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When Hurricane Helene slammed into Florida’s shoulder earlier this fall, it brought the largest storm surge ever recorded in the area. The storm had formed just four days earlier as a tropical depression, but when it made landfall, it was already a Category 4 hurricane, lashing the Tampa Bay area with savage winds and rain, flooding and laying waste to whole communities. Two weeks later, Hurricane Milton deepened the tragedy when it hit the Florida peninsula, unleashing catastrophic flooding and 100-mile-per-hour gusts, killing multiple people, and breaking meteorological records.
Climate scientists have been warning for years that climate change is supercharging storms, broadly speaking. But connecting specific rates of warming to the ferocity of specific storms was out of reach. Now a team of scientists has developed a model that, for the first time, allows them to calculate how warming ocean temperatures have contributed directly to wind speeds in individual hurricanes. Using this model, they were able to determine, for instance, that climate change bumped Hurricane Rafael up two whole categories (from 1 to 3) earlier this month, and pushed another two hurricanes this year into category 5, the highest category, in which wind speeds exceed 157 mph.
“It’s really the evolution of our science on sea surface temperature attribution that has allowed this work to take place,” Daniel Gilford, an atmospheric scientist with the independent nonprofit research outfit Climate Central and the lead author of the study said in a press briefing. Gilford and his colleagues found that due to higher sea surface temperatures, maximum wind speeds were 19 mph higher on average in 84 percent of the hurricanes in the north Atlantic that occurred between 2019 and 2023, and, according to an additional analysis, most all hurricanes thus far in 2024 as well—enough to elevate them an entire category on the Saffir-Simpson scale. Moreover, global warming caused wind speeds in three of the hurricanes to course roughly 34 mph faster than they would have otherwise.
When storms double their wind speed, they can cause 256 times as much damage.
To make these calculations, Gilford and his team first determined how much cooler the surface of the sea would be without human-induced climate change. “Climate models and observations are both showing us that, in a world without climate change, temperatures would be somewhere between 2 to 3 degrees Fahrenheit cooler,” Gilford said. Because the intensity of a hurricane is determined foremost by the temperature of the seas over which it passes, Gilford and team used the pre-warming sea surface temperatures to determine the maximum wind speeds that any particular hurricane theoretically would have reached without climate change. From there, they used statistical relationships gleaned from past hurricane seasons to estimate what the wind speeds might have been without warming. They could then compare these numbers against the speeds that were actually recorded to determine how much climate change likely ramped up the intensity.
Friederike Otto, a climatologist with World Weather Attribution, a nonprofit research group based in the United Kingdom, who wasn’t involved in Gilford’s study but who does work with Climate Central, says the methodology the scientists used looks solid. She has done similar work using historical data to determine how climate change has also increased the amount of rainfall that hurricanes cause. “We now have a lot of observations and many years of data where we see these changes.”
Gilford knows firsthand how hurricanes affect people’s lives. A tree fell on his family’s home in central Florida during Hurricane Jeanne in 2004, which he said catalyzed his current career. Today, he lives in Orlando, and hurricanes continue to impact his life year after year. “I care a lot about this problem,” Gilford said in a press briefing about his study, “and we should care about this problem because hurricanes are changing.”
Jumps in category strength carry tremendous hazards. According to the National Oceanic and Atmospheric Administration, the potential damages caused by a storm increase exponentially—by a power of eight—with increases in wind speed. So, for example, when storms double their wind speed, they can cause 256 times as much damage.
The new study does more than just reveal how climate change has worsened major hurricanes to date. It provides a method that scientists can use in the future to say, in near-real time, how global warming is affecting a specific, singular cyclone. This should help communities not only prepare for the supercharged storms that are becoming more standard fare, but also to better understand the critical connections between those storms and the forces of climate change. 
Lead image: BEST-BACKGROUNDS / Shutterstock
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