In a new study, scientists say Earth’s oceans are already locked into nearly 10.8 inches of sea-level rise from Greenland’s melting ice sheet, even if humans stopped emitting planet-warming greenhouse gases today.
And if our burning of fossil fuels continues, the total sea-level rise from the massive island’s melting ice could be much higher, researchers warn.
In the paper, published Monday in the journal Nature Climate Change, the researchers examined the snow line, or the boundary between a higher-elevation section of Greenland’s ice sheet where snow and ice accumulates and a lower section where snow melts, writes USA Today’s Dinah Voyles Pulver. Currently, the melting area is growing larger, and the ice accumulation area is shrinking.
“We have caused the ice sheet to go out of equilibrium,” David Bahr, a co-author of the study and a glaciologist at the University of Colorado Boulder, tells USA Today. “We’re melting it faster than the ice can move downstream and replenish areas that are melting.”
Greenland is the world’s largest source of sea-level rise from melting ice, according to the Washington Post’s Chris Mooney. The island is virtually the size of Alaska, blanketed by an ice sheet that’s one to two miles thick. Since 2000, melt rates have accelerated in Greenland, as Arctic temperatures are rising faster than in other parts of the globe. If all of Greenland’s ice melts, scientists agree, Earth would be in for about 20 feet of rising seas, per the Post.
The new 10-inch metric, which represents about 3.3 percent of Greenland’s total ice, is a higher figure than sea-level rise estimates in other recent forecasts. Last year’s Intergovernmental Panel on Climate Change (IPCC) report, for example, only predicted that Greenland’s melting ice would cause 2 to 5 inches of global sea-level rise by 2100, writes Seth Borenstein for the Associated Press (AP).
This new paper may have come up with a higher number for a few reasons. For one, it relied on satellite measurements instead of the computer modeling that past research used, which are "not up to the task," as study lead author and glaciologist Jason Box says to the New York Times’ Elena Shao. It’s also based only on data from between 2000 and 2019, a period of faster ice melt than the 20 years before it, which are included in the IPCC estimate, the Post writes.
Finally, the new forecast does not give a deadline for when the 10-plus inches of sea-level rise would occur, per the Times, though the researchers hypothesize that most will happen by 2100. But Ted Scambos, an ice sheet expert at the University of Colorado Boulder who did not contribute to the study, tells the Post that a longer timescale is probably more accurate: “A lot of the change they forecast would happen in this century, but to get [that level of retreat] would require several centuries, more perhaps.”
The bottom line, researchers say, is that the melting will happen. “Whether it’s coming in 100 years or 150 years, it’s coming,” William Colgan, a paper co-author who studies glaciers with the Geological Survey of Denmark and Greenland, tells the Guardian’s Damian Carrington. “And the sea-level rise we are committed to is growing at present, because of the climate trajectory we’re on.”
Ten inches of sea-level rise “will have huge societal, economic and environmental impacts,” Ellyn Enderlin, a geoscientist at Boise State University who didn’t contribute to the study, tells the AP. And like any sea-level rise, the effects won’t be felt evenly across the globe: Low-lying island nations and developing countries are particularly vulnerable, writes the Post.
The research team emphasizes that the 10-inch prediction is a low estimate. Colgan tells the AP that if we see more years like 2012, when there was a much greater amount of melting, we could see as much as 30 inches of sea-level rise from Greenland’s ice sheet.
Essentially, melt amounts that once seemed extreme could become the new normal. “That’s how climate change works,” Colgan tells the AP. “Today’s outliers become tomorrow’s averages.”