glaciers; everyone who has anything to do with water.” To raise awareness, the United Nations (UN) proclaimed 21 March 2025 as the first World Day for Glaciers. The latest figures presented by the WGMS are alarming.

Each year, the WGMS publishes a report on the state of glaciers worldwide. For their report, the researchers at the WGMS consolidate field and satellite measurements from glaciers in all regions of the world. The publication date of the report now coincides with World Day of Glaciers.

As in previous years, the findings are bleak: in 2024, glaciers worldwide have lost an estimated 450 billion tons in mass, not including the continental ice sheets of Greenland and Antarctica. It is also the third consecutive year that all regions have reported glacier melt. The five largest glacier meltdowns have occurred within the last six years.

The latest data indicate a massive acceleration of the loss of eternal ice, says Zemp: “The fact that glaciers are melting in almost all regions of the world is extraordinary. The climate system is not actually linear; we would expect glaciers to gain mass in at least some regions.”

Measurement series need to run for more than 30 years to enable researchers to draw conclusions about climate change. However, it is difficult to finance monitoring over such a long period. “Often, it depends on the researchers’ keen personal interest in ‘their’ glaciers,” says Zemp. “Fortunately, there are glaciologists who are so dedicated to their work that they continue to take measurements for decades, regardless of whether or not they are funded, whether or not there is a war going on, and then share their valuable data freely with everyone.”

The significance of such long-term monitoring data is also recognized by the first Glacier of the Year award. The South Cascade Glacier in the US state of Washington was chosen because it boasts the longest continuous data series in the western hemisphere. The US Geological Survey has been measuring the glacier’s mass balance at this site since 1958.

“In the region from the Rocky Mountains to Alaska, we only have long-term data from a handful of glaciers. Without these long-term measurements, we would suffer from a blind spot in this part of the world,” explains Zemp. As the latest paper published in Nature under the direction of the WGMS established, one-third of the sea level rise caused by melting glaciers originates in Alaska. “This clearly shows how important the work of glaciologists in this region is – and how crucial it is that these measurement series continue.”

“The South Cascade Glacier also happens to be in a region where glaciers are under severe threat. Just like the Alps, the Rocky Mountains are in a region where glaciers will not survive the century at the current melting rate,” adds Zemp. The damage has been done, and the melted ice – and with it valuable drinking water reserves – cannot be restored. This makes it all the more important to mitigate the damage. “We need to act now,” says Zemp. “For every tenth of a degree of global warming we can prevent, we save part of the glaciers, reduce the damage – such as flooding, sea level rise and freshwater scarcity – and reduce downstream costs.”

As a scientist, it is extremely exciting to research a change that is currently taking place, even if the objective is ultimately to document the irreversible disappearance of the glaciers, says the WGMS director. “My predecessors in glaciology were concerned with ice ages that took place 25,000 years ago or will take place in 30,000 years – I am concerned with glaciers in the current climate change.”

For a long time, glaciers were an early warning system for climate change. “Today, they are increasingly becoming monuments to how successfully – or not – we as a society are dealing with the climate crisis,” Zemp concludes on the first World Day of Glaciers.