BENGALURU, India (AP) — A report released by the World Weather Attribution indicates that human-caused global warming has contributed to the thinning of glaciers and thawing of mountain permafrost, which likely destabilized the Himalayan slope that collapsed on August 26, leading to catastrophic flooding in Nepal. The report notes that while climate change played a role, it was not the sole cause of the disaster, as a significant earthquake in Nepal in 2015 may have weakened the rock prior to the collapse.
Ben Clarke, a climate researcher at Imperial College London involved in the analysis, stated, "This disaster was not an extreme weather event, but the fingerprints of climate change are still clear to see in long-term changes."
The collapse resulted in over 1,300 fatalities and left more than 5,000 individuals missing, as a large section of rock and glacier fell near the Nepal-China border, causing extensive damage along the Trishuli River corridor.
Climate scientists have observed that rising temperatures in the Himalayas are causing glaciers to retreat and thawing permanently frozen ground, which helps stabilize fractured mountain rock. This change in stability poses risks to communities located in narrow river valleys below.
The report did not conclude whether the collapse would have occurred without climate change, which is primarily driven by greenhouse gas emissions from burning fossil fuels. However, researchers determined that warming has intensified processes that have made the slope less stable over decades.
One significant finding of the report is that the elevation of the freezing threshold has risen by approximately 100 meters (328 feet) per decade, exposing rock at higher elevations to longer periods above freezing, leading to thawing permafrost and cracks in the ice that weaken the rock face.
Jakob Steiner, a geoscientist at the University of Graz, noted that monitoring instruments at elevations around 5,000 meters (16,404 feet) indicate that some rock and ground no longer remain frozen year-round. He stated, "This means that the ground that was sitting below ice for hundreds and thousands of years is now becoming exposed."
The report also highlighted glacier retreat as a destabilizing factor, with glaciers in the region losing mass at a rate of more than half a meter (about 1.6 feet) each year. The Langtang Lirung glacier, near where the disaster occurred, has retreated about half a kilometer (0.3 miles) since the 1990s, exposing previously ice-covered rock.
The Himalayan region contains the largest volume of snow and ice outside the polar regions, with over 63,000 glaciers feeding at least 10 major Asian river systems. Studies indicate that around 78% of the glacier area between 4,500 and 6,000 meters (14,763 to 19,685 feet) is highly vulnerable to warming. Reports from the United Nations show that glaciers lost 267 billion tons of ice per year from 2000 to 2019.
As glaciers shrink, they can relieve pressure on adjoining rock walls and produce additional meltwater. The weeks leading up to the August 26 collapse were marked by unusually warm temperatures, with July and August 2026 recorded as the warmest months locally.
Friederike Otto, a climate scientist at Imperial College London and co-author of the report, stated, "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."
The report emphasizes that the disaster illustrates how some climate-related risks in the Himalayas may exceed the protective capabilities of early warning systems and adaptation measures. Although Nepal has developed disaster risk reduction plans, the scale and speed of the collapse overwhelmed existing defenses. Unlike rainfall-induced floods, which can be forecasted, catastrophic slope failures in remote mountainous areas can occur suddenly and are difficult to predict.
Otto added that mountain ecosystems and societies are more vulnerable to climate impacts than those in plains areas, noting that "small changes in temperatures affect the stability of the land itself."
The report suggests that improved high-altitude monitoring and warning systems could help mitigate some risks, but researchers caution that there are limits to adaptation in Himalayan valleys where infrastructure is concentrated along rivers. Since glaciers and permafrost respond to temperature changes over decades, some mountain destabilization caused by warming is already underway.
Otto concluded, "The most important thing to minimize the risk in this region is to rapidly stop using fossil fuels that lead to increasing global temperatures. 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."