Key figures
- Glaciers lost about 408 billion tonnes of ice in 2025 (WGMS)
- That loss alone raised global sea level by about 1.1 mm
- Average annual loss 2016–2025: 390 billion tonnes, vs. under 100 billion in 1976–1995
- Around two billion people depend on water from mountain glaciers and snow
It is hard to picture 408 billion tonnes of ice. The World Glacier Monitoring Service (WGMS), based at the University of Zurich, offers a comparison: the mass that the world’s glaciers lost in 2025 would have filled about five Olympic swimming pools every second of the entire year. It was the sixth most negative year since global records began in 1975, and six of the seven largest annual losses have occurred since 2018.
The findings, compiled from field measurements and satellite observations by scientists around the world and published in Nature Reviews Earth & Environment in April 2026, were confirmed by the World Meteorological Organization’s State of Global Water Resources report. Together they paint a clear picture: the world’s mountain glaciers are not approaching a new balance. They are disappearing.
The challenge: a loss that is accelerating
Glacier loss is not only continuing; it is speeding up. Between 1976 and 1995, glaciers lost on average less than 100 billion tonnes of ice per year, with some years even showing modest gains. That rose to about 230 billion tonnes per year between 1996 and 2015, and to 390 billion tonnes per year over the decade from 2016 to 2025. Since 1975, the world’s glaciers have lost more than 9,500 billion tonnes of ice, enough to raise global sea levels by about 26 millimetres. Nearly 80% of that total has been lost since 2000.
In 2025, all 19 of the world’s major glacier regions lost mass — the fourth consecutive year in which not a single region gained ice. The largest contributions to the global total came from High Mountain Asia, Alaska and the Russian Arctic. In relative terms, western North America and Central Europe suffered some of the heaviest losses. Western Canada and the United States recorded one of their three most negative years since measurements began in the 1940s, and the Alps continued a long run of severe melting. Mountain glaciers worldwide have lost about 6% of their total mass since 2000, and some regions have lost far more over past decades.
Glaciers are also vanishing entirely. The Global Land Ice Measurement from Space inventory now includes a new category for glaciers that no longer exist, already listing 181 glaciers that appeared in earlier surveys. The United Nations declared 2025 the International Year of Glaciers’ Preservation, and scientists created a ‘casualty list’ to document glaciers lost in each region of the world.
Why it matters
Rising seas are the most global consequence. Glaciers are currently one of the largest contributors to sea-level rise, alongside the ice sheets of Greenland and Antarctica and the expansion of warming ocean water. Every millimetre of sea-level rise increases the reach of storm surges and high tides, threatening coastal cities, farmland and freshwater aquifers.
But the most immediate impacts are felt closer to the mountains. Glaciers act as natural water towers. They store precipitation as ice during cold seasons and release it as meltwater during hot, dry summers — precisely when rivers are lowest and water demand for farming and cities is highest. Around two billion people in the Himalayas, the Andes, Central Asia and other mountain regions depend on this water for drinking, irrigation and hydropower.
In the short term, faster melting can actually increase river flows, masking the problem. But as glaciers shrink, they eventually pass a point known as ‘peak water’, after which summer meltwater declines year after year. Many smaller glaciers in the Andes and the Alps have already passed that point. For communities that rely on them, the dry-season water supply is shrinking.
Melting ice also creates new hazards. Meltwater collects in lakes held back by unstable walls of rock and ice. When these walls fail, they can release sudden, devastating floods known as glacial lake outburst floods, which have destroyed villages and hydropower plants in the Himalayas and the Andes. Thawing permafrost and retreating ice also destabilise mountain slopes, increasing the risk of rockfalls and landslides. In 2025, a massive landslide linked to glacier collapse buried much of a village in the Swiss Alps, whose residents had been evacuated in time thanks to monitoring.
In Canada, glaciers in the Rocky Mountains and the Coast Mountains feed rivers such as the Bow, the North Saskatchewan and the Fraser. Late-summer flows in these rivers support cities, farms and ecosystems across Alberta, Saskatchewan and British Columbia. As glaciers retreat, water managers are preparing for lower flows in dry years, with consequences for irrigation, salmon and hydropower.
What can be done
Scientists are candid that some future loss is already locked in. Even if global temperatures stabilised today, a substantial share of today’s glacier ice would still melt, because glaciers take decades to adjust to a warmer climate. But they are equally clear that every fraction of a degree matters. A major study published in Science in 2025 found that limiting global warming to 1.5 °C, rather than the roughly 2.7 °C implied by current policies, would roughly double the amount of glacier ice preserved worldwide by the end of the century.
Cutting greenhouse gas emissions is therefore the single most important action for the world’s glaciers. Reducing black carbon — the soot from diesel engines, crop burning and inefficient stoves — can also help, because dark particles that settle on snow and ice absorb sunlight and speed up melting, particularly in the Himalayas.
At the same time, mountain communities and downstream regions need to adapt. Early warning systems for glacial lake outburst floods, combining sensors, satellite monitoring and sirens, have already saved lives in Nepal, Pakistan, Bhutan and Peru. In some places, engineers have lowered the water level of dangerous lakes to reduce the risk.
Water managers are planning new ways to store water to replace the buffer that glaciers once provided. These range from reservoirs to nature-based solutions such as restoring wetlands and mountain meadows that soak up water and release it slowly, and ‘managed aquifer recharge’, which channels seasonal floods into underground aquifers. In the high valleys of Ladakh, in northern India, communities build ‘ice stupas’ — artificial glaciers formed by freezing winter water into tall cones that melt slowly in spring, when farmers need it for planting.
Better monitoring and cooperation are also essential. Regions such as the Hindu Kush Himalaya, whose glaciers sustain water supplies for hundreds of millions of people, remain underrepresented in global datasets. Expanding long-term, standardised observations helps governments plan for the water future ahead, and because major rivers cross borders, sharing data between upstream and downstream countries is vital.
What you can do
Supporting strong climate policies, reducing personal emissions and backing scientific monitoring all help. For travellers, visiting mountain regions responsibly and learning about local glaciers can deepen understanding of what is at stake.
Glaciers are among the most visible witnesses of climate change. Their retreat, measured year after year, is a message written in ice. Whether future generations inherit mountains that still carry glaciers depends on how quickly the world acts now.
Sources
WGMS, ‘Global glacier mass change in 2025’, Nature Reviews Earth & Environment (April 2026); Copernicus European State of the Climate 2025; WMO, State of Global Water Resources 2025 (September 2026); Zekollari et al., Science (2025); Monash University and phys.org reporting (April 2026).
