Human-caused climate change has made Atlantic hurricanes about 18 miles per hour stronger over the past six years, according to a new scientific study released Wednesday.
For most of the storms, 40 of them, the added boost from warmer oceans bumped the systems up a full hurricane category, according to the study published in the journal Environmental Research: Climate.
A Category 5 storm causes more than 400 times the damage of a minimum Category 1 hurricane, more than 140 times the damage of a minimum Category 3 hurricane, and more than five times the damage of a minimum Category 4 storm, according to the United States Oceanic and Atmospheric Administration.
For three storms, including Rafael this month, the climate change factor boosted wind speeds so much that winds increased in two storm categories.
It’s not a matter of there being more storms, but rather the worst ones becoming more powerful, the authors said.
“We know that the intensity of these storms is causing much more catastrophic damage overall,” said the study’s lead author, Daniel Gifford, a climate scientist at Climate Central, who does research on global warming. “The damage escalates with intensity.”
The effect was especially noticeable in stronger storms, including those that reached the top of the Saffir-Simpson intensity scale: category five, the study authors said. The study looked at data between 2019 and 2023, but the authors later added this year’s named storms, all of which had an increase due to climate change.
“This year we had two category five storms,” Gifford said. “Our analysis shows that we would not have had category five storms without human-caused climate change.”
This year’s three most devastating storms — Beryl, Helene and Milton — increased by 29 km/h, 26 km/h and 39 km/h respectively due to climate change, the authors said.
A different study by World Weather Attribution estimated Helene’s wind speed increase at about 21 km/h, a similar figure, said Friederike Otto, a climate scientist at Imperial College London who coordinates the WWA team and praised the work of ClimateCentral.
Since 2019, eight storms—2019 Humberto, 2020 Zeta, 2021 Sam and Larry, 2022 Earl, 2023 Franklin, and 2024 Isaac and Rafael—gained at least 25 mph in wind speed. Humberto and Zeta gained more: 50 km/h.
In 85% of the storms studied over the past six years, the authors saw an imprint of climate change in the strength of the storm, Gifford said.
Hot water is the main fuel for hurricanes. The warmer the Atlantic, Caribbean and Gulf of Mexico are, the more potential energy goes into storms. Other factors, such as high-level crosswinds and dry air, can act to weaken hurricanes.
Waters in the hurricane zone have risen between 1.1 to 1.6 degrees Celsius overall and up to 2.2 degrees Celsius due to climate change, Gifford said. They know this because Climate Central has used scientifically accepted techniques to regularly track rising temperatures in the oceans due to the burning of coal, oil, and natural gas.
That technique basically uses computer simulations to create a fictional world without human-caused warming and then compares it to today’s reality, with the difference being caused by greenhouse gases. They take into account other factors, such as the decrease in sulfate pollution from merchant traffic, which had somewhat offset warming.
To move from warmer waters to stronger storms, the authors used a calculation called potential intensity, which is basically the speed limit for any given storm based on the environmental conditions surrounding it, Gifford said.
Hurricane expert and MIT meteorology professor Kerry Emanuel, who pioneered potential intensity measurements, was not part of the study but said it made sense. It shows an increase in storm strength that he predicted would occur 37 years ago, he said.
Previous studies have shown that climate change has caused hurricanes to intensify faster and move more slowly, causing even more rain.
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