Three weeks after the United Nations issued a sobering climate report that called for “rapid and unprecedented” changes in energy use, a study examining ocean temperatures suggests that global warming could happen at a faster pace than previously believed.

The study, published in Nature Wednesday and conducted by researchers at Princeton University and the Scripps Institution of Oceanography, estimated that the world’s oceans absorbed 60% more heat energy between 1991 and 2016 than previous studies have indicated. That could indicate the Earth is warming faster than scientists have been estimating.

“We thought that we got away with not a lot of warming in both the ocean and the atmosphere for the amount of CO2 that we emitted,” Laure Resplandy, a Princeton geoscientist who led the study told the Washington Post. “But we were wrong. The planet warmed more than we thought. It was hidden from us just because we didn’t sample it right. But it was there. It was in the ocean already.”

Image: Nature

Previous efforts to measure ocean temperature involved an “imperfect ocean dataset” limited by incomplete or differing measurements, the study’s abstract says. The researchers used a different way to measure ocean warmth, “an independent estimate by using measurements of atmospheric oxygen and carbon dioxide—levels of which increase as the ocean warms and releases gases—as a whole-ocean thermometer.”

Earlier this month, the U.N. issued a landmark report that said a rise in global temperatures above 1.5 degrees Celsius—which could come as early as 2030—could cause catastrophic damage unless “rapid and unprecedented” changes in energy use is made before then.