Earth’s glaciers are melting much faster than scientists thought. A new study shows they are losing 369 billion tons of snow and ice each year, more than half of that in North America.
The world’s glaciers are shrinking five times faster now than they were in the 1960s. Their melt is accelerating due to global warming, and adding more water to already rising seas, the study found.
Since 1961, the world has lost 10 trillion tons of ice and snow. That’s enough to cover the Lower 48 U.S. states in about four feet of ice.
“Over 30 years suddenly almost all regions started losing mass at the same time,” said Michael Zemp, lead author of the study and director of the World Glacier Monitoring Service at the University of Zurich in Switzerland. “That’s clearly climate change if you look at the global picture.”
The glaciers shrinking fastest are in central Europe, western Canada, the United States and New Zealand. Glaciers in these places on average are losing more than 1 percent of their mass each year, according to a study in Monday’s journal Nature.
“In these regions, at the current glacier loss rate, the glaciers will not survive the century,” Zemp said.
Zemp’s team used ground and satellite measurements to look at 19,000 glaciers, far more than previous studies. They determined that southwestern Asia is the only region of 19 where glaciers are not shrinking, which Zemp said is due to local climate conditions.
Scientists have known for a long time that global warming caused by human activities such as burning coal, gasoline and diesel for electricity and transportation is making Earth lose its ice. They have been especially concerned with the large ice sheets covering Greenland and Antarctica.
A number of factors are making sea levels rise. The biggest cause is that oceans are getting warmer, which makes water expand. The new figures show glacier melt is a bigger contributor than thought, responsible for about 25 percent to 30 percent of the yearly rise in oceans, Zemp said.
Rising seas threaten coastal cities around the world and put more people at risk of flooding during storms.
Glaciers grow in winter and shrink in summer, but as the Earth has warmed, they are growing less and shrinking more. Zemp said warmer summer temperatures are the main reason glaciers are shrinking faster.
While people think of glaciers as polar issues, shrinking mountain glaciers closer to the equator can cause serious problems for people who depend on them, said Twila Moon, a snow and ice data center scientist. She said people in the Andes mountains, for example, rely on the glaciers for drinking and irrigation water each summer.
A separate study Monday in Environmental Research Letters confirmed faster melting and other changes in the Arctic. It found that in winter, the Arctic is warming 2.8 times faster than the rest of the Northern Hemisphere. Overall, the region is getting more humid, cloudier and wetter.
“It’s on steroids; it’s hyperactive,” said lead author Jason Box, a scientist for the Danish Meteorological Institute.