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The hurricane season in the Atlantic is finally over, and we're going to get an assessment of it now. There were ten hurricanes in the region this year. Three of them made landfall at Category 4 or higher, bringing devastation from Texas to the Caribbean. NPR's Christopher Joyce reports that scientists agree it was a monumental season, and it was a taste of the future.
CHRISTOPHER JOYCE, BYLINE: The Atlantic is a mighty ocean - so mighty it makes its own weather. A breeze blowing west from Africa can mutate into a 150-mile-an-hour blockbuster that uproots trees and crushes buildings. A typical year sees about six hurricanes, not 10. So what's up with this? Meteorologist Kevin Trenberth at the National Center for Atmospheric Research says hurricanes feed off ocean heat.
KEVIN TRENBERTH: Having high ocean