Hurricane Ian: 10% more rain due to climate change

Ian could, according to US President Joe Biden, “be the deadliest hurricane in Florida history”, but no official report was available as of Friday. Before Florida, Ian had hit Cuba, killing three people and causing extensive damage, leaving many homes without power.

“Climate change didn't cause the hurricane, but it did make it wetter,” said Michael Wehner of the US Department of Energy's Lawrence Berkeley National Laboratory, one of the scientists involved in the this study.

The researchers based themselves on the comparison of the current situation, marked by a global warming of nearly 1.2°C compared to the pre-industrial era, with models in a world without this warming.

“We can say with confidence that the precipitation is heavier. At least 10% and even, according to my estimates, 14%,” said Michael Wehner. The study, which due to its speed could not be validated by a review committee, however used a methodology already used for a study on the 2020 hurricane season, validated by other scientists and published in April in the journal Nature Communication.

According to a physical law (known as the Clausius-Clapeyron formula), for every increase in temperature of 1°C, the humidity contained in the atmosphere increases by 7%.

The results of the American researchers' modeling therefore show an even greater increase in precipitation linked to Ian, suggesting a better “efficiency” of the hurricane in transforming this increased humidity into rain.

Global warming, which notably raises the temperature of the surface of the oceans, therefore correlatively increases the humidity of the atmosphere and therefore reinforces, according to scientists, the intensity of storms.