A study, published in the journal Science Advances in June 2019, warned that glaciers have been losing the equivalent of more than a vertical foot and half of the ice each year since 2000 — double the amount of melting that took place from 1975 to 2000. The study, spanning 40 years of satellite observations across India, China, Nepal and Bhutan, had indicated that climate change has affected the Himalayas’ glaciers.

A part of the Nanda Devi glacier broke off in Uttarakhand’s Chamoli district on Sunday, leading to massive floods.

The glacier collapse at Joshimath led to a massive flood in the Alaknanda river system and caused large-scale devastation in the upper reaches of the ecologically fragile Himalayas.

“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why,” said Joshua Maurer, a PhD candidate at Columbia University in the US.

While not specifically calculated in the study, the glaciers may have lost as much as a quarter of their enormous mass over the last four decades, said Maurer, lead author of the study.

The study synthesised data from across the region, stretching from early satellite observations to the present.

The data shows that rising temperatures are causing the untimely melting of the glaciers.

Temperatures vary from place to place, but from 2000 to 2016 they have averaged one degree Celsius higher than those from 1975 to 2000, they said.

Researchers analysed repeat satellite images of some 650 glaciers spanning 2,000 kilometres from west to east.

Many of the 20th-century observations came from declassified photographic images taken by the US spy satellites.

They found that from 1975 to 2000, glaciers across the region lost an average of about 0.25 metres of ice each year in the face of slight warming.

Following a more pronounced warming trend starting in the 1990s, starting in 2000 the loss accelerated to about half a metre annually.

Researchers noted that Asian nations are burning ever-greater loads of fossil fuels and biomass, sending soot into the sky, adding much of it eventually lands on snowy glacier surfaces, where it absorbs solar energy and hastens to melt.

“It looks just like what we would expect if warming were the dominant driver of ice loss,” Maurer said.

The Himalayas are generally not melting as fast as the Alps, but the general progression is similar, the researchers said.

The study did not include the huge adjoining ranges of high-mountain Asia such as the Pamir, Hindu Kush or Tian Shan, but other studies suggest similar melting is underway there as well.