Alpine Glaciers: Nearly 150 Years of Measurements, and a Faster Retreat

2026, the second-worst year on record in Switzerland

In September 2026, even at 11,500 feet (3,500 m), not a flake of the winter’s snow was left on Switzerland’s glaciers [1]. On the 23 glaciers where scientists from GLAMOS, Switzerland’s glacier monitoring network, hiked up to read their stakes, the winter snow was gone everywhere, right up to the highest measuring points [2]. The numbers came out on October 1: in a single year, Switzerland lost 5.5% of its glacier ice, and almost 20% since 2021 [1, 2].

Over the hydrological year, October 2025 through September 2026, the average balance of Swiss glaciers came to -2.86 m water equivalentThe depth of the layer of water you’d get by melting the ice lost and spreading it over the glacier’s entire surface. Scientists write it m w.e.; 1 m w.e. is a water layer 3.3 feet deep, or slightly more than that in ice. (m w.e.), barely short of the 2022 record of -3.13 m w.e. [2]. Some glaciers thinned by 8 to 13 feet (2.5 to 4 m) on average, and by up to 33 feet (10 m) in places on their tongues, in a single summer [1]. For four large glaciers, Allalin, Clariden, the Great Aletsch, and the Rhône, 2026 was even worse than 2022 [2]. The table below compares it with the last five years [2, 3, 4].

Why such a bad year? First, a thin winter: from November 2025 to April 2026, average snow depth ranked among the ten lowest since measurements began [1]. Then a summer with no break. From May to September, the freezing level, the altitude where the air drops to 32 °F (0 °C), stayed above 13,100 feet (4,000 m) on 76 days, more than twice the average and a record [1]. June, July, and August were the hottest ever measured in Switzerland, according to MeteoSwiss, the national weather service, as cited by GLAMOS [2]. Stripped in places of their protective snow as early as June, the glaciers melted bare all summer long.

If 2026 didn’t quite beat 2022 nationwide, it’s because the spring snowpack was slightly less depleted (25% below normal on April 30, versus 32% in 2022), and less Saharan dust, which darkens the snow and speeds up melting, settled on it [2]. Two small glaciers, Bella Tola in the canton of Valais and Griessfiren/Plattalvafirn in the canton of Glarus, didn’t survive the summer [1, 2].

Length, area, volume, mass balance: four measurements not to mix up

“The glacier retreated 177 feet” and “the glacier lost 23 feet of thickness” aren’t the same statement, yet they can describe the same glacier in the same year. Take the Pasterze, Austria’s largest glacier, at the foot of the Grossglockner, the country’s highest peak: in 2024-2025, its snout retreated 177 feet (54 m), its tongue sank 24 feet (7.3 m) on average, and the ice there now moves forward less than 16 feet (5 m) a year [6]. You can measure a glacier in four ways, and each tells a different story.

• Length: the position of the snout, the end of the tongue, surveyed at the end of each summer with a tape, GPS, or a drone. It responds to the climate years later, and depends heavily on the terrain.
• Area: the outline of the glacier, mapped from aerial photos. Switzerland has compiled several inventories, from 1850, reconstructed, to 2023 [7, 8].
• Volume: the amount of ice, calculated by comparing elevation surveys taken several years apart, and from thickness measurements.
• Mass balance: what the glacier gains in snow over the winter, minus what it loses to melt in the summer. It’s measured with stakes drilled into the ice and snow cores, and expressed in meters of water equivalent [5].

In France, this painstaking work is done by the GLACIOCLIM observatory, founded in 2003 and run by the Institute of Environmental Geosciences in Grenoble, with the equivalent of two and a half full-time staff, plus students [10]. On each glacier it monitors in the French Alps, 20 to 25 wooden stakes measure the melt, 5 to 10 cores measure the winter snow, and roughly every five years, aerial photos are used to cross-check the whole picture [5].

These four quantities can’t be added together or compared with one another: a snout can stay put while the glacier thins, or retreat 1,150 feet (350 m), even nearly 3,000 feet (900 m), in a year because a tongue grown too thin has broken off above a rock step. That’s why our charts never mix them.

Before 1880, engravings and moraines instead of measurements

Around the middle of the 19th century, Alpine glaciers reached their last great extent, at the end of the Little Ice AgeA colder period, several centuries long, when Alpine glaciers were far larger than today; it ended around the middle of the 19th century.. Nobody was measuring them regularly yet. What we know of their size comes from reconstructions: engravings, paintings, old maps, travelers’ accounts, then the first photographs, and the morainesThe ridges of rocks and boulders a glacier pushes up and drops along its sides and at its snout. They trace its former extent. left behind [8, 9].

