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Attribution study ties Nepal's deadly mountain collapse to decades of climate warming
September 18, 2026
Scientists studying the August 26 collapse of rock and ice in northern Nepal found that warming thawed permafrost and thinned glaciers, weakening the slope over decades.
Nepal lies along the Himalaya, where more frozen water sits than anywhere beyond the poles, and where towns, roads and power schemes are packed into tight river valleys beneath the peaks.
Key facts
- Jakob Steiner, a University of Graz geoscientist who began working in the Himalaya in 2006 and did not help write Thursday's report, said monitoring gear at roughly 5,000 meters (16,404 feet) now shows rock and ground that stay unfrozen for part of the year.
- Alongside at least 1,300 known dead, over 5,000 people are unaccounted for, among them some caught in tunnels serving the 13 hydropower plants the floods damaged.
- On August 26 an unstoppable surge of rock, mud and water tore through Nepal's north, killing more than 1,200 people and leaving thousands unaccounted for.
- Kargel and colleagues wrote in Science in 2021 that comparable weak zones in metasedimentary rock appear to have figured in a separate rock-ice avalanche behind a ruinous debris flow at Chamoli, India, that year.
AP News reports that scientists working under World Weather Attribution found the sharpest climate signal in how far up the mountains the freezing line has climbed. Rock at greater height now spends longer stretches above the freezing mark, so the permafrost that glues broken stone together thaws and the cracks inside it widen. Friederike Otto, one of the authors and a climate scientist with Imperial College in London, tells AP News that apart from geology such as quake damage to bedrock, heating driven by people makes every other driver worse. CNN reports the same conclusion from another angle. No lone burst of severe weather tipped the slope, CNN says; a stack of slower processes did, pushed along by decades of heating from burning fuels. CNN adds that the team applied peer-reviewed methods in work that has not yet gone through peer review of its own, and that the tie between warming and heavier snow or rain proved weaker, partly because instruments struggle in terrain this broken.
Science News reports what the mountain itself did. Images from orbit let researchers rebuild the sequence: a huge block of rock capped with ice tore loose from Langtang Lirung and sent a churning mass of debris racing down the valley in the direction of India. Walter Immerzeel, a mountain hydrologist at Utrecht University, said during a September 16 briefing that the 2015 Gorkha earthquake, magnitude 7.8, may have left the bedrock damaged. Jeffrey Kargel, a Tucson geologist at Planetary Science Institute, said meltwater seeping into fissures and freezing again could have levered them apart, and he expects the same thing is possible at many other points along the Himalaya. Alton Byers, a mountain geographer who studies what warming does to the range, tells Science News that nothing on this scale has crossed his path before. The Guardian reports the money and the politics around it. Nepal answers for a sliver of the world's greenhouse gas output, under a tenth of one percent, and its leaders, in office only half a year after protests brought down their predecessors, are pressing wealthier states to help pay for recovery. The New York Times tells readers the hazard reaches eight countries along the Himalaya.
The cause reads the same across all four accounts, as does the damage to hydropower work in the valleys and the finding that warning systems could not blunt a failure this fast and this large. The human toll does not: one account puts the dead and the missing at one pair of figures, another at a different pair.
Ben Clarke, who studies climate at Imperial College London, told a briefing on Sept. 16 that the pace outstrips what the planet as a whole is doing: “That’s much faster than the average rate of global warming,”
Ben Clarke
Still developing
The number of people killed and still missing remains open, and the figures do not line up between the accounts.
How settled the reporting is
Sources
- AP News — Climate change made deadly Nepal glacier and rock collapse more likely, analysis finds
- Science News — Nepal’s deadly debris flow points to risks in other high mountain regions
- CNN — Here’s what one team of scientists thinks happened in Nepal’s deadly flood wave
- theguardian.com — The Guardian view on the Nepal-Tibet floods: a spur to action on climate | Editorial
Toggle read the full reports of 4 of the 5 outlets counted on this event. The other 1 are counted from their headlines and opening sentences.