Study: 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 melt out of existence by the end of the century at current climate change trends, according to a new study.

But if the world can limit future warming to just a few more tenths of a degree and fulfill international goals — technically possible but unlikely according to many scientists — then slightly less than half the globe’s glaciers will disappear, said the same study. Mostly small but well-known glaciers are marching to extinction, study authors said.

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

The study in Thursday’s journal Science examined all of the globe’s 215,000 land-based glaciers -- not counting those on ice sheets in Greenland and Antarctica -- in a more comprehensive way than past studies. Scientists then used computer simulations to calculate, using different levels of warming, how many glaciers would disappear, how many trillions of tons of ice would melt, and how much it would contribute to sea level rise.

The world is now on track for a 2.7-degree Celsius (4.9 degrees Fahrenheit) temperature rise 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) in addition to seas already getting larger from melting ice sheets and warmer water, said study lead author David Rounce.

“No matter what, we’re going to lose a lot of the glaciers,” Rounce, a glaciologist and engineering professor at Carnegie Mellon University, said. “But we have the...