Human-induced climate change increased extreme rainfall from Hurricane Ian, which has devastated parts of Florida, by more than 10%, according to a new preliminary analysis.
Ian has caused widespread damage and at least 21 deaths since it swept through southwest Florida on Wednesday, ripping apart cities like Fort Myers and Cape Coral with winds reaching nearly 150 mph and a storm surge reaching 18 feet in some places. More than 2 million people were without power as the storm tore through the state and moved north toward the Carolinas.
Much of the damage has been due to torrential rains, with the new analysis finding that warming of the atmosphere and ocean due to human activity has added significantly to the intensity of these downpours.
The study, which is preliminary and has yet to be peer-reviewed, found that the amount of rain dumped by the storm was 10% higher due to the climate crisis. The scientists used a method established in previous research Rainfall during the 2020 Atlantic hurricane season was up to 11% heavier due to global warming.
“That kind of increase in rainfall is not small when added to an already intense storm,” said Kevin Reed, a researcher at Stony Brook University who conducted the new work. “It can really have significant effects, as we’ve seen with the heavy rains in Florida. It has had a widespread effect.
“If you get 1 foot of rain in a day, 10% more adds another inch, which is a lot in itself. It can really amplify the impacts.”
The warming of the atmosphere, through the burning of fossil fuels, has caused more water to accumulate in many places: around 7% more water for every additional 1C (1.8F) warmed. This can then be triggered into heavy rainfall events that can rapidly flood homes and businesses.
“These are conservative estimates of human-induced rainfall increases using our peer-reviewed method,” said Michael Wehner, a climate scientist at Lawrence Berkeley National Laboratory who worked on the new analysis with Reed. “Climate change didn’t cause the storm, but it did cause the weather.”
Hurricanes derive much of their strength from heat in the ocean, and the water temperature of the Gulf of Mexico is about 0.8°C (1.4°F) above long-term normal, leading to scientists point to a trend of rapidly accelerating storms, in part due to global warming.
In Ian’s case, what was a tropical storm transformed into a hurricane in less than 24 hours, further building to something close to a Category 5 storm, the fiercest storm category, which has winds strong enough powerful enough to rip roofs off buildings. . This type of rapid intensification has happened several times in recent years just on the US Gulf Coast, such as Hurricane Ida, which caused widespread chaos in Louisiana last year.
“We’re seeing much clearer indicators in these events, for sure,” Reed said. “It’s a good reminder that while we’ve had a relatively quiet hurricane season until this storm, we still have two months of the season left and we need to be really prepared.
“The reality is that climate change is here and they are aging events here and around the world. It’s important that we realize this when we think about disasters like this.”