The world’s glaciers are shrinking and disappearing faster than scientists thought, with two-thirds of them expected to melt by the end of the century today. climate change trends, according to a new study.
But if the world can limit future warming to a few tenths of a degree higher and meet international targets – technically possible but unlikely according to many scientists – then just under half of the globe’s glaciers will disappear, according to the same study. Mostly small but well-known glaciers are on the verge of extinction, the study authors said.
In an equally unlikely worst-case scenario of several degrees of warming, 83% of the world’s glaciers would likely disappear by the year 2100, the study authors said.
The study published Thursday in the journal Science looked at all 215,000 terrestrial glaciers around the globe, not counting those on the ice caps in Greenland and Antarctic — in a more comprehensive way than previous studies. Scientists then used computer simulations to calculate, using different levels of warming, how many glaciers would disappear, how many trillions of tonnes of ice would melt, and how much that would contribute to sea level rise.
The world is now on track for a temperature increase of 2.7 degrees Celsius (4.9 degrees Fahrenheit) since pre-industrial times, which by the year 2100 means the loss of 32% of the world’s glacial mass, i.e. 48.5 trillion metric tons of ice as well as 68% of the glacier disappear. This would increase sea level rise by 4.5 inches (115 millimeters) on top of already rising seas from melting ice caps and warmer water, the lead author said. of the study, David Rounce.
“No matter what, we’re going to lose a lot of glaciers,” said Rounce, a glaciologist and professor of engineering at Carnegie Mellon University. “But we have the ability to make a difference by limiting the number of glaciers we lose.”
“For many small glaciers, it’s too late,” said study co-author Regine Hock, a glaciologist at the University of Alaska Fairbanks and the University of Oslo in Norway. “However, on a global scale, our results clearly show that every degree of global temperature is important in keeping as much ice as possible locked up in glaciers.”
According to the study, the projected ice loss by 2100 ranges from 38.7 trillion metric tons to 64.4 trillion tons, depending on global warming and the amount of coal, oil and gas burned.
The study calculates that all of this ice melt will add 3.5 inches (90 millimeters) best-case to 6.5 inches (166 millimeters) worst-case at global sea level, or 4% to 14% more than previous projections.
This 4.5 inch sea level rise from the glaciers would mean that more than 10 million people worldwide – and more than 100,000 people in the United States – would live below the high tide line, who would otherwise be above, said sea level rise researcher Ben Strauss, CEO of Climate Central. Twentieth-century sea level rise due to climate change added about 4 inches to the surge from 2012’s Superstorm Sandy, costing about $8 billion in damage alone, he said.
Scientists say future sea level rise will be driven more by melting ice caps than glaciers.
But the loss of glaciers is not limited to rising seas. This means diminished water supplies for much of the world’s population, an increased risk of flooding from melting glaciers, and the loss of historic ice-covered sites from Alaska to Alps even near Mount Everest Base Camp, several scientists told The Associated Press.
“For places like the Alps or Iceland…the glaciers are part of what makes these landscapes so special,” said National Snow and Ice Data Center director Mark Serreze, who doesn’t did not participate in the study but rented it. “As they lose their ice in a sense, they also lose their soul.”
Hock pointed to the Vernagtferner Glacier in the Austrian Alps, which is one of the best-studied glaciers in the world, but said “the glacier will be gone.”
The Columbia Glacier in Alaska had 216 billion tons of ice in 2015, but with just a few tenths of a degree more warming, Rounce calculated it would be half that size. If there is 4 degrees Celsius (7.2 degrees Fahrenheit) of warming since pre-industrial times, an unlikely worst-case scenario, it will lose two-thirds of its mass, he said.
“It’s definitely hard to watch and not let down,” Rounce said.
Glaciers are crucial to people’s lives in much of the world, said Twila Moon, deputy senior scientist at the National Snow and Ice Center, who was not part of the study.
“Glaciers provide drinking water, agricultural water, hydropower and other services that support billions (yes, billions!) of people,” Moon said in an email.
Moon said the study “represents significant advances in projecting how the world’s glaciers could change over the next 80 years due to human-made climate change.”
This is because the study includes factors of glacial changes that previous studies did not have and are more detailed, said Ruth Mottram and Martin Stendel, climatologists at the Danish Meteorological Institute who were not part of the research. .
This new study takes better account of how glacier ice is melting not only from warmer air, but also from water under and on the edges of glaciers and how debris can slow the melt, said Stendel and Mottram. Previous studies have focused on large glaciers and made regional estimates instead of calculations for each individual glacier.
In most cases, the loss figures estimated by Rounce’s team are slightly worse than previous estimates.
If the world somehow manages to limit warming to the global goal of 1.5 degrees Celsius (2.7 degrees Fahrenheit) of warming since pre-industrial times — the world is already at 1.1 degrees (2 degrees Fahrenheit) — Earth will likely lose 26% of total glacial mass by the end of the century , or 38.7 trillion metric tons of melting ice. Previous best estimates had this level of warming that translated to only 18% of the total mass loss.
“I’ve worked on glaciers in the Alps and in Norway that are disappearing very quickly,” Mottram said in an email. “It’s kind of devastating to see.”
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