How climate change worsened Nepal's deadly mountain collapse

A drone view of flood damage along the Trishuli River in Nuwakot district, Nepal. Image: Rajesh Kumar Singh/AP Photo/picture alliance

Nearly 1,400 people have died after a mountain slope collapsed and flash floods swept through the valleys of Nepal and Tibet. More than 5,000 people remain missing .

The collapse was initially thought to have been caused by an earthquake. Now, glaciologists and climate scientists have determined that a complex series of factors led to the disaster, with climate change laying the groundwork several times over: Warming temperatures receded the glacier, thawed permafrost and increased meltwater, destabilizing the slope until it gave way on August 26.

"This was not a single trigger event," Walter Immerzeel, a mountain hydrologist at Utrecht University in the Netherlands, told journalists on a press call. "The failure occurred at an elevation of about 5150 meters (about 16,896 feet) and there were several processes acting together over time scales of years to decades, rather than one factor acting alone."

The floods began upstream with a large rock avalanche on the north face of Langtang Lirung. That caused a section of the glacier to collapse at the same time, sending roughly 110 million cubic meters of rock and glacier ice, the size of 44,000 Olympic swimming pools, hurtling downward. That type of rock avalanche is rare, occurring at this size only once every 1,000-10,000 years.

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