Half of Earth’s glaciers, especially smaller ones, will disappear by the end of the century due to climate change, according to a new study, but limiting global warming may save others. Findings published in the journal Science Get the most comprehensive look into the future of the world’s 215,000 glaciers on Thursday. The authors stressed the importance of limiting greenhouse gas emissions to mitigate the effects of melting glaciers, such as sea level rise and water depletion.

To guide policymakers, the study looked at the effects on glaciers of four scenarios where the global average temperature change was 1.5 degrees Celsius (2.7 degrees Fahrenheit), 2.0 degrees Celsius, 3.0 degrees Celsius and 4.0 degrees Celsius.

“Every increase in grade leads to more meltdowns and losses,” said Regine Hock of the University of Oslo and the University of Alaska Fairbanks, co-author of the study. “But it also means that if you reduce the temperature rise, you can also reduce the mass loss,” Hawke told AFP. “So there’s some hope in that sense as well.”

Even if global warming is limited to 1.5 degrees Celsius above pre-industrial levels, the most ambitious goal of the Paris Agreement, researchers estimate that 49 percent of the world’s glaciers will disappear by 2100. That would be about 26 percent of the world’s glacier mass because the smallest glaciers would be first. Global average temperatures are currently expected to rise by 2.7 degrees Celsius, leading to almost complete glacier loss in central Europe, western Canada, the continental United States and New Zealand.

“Regions with relatively little ice, such as the European Alps, the Caucasus, the Andes, or the western United States, are losing almost all of their ice by the end of the century, almost regardless of the emissions scenario,” Hoke said. “So these glaciers are more or less doomed.”

In the worst-case scenario, such as a 4 degree Celsius increase in global temperature, giant glaciers such as those in Alaska will suffer more and 83 percent of the glaciers will disappear by the end of the century.

The loss of glacier will also exacerbate sea level rise.

“The glaciers we studied make up only one percent of all the ice on Earth,” Hoke said, “which is much smaller than the Greenland ice sheet and the Antarctic ice sheet.

“But they’ve contributed almost as much to sea level rise as the Greenland and Antarctic ice sheets coalesced over the past three decades,” he said.

A warming of 1.5 degrees Celsius would result in a 9-centimeter rise in mean sea level, and a temperature of 4.0 degrees Celsius would result in a 15-centimeter rise in sea level.

“9 to 15 centimeters doesn’t seem like a lot,” Hoke said, “but it’s not global sea level that’s causing so much concern.

“It’s mostly caused by storm surges,” he said, and could cause “much more damage.”

The disappearance of glaciers will also affect water resources, as they provide fresh water to nearly two billion people.

“Glaciers compensate for water loss when there is little rain in the summer and the weather is warm,” Hock said.

More pessimistic than those of UN climate experts, the study’s estimates were obtained through decades of observation and computer simulations of the mass of each glacier.

Despite the disturbing findings, Hawke said, “it is possible to reduce mass loss through human action.”

“If it does, of course that’s another matter,” he said. If something like this happens, of course it is the job of politicians,” he said.