Human-driven global warming has caused glaciers to thin and mountain permafrost to thaw, likely contributing to the destabilization of a Himalayan slope that collapsed last month and triggered catastrophic flooding in Nepal, according to an analysis released Thursday.
The analysis by World Weather Attribution said climate change was not the only factor behind the Aug. 26 disaster. Researchers found that a major earthquake in Nepal in 2015 may have weakened the rock in the area years before the collapse.
“This disaster was not an extreme weather event, but the fingerprints of climate change are still clear to see in long-term changes,” said Ben Clarke, a climate researcher at Imperial College London who contributed to the analysis, in a press statement.
More than 1,300 people were killed and more than 5,000 remained missing after a huge section of rock and an overlying glacier collapsed near Nepal’s border with China. The resulting surge of water, ice, boulders and sediment swept through communities along the Trishuli River corridor, causing billions of dollars in damage.
Scientists said rising temperatures across the Himalayas are causing glaciers to retreat and permanently frozen ground to thaw. Such permafrost helps hold fractured mountain rock together.
As a result, climate change can affect not only weather-related hazards such as extreme heat and heavy rainfall but also the stability of mountains, posing risks to communities concentrated in narrow river valleys below.
The analysis did not establish whether the collapse would have occurred without climate change, which is primarily driven by greenhouse gas emissions from burning fossil fuels such as oil, gas and coal. However, researchers concluded that warming had intensified several processes over decades that contributed to making the slope less stable.
Global warming weakening high mountain slopes
One of the clearest climate-related changes identified in the report was the rise in the elevation of the freezing threshold.
According to the analysis, warming has raised the altitude at which the ground remains consistently frozen by about 100 meters (328 feet) per decade. This has exposed rock at increasingly higher elevations to longer periods above freezing, causing permafrost to thaw and cracks to develop in the ice, ultimately weakening the rock beneath it.
Jakob Steiner, a geoscientist at the University of Graz who has worked in the Himalayan region since 2006 but was not involved in Thursday’s report, said monitoring equipment around 5,000 meters (16,404 feet) now shows that some rock and ground no longer remain frozen year-round.
“This means that the ground that was sitting below ice for hundreds and thousands of years is now becoming exposed,” Steiner said.
Glacier retreat was identified as another factor contributing to instability.
Glaciers in the region have been losing mass for decades at a rate equivalent to more than half a meter (about 1.6 feet) of thinning each year, the report said. The Langtang Lirung glacier, located in the area where last month’s disaster occurred, has retreated by about half a kilometer (0.3 miles) since the 1990s, exposing rock that had previously been covered by ice.
The Himalayan region holds the world’s largest volume of snow and ice outside the polar regions. More than 63,000 glaciers there feed at least 10 major Asian river systems and support the food, water, energy and livelihood security of billions of people.
However, studies have found that about 78% of the glacier area located between 4,500 and 6,000 meters (14,763 to 19,685 feet) above sea level is highly exposed to warming. United Nations reports have found that glaciers lost 267 billion tons of ice annually between 2000 and 2019, roughly equal to the mass of 46,500 Great Pyramids of Giza.
As glaciers retreat, they can reduce pressure that once helped support nearby rock walls while also generating additional meltwater.
The period preceding the Aug. 26 collapse was also unusually warm. July and August 2026 were the warmest such months recorded locally, according to the analysis.
“Apart from potential geological factors like earthquakes that are weakening the bedrock, all these other factors are made worse by human-induced climate change,” said Friederike Otto, a climate scientist at Imperial College London and one of the report’s authors.
Disaster highlights limits of adaptation
The catastrophe also illustrates how some climate-related risks in the world’s highest mountains may surpass the protection offered by early warning systems and other adaptation measures, the report said.
Nepal has introduced disaster risk reduction plans and warning systems, but researchers said the scale and speed of the collapse overwhelmed those safeguards.
Unlike rainfall-triggered floods, which can sometimes be predicted hours or days in advance, major slope failures in remote high-altitude areas can happen suddenly and remain extremely difficult to forecast.
Otto said mountain ecosystems and communities are more vulnerable to climate impacts than people living in the plains.
“Small changes in temperatures affect the stability of the land itself,” she said.
The report said improved high-altitude monitoring, earth observation and warning systems could help reduce some risks. However, researchers cautioned that adaptation has limits in Himalayan valleys where settlements, roads, hydropower facilities and other infrastructure are concentrated along rivers.
Because glaciers and permafrost respond to temperature changes over decades, some of the mountain destabilization caused by warming has already been set in motion, according to the report.
“The most important thing to minimize the risk in this region is to rapidly stop using fossil fuels that lead to increasing global temperatures,” Otto said. “All these drivers that we’ve talked about, permafrost melting, glacial melting, etc., will just become worse. And that means that events like this become more frequent.”