Climate Change Identified as Key Factor in Nepal’s Deadly Mountain Collapse

Approximately 1,400 people have lost their lives and more than 5,000 remain missing following a catastrophic mountain slope collapse and subsequent flash floods that devastated valleys across Nepal and Tibet. While initial reports suggested an earthquake triggered the disaster, a new analysis by glaciologists and climate scientists has determined that climate change was a primary driver, creating destabilizing conditions over decades.

The event occurred on August 26 when a massive rock avalanche struck the north face of Langtang Lirung. This triggered a concurrent glacier collapse, releasing roughly 110 million cubic meters of rock and ice—equivalent to 44,000 Olympic swimming pools—down the mountainside. The impact generated energy comparable to a magnitude 5.2 earthquake and tore up an additional 30 million cubic meters of buried ice and debris as it crashed into the valley floor.

The resulting flood wave traveled at an average speed of 170 kilometers per hour, reaching the Nepal-China border just 20 kilometers downstream within seven minutes. It continued downstream, covering 200 kilometers in under seven hours. Researchers note that rock avalanches of this magnitude are rare events, occurring only once every 1,000 to 10,000 years.

“This was not a single trigger event,” Walter Immerzeel, a mountain hydrologist at Utrecht University, told journalists. “The failure occurred at an elevation of about 5,150 meters, and there were several processes acting together over time scales of years to decades, rather than one factor acting alone.”

According to World Weather Attribution, an international coalition of scientists, rising temperatures from fossil fuel emissions fundamentally altered the Himalayan landscape. Near the collapse site, the glacier edge retreated 75 meters between 1964 and 2000, but accelerated dramatically to retreat another 373 meters between 2010 and 2026. This rapid melting removed critical ice support for the overlying rock walls.

Permafrost within the 4,500 to 5,500-meter elevation band also began to thaw, further destabilizing the mountain structure. In the days leading up to the collapse, the region experienced extreme heat, with late August temperatures running 2.5 to 2.7 degrees Celsius above the 10-year average. Just one day before the disaster, temperatures spiked approximately 7 degrees Celsius above the reference mean.

Additional contributing factors included an unusually snowy October in 2025, which increased meltwater volume, and the legacy effects of the 2015 magnitude-7.8 earthquake, which previously weakened the rock mass at Langtang Lirung.

The disaster highlighted significant gaps in regional safety infrastructure. Nepal’s early warning systems, designed primarily for rainfall-driven floods, were ineffective against such rapid, cascading events. The flood destroyed several monitoring gauges and reached the border before the first mass SMS warning was issued 38 minutes after the initial collapse.

Friederike Otto, a professor of climate science at Imperial College London, emphasized the severity of the situation. “When warming destabilizes the roof of the world, no amount of local adaptation can fully shield vulnerable people downstream from this scale of destruction,” she said. She warned that without a rapid transition to zero fossil fuel emissions, similar catastrophes will become increasingly frequent in the coming years.