Two thirds of glaciers on track to disappear by 2100

Two thirds of glaciers on track to disappear by 2100

Two thirds of glaciers on track to disappear by 2100

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

But if the world can limit future warming to just a few tenths of a degree more and meet international targets (technically possible but unlikely according to many scientists), then slightly less than half of the world’s glaciers will disappear, he says. study. The mostly small but well-known glaciers are marching toward extinction, the study authors said.

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

The study, published Thursday in the journal Science, looked at the world’s 215,000 terrestrial glaciers, not counting those found in the Greenland and Antarctic ice sheets, in a more comprehensive way than previous studies. The scientists then used computer simulations to calculate, using different levels of warming, how many glaciers would disappear, how many trillion tons of ice would melt, and how much they 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 losing 32% of the world’s glacier mass, or 48 .5 trillion metric tons of ice, as well as 68% of the glaciers disappearing. That would increase sea level rise by 4.5 inches (115 millimeters), on top of seas already rising from melting ice sheets and warmer water, said study lead author David Rounce.

“Whatever happens, we’re going to lose a lot of the 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 amount 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, globally, our results clearly show that every degree of global temperature is important in keeping as much ice as possible locked up in glaciers.”

Projected ice loss for 2100 ranges from 38.7 trillion metric tons to 64.4 trillion tons, depending on how much the planet warms and how much coal, oil and gas is burned, according to the study.

The study calculates that all that melting ice will add between 3.5 inches (90 millimeters) at best and 6.5 inches (166 millimeters) at worst to world sea level, about 4 percent. and 14% more than previous projections.

That 4.5-inch sea level rise due to 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, that would otherwise be above said sea level rise. researcher Ben Strauss, CEO of Climate Central. Sea level rise in the 20th century due to climate change added about 4 inches to the rise from 2012 Superstorm Sandy that cost about $8 billion in damage itself, he said.

Scientists say future sea level rise will be driven more by melting ice sheets than by glaciers.

But glacier loss is about more than just sea level rise. It means reduced water supplies for much of the world’s population, increased risk of flooding from melting glaciers, and the loss of ice-covered historic sites from Alaska to the Alps and even near Mount Everest Base Camp. , several scientists told The Associated Press.

“For places like the Alps or Iceland…glaciers are part of what makes these landscapes so special,” said National Snow and Ice Data Center director Mark Serreze, who was not part of the study but praised 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 disappear.”

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 estimated it will be half that size. If there’s 4 degrees Celsius (7.2 degrees Fahrenheit) of warming since pre-industrial times, the unlikely worst-case scenario, it will lose two-thirds of its mass, he said.

“It’s definitely hard to watch and not gawk,” Rounce said.

Glaciers are crucial to people’s lives in much of the world, said National Snow and Ice Center deputy principal scientist Twila Moon, who was not part of the study.

“Glaciers provide drinking water, water for agriculture, 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 may change over the next 80 years due to human-made climate change.”

That’s because the study includes factors in glacier changes that previous studies didn’t include and is more detailed, said Ruth Mottram and Martin Stendel, climatologists at the Danish Meteorological Institute who were not part of the research.

This new study better considers how glacier ice is melted not only by warmer air, but also by water below and at the edges of glaciers and how slowly debris may melt, Stendel and Mottram said. Previous studies concentrated on large glaciers and made regional estimates rather than calculations for each individual glacier.

In most cases, the estimated loss numbers Rounce’s team came up with are slightly more dire than previous estimates.

If the world can somehow 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, which is 38.7 trillion metric tons of melted ice. Previous best estimates had that level of heating and melting translating to only 18% of the total mass loss.

“I have worked on glaciers in the Alps and Norway that are disappearing very quickly,” Mottram said in an email. “It’s a devastating thing to see.”


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