The world’s glaciers are losing three Olympic-sized swimming pools every second: WMO warns of ‘avalanche of cascading impacts’

The World Meteorological Organization (WMO) warned on Friday that “accelerating glacier melt risks unleashing an avalanche of cascading impacts on economies, ecosystems and communities, not just in mountain regions but at a global level.” This warning comes on March 21, the first World Glacier Day of 2025, which has also been designated as the International Year of Glaciers’ Conservation.

While the retreat of glaciers is one of the most well-known and indisputable signs of global warming, the United Nations aims to highlight the broader significance of this melting. There is far more at stake than just unique landscapes, even for countries like Spain, which are distant from the mountain ranges home to the largest glaciers. “Preservation of glaciers is a not just an environmental, economic and societal necessity. It’s a matter of survival,” said Celeste Saulo, Secretary-General of the WMO.

A recent international study published in Nature, coordinated by the World Glacier Monitoring Service (WGMS) and involving 35 research groups, estimates that the world’s glaciers have lost an average of 273 billion tons of ice annually since 2000 — equivalent to three Olympic-sized swimming pools per second.

This trend has worsened in the last decade, with ice loss accelerating by 36% during the second half of the study period (2012–2023) compared to the first half (2000–2011). The research, called GlaMBIE (Glacier Mass Balance Intercomparison Exercise), which combines four different measurement methodologies, reveals that glaciers have lost 5% of their total volume. This loss ranges from 2% in the Antarctic and subantarctic islands to 39% in the Alps and Pyrenees, which are in the most dire condition. At this rate, scientists predict that, despite their reputation as “eternal ice,” many glaciers in western Canada and the United States, Scandinavia, Europe, the Caucasus, New Zealand, and the Tropics will not survive the 21st century.

One of the most serious consequences of the reduction in ice cover is the impact on future water supplies in certain parts of the world, particularly in Asia, where glaciers serve as massive reservoirs of freshwater. However, the effects are varied, leading to concerns about an “avalanche of cascading impacts.”

As Samuel Nussbaumer, a researcher at the Global Glacier Monitoring Service at the University of Zurich in Switzerland, points out, the retreat of glaciers can, for example, lead to the formation of lakes, which in turn can trigger slope instability and flash floods. “Changes in glaciers impact us at different levels—from local natural hazards to regional water availability and global sea level rise,” explains Nussbaumer, one of the authors of the GlaMBIE team.

The most widespread impact on humanity is the rise in sea level. After the warming of the oceans themselves (which causes their volume to expand), the other causes of rising water levels are the melting of glaciers and the melting of the Greenland and Antarctic ice caps, each contributing roughly a third.

As Alejandro Blázquez, another GlaMBIE author and a scientist at the Laboratory for Space Geophysics and Oceanography Studies (LEGOS) in Toulouse, France, explains, sea levels are currently rising at a rate of 3.5 millimeters per year. However, glaciers outside of Antarctica and Greenland contain enough ice to potentially cause a rise of 30–35 centimeters.

“In Greenland, there is about seven meters of water, and in Antarctica, about 40 meters, but that’s another level. We’re already talking about a radical change in the Earth, and no model predicts that Antarctica will melt entirely in the next 200 to 300 years.” Glaciers outside these regions are melting much faster. “The problem with the sea level rising just a few centimeters is that it makes coastal storms and extreme events much more severe,” says Blázquez.

According to the WMO, the 2024 hydrological year marked the third consecutive year in which all 19 glacial regions experienced a net loss of mass. Glacier mass loss reached 450 billion tonnes in the 2024 hydrological year, the fourth-largest on record. While mass loss was relatively moderate in regions such as the Canadian Arctic and the Greenland periphery, glaciers in Scandinavia, Svalbard, and northern Asia saw the largest annual mass loss on record.

“We are in a truly worrying situation, and glaciers are one of the clearest signs of the climate crisis, even if they are just one piece of the puzzle,” says Nussbaumer. “We must recognize that many of today’s glaciers will continue to melt in the coming years, and many will disappear. However, depending on future emissions trajectories, some glaciers can still be preserved. We will have less ice in the future, but I hope that the same proportion can be saved. This is also the meaning of the International Year of Glacier Conservation and World Glacier Day on March 21: any additional warming that can be prevented directly impacts glaciers; this is the key to preserving [part of] our glaciers.”

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