Global retreat of glaciers has strongly accelerated

There are currently around 275,000 glaciers worldwide, in which huge quantities of fresh water are stored. But this reservoir is increasingly shrinking. Since the turn of the millennium, glaciers around the world – i.e. ice masses on land excluding the Greenland and Antarctic ice sheets – have lost around 273 billion tonnes of ice per year. This corresponds to about five and a half times the volume of Lake Constance. Overall, the world’s glaciers have lost around five per cent of their total volume since the year 2000. This is the conclusion reached by an international research team of which Tobias Bolch from the Institute of Geodesy at Graz University of Technology (TU Graz) is a member. The team published the corresponding, comprehensive study today in the scientific journal Nature. It is striking that ice loss has accelerated significantly in recent years. In the second half of the period under investigation (2012 to 2023), it was 36 per cent higher than in the period from 2000 to 2011.

For their study, the researchers collected, homogenised and evaluated glacier data from different sources, including field measurements directly on glaciers as well as radar, laser and gravimetric data from numerous satellite missions. “We compiled 233 estimates of regional glacier mass changes from about 450 data contributors organised in 35 research teams,” explains Michael Zemp, who led the study. Tobias Bolch adds: “The data from ESA Earth observation satellites, as well as from other international space organisations, is particularly important for our research. By analysing this data – measurements of elevation changes are particularly valuable here – we were able to determine the condition of glaciers worldwide.” The result is a unique time series of annual glacier mass changes in the years from 2000 to 2023 for all glacier regions of the world. Due to the large amount of precise data, this study is much more reliable than previous studies of global glacier changes, which were based on less accurate or incomplete data.

18 millimetres sea level rise

The loss of ice from the glaciers since 2000 has led to a rise in sea level of 18 millimetres. This makes the melting of glaciers the second strongest driver of sea level rise after ocean warming, well ahead of the mass loss of the Greenland and Antarctic ice sheets.

Strong regional differences

However, not all glacier regions are affected to the same extent. While the glaciers of the Antarctic and sub-Antarctic islands have only lost 1.5 per cent of their mass, they have shrunk the most in the Alps and the Pyrenees, at around 39 per cent. “Due to their low altitude, they are particularly affected by the higher temperatures,” explains Tobias Bolch. “Additionally, the Alpine and Pyrenean glaciers are comparatively small, which is also a disadvantage. Glaciers generally have a cooling effect on the microclimate of their surroundings. However, this effect is only weakl for small glaciers, which is another reason why the glaciers in the Alps and Pyrenees are shrinking the most.”

Declining meltwater supply in Alpine streams

Valuable freshwater supplies are being lost with the ice from the glaciers. Paradoxically, this is not yet noticeable in many of the world’s glacier-fed rivers; the water volumes from glacier melt have actually increased in most cases. However, these outflows will peak in the future and then decline steadily. “In the European Alps, we have already exceeded this peak discharge. Hence our glaciers will supply the rivers with less and less water,” says Tobias Bolch. “This is becoming a problem especially during longer dry periods. Glacier tributaries are then particularly important as continuous water suppliers. This stabilising effect is increasingly being lost.”

The study on the development of glaciers was carried out as part of the ESA-supported research initiative “Glacier Mass Balance Intercomparison Exercise (GlaMBIE)”. GlaMBIE is coordinated by the World Glacier Monitoring Service (WGMS) hosted at the University of Zurich in collaboration with the University of Edinburgh and the company Earthwave.

Publication:
Community estimate of global glacier mass changes from 2000 to 2023

Authors: The GlaMBIE Team (Michael Zemp, Livia Jakob, Inés Dussaillant, Samuel U. Nussbaumer, Noel Gourmelen, Sophie Dubber, Geruo A, Sahra Abdullah, Liss Marie Andreassen, Etienne Berthier, Atanu Bhattacharya, Alejandro Blazquez,, Laura F. Boehm Vock, Tobias Bolch, Jason Box, Matthias H. Braun, Fanny Brun, Eric Cicero, William Colgan, Nicolas Eckert, Daniel Farinotti, Caitlyn Florentine, Dana Floricioiu, Alex Gardner, Christopher Harig, Javed Hassan, Romain Hugonnet, Matthias Huss, Tómas Jóhannesson, Chia-Chun Angela Liang, Chang-Qing Ke, Shfaqat Abbas Khan, Owen King, Marin Kneib, Lukas Krieger, Fabien Maussion, Enrico Mattea, Robert McNabb, Brian Menounos, Evan Miles, Geir Moholdt, Johan Nilsson, Finnur Pálsson, Julia Pfeffer, Livia Piermattei, Stephen Plummer, Andreas Richter, Ingo Sasgen, Lilian Schuster, Thorsten Seehaus, Xiaoyi Shen, Christian Sommer, Tyler Sutterley, Désirée Treichler, Isabella Velicogna, Bert Wouters, Harry Zekollari, Whyjay Zheng)

In: Nature, 2025

DOI: https://doi.org/10.1038/s41586-024-08545-z

Video of the Glacier Mass Balance Intercomparison Exercise (GlaMBIE)

The animation illustrates the different observation methods at the example of Vatnajökull in Iceland and shows the combined results of glacier mass changes from 2000 to 2023 for all glacier regions worldwide. (Animation by Planetary Visions)
https://www.esa.int/ESA_Multimedia/Videos/2025/02/Revealed_glacier_ice_loss_over_two_decades/