Climate change is “eating” the glaciers of the Himalayas, posing a grave threat to hundreds of millions of people who live downstream, a study based on 40 years of satellite data has shown.
The study, published Wednesday in the journal Science Advances, concluded that the glaciers have lost a foot and a half of ice every year since 2000, melting at a far faster pace than in the previous 25-year period. In recent years, the glaciers have lost about eight billion tons of water a year. The study’s authors described it as equivalent to the amount of water held by 3.2 million Olympic-size swimming pools.
The study adds to a growing and grim body of work that points to the dangers of global warming for the Himalayas, which are considered the water towers of Asia and an insurance policy against drought.
In February, a report produced by the International Center for Integrated Mountain Development warned that the Himalayas could lose up to a third of their ice by the end of the century, even if the world can fulfill its most ambitious goal of keeping global average temperatures from rising only 1.5 degrees above preindustrial levels.
That goal, which scientists have identified as vital to avert catastrophic heat waves and other extreme weather events, is nowhere close to being met. Average global temperatures have risen by one degree already in the last 150 years. Greenhouse gas emissions continue to climb. And scientists estimate that we are on track to raise the average global temperature between 3 to 5 degrees Celsius by the end of this century.
Another study, published in May in Nature, found that Himalayan glaciers are melting faster in summer than they are being replenished by snow in winter. In the warm seasons, meltwater from the mountains feeds rivers that provide drinking water and irrigation for crops.
The retreat of glaciers is one of the most glaring consequences of rising global temperatures. Around the world, vanishing glaciers will mean less water for people, livestock and crops.
In the Himalayas, the loss of glaciers poses two profound risks. In the short term, melting glaciers leave behind rock debris that creates dams, and if these debris dams burst, the resulting floods could destroy villages. In the long term, the loss of glacier ice means the loss of Asia’s future bank of water — a safeguard against periods of extreme heat and drought. Receding glaciers can also threaten the ecosystems they support, which can in turn affect communities in the region.
The latest study, led by researchers at the Lamont-Doherty Earth Observatory at Columbia University, relied on the analysis of satellite images of 650 glaciers across 2,000 kilometers, or more than 1,200 miles, of the Himalayas, including recently declassified United States spy satellite data. The researchers turned the images into 3-D models that showed changes in the area and the volume of the glaciers.
They found that from 1975 to 2000, glaciers across the region lost 10 inches of ice each year. Starting in 2000, the rate of loss doubled, to about 20 inches of ice each year. The study also concluded that while soot from fossil fuel burning is likely to have contributed to the ice melt, the bigger factor was rising temperatures. While temperatures varied across the vast mountain range, on average, they rose faster between 2000 and 2016 compared with earlier years.
For more news on climate and the environment, follow @NYTClimate on Twitter.