Climate change is highly likely to have contributed to the catastrophic glacier collapse that flooded parts of Nepal and Tibet in late August, killing around 1,400 people and leaving thousands still missing, scientists said on Thursday.
Researchers from the World Weather Attribution (WWA) group found that rapidly warming temperatures in the region have caused glaciers to thin and melted ice and permafrost buried deep in the bedrock of the Himalayas. These conditions increased the likelihood of the collapse, which involved around 2 sq km of rock wall and glacier ice on Langtang Lirung mountain. The WWA, known for its peer-reviewed methods, emphasizes that while ascertaining the precise role of climate change is difficult, its influence on creating unstable conditions is clear.
“There’s absolutely no doubt that human induced climate change played a role here in the preconditioning of the disaster through permafrost thawing, through thinning of the glaciers, through having more rainfall instead of snow,” said Friederike Otto, a climatologist at Imperial College London.
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The study revealed that mean temperatures in the Himalayan region were 5 degrees Celsius higher than normal in August, with 1.5 degrees of the increase attributed to climate change. Unusually high levels of snowfall in October and November of the previous year also added to the volume of meltwater once temperatures began to rise, which could have helped trigger the collapse.
Since 2000, glaciers in the region have thinned by about half a metre annually, changing stresses on the rock. Melting permafrost is also likely to have weakened the rock wall. A 7.8 magnitude earthquake in 2015 may have played a role by weakening the bedrock, though its precise impact is unclear. “We conclude that this was a geologically vulnerable slope, potentially weakened by the 2015 earthquake, but it was destabilised further by glacier and permafrost retreat and by the excessive meltwater and exceptional warmth in the final period before the collapse,” said Walter Immerzeel, a mountain hydrologist from Utrecht University.