The Earth’s atmosphere is hotter than it was just a few decades ago, and scientists are starting to grapple with how hurricanes and storms have already changed in the warmer world — and how they might continue to change in the future.
The latest research paper to tackle the issue suggests that climate change may be why stronger hurricanes are forming “significantly” earlier in the season. It also finds, however, that the impact seems less apparent in the Atlantic Ocean basin, the breeding ground for hurricanes that threaten Florida and the rest of the United States coastline.
The study, published in the journal Nature, found a worldwide trend: Category 4 and 5 hurricanes are occurring about 15 days earlier across the planet than they were in the 1980s. In this case, “earlier” is defined as June through August, while the “late” end of the season is considered September through November.
That’s a big deal, the authors said, because the earlier part of storm seasons around the world usually coincide with rainy season, increasing the chances for big floods.
Researchers also found that rapid intensification — the process where a storm gets significantly stronger over a short period of time — is now occurring about two weeks earlier in the season, said Fengfei Song, a co-author and researcher at the Ocean University of China in Qingdao.
“The seasonal advance of intense tropical cyclones made us wonder if the rapid intensification events may also experience a similar change, which was proved to be the case,” he wrote in an email.
The paper didn’t find a similar pattern for storms of all strength, just the most powerful ones. And although researchers found evidence of this trend around the globe, there were differences in some basins.
The pattern was strongest in the western North Pacific. But the Atlantic basin, where all of the storms that hit the Caribbean, and U.S. East and Gulf coast originate, showed less evidence of the trend.
That didn’t surprise Bryan Norcross, Fox Weather’s hurricane specialist. While he agreed overall with the study’s findings, he said he’s skeptical of the conclusions drawn about the Atlantic basin.
“The factors that they’re talking about might have some contribution to storms developing a little sooner, but we have all these other things going on,” he said. “The Atlantic is a unique basin because it’s so small, so there’s always many factors that affect the season.”
For one, Norcross said, the authors only reviewed storms from 1981 to 2017. During that period, the world dramatically cut down on air pollution, which made the world a safer and healthier place for many.
But, scientists found out years later, that air pollution clouded the skies above places like the Atlantic Ocean, cooling the water below and suppressing storm activity. Now, with less pollution in the air, the Atlantic is experiencing more storms than it did with dirtier air.
“We know the atmosphere over the Atlantic from 1981 to 1995 was different from what it is now, so comparing across that time period where half of that time period was in this suppressed situation, doesn’t work,” he said.
The complexities of the Atlantic basin, and the many factors that weigh into how, where and whether a hurricane forms, make it tough for scientists to untangle the effects of climate change specifically.