Rescue efforts continued today in Nepal’s Rasuwa and Nuwakot districts, where at least 350 people are known to have been killed by a massive flash flood, while more than 1,400 are still missing. But while it is still too early to attribute a direct cause to the devastating flood, experts said they are confident about the human-caused trend that lies beneath it.

“We can't say definitively yet what the links to climate change are,” said Ella Gilbert, a climate scientist at the British Antarctic Survey. Nevertheless, Gilbert said: “climate heating is destabilizing glaciers in the Himalaya, with the rate of loss doubling since 2000. When glacier stability is undermined, sudden failures can occur, leading to horrible incidents like this one.”

That trend is well understood by scientists. Research led by Gunjan Silwal, cited by Bethan Davies, chair in glaciology at Newcastle University in the U.K., found that the Langtang catchment, which is the glacierized region above where the event began, lost ice one-and-a-half times faster between 2000 and 2023 than it did throughout the preceding 36 years. “Glacier loss rates have been accelerating, especially after 2000,” Davies said, “with rising snowlines increasingly intersecting with areas of steep ice, causing glacier recession, fragmentation, and warming.”

That is how the flash flood could have occurred despite there having been little rain in the region.

“Most people think of flash floods as being caused by heavy rainfall,” said Liz Stephens, professor in climate risks and resilience in the Department of Meteorology at the University of Reading, “but in Nepal and Tibet, as in many other high-mountain regions, they can also result from complex chains of hazards, including landslides, avalanches and glacial lake outburst floods. This complexity makes early warning especially difficult.”

Scientists now believe the trigger for the flood was a chunk of glacier ice breaking away high above the Lhende Khola, a tributary in Rasuwa district. What followed, in the words of Jon Tunnicliffe, associate professor of the environment at the University of Auckland, is what geomorphologists call a “hazard cascade”: instability high on a glacierized slope becomes an ice-rock avalanche; that avalanche blocks a river; the blocked river entrains water and sediment; and the whole mass turns into a debris-laden flood that travels miles downstream, gathering force as it goes.

“A localized failure at more than 5,000 meters can very rapidly become a catastrophe for people far down the valley,” Tunnicliffe said. Indeed, satellite imagery indicates the collapse originated around 5,200 meters up; downstream at Galchhi, river levels reportedly rose by as much as nine meters within 30 minutes, feeding into the Bhote Koshi and Trishuli river system that, a day later, devastated Nuwakot district.

Such failures are “exactly the type of event that is triggered by climate change,” said Wouter Buytaert, a reader in hydrology and water resources at Imperial College London. “Global warming shrinks glaciers, making it more likely for them to break apart … In mountain regions with steep slopes and narrow valleys, this creates the perfect conditions for events such as this.”

What’s Settled, And What Isn’t

Researchers aren’t disputing the physics or the decades-long pattern behind it — both are settled. What's unsettled is how much certainty to attach to this one event.

That pattern is not new, and it is not confined to Nepal. Similar glacier failures left 200 people killed or missing at Chamoli, India, in 2021 ; at Melamchi, Nepal, the same year; at Switzerland’s Birch Glacier ; and, on a far larger scale, in Peru's 1970 Huascarán avalanche, which killed roughly 6,000 people.

“Early signs suggest that this may have been a similar event to the collapse at Chamoli glacier,” Davies said. “The area has steep slopes, high topographic relief, and seismic activity that make it prone to mass movements.”

The bigger failure here may not be glaciological at all. A similar flood swept down the same river corridor from Tibet into Nepal in July 2025, according to Jeff Da Costa, a researcher in hydrometeorological hazards at the University of Reading — and Nepalese officials said afterward that they had received no advance warning from China, and that no formal mechanism existed to share one. Nepal pledged to fix that. “We do not yet know what information was available before today’s flood, when it became available, or how it moved across the border,” Da Costa said. “Establishing that timeline will be important.”

For its part, Nepal is well aware of the risks associated with the changing climate. In 2021, the country published its first National Adaptation Plan , laying out steps to build resilience against this kind of event. Whether that plan, or a promised warning system, made any difference this week is one of the questions likely to define the days to come, as the people of Nepal and Tibet come to terms with this disaster.