Save twice the ice by limiting global warming

In the new study, an international team of 21 scientists from ten countries used eight glacier models to calculate the potential ice loss from more than 200,000 glaciers outside of Greenland and Antarctica. The team evaluated a wide range of global temperature scenarios, assuming that temperatures would remain constant for thousands of years in each scenario.

"The choices we make today will resonate for centuries, determining how much of our glaciers can be preserved," says Harry Zekollari, co-lead author from Vrije Universiteit Brussel, who began this research as a postdoctoral fellow at the Chair of Glaciology in the Department of Civil, Environmental and Geomatic Engineering (D-BAUG) at ETH Zurich.

Looking beyond 2100 reveals new insights

In all scenarios, the glaciers lose mass rapidly over decades and then continue to melt at a slower pace for centuries -- even without additional warming. This long-term response means glaciers will continue to feel the effects of today's heat far into the future, gradually retreating to higher altitudes before reaching a new equilibrium.

"One of the key strengths of our study is that we were able, for the first time, to project global glacier evolution over multi-centennial timescales, and did so using eight models instead of one or two," explains Harry Zekollari. "Most glacier studies stop at 2100, which is problematic when simulating the long-term impact of today's climate policies, given the long-term response of glaciers over time."

For example, while studies limited to the year 2100 estimate that around 20 per cent of today's glacier mass will be lost regardless of future warming, the new study reveals that nearly twice as much would vanish under present-day conditions when multi-centennial timescales are considered. "We find that around 40 per cent of glacier mass is effectively 'doomed' to disappear," says co-lead author Harry Zekollari.

Melting glaciers reveal the reality of global warming

"Glaciers are good indicators of climate change because their retreat allows us to see with our own eyes how climate is changing. However, since they adjust over longer timescales, their current size vastly understates the magnitude of climate change that has already happened. The situation for glaciers is actually far worse than visible in the mountains today," says co-lead author Lilian Schuster from the University of Innsbruck.

Beyond contributing to sea-level rise, glacier loss has far-reaching consequences. It threatens freshwater availability, increases the risk of glacier-related hazards such as floods and landslides, and jeopardizes glacier-fed tourism economies. These cascading impacts will be felt across regions and generations.

"These effects underscore the critical importance of present-day climate policies," says Harry Zekollari. "Our study makes it painfully clear that every fraction of a degree matters. If we manage to limit global warming to +1.5°C instead of +2.7°C, we could still save twice as much glacier ice."

Current policies are projected to lead to an average global warming of around +2.7°C. As Zekollari emphasizes, the degree of warming between +1.5°C and +3.0°C plays a decisive role in glacier loss. Put simply: for every additional 0.1°C of warming, the world risks losing approximately 2per cent more of its glacier ice.

Contributing to the UN-Year of Glaciers' Preservation

"This study is a major contribution to the United Nations International Year of Glaciers' Preservation, emphasizing the urgent need for global climate action to protect the world's glaciers," says Daniel Farinotti, Professor of Glaciology at ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research WSL.

His research group at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) played a central role in producing the new findings. The entire study led by Zekollari and Schuster was conducted as part of the Glacier Model Intercomparison Project (GlacierMIP) and coordinated by the Climate and Cryosphere (CliC) Project of the World Climate Research Programme (WCRP).

Farinotti notes that the release of the Science study coincides with the opening of the High-Level International Conference on Glaciers' Preservation, initiated by the President of Tajikistan through the United Nations (UN) Resolution that established both the UN Year of Glaciers' Preservation and, later, the UN Decade of Action for the Cryospheric Sciences 2025-2034.

On the Swiss side, the Federal Department of Foreign Affairs (FDFA) was invited to support the organisation of the event, particularly in drafting what is intended to become the "Dushanbe Glacier Declaration." Daniel Farinotti, for his part, is acting as an advisor to the FDFA in the preparation of the declaration.