Kathmandu, September 8
The mountain glacier whose collapse triggered deadly floods in Nepal and China on August 26 experienced exceptionally high temperatures in the days before the disaster, according to an analysis of meteorological data by a researcher.
Average temperatures at the glacier, located at an altitude of 5,200 metres, were estimated at around 5°C between August 21 and 26.
That is unusually high for the time of year. Temperatures at the site had not exceeded 4°C during the same period in more than 55 years of recorded data.
The localised temperature estimates were reconstructed by Robert Rohde, chief scientist at Berkeley Earth, an independent climate research organisation based in California.
Rohde’s analysis found that the average temperature at the collapse site during the six-day period has increased by about 1.8°C since the mid-20th century.
Without the additional warming associated with climate change, a comparable temperature pattern would probably occur only once in several thousand years, Rohde told AFP.
The collapse occurred during the Langtang region’s fourth-hottest summer on record, according to AFP’s analysis of data from Europe’s Copernicus climate monitoring programme dating back to 1970.
Possible role of heat
Scientists say the unusually warm conditions could have contributed to processes that weakened the mountain.
“These hot conditions can also explain permafrost thaw and combined slope and glacier collapse,” French climatologist Valerie Masson-Delmotte said.
Permafrost acts like ice cement, helping hold rock faces together. As it thaws, mountain slopes can become increasingly unstable.
Satellite imagery also showed substantial snowmelt in the days before the disaster.
The meltwater could have infiltrated cracks in the mountain and contributed to slope failure, according to Etienne Berthier, a glaciologist at France’s CNRS research agency.
Experts, however, caution against directly attributing the collapse to the heat.
“It’s not as straightforward as ‘high temperature equals collapse’,” Kristen Cook, a geomorphologist at Grenoble Alpes University in France, told AFP.
“If the temperature acted as a trigger, it seems that it needed to wait until the rock was right at the tipping point of collapse,” she said.
Researchers are now examining small movements detected in the mountain in the years before the collapse and how those movements interacted with changes in temperature.
Rohde said evidence that meltwater or permafrost thaw had significantly weakened the rock near the fracture plane would provide a strong link to climate change.
His temperature analysis used data from the European Union’s Copernicus programme and its ERA5 climate model, along with observations from 14 high-altitude weather stations located between nine and 140 kilometres from the collapsed glacier.
