Melting of Himalayan glaciers has doubled since the start of the 21st century due to rising temperatures, losing over a vertical foot and half of the ice each year, and potentially threatening the water supply for hundreds of millions of people in countries, including India, according to a study published in 2019.
The study, which appeared in Science Advances on Wednesday, is the latest indication that climate change is eating the Himalayan glaciers, threatening water supplies for hundreds of millions of people downstream across South Asia.
“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why,” said lead author Joshua Maurer, a doctoral candidate at Columbia University in New York.
Scientists combed 40 years of satellite observations spanning 2,000 kilometers (1,243 miles) across India, China, Nepal, and Bhutan, and found that the glaciers have been losing the equivalent of a foot-and-a-half (45 centimeters) of ice each year since 2000.
The study, published in the journal Science Advances in June 2019, shows 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 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 reason behind the Melting of Himalayan Glaciers
Past research has found similar trends, but the latest work is bigger in its geographic and historic scope.
It concluded that rising temperatures are the biggest factor.
Though temperatures vary from place to place, average temperatures were one degree Celsius (1.8 degrees Fahrenheit) higher between 2000 to 2016 than they were between 1975 and 2000.
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 US spy satellites.
They created an automated system to turn these into three dimensional (3D) models that could show the changing elevations of glaciers over time.
Other factors the researchers blamed were changes in rainfall, with reductions tending to reduce ice cover, and the burning of fossil fuels which lead to soot that lands on snowy glacier surfaces, absorbing sunlight and hastening to melt.