
World Weather Attribution study says rising temperatures and thinning glaciers played a key role in the deadly rock and ice avalanche.
A World Weather Attribution study concludes that human-induced climate change likely contributed to the rock and ice avalanche that caused devastating floods on the Nepal-Tibet border, leaving thousands missing.
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A rock and ice avalanche on Langtang Lirung triggered massive floods and landslides across the Nepal-Tibet border, leaving thousands dead or missing.
A study has found that climate change likelycontributed to the avalanche of rock and ice that unleashed devastating floods on the Nepal-Tibet border.
There was "absolutely no doubt that human-induced climate change played a role here in the preconditioning of the disaster", said Dr Friederike Otto, a climatologist at Imperial College London who co-authored the study.
The World Weather Attribution study said the disaster was the result of a "compound event" caused by rising temperatures, thinning glaciers, thawing permafrost and pre-existing geological weaknesses.
The findings came as Nepali authorities significantly revised the number of people missing in the disaster from 5,179 to 6,150.
The death toll still remains at around 1,400, according to figures released on Wednesday.
Massive floods and landslides swept through border towns and villages in Nepal and Tibet, wiping out thousands of houses, destroying energy infrastructure and leaving thousands dead or missing.
Scientists say the floods were caused by a collapse of rock wall and glacier ice near the peak of Langtang Lirung, a mountain on Nepal's side of the Himalayas.
The collapsing debris hit the bottom of a valley with such force that it registered as a magnitude 5.2 earthquake, according to United States Geological Survey (USGS) data.
The World Weather Attribution study published on Thursday said climate change was a "destabilising factor acting on a pre-existing geological predisposition", but it was not the only cause of the disaster.
According to the study, July and August temperatures in the area were around 1.5C (34.7F) warmer "due to human influence on the climate".
Meanwhile, glaciers in the region had also been thinning by about half a metre (1.6ft) a year, which could weaken existing fractures and increase instability.
Heavy snowfall last October and November also added to a large amount of meltwater early this year.
This combination of activities "may have interacted to amplify the compound event," the study said.
A magnitude 7.8 earthquake that struck the area in 2015 and triggered a rock-ice avalanche could have also weakened the underlying rock mass, according to the study.
However, authorities said they could not confirm that earthquake's exact impact on the disaster last month.
Another co-author of the report, Utrecht University mountain hydrologist Dr Walter Immerzeel, told reporters that the area was a "geologically vulnerable slope".
Immerzeel said it was "potentially weakened by the 2015 earthquake" and "destabilised further" by glacier and permafrost retreat.
The study has not been published in a peer-reviewed journal, but according to the World Weather Attribution website its studies all use the same peer-reviewed method in analysing extreme weather events.
And its findings build on what other experts had suggested in the immediate aftermath of the disaster.
Some had previously told the BBC that rising temperatures in the Himalayas was a likely factor in the rock-ice avalanche.
Dr Simon Cook, a glacier expert with the University of Dundee, told the BBC last month that while it was hard to attribute any single event to climate change, "climate warming ultimately destabilises these high mountain environments".
Cook tells the BBC on Wednesday that the World Weather Attribution report was a "very worthwhile study" about the underlying causes of the recent disaster.
And while it provides "some strong evidence that climate change was a key factor", "we are not yet at a point of being able to say exactly how this happened," he says.
"There remains much to learn about the processes involved... and what we can do to monitor these high-mountain regions to provide early warnings of such events in the future."
In the wake of the disaster, Nepali authorities have called for global efforts to tackle climate change, saying the country is one of the lowest contributors to greenhouse emissions yet one of the most vulnerable places to the effects of global warming.
In his first foreign trip as Nepali Prime Minister, Balendra Shah is set to appear at United Nations General Assembly in New York next week to talk about the recent disaster and climate justice.
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Balendra Shah to speak at UN General Assembly on climate justice
Very likely · Within weeks
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