As the Earth warms due to climate change, we could reach a catastrophic “tipping point” marked by a drastic reduction in cloud cover that would lead to an additional eight degrees Fahrenheit of global warming in as little as a century, according to a horrifying new study in Nature Geoscience cited Monday by Quanta Magazine. That eight degree uptick, combined with the expected 4 degree rise, “would be truly devastating climate change,” said one of the study authors, and would lead to massive amounts of human casualties and environmental destruction.

Climate researchers have long known that clouds play a vital role in climate control by reflecting sunlight away from the earth’s surface. But because clouds are so small, they’ve been tough to measure in large-scale climate models—this simulation took 2 million core hours on computers in Switzerland and California. We’re not entirely doomed, the Quanta article notes—a drastic reduction of carbon emissions could slow global warming before that tipping point. But researchers are concerned that the world isn’t responding quickly enough. “I’m worried,” one paleoceanographer said. “Are you kidding? As far as I’m concerned, global warming is the major issue of our time.”