Climate breakdown probably weakened the glacier that collapsed causing catastrophic floods and killing hundreds of people in Nepal and Tibet last month, the first scientific study of the disaster has found.
Researchers identified unusually warm conditions before the glacier’s collapse, which sent an avalanche of ۱۱۰m cubic metres (۳,۸۸۵ cu ft) of snow and ice into the valley below. This triggered flash floods on an almost unprecedented scale, hitting communities downstream without warning.
“Communities in Nepal are paying with their lives for a crisis driven by fossil fuel emissions thousands of miles away,” said Dr Friederike Otto, a climate science professor at Imperial College London, which carried out the study.
“When warming destabilises the roof of the world, no amount of local adaptation can fully shield vulnerable people downstream from this scale of destruction. Without much faster action to transition to zero fossil fuel emissions we will inevitably see more disasters of this scale occurring in the years to come.”
More than ۱,۳۰۰ people were killed and more than ۵,۰۰۰ people remain missing after a massive section of overhanging glacier and rock measuring roughly ۲۰۰,۰۰۰ sq metres (۲,۱۵۳,۰۰۰ sq ft) fell from Langtang Lirung mountain on ۲۶ August.
It dropped about ۱,۴۰۰ metres (۴,۶۶۰ft), slamming into the valley floor with such intensity that it registered as an earthquake, liquidising ice and sparking a freezing flood that careened downriver at speeds exceeding ۱۱۰ mph.
The devastating flood of water, ice, rock and sediment swept away families, homes, settlements, roads, bridges and other infrastructure, leaving survivors stranded and cut off.
“Rock avalanches of this size are rare, with annual frequency estimates of approximately one event this size every ۱,۰۰۰–۱۰,۰۰۰ years,” the study said. “This event shows that limits to adaptation are already being reached.”
The research was unlike previous studies by Otto and her team at World Weather Attribution (WWA) – a collaborative project between Imperial and other climate specialists worldwide – in that the role of climate breakdown could not be ascribed to one particular weather event.
Instead, the researchers found the disaster was the result of a compound crisis, with a number of factors made worse by decades of atmospheric heating as a result of greenhouse gas pollution.
Dr Ben Clarke, who researches extreme weather and climate change at Imperial, said the “fingerprints of climate change” were clear in the long-term changes that happened around the glacier before its catastrophic collapse.
Among the study’s key findings were:
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In the region where the collapse happened, climate breakdown has caused about ۲C of warming since pre-industrial times, and about ۱.۵C of warming in July and August specifically;
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July and August ۲۰۲۶ were the warmest on record locally, reaching ۵C above the ۳۰-year average in the days before the collapse;
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The freezing threshold in the Himalayas has risen by about ۱۰۰ metres per decade since the ۱۹۸۰s, with higher and longer thaw temperatures weakening mountain slopes shaped by permafrost;
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The warming temperature had already driven substantial glacier recession, removing stabilising ice from around the site where the collapse occurred and contributing meltwater;
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A ۷.۸ magnitude earthquake in ۲۰۱۵ further contributed to slope failure, though its specific contribution to the disaster in August could not be confirmed.
Otto, Clarke and the WWA team said their study did not directly ascribe climate breakdown as the fundamental cause of the catastrophe. Instead, it was best understood as a destabilising factor on the existing geology.
Clarke said: “We found that climate change is transforming the high mountain environment, influencing many of the possible drivers of this collapse.”
Nepal has filed a formal request with the UN loss and damage fund for financial support to address the destruction caused by the flood, a process that requires proof of a link to the climate crisis. The country’s foreign minister, Shisir Khanal, has also demanded that top emitting nations such as China and India “wake up” and accept shared responsibility for the disaster.
Madhab Uprety, senior technical advisor for the Red Cross Red Crescent Climate Centre, which is part of WWA, said only aggressive cuts to global emissions could begin to address the “losses and damages faced by vulnerable frontline communities”.
He added: “In addition to the human tragedy on an unimaginable scale, the cost of recovery for this disaster is substantial. For a nation that’s done virtually nothing to contribute to this problem, it underlines the need to find fairness in helping climate vulnerable nations cope with the problems they have not unleashed.”
