Researchers in Germany and Norway said Tuesday that a major portion of Greenland’s ice sheet is “at the brink” of reaching a frightening “tipping point”—the latest sign that global heating is causing irreversible damage to the world’s glaciers and that policymakers must halt fossil fuel emissions without further delay.

According to new research published in the Proceedings of the National Academy of Sciences, the melting of the central-western Greenland ice sheet has surged over the last 140 years.

Niklas Boers at the Potsdam Institute for Climate Impact Research in Germany conducted the research with Martin Rypdal from the Arctic University of Norway, examining the height changes of the ice sheet since 1880 and comparing them to model simulations.

“We’re at the brink, and every year with CO2 emissions continuing as usual exponentially increases the probability of crossing the tipping point,” Boers told the Guardian. “It might have passed [the tipping point], but it’s not clear.”