Himalayan glaciers melting doubled since 2000: Study

Melting of Himalayan glaciers has doubled since start of 21st century due to rising temperatures, losing over a vertical foot and half of ice each year and potentially threatening water supply for hundreds of millions of people in countries including India, a study has found.

analysis, spanning 40 years of satellite observations across India, China, Nepal and Bhutan, is latest and perhaps most convincing indication that climate change is eating Himalayas' glaciers, researchers said.

It indicates that glaciers have been losing equivalent of more than a vertical foot and half of ice each year since 2000 -- double amount of melting that took place from 1975 to 2000. 

"This is 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 US.

While t specifically calculated in study, glaciers may have lost as much as a quarter of ir ermous mass over last four deces, said Maurer, le author of study published in journal Science vances.

Currently harbouring some 600 billion tonnes of ice, Himalayas are sometimes called earth's "Third Pole." 

study synsises data from across region, stretching from early satellite observations to present. synsis indicates that melting is consistent in time and , and that rising temperatures are to blame.

Temperatures vary from place to place, but from 2000 to 2016 y have averd one degree Celsius higher than those from 1975 to 2000.

Researchers analysed repeat satellite ims of some 650 glaciers spanning 2,000 kilometers from west to east. Many of 20th-century observations came from recently declassified photographic ims taken by US spy satellites. 

y created an automated system to turn se into 3D models that could show changing elevations of glaciers over time. y n compared se ims with post-2000 optical data from more sophisticated satellites, which more directly convey elevation changes.

y found that from 1975 to 2000, glaciers across region lost an aver of about 0.25 metres of ice each year in face of slight warming. Following a more prounced warming trend starting in 1990s, starting in 2000 loss accelerated to about half a metre annually. 

Recent yearly losses have averd about 8 billion tonnes of water, or equivalent 3.2 million Olympic-size swimming pools, said Maurer. 

Asian nations are burning ever-greater los of fossil fuels and biomass, sending soot into sky, researchers said. Much of it eventually lands on swy glacier surfaces, where it absorbs solar energy and hastens melting.

Researchers compiled temperature data during study period from ground stations and n calculated amount of melting that observed temperature increases would be expected to produce. 

y n compared those figures with what actually happened. y matched. 

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

Himalayas are generally t melting as fast as Alps, but general progression is similar, say researchers. 

study does t include huge joining ranges of high-mountain Asia such as Pamir, Hindu Kush or Tian Shan, but or studies suggest similar melting is underway re as well.

Some 800 million people depend in part on seasonal ruff from Himalayan glaciers for irrigation, hydropower and drinking water. 

accelerated melting appears so far to be swelling ruff during warm seasons, but scientists project that this will taper off within deces as glaciers lose mass. This will eventually le to water shorts. 

Even on Mount Everest, long-lost corpses of climbers who failed to return are emerging from melting ice and sw along trails.

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study shows that "even glaciers in highest mountains of world are responding to global air temperature increases driven by combustion of fossil fuels," said Joseph Shea, a glacial geographer at University of rrn British Columbia in Cania who was t involved in study.

"In long term, this will le to changes in timing and magnitude of streamflow in a heavily populated region," said Shea