April 28, 2021 | Earth’s glaciers are shrinking, and in the past 20 years, the rate of shrinkage has steadily sped up, according to a new study of nearly every glacier on the planet.

Glaciers mostly lose mass through ice melt, but they also shrink due to other processes, such as sublimation, where water evaporates directly from the ice, and calving, where large chunks of ice break off the edge of a glacier, according to the National Oceanic and Atmospheric Administration (NOAA). By tracking how quickly glaciers are shrinking, scientists can better predict how quickly sea levels may rise, particularly as climate change drives up average global temperatures.

But estimating the rate of glacier shrinkage can be notoriously difficult; past estimates relied on field studies of only a few hundred glaciers out of the more than 200,000 on Earth, as well as sparse satellite data with limited resolution, the authors noted in their new study, published Wednesday (April 28) in the journal Nature.

Some of this satellite data captured changes in surface elevation, but only sampled a few places and at sparse time points. Other satellites detected slight shifts in the Earth’s gravitational field, but could not disentangle how much glacier shrinkage contributed to these shifts, as opposed to mass changes in ice sheets or solid earth, for instance.