Hurricane Florence measures 50 miles wider and will drop 50 percent more rainfall on the U.S. East Coast in the heaviest precipitating parts of the storm than it would have without global warming, according to a new attribution study by a team of U.S. scientists. The research is the first to examine climate change’s impact on extreme weather before a storm hits, rather than in the weeks following a disaster.

The scientists — from Stony Brook University, the Lawrence Berkeley National Laboratory, and the National Center for Atmospheric Research — used real-time forecasts and climate conditions to model the storm, and then re-ran the models with what those values would have been without climate change.

“This is the first time we’ve done this predictively,” Michael Wehner, a climate scientist at the Lawrence Berkeley National Laboratory and co-author of the new study, told National Geographic. “Climate change increases the amount of water in the atmosphere that can rain out in a hurricane. It also changes the structure of the storm to make it more efficient at precipitation.”

Hurricane Florence is expected to bring as much as 40 inches of rain and “life-threatening, catastrophic flooding” to parts of North and South Carolina in the coming days, according to the U.S. National Weather Service. While the storm has weakened from its peak as a Category 4 hurricane and is now a Category 2, it is still expected to deliver a storm surge of up to 13 feet and winds around 100 miles per hour. More than a million people in the southeastern U.S. have been told to evacuate coastal areas, and officials are warning floodwaters and power outages could last for weeks following the storm.

“There is a very clear message here. Dangerous climate change is here and now. It is not something in the future,” Wehner told National Geographic. “If this storm had happened in a world where humans had not interfered in the climate system, there wouldn’t be as much rain. By a large amount.”