By Matthew Green
LONDON (Reuters) - Himalayan glaciers have been melting twice as fast since the start of this century, underscoring the threat the climate crisis poses to water supplies for hundreds of millions of people across Asia, according to a study published on Wednesday.
Scientists have long been trying to establish how quickly rising global temperatures caused by the burning of coal, oil and gas are eating away at the region's icebound landscapes, sometimes referred to as Earth's third pole.
The new analysis, spanning 40 years of satellite observations across India, China, Nepal and Bhutan, showed glaciers have been losing the equivalent of more than a vertical foot-and-a-half of ice each year since 2000. That represents double the rate between 1975 and 2000.
"This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why," lead author Joshua Maurer, a PhD candidate at Columbia University's Lamont-Doherty Earth Observatory, said in a statement.
Although the study, published in Science Advances, did not attempt to ascertain precisely how much ice had melted, Maurer said the glaciers may have lost as much as a quarter of their mass over the last 40 years.
The accelerated melting appears to be swelling rivers during warm seasons, but scientists are concerned about the long-term impact on irrigation, hydropower and drinking water supplies that support some 800 million people.
Joseph Shea, a glacial geographer at the University of Northern British Columbia, who was not involved in the study, said the findings demonstrated that even glaciers in the world's highest mountains were being affected by higher temperatures.
"In the long term, this will lead to changes in the timing and magnitude of streamflow in a heavily populated region," Shea said.
(Reporting by Matthew Green; Editing by Andrew Cawthorne)