Two-thirds of glaciers are on track to disappear by 2100

The world’s glaciers are shrinking and disappearing faster than scientists thought, and two-thirds of them are expected to melt away by the end of the century, according to current climate change trends, according to a new study.

But if the world can limit future warming to a few tenths of a degree and meet international goals — technically possible, but highly unlikely according to many scientists — then slightly less than half of the world’s glaciers will disappear, the same study says. For the most part, small but well-known glaciers are heading towards extinction, the study authors said.

In the unexpected worst-case scenario of a few degrees of warming, 83% of the world’s glaciers would likely disappear by 2100, the study authors said.

The study, published Thursday in Science, examined all 215,000 land-based glaciers around the world more extensively than past studies, not counting those on ice sheets in Greenland and Antarctica. Using different levels of warming, the scientists then used computer simulations to calculate how many glaciers would disappear, how many trillions of tons of ice would melt, and how much this would contribute to sea level rise.

The world is currently on the path of a temperature increase of 2.7 degrees Celsius (4.9 degrees Fahrenheit) since pre-industrial times; That’s 32% of the world’s glacier mass, or 48.5 trillion metric tons of ice, by 2100, as well as 68% of the Glaciers disappearing. David Rounce, the study’s lead author, said this would increase sea level rise by 4.5 inches (115 millimeters), while seas would grow larger from melting ice sheets and warmer water.

“No matter what happens, we’re going to lose a lot of glacier,” said Rounce, a glaciologist and professor of engineering at Carnegie Mellon University. “But we have the ability to make a difference by limiting how many glaciers we lose.”

“It’s too late for many small glaciers,” said study co-author Regine Hock, a glaciologist at the University of Alaska Fairbanks and the University of Oslo in Norway. “But globally, our results clearly show that every degree of global temperature is important to keeping as much ice locked in glaciers as possible.”

According to the study, estimated ice loss by 2100 ranges from 38.7 trillion metric tons to 64.4 trillion tons, depending on how much the world warms and how much coal, oil and gas is burned.

The study calculates that all that melting ice will add 3.5 inches (90 millimeters) at best to 6.5 inches (166 millimeters) at worst; this is 4% to 14% more than previous projections.

4.5 inches of sea level rise from glaciers means that more than 10 million people worldwide – and more than 100,000 people in the United States – will live below the high tide line, otherwise those who say sea level rise would be above that level. researcher Ben Strauss, CEO of Climate Central. Sea level rise from climate change in the twentieth century added about 4 more inches to the surge in the 2012 Superstorm Sandy and cost about $8 billion on its own alone, he said.

Scientists say future sea level rise will be caused by melting ice sheets rather than glaciers.

But the loss of glaciers is more than rising seas. A few scientists speaking to the Associated Press said this would mean depletion of water supplies for much of the world’s population, greater risk from flooding from melting glaciers, and the loss of historic ice-covered areas from Alaska to the Alps to the base camp of Mount Everest. He said he was coming.

“For places like the Alps or Iceland… the glaciers are part of what makes these landscapes so special,” said Mark Serreze, Director of the National Snow and Ice Data Center, who was not part of the study but praised the work. “They’re losing their souls in a sense, just as they’re losing their ice.”

Hock pointed to the Vernagtferner glacier, one of the world’s best-studied glaciers in the Austrian Alps, but “the glacier will disappear,” he said.

Alaska’s Columbia Glacier had 216 billion tons of ice in 2015, but Rounce calculated that it would only be a few-tenths to half the extent of warming. If there were 4 degrees Celsius (7.2 degrees Fahrenheit) warming since pre-industrial times, this worst-case scenario would lose two-thirds of its mass, he said.

“It’s definitely hard for him to stare and not leave his mouth open,” Rounce said.

Twila Moon, Deputy Chief Scientist at the National Snow and Ice Center, who was not part of the study, said glaciers are crucial to the lives of people in many parts of the world.

“Glaciers provide drinking water, agricultural water, hydropower and other services that support billions (yes, billions!) people,” Moon said in an email.

Moon said the study “represents significant advances in predicting how glaciers around the world may change over the next 80 years due to human-induced climate change.”

Ruth Mottram and Martin Stendel, climate scientists at the Danish Meteorological Institute and who were not part of the research, said the study includes factors in glacial changes that were not present in previous studies and were more detailed.

Stendel and Mottram said this new study better influences how ice from glaciers melts not only from warmer air, but also from water on both the bottom and sides of glaciers, and how debris can gradually melt. Previous studies focused on large glaciers and made regional estimates rather than calculations for each glacier.

In most cases, the estimated loss figures Rounce’s team found are slightly more dire than previous estimates.

If the world can somehow limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit), the global warming target since pre-industrial times — the world is already 1.1 degrees (2 degrees Fahrenheit) — the world will likely lose 26% by the end of the century total ice mass, ie 38.7 trillion mt of ice melt. The previous best estimates had a warming melt level corresponding to only 18% of the total mass loss.

“I’ve worked on glaciers in the Alps and Norway that are disappearing really fast,” Mottram said in an email. “It’s a bit devastating to see.”


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