Following two historic hurricanes this summer, scientists, climatologists and local officials are raising the alarm that global climate change could be contributing to the size and scope of storms that bear down on the Southeast each year.
The complex science and politically charged debate on climate change complicate assessments of whether or how global warming is affecting hurricanes’ scale or could make them worse in the near future.
At the very least, though, scientists agree some combination of climate change, warming and rising oceans and Florida’s booming growth are sure to make the area more susceptible to potentially stronger storms.
“The perfect storm of the future is going to be a lot more intense than the perfect storm of the present,” said Jeff Masters, director of meteorology for Weather Underground.
Referring to the record-setting, devastating major hurricanes that slammed Florida and Texas recently, he added: “There will be a lot more Irmas and a lot more Harveys in the future.”
Masters’ prediction is one of two schools of thought on whether climate change could lead to bigger, wetter hurricanes — though not necessarily more storms.
“Hurricanes are powered by the warm waters of the ocean and the warmer the waters, potentially the stronger a hurricane can get,” Masters said after Irma cut a destructive path across Florida last week. “Computer modeling consistently shows that the strongest hurricane should get stronger in the coming decades as the ocean temperatures warm.
“That doesn’t mean that the total number of hurricanes is going to go up,” he continued. “Although it may seem contradictory, a lot of modeling shows the total number of named storms may go down in coming decades. But when we do get them, they’re going to be stronger. That’s a big concern.”
Warmer water and potentially more moisture could mean more intense storms that dump more rain, he said. It also could mean more major storms much closer together, like Hurricanes Harvey and Irma.
But it’s difficult to pinpoint any effects of climate change as very direct contributors to the size and scopes of those two storms, and scientists have only about 30 years of high-quality data on hurricanes to try to make a judgment about those effects.
That’s simply not conclusive enough to make a claim that climate change will intensify storms, said Phil Klotzbach, an atmospheric research scientist at Colorado State University.
“If I started a trend line in 1950 and ended in 2000, it’ll be a big down trend,” he said. “Start in 1970 and go to 2010, it’s a huge uptrend. Start your trend line and end your trend lines in a reasonable part of the cycle or you’re going to get trends that aren’t real. It’s not that (climate change) won’t make the storm stronger, I just don’t think we have the data to detect it yet.”
Instead, the most damaging effects of climate change likely will not be those that make storms stronger but those that already do the most damage now, he said.
Creeping sea level rise will make storm surges and inundation worse, particularly for already low-lying areas, and storms that do form are likely to bring more precipitation with them, he said.
That wasn’t necessarily the case for Hurricane Harvey, which dumped record-breaking rains of more than 50 inches in parts of Texas, Klotzbach and Masters agree. Harvey’s dangerous rains came more from its almost glacial pace across the state, not because it was extraordinarily bigger or stronger than other storms.
“Harvey is a very different beast because it wasn’t that it rained hard, it was just that the storm didn’t move,” he said. “But if the storm was moving, we would have talked about Harvey for a day when it made landfall. But because the storm stalled, that was what caused the problem there.”
There are some factors that could dampen climate change’s influence on future hurricane systems, but others could expand it, Masters agreed.
Some models note increasing upper-level wind shear, which could help tear apart would-be hurricanes and actually ward off major storms, he said. But warmer waters could open up more of the eastern seaboard and New England to more frequent major storms, he added.
So-called Great Swan storms — which is a storm never observed in the historical record, but which scientists reasonably conclude could occur with ongoing climate change — could be up to 14 times more likely to occur in the Tampa Bay area by the end of the century, he said. He noted the National Science Board recommended a decade ago that the U.S. should spend $300 million per year on hurricane research and climate, but it currently spends about $20 million per year.
Last week Gov. Rick Scott shrugged off the suggestion that human-induced climate change could have contributed to Hurricane Irma’s record size and strength.
Despite any political disagreement about the present or any scientific disagreement about future models, it is clear climate change will play a role in the next devastating storm — whether that is next month or next century, scientists agreed.
“I spent 15 years looking at these observational data sets; there’s a lot of nuances to what’s in there before you have bold proclamations,” Klotzbach said. “Even if climate change amounts to be nothing, you’re going to be seeing more damage from storms. I think that’s something pretty much everyone could agree on from a person who says global warming isn’t happening to anyone.”