These reconstructions are valuable, but they aren’t measurements. In the database of the World Glacier Monitoring Service (WGMS), the record for the Mer de Glace, the big glacier above Chamonix, goes back to 1570, pieced together from texts, maps, drawings, engravings, and later photos [9]. The record for the Rhône Glacier shows its snout at its farthest point down the valley in 1856, then a retreat of about 2,760 feet (840 m) through 1879, again based on old documents [9].

Regular measurements came next: snout positions have been surveyed every September since 1870 at the Mer de Glace and the Argentière Glacier [10], and systematically in Switzerland since 1880 [7]. In Austria, the Alpine Club’s glacier survey service has 135 years of history [6]. In 1894, an International Glacier Commission, set up at the urging of Swiss scientist François-Alphonse Forel, launched the worldwide coordination that the WGMS carries on today [11]. Mass balance came later: starting in 1914 in Switzerland [2], then 1949 at Sarennes and 1957 at Saint-Sorlin in France, and 1953 at Hintereisferner in Austria [9].

Since 1850, how many miles of retreat?

To answer that, you need long, unbroken records. The Swiss network has several, and we picked four of them, among the glaciers hikers know best, from the measurement file published by GLAMOS [8]. Each line starts at zero at the beginning of its record; the Rhône starts from its reconstructed maximum of 1856.

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The Great Aletsch Glacier, the largest in the Alps, has retreated 2 miles (3.2 km) since 1892, and the Morteratsch, in the Engadine valley of eastern Switzerland, 1.7 miles (2.8 km) since 1894. The Rhône Glacier has lost 1.1 miles (1.8 km) since 1879, on top of the 2,760 feet (840 m) reconstructed for the two previous decades. The Trient Glacier, above the village of the same name on the Tour du Mont-Blanc, has retreated 0.9 mile (1.4 km) since 1879 [8]. And the pace isn’t slowing: since 2000, the Morteratsch has lost about 3,500 feet (a little over 1 km), the Aletsch about 3,250 feet (nearly 1 km), the Trient 2,450 feet (750 m), and the Rhône 2,120 feet (650 m) [8].

Yet the records hold a surprise: the Trient has also advanced, twice. From 1879 to 1896, its snout gained about 590 feet (180 m); then, from 1957 to 1987, about 1,280 feet (390 m) [8]. Glaciers with a steep tongue can advance during short runs of good years, Swiss glaciologists explain, while large glaciers with a long, gently sloping tongue, like the Aletsch, retreat steadily [7]. In France, the Argentière Glacier also advanced nearly 1,300 feet (400 m) between 1970 and 1990, after a run of cool summers and snowy winters [5].

Since then, the trend has been clear. In 2024, 66 of the 69 Swiss glaciers surveyed retreated, by 3 to 210 feet (1 to 64 m) for nine out of ten [7]. In Austria, the glaciers surveyed in both 2024 and 2025 got 67 feet (20.3 m) shorter on average in one year, the eighth-largest retreat in 135 years of measurements, and 94 of the 96 glaciers observed retreated [6].

Mass balance, or what a glacier really loses each year

Mass balance tracks the year’s climate: it comes from the snow that fell in winter and the melt of summer [5], while length responds years later and depends on the terrain [7]. Every spring, glaciologists core the winter snow; every summer, they read stakes drilled about 33 feet (10 m) into the ice, two to four times a season in the French Alps [5]. We added up these balances for three glaciers in three countries, monitored without a break since 1957, using the WGMS database [9].

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All three lines tell the same story. Until the mid-1980s, they barely dip: in France, glaciers even grew between 1954 and 1981, thanks to cool summers followed by wet winters [5]. Then they plunge. Since 1957, the Saint-Sorlin Glacier, in the Grandes Rousses range of the French Alps, has lost 69 m w.e., the equivalent of a layer of water 226 feet deep across its whole surface; Hintereisferner, in Austria’s Ötztal Alps, 52 m w.e.; Silvretta, in eastern Switzerland, 38 m w.e. [9]. In all three records, 2022 remains the worst year [9].

The slope of the lines shows the speed. By our calculations from the WGMS data, Saint-Sorlin lost an average of 0.1 m w.e. a year between 1957 and 1985, and 2.1 m w.e. a year since 2001, about twenty times as much. Hintereisferner went from 0.3 to 1.3 m w.e. a year, and Silvretta, in balance until the mid-1980s, now loses 1.2 m w.e. a year [9].

Other records say the same thing. The five glaciers monitored in France, four in the Alps and one in the Pyrenees, have lost an average of 39 m w.e. since 2001 [5]. The twelve Austrian balances available for 2024-2025 average -1.72 m w.e. [6]. And worldwide, the WGMS reference glaciers have lost more than 25 m w.e. on average since 1980 [12].

How much ice is left in Switzerland?

To work out the total volume, Swiss glaciologists measured ice thickness by radar and modeled it across all the country’s glaciers; the annual balances then let them track that stock year by year [2]. At the end of 2026, Switzerland still had about 10 cubic miles (42.6 km³) of ice, more than 7 cubic miles (30 km³) less than in 2000, and its glaciers covered about 276 square miles (714 km²), a third less than in 2000 [2]. The loss is speeding up, decade after decade [2].

This melting ice feeds rivers in summer, but the contribution is shrinking: with 0.6 cubic mile (2.5 km³) of ice lost, 2026 ranks only third in recent decades and supplied less water than 2003, because there’s less ice left to melt. According to GLAMOS, peak meltwater has probably passed [2].

Small glaciers, meanwhile, simply vanish. More than 1,000 Swiss glaciers disappeared between 1973 and 2016 [2], then 159 between the 2016 and 2023 inventories, or 11%; in the southern canton of Ticino, almost 40% in six years [7]. The 2023 inventory still lists 1,299 [7].

Will the glaciers of the Alps disappear? What the projections say

A projection isn’t a forecast: it describes what would happen under a given greenhouse gas emissions scenario. In 2019, a study simulated the future of every glacier in the Alps using the IPCC scenarios [13]. Whatever the scenario, they would lose 47 to 52% of their 2017 volume by 2050. After that, it all depends on emissions: with deep cuts (the RCP2.6 scenario), about a third of the 2017 volume would remain in 2100; with emissions that keep rising (RCP8.5), the glaciers would have largely disappeared by 2100, with 94% of their volume gone [13]. That study was published before the summers of 2022 through 2026.

A study published in December 2025 counts instead the glaciers that vanish, for warming of 2.7 to 7.2 °F (1.5 to 4 °C) by 2100 compared with pre-industrial times [14]. In the Alps, where small glaciers dominate, more than half would disappear within the next twenty years, a timeline that depends little on the scenario; with 7.2 °F (4 °C) of warming, about twenty would remain in 2100 in the study’s “Central Europe” region, that of the Alps, 99% fewer than today [14].

Moraines, ladders, rerouted trails: what changes for hikers

Where the ice retreats, it leaves a new and unstable landscape: steep moraine slopes, scree, meltwater lakes, and dead ice buried under the rocks. The German Alpine Club sums it up in its research program on the Eastern Alps: steep moraines are unstable and prone to rockfall, rock faces freed from the ice to rock avalanches, and dead ice can cause unpredictable ground collapse. Routes have to be adjusted year after year, or abandoned [15].

Around the Mer de Glace, a study traced the approaches to five mountain huts over more than a century: largely unchanged for most of the 20th century, these trails have been altered many times since the 1990s, because of the thinning glacier and the erosion of the moraines. In 2017, they included 2,080 feet (633 m) of ladders, and the danger they pose keeps rising, the authors note [16]. At Montenvers, the terminus of a cog railway from Chamonix, a new gondola opened in February 2024 just a few yards from the glacier, cutting the walk for visitors heading down to the ice cave [17].

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Elsewhere, the examples are right there in the official reports. On the Dachstein, in Austria, rockfall from the faces of the Mitterspitz increased so much, with the glacier’s retreat and changes in the permafrost, that the standard route from the Adamek hut had to be moved in 2024; the Austrian Alpine Club also reports routes that have become harder to travel [6]. In Switzerland, cavities carved under glacier tongues collapse and leave deep craters, as on the Rhône Glacier [1, 2].

What this means for you on a marked trail: an old guidebook may describe an approach that no longer exists, and a moraine that looks solid can give way underfoot. The Swiss Alpine Club’s hiking scale, used on Swiss trails, mentions sections on glaciers from grade T4 up; we explain it in our guide to hiking difficulty ratings.

Going to see the glaciers, with the numbers in mind

No need to set foot on the ice to see these glaciers. A valley trail, a cog railway, or a mountain pass road is often enough to read in the landscape what the records say: the gray tongue below, the smooth rock it has polished, and the long crests of moraine. Many of these places can be reached by train and bus, and a night in a mountain hut lets you see them in the evening light, then again in the morning.

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The moraines lining Alpine glaciers often trace their extent in 1850: the Swiss inventory of 1850 relies partly on them, and on old maps [8]. The smart move, next time a trail takes you along one of those ridges of rock: look up at the ice, far above, and size up the distance. You’ll have a century and a half of data under your boots.

Guillaume Hoarau

Camping, backpacking, bushcraft and hiking

Guillaume Hoarau writes for Outfarer about camping, backpacking, bushcraft, and hiking. A survival-skills buff and a collector of vintage field manuals, he loves clear explanations, lists that actually help and other people’s stories, which he tells well.

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