Himalayan glaciers are melting twice faster since the turn of the century, and last four decades witnessed the loss of a quarter and more of all ice, scientists have revealed. The fast ice losses indicate the region’s “devastating” future on which people in billion depend for regular water.
The scientists have prepared the first detailed, four-decade record of ice along the 2,000km (1,200-mile) mountain chain by combining declassified US spy satellite images from the mid-1970s along with data from the modern satellite.
Every year 8bn tonnes of ice are being lost as per the analysis which is not replaced by snow, and the height of lower level glaciers are shrinking by 5 meters annually. The study shows that only global heating resulted from human activities can explain this massive melting. The picture in the previous work became complicated due to local weather and the air pollution impacts.
Joshua Maurer from Lamont-Doherty Earth Observatory, Columbia University, who led the new research published in the journal Science Advances, said: “This is the clearest picture yet of how fast Himalayan glaciers are melting since 1975, and why.”
Prof Joerg Schaefer, also at Columbia University and team member, said: “It is really the doubling of the speed of glacier melt that is most concerning.” Now forecasts can be made with much more confidence with the help of the new understanding of past melting, but the outlook is severe, he asserted adding “it looks devastating, and there is no doubt in my mind, not a single grain of doubt, that [the impact of the climate crisis] is what we are seeing.”
According to a landmark report published in February, despite a drastic action taken immediately to reduce emissions, one-third of the vast ice fields of the mighty Hindu Kush-Himalaya (HKH) glaciers set to melt by 2100 and that without any effort, two-thirds of them would vanish.
Either way, people who depend on the great rivers that flow from the peaks into India, Pakistan, China, and other nations, will face serious consequences. “It’s the climate crisis you haven’t heard of,” said Philippus Wester, at the International Centre for Integrated Mountain Development, who led the February study and the new work according to him was persuasive. “Increasingly uncertain and irregular water supplies will impact the 1 billion people living downstream from the Himalaya Mountains in South Asia,” he said.
The photographs taken from spy satellites used in the research remained in archives unused for some years. However, Maurer and colleagues developed a computer tool to enable these 1970s photos to be turned into 3D maps.
This data had been used by the scientists to track the changes in 650 Himalayan glaciers. From 1975 to 2000 the glacier surfaces sank by 22cm (8.6 inches) on an average every year. However, the melting has gained momentum with an average loss of 43cm per year from 2000 to 2016.
All the evidence point to a principal cause of the melting, and that is human-caused climate change. As the glaciers are shrinking at similar rates all along the mountain chain, it is indicating a common cause. The changes in weather and the settling of black air pollution absorbing heat from the sun and speeding up melting, have only local effects.
The region’s temperature data also shows an average 1C rise from 2000-2016 than during 1975-2000. Calculations show that this rise in temperature is consistent with the amount of ice being lost. “Even glaciers in the highest mountains of the world are responding to global air temperature increases driven by the combustion of fossil fuels,” said Joseph Shea, at the Northern British Columbia University in Canada, who was not involved in the study.
Schaefer said: “For the wellbeing of the people there, our results are of course the worst possible. But it is what it is, and now we have to prepare for that scenario. We have to worry a lot, because so many people are affected.
“To stop the temperature rises, we have to cool the planet,” he said. “We have to not only slow down greenhouse gas emissions, we have to reverse them. That is the challenge for the next 20 years.”