Climate change increased the rainfall from Hurricane Ian by more than 10 percent, two U.S. researchers have found.
Ian pummeled parts of Florida, killing dozens and inflicting tens of billions of dollars in damage. The state has been a hurricane hotspot for decades, but Ian was likely one of the deadliest storms it’s ever seen, and President Biden said last week it will probably rank as one of the most destructive storms in the nation’s history. Much of the devastation has been due to the storm’s relentless rainfall, which the new quickfire analysis found was made worse because of planet-warming greenhouse gas pollution.
The authors employed a rapidly growing field of science called climate attribution, which illuminates the links between climate change and individual weather disasters. Weather has always been variable, but the scientists used computer models to separate natural variability in weather patterns from the bigger shifts that are attributable to greenhouse gas emissions.
The world has warmed by nearly 1.2 degrees Celsius (2.2 degrees Fahrenheit) since the Industrial Revolution, thanks mostly to the use of coal, oil, and gas. The researchers used a method that they established in previous research to compare simulations of the existing climate with simulations of a world where that warming never happened.
The difference in rainfall was about 10 percent — and “those are conservative estimates,” Michael Wehner, a senior scientist at the Lawrence Berkeley National Laboratory, who worked on the analysis with researcher Kevin Reed of Stony Brook University, wrote in a Tweet.
The study is preliminary and has yet to be peer-reviewed. It only looked at rainfall, not other destructive elements of the hurricane, like strength, rate of intensification, and storm surge, which may have also been more severe due to planetary warming.
Still, the analysis offers yet more evidence of a simple but scary trend demonstrated in previous research: Warmer air can hold more water vapor, meaning storms are getting wetter. For every 1 degree Celsius (1.8 degrees Fahrenheit) of warming, the atmosphere can hold 7 percent more moisture, scientific calculations suggest.
Previous analyses suggest climate change also fueled other destructive hurricanes, like Harvey and Katrina. And an April study co-authored by Wehner and Reed suggests that during the disastrous 2020 North Atlantic hurricane season, rainfall was significantly higher than it would have been in the pre-industrial era before greenhouse gas emissions started to rise.