Study: Climate Change Added 10% to Hurricane Ian’s Rainfall

FLORIDA, USA – Climate change A study prepared immediately after the storm shows that Hurricane Ian added at least 10% more rainfall.

A non-peer-reviewed study released Thursday compared the peak rainfall of a real storm to about 20 different computer model scenarios with the characteristics of Hurricane Ian hitting the Sun state in a world where climate change is not caused by humans.

“The actual storm was 10% wetter than the storm could have been,” said Michael Wehner, a climatologist at Lawrence Berkeley National Laboratory who co-authored the study.

Forecasters predicted Ian would drop up to two feet (61 centimeters) of rain in parts of Florida by the time it stalled.

Wehner and Kevin Reed, an atmospheric scientist at Stony Brook University, published the study in Nature Communications earlier this year, looking at hurricanes from 2020 and finding that their wettest three-hour periods were more than 10% wetter than in a world without heat-trapping greenhouse gases. Venner and Reed applied the same scientifically accepted attribution technique to Hurricane Ian.

An old rule of physics is that for every additional degree Celsius (1.8 degrees Fahrenheit) of heat, the air in the atmosphere can hold 7% more water. The Gulf of Mexico was 0.8 degrees warmer than normal this week, which should mean about 5% more precipitation. The reality turned out to be even worse. The study found that the hurricane dropped twice as much – 10% more rainfall.

Ten percent may not seem like a lot, but 10% of 20 inches is two inches, which is a lot of rain, especially on top of the 20 inches that already fell, Reid said.

Other studies have seen similar feedback mechanisms for stronger storms in warmer weather, said Princeton University atmospheric scientist Gabriel Vecchi, who was not involved in the study.

MIT hurricane researcher Kerry Emanuel said generally that a warmer world makes storms rainier. But he said he was uncomfortable drawing conclusions about individual storms.

“This business of very, very heavy rain is what we expected to see because of climate change,” he said. “We’re going to see more storms like Ian.”

Princeton’s Vecchi said in an email that if the world is going to recover from disasters, “we need to plan for wetter storms in the future because global warming will not go away.”