In just over two decades, the world has lost a staggering 6.5 trillion tons of glacier ice, raising sea levels by 18 millimeters. This rapid decline is not only a stark indicator of climate change but also a looming threat to freshwater supplies and coastal communities worldwide.
The most comprehensive study to date, coordinated by the World Glacier Monitoring Service (WGMS) at the University of Zurich, and published in the scientific journal Nature on Wednesday, offers unprecedented insight into global glacier changes. Known as the Glacier Mass Balance Intercomparison Exercise (GlaMBIE), the research combined 233 regional assessments from 450 data sources, using both ground-based and satellite observations spanning 2000 to 2023.
According to the study, back in 2000, glaciers—excluding the massive ice sheets of Greenland and Antarctica—covered 705,221 square kilometers and held 121.7 trillion tons of ice. Since then, they have been shrinking at an alarming rate, losing around 5% of their mass annually. Locally, the picture is even bleaker: Antarctica sheds 2% of its glaciers each year, while Central Europe has lost an astonishing 39%.
A Landmark Study Reveals the Full Picture
“Benefiting from the different observation methods, GlaMBIE not only provides new insights into regional trends and year-to-year variability, but we could also identify differences among observation methods,” says Professor Michael Zemp, study co-lead and WGMS Director at the University of Zurich. ”This means that we can provide a new observational baseline for future studies on the impact of glacier melt on regional water availability and global sea-level rise.“
Ice melts on the Aletsch Glacier in Fiesch, Switzerland, August 12, 2015. One of Europe’s biggest glaciers, the Great Aletsch coils 23 km (14 miles) through the Swiss Alps – and yet this mighty river of ice could almost vanish in the lifetimes of people born today because of climate change. The glacier, 900 metres (2,950 feet) thick at one point, has retreated about 3 km (1.9 miles) since 1870 and that pace is quickening. REUTERS/Denis Balibouse
Sea Levels Rise as Glaciers Shrink
Between 2000 and 2023, glaciers worldwide lost 6.5 trillion tons of ice—raising sea levels by 18 millimeters at a pace of 0.75 millimeters per year. This makes glacier melt the second-largest contributor to global sea-level rise, surpassed only by ocean warming.
Alarmingly, the data showed that the annual rate of ice loss has surged by 36% in recent years. Glaciers now lose 273 billion tons of ice each year—18% more than Greenland’s ice sheet loss and over twice that of Antarctica.
“Our observations and recent modeling studies indicate that glacier mass loss will continue and possibly accelerate until the end of this century”, says UZH glaciologist and GlaMBIE project manager Samuel Nussbaumer. “This underpins the Intergovernmental Panel on Climate Change’s call for urgent and concrete actions to reduce greenhouse gas emissions and associated warming to limit the impact of glacier wastage on local geohazards, regional freshwater availability, and global sea-level rise.”
In eastern Tibet, runoff from the Zepu glacier, seen here in Oct. 2004, during a hike from a village named Yuren, in eastern Tibet, is melting with rising temperatures. The result has formed the powerful headwaters of a new river. (Howard W. French/The New York Times)
The Disappearing Freshwater Reserves
Beyond rising seas, glacier melt threatens the world’s freshwater reserves. “To put it into perspective, the 273 billion tons of ice lost every year equates to the amount of freshwater consumed by the entire global population over 30 years, assuming a daily intake of three liters per person,” Professor Zemp noted.
Arctic and Antarctic: The Epicenters of Change
Glaciologist Inés Dussaillant emphasized the vital role glaciers play in providing freshwater to regions like Central Asia and the Andes during dry seasons. However, when it comes to sea-level rise, the Arctic and Antarctic are key. Alaska alone accounts for nearly 25% of glacier-driven sea-level rise.
Presenting the GlaMBIE results and celebrating the end of the project’s first cycle with the team at the ESA Polar Science Week. Looking forward to the continuation of this important, integrative and collaborative work! pic.twitter.com/SHqeafAUPD
— Ines Dussaillant (@DussaillantInes) September 10, 2024
With 2025 designated by the United Nations as the International Year of Glacier Preservation, the GlaMBIE study serves as a wake-up call.
