A new analysis released Thursday concludes that human-induced global warming likely contributed to the destabilization of a Himalayan slope that collapsed last month in Nepal, triggering catastrophic flooding that killed more than 1,300 people and left thousands missing. The report, from the World Weather Attribution network, says that thinning glaciers and thawing permafrost—both driven by rising temperatures—weakened the mountain face, making the disaster more probable.
The collapse occurred near Nepal's border with China on August 26, sending a torrent of water, ice, rocks, and debris down the Trishuli River corridor. The deluge swept through communities, causing billions of dollars in damage and leaving over 5,000 people unaccounted for. The report cautions that climate change was not the sole cause; a powerful earthquake in 2015 may have fractured the bedrock years earlier, setting the stage for failure.
Ben Clarke, a climate researcher at Imperial College London who worked on the analysis, said in a statement: "This disaster was not an extreme weather event, but the fingerprints of climate change are still clear to see in long-term changes." The researchers emphasized that while the immediate trigger may have been geological, the long-term warming trend has systematically weakened high-mountain environments.
Warming destabilizes high-altitude slopes
One of the most direct climate signals identified in the report is the upward shift of the freezing level. The altitude at which ground remains frozen year-round has risen by roughly 100 meters (328 feet) per decade. That exposes previously frozen rock to above-freezing temperatures for longer periods, thawing permafrost and creating cracks that undermine slope stability.
Jakob Steiner, a geoscientist at the University of Graz who has worked in the region since 2006 but was not involved in the study, noted that monitoring instruments at around 5,000 meters (16,404 feet) now show ground that no longer stays frozen throughout the year. "This means that the ground that was sitting below ice for hundreds and thousands of years is now becoming exposed," he said.
Glacier retreat adds another destabilizing force. The report finds that glaciers in the region have been losing mass at a rate equivalent to more than half a meter (about 1.6 feet) of thinning per year. The Langtang Lirung glacier, near the disaster site, has retreated roughly half a kilometer (0.3 miles) since the 1990s, exposing rock that was previously ice-covered.
The Himalayas hold the largest volume of snow and ice outside the polar regions, feeding at least 10 major Asian river systems that support billions of people. Yet studies show that about 78% of the region's glacier area, situated between 4,500 and 6,000 meters (14,763 to 19,685 feet) above sea level, is highly exposed to warming. UN reports indicate that between 2000 and 2019, glaciers lost 267 billion tons of ice per year—equivalent to the mass of 46,500 Great Pyramids of Giza.
As glaciers shrink, they relieve pressure on adjoining rock walls and produce additional meltwater, both of which can contribute to slope failure. The weeks before the collapse were also unusually warm, with July and August recording the highest local temperatures on record, according to the analysis.
Friederike Otto, a climate scientist at Imperial College London and one of the report's authors, said: "Other than the potential geological factors like earthquakes that are weakening the bedrock, all these other factors are made worse by human-induced climate change."
Adaptation limits exposed
The catastrophe also underscores the limits of adaptation in high-mountain regions. Nepal has developed disaster risk reduction plans and early warning systems, but the scale and speed of this collapse overwhelmed them. Unlike rainfall-driven floods, which can sometimes be forecast days ahead, sudden slope failures in remote mountains are extremely difficult to predict.
Otto noted that mountain communities are more vulnerable than those on plains. "Small changes in temperatures affect the stability of the land itself," she said. The report recommends better high-altitude monitoring, earth observation, and warning systems to reduce some risks, but warns that adaptation has limits in valleys where settlements, roads, and hydropower projects are concentrated along rivers.
Since glaciers and permafrost respond to temperature changes over decades, some destabilization is already locked in. The report's authors stress that the most effective way to minimize future risk is to rapidly phase out fossil fuels—a point that aligns with broader voter demand for climate action but faces political hurdles. As Otto put it, "All these drivers that we've talked about, permafrost melting, glacial melting, etc., will just become worse." The disaster serves as a stark reminder that climate change is not just about extreme weather, but also about the very stability of the land beneath our feet.
