Climate change had major role in triggering Nepal floods, scientists say

Scientists say climate change was a core contributing factor in last month’s deadly glacial mountain collapse that flooded parts of Nepal and Tibet, killing more than 1,400 people and leaving thousands still missing.

Researchers from the World Weather Attribution (WWA) group said in a report released on Thursday that the disaster was not caused by a single extreme weather event, but rather a “compound crisis” shaped by long-term warming, glacier retreat, permafrost thaw and geological instability.

WWA uses peer-reviewed methods to assess the role played by global warming in extreme weather events, according to its website.

A huge section of rock and glacier broke away from Langtang Lirung mountain on August 26, triggering a flood of water, ice and debris that swept downstream, destroying communities and infrastructure.

“Relentless warming has lifted the altitude of the freezing threshold on the high Himalaya, exposing ice and permafrost deep in the bedrock to higher and longer thaw temperatures, weakening mountain slopes,” according to the report, Rapid Warming in the Himalaya Exacerbates Geohazard Cascades Beyond Adaptation Limits.

Report co-author Walter Immerzeel, a mountain hydrologist at Utrecht University, said the region was undergoing “fundamental, irreversible shifts”, with glacier retreat and permafrost degradation undermining mountain stability.

Nepal, a largely rural nation of 30 million people, contributes a fraction of global greenhouse gas emissions compared with industrialised nations.

The study found that this July and August were the warmest months locally recorded, with temperatures about 5 degrees Celsius (9 degrees Fahrenheit) higher than normal, while heavy snowfall in late 2025 contributed to increased meltwater before the collapse.

A magnitude 7.8 earthquake in Nepal in 2015 may have further weakened the slope, although its precise role remains uncertain, the report said.

Last month’s disaster has also raised concerns about the limits of adaptation.

Prime Minister Balendra Shah will address the United Nations General Assembly on the urgent issue next week, in his first foreign trip as Nepal’s leader.

Nepal estimates the reconstruction bill from last month’s flood will cost $4.78bn.

“There is no doubt that climate change is one of the drivers, and therefore obviously it needs to be discussed in the context of loss and damage,” Friederike Otto, a professor of climate science at Imperial College London, told reporters.

Nepal’s disaster authority said Wednesday it had revised up the number of people considered missing to 6,150, following data collection and verification in affected districts.

The number of bodies retrieved stands at 1,403, 105 of which have been identified, according to the disaster agency.

In China, the toll is 43 dead and 519 missing, according to state media.

The combined toll from both nations now stands at 1,446 people dead and at least 6,669 missing.