2025 Was Only the Sixth-Worst Year for Glaciers. Six of the Seven Worst Are the Last Seven Years.

In the 2025 hydrological year, the world's glaciers lost 408 ± 132 gigatonnes of ice — enough to raise global sea level by 1.1 ± 0.4 mm.

That ranks as the sixth-most negative year on record.

Sixth. Not first. On its own that reads like a reprieve.

Here is the same fact from the other side: six of the seven highest mass-loss years on record have occurred in the past seven years.

"Sixth worst ever" and "an ordinary year lately" are now the same statement. That is what a shifted baseline looks like in a single sentence.

The rate, in three twenty-year windows

This is the cleanest data in climate science, and it needs no interpretation:

Roughly a quadrupling across two generations, in three steps, each one clearly above the last.

Note the detail in the first row. Within living memory there were years when the world's glaciers put on mass. Not many, and not much — but the sign of the number could still go either way. That has not happened in decades and is not going to happen again this century.

"All regions" is the phrase to hold

In 2025, glaciers lost mass in every region.

Not most. Not the vulnerable ones. All of them.

Glaciers are local. They respond to local temperature, local precipitation, local shading and aspect and debris cover. A warm year in the Alps can coincide with a snowy year in the Andes. Regional variation is the normal texture of this data, and it is the reason a single glacier's retreat has never been strong evidence of anything global — a point sceptics have historically made fairly.

When every region loses in the same year, that texture is gone. The local noise has been overwhelmed by something that is not local.

Where it came from in 2025

Two different questions, two different answers, and they are easy to conflate:

Which regions lost the most ice by volume? High Mountain Asia, Alaska, and the Russian Arctic. These are the big contributors to global mass loss — because they have the most ice to lose.

Which regions lost the most relative to their size? Western Canada and the USA, Iceland, and Central Europe. Area-averaged loss was largest here.

Which regions were most anomalous versus their own 1991–2020 climate? Western Canada and the USA, South Asia West, and Svalbard.

A region can dominate the sea-level number while behaving normally for itself, or behave extraordinarily while contributing little to the global total. Both matter, for different reasons — one for coastlines, the other for what is coming.

Central Asia's 2025 was described in the peer-reviewed literature as record-breaking, and the Pamir's as unprecedented. That is not the language of a middling year, and it sits inside a year the global figure called sixth-worst.

The number under the number

Since 1975, cumulative glacier mass loss totals 9,583 ± 1,211 Gt — 26.4 ± 3.3 mm of sea-level rise.

About two and a half centimetres, from mountain glaciers alone, in fifty years.

Two and a half centimetres does not sound like much, and on its own it isn't. Mountain glaciers are also not the main event for sea level — thermal expansion and the great ice sheets dominate. This is the contribution of the small ice.

Its importance is somewhere else entirely. Glaciers are water storage. They bank snow in the wet season and release it in the dry one, which is why rivers fed by High Mountain Asia's ice keep running in late summer for a very large number of people downstream. A glacier in retreat increases runoff for a while — and then it doesn't.

The sea-level figure is what glaciers do to the coast. The runoff is what they do to everyone living below them, and it does not appear in this number at all.

Why we trust this

Glacier mass balance is measured, not modelled — stakes drilled into ice, repeated surveys, and satellite gravimetry and altimetry, compiled by the World Glacier Monitoring Service across a network built over more than a century.

The uncertainty is stated honestly and it is not small: 408 ± 132 Gt is a ±32% band. WGMS publishes it that way rather than quoting a clean figure. As with the WMO temperature record, the visible error bars are a sign of the discipline, not a weakness in it.

Why this is on AEDO1

A glacier is the least ambiguous instrument in climate science. It does not have an opinion, a funding source, or a methodology dispute. It integrates decades of temperature and snowfall into a single physical quantity: how much ice is there.

The reading for 2025 is sixth-worst on record, and unremarkable for this decade. Both halves of that are true, and the second one is the finding.