The sudden flood that occurred in August on the Nepal-China border resulted from a confluence of climatic and geological factors stimulated by global warming, according to a study released on Thursday.
The collapse of a block of ice and rock from Langtang Lirung mountain formed a massive surge of water, ice, and debris that raced down the valleys, carrying everything in its path.
The World Weather Attribution study explains that the catastrophe did not result from an extreme meteorological phenomenon, but from a “combination of elements” arising from rising temperatures, melting ice, and geological instability.
The region suffered “fundamental and irreversible changes,” underscored one of its authors, hydrologist Walter Immerzeel, of Utrecht University in the Netherlands, adding that the retreat of glaciers and of the ‘permafrost’ — the layer of soil that remains frozen — had compromised the mountain’s stability.
“We conclude that this slope was geologically unstable, perhaps because of the 2015 earthquake, and that it was amplified by the retreat of the glacier and of the ‘permafrost’,” Immerzeel said in statements to reporters.
The study confirmed that July and August 2026 were the hottest months ever recorded in the region and that heavy snowfalls at the end of 2025 increased the volume of meltwater.
“There is no doubt that climate change was one of the drivers of the disaster,” said Friederike Otto, a climatologist at Imperial College London.
“The Bhote Koshi disaster is a stark warning of the increasing risks to which the rapid warming of the Himalaya exposes populations,” specified another author of the study, Manjeet Dhakal, of Climate Analytics South Asia.
In Nepal, the floods left more than 1,400 dead, with 6,150 others reported missing. In China, the toll stands at 43 dead and 519 missing.
The Nepalese government estimated the cost of physical reconstruction at 4.78 billion dollars.
