Increase in the severity of Atlantic hurricanes due to warming oceans

Increase in the severity of Atlantic hurricanes due to warming oceans

Climate change Significantly strengthened nearly 85% of hurricanes that hit the North Atlantic between 2019 and 2023, according to a modeling study 1. The wind speeds of these hurricanes increased on average by nearly 30 kilometers per hour - enough to move 30 storms up a category on the Saffir-Simpson scale of hurricane intensity.

The study, published today in the journal Environmental Research: Climate, leads the way Increase in hurricane intensity due to the warming of the Atlantic Ocean, which in turn is caused by human-caused climate change. An accompanying report, based on the new study's methodology, suggests that climate change has strengthened all 11 North Atlantic hurricanes this year.

“We humans leave our mark everywhere, including these hurricanes,” said Daniel Gilford, the study’s lead author and a climate scientist at Climate Central, a nonprofit research organization in Princeton, New Jersey, which prepared the accompanying report. “If we can increase sea surface temperatures, then we can also increase the speed at which a hurricane spins.”

The study adds to a growing body of research showing that global warming is increasing hurricanes. Rising seas due to global warming are also intensifying hurricanes, research has shown. Additionally, the storms strike earlier in the season and bring more rainfall than previous hurricanes.

Devastating consequences

The Atlantic hurricane season was devastating this year. For example, Hurricane Helene, which passed through the southeastern United States in August, brought nearly 80 centimeters of rain in some places. The storm claimed more than 200 lives and caused up to $250 billion in damages - a sum that would catapult Helene ahead of 2005's Hurricane Katrina as the costliest hurricane in the United States.

In Asheville, North Carolina, Helene's hardest-hit U.S. city, areas adjacent to the French Broad River were "completely devastated and ripped away," reports Carl Schreck, a tropical meteorologist at North Carolina State University in Asheville. The region “experienced more wind damage than I would have expected from a hurricane at this low inland location,” he adds, explaining that the wind snapped trees and power lines and disrupted communications with the city for several days. According to the Climate Central report, Helene's wind speeds, which were 140 miles per hour at their peak, were about 16 miles per hour higher than they would have been without the warming effect on the Atlantic.

Flooding damaged the water main at the National Centers for Environmental Information, a branch of the National Oceanic and Atmospheric Administration (NOAA) in downtown Asheville that archives global weather and climate data. This interrupted the cooling of the center's supercomputers, reports Schreck. “In the days after the storm, they actually drove a fire truck to one of the local lakes” and pumped lake water to replenish the cooling system. Some computers overheated and need to be replaced, and the event delayed Climate Central's report, which relied on data from the center. However, data was not lost, the papers remained dry and the center is operational again, he says.

Dangerous waters

Hurricanes are powered by warm ocean water. Theoretically, the warmer the water, the greater the hurricane's intensity, as measured by wind speed. Climate change has provided plenty of fuel: sea surface temperatures have increased by about 1°C in the North Atlantic since 1900 due to climate change.

To shed light on the influence of climate change on the intensity of recent hurricanes in this region, Gilford and his co-authors simulated how all 49 hurricanes that hit the North Atlantic between 2019 and 2024 would have developed if climate change had not warmed the ocean. The scientists then compared the wind speeds of the simulated storms with those of the actual storms.

Climate change intensified 30 of the hurricanes so much that they could be placed one category higher on the Saffir-Simpson scale than they would have been without climate change. It is likely that climate change has upgraded five storms - Lorenzo (2019), Ian (2022), Lee (2023), Milton (2024) and Beryl (2024) - to Category 5 hurricanes in the past five years, described by NOAA as "catastrophic."

“The study does an excellent job of quantifying the changes we observed,” said Ryan Truchelut, co-founder and chief meteorologist at Weather Tiger, a weather and climate forecasting company in Tallahassee, Florida. He emphasizes that the study authors used the best available data and appropriate statistical methods to try to determine whether a hurricane was affected by climate change.

Schreck believes the study is necessary, but criticizes that specifying a single increase in wind speed for each storm, as the authors did, instead of specifying a range of values ​​with error limits, is "too simple." The study's model doesn't take into account all the real-world complexities of ocean conditions and storm behavior that create uncertainties, he says.

“Climate change is here,” explains Gilford. “We urgently need to have more conversations about reducing our greenhouse gas emissions.”

1. Gilford, D. M., Giguere, J. & Pershing, A. J. Environ Res Climate https://iopscience.iop.org/article/10.1088/2752-5295/ad8d02 (2024).

   
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