Glaciers have been melting worldwide as a result of higher temperatures from climate change, but just how fast they have been in retreat should be a cause for concern.

In the largest-scale study of its kind, an international team of researchers from ETH Zurich and the University of Toulouse looked at all the world’s 220,000 or so glaciers, excluding the ice sheets on Greenland and in the Antarctic, to see how rapidly glaciers have been losing their mass and thickness in this new century.

Their findings make for sobering reading: the planet’s glaciers lost a total of 267 gigatons of ice each year on average between 2000 and 2019. That amount of lost glacier, the researchers say, would be enough to submerge Switzerland under six meters of water every year.

Disconcertingly, the loss of glacial mass has been accelerating. Between 2000 and 2004 glaciers lost 227 gigatons of ice a year whereas between 2015 and 2019 the annual loss amounted to 298 gigatons. Some of the fastest-melting glaciers are in Alaska, Iceland and the Alps, but mountain glaciers in the Pamirs, the Hindu Kush and the Himalayas are losing much of their mass and thickness, too.

“The situation in the Himalayas is particularly worrying,” says Romain Hugonnet, a researcher at ETH Zurich and the University of Toulouse who was the study’s lead author and whose team studied imagery taken by NASA’s Terra satellite, which orbits the Earth once every 100 minutes and is equipped with two cameras that record pairs of stereo images that yield high-resolution digital elevation models of all the world’s glaciers.

“During the dry season, glacial meltwater is an important source that feeds major waterways such as the Ganges, Brahmaputra and Indus rivers,” Hugonnet explains. “Right now, this increased melting acts as a buffer for people living in the region, but if Himalayan glacier shrinkage keeps accelerating, populous countries like India and Bangladesh could face water or food shortages in a few decades.”

Meanwhile, much of all that water from glaciers has ended up in the seas, whose levels rose around 0.74 millimeters a year during the observed period, the researchers say.

This latest research has been unique in its global scope, yet its findings underline those in earlier studies. Almost everywhere glaciers have been shrinking at a rapid pace with noticeable changes to local environments.

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