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.