Scientists link Nepal avalanche to climate-induced permafrost thaw and prior earthquake

More than 20 international scientists have concluded that the August 2023 avalanche on the Nepal-China border resulted from a series of interacting processes rather than a single weather event. The collapse of a 2,000-foot-wide section of rock and glacier ice from Langtang Lirung released energy comparable to a magnitude 5.2 earthquake and generated a flood wave that traveled over 20 miles downstream.

The analysis, released by the World Weather Attribution network, cites a 7.8-magnitude earthquake in April 2015 that likely weakened the mountain slope, increasing the frequency of landslides in the area. Subsequent warming has raised the altitude of the 0 °C isotherm by more than 320 feet per decade, leading to permafrost thaw that reduces rock cohesion and allows water infiltration, according to mountain hydrologist Walter Immerzeel.

Glacier observations show significant thinning of the Langtang-Lirung glacier since the early 2010s, which the report says contributed to slope instability and added meltwater to fractures. Exceptional snowfall in October-November 2022 followed by record-high July-August temperatures in 2023 created additional meltwater, further weakening the slope. Climate models indicate that July-August temperatures in the region are now about 1.5 °C warmer because of human-induced climate change, with annual temperatures up to 2 °C above the global average.

"There is absolutely no doubt that human-induced climate change played a role in the preconditioning of the disaster," said Friederike Otto, a climate science professor at Imperial College London. The researchers note that existing early-warning systems were insufficient for an event of this magnitude and speed, and they warn that without rapid reductions in fossil-fuel emissions, similar large-scale disasters could become more frequent.