Nepal glacier collapse: Researcher finds exceptional heat before deadly floods

The mountain section whose collapse triggered fatal floods in Nepal and China on August 26 had experienced unprecedented heat for the time of year.

That is according to meteorological data analyzed by Robert Rohde, chief scientist at Berkeley Earth. No direct link to the collapse has yet been confirmed.

What caused the glacier collapse in Nepal?

Researchers have not confirmed a single cause. Preliminary findings point to a combination of factors: exceptional heat in the days beforehand, permafrost thaw that destabilized the rock face, and significant snowmelt that added liquid water to cracks in the mountain.

Experts caution that heat alone does not explain the collapse; the rock likely also needed to be close to a structural tipping point.

How hot was it before the glacier collapsed?

Average temperatures on the glacier, at an altitude of 5,200 meters, were estimated at around 5.0C between August 21 and 26. Over more than 55 years of recorded data, temperatures at the site had never exceeded 4.0C in that same window. At the collapse site, the average temperature recorded over that six-day period has risen by about 1.8C since the mid-20th century.

Rohde calculated that without the added heat from climate change, a comparable pattern would probably occur only once in a few thousand years. The collapse also came during the Langtang region's fourth-hottest summer on record, based on Copernicus data going back to 1970.

What role did permafrost and snowmelt play?

French climatologist Valerie Masson-Delmotte said the hot conditions could explain both permafrost thaw and the combined slope and glacier collapse. Permafrost acts as ice cement, holding rock faces together, so its degradation makes them more unstable. Satellite images also showed significant snowmelt in the days before the disaster. Glaciologist Etienne Berthier of France's CNRS research agency said this provided a substantial source of liquid water that could infiltrate fractures in the mountain and facilitate landslides.

Was the heatwave alone enough to trigger the collapse?

Experts remain cautious about how much weight to give the heatwave on its own. Geomorphologist Kristen Cook of Grenoble Alpes University said it is not as simple as high temperature causing collapse.

She said that if temperature acted as a trigger, the rock likely needed to already be close to the point of failure. Researchers are now studying small movements detected in the mountain in the years before the collapse and how they interacted with temperature changes.

Is climate change to blame for the Nepal glacier collapse?

Rohde said that proving the rock near the fracture plane was significantly weakened by meltwater or permafrost thaw would be a "smoking gun" for climate change's role.

His analysis drew on data from the Copernicus program's ERA5 climate model and 14 high-altitude weather stations located between nine and 140 kilometers from the collapsed glacier. The findings add to a broader case linking the disaster to warming trends, though researchers say the exact mechanism is still under investigation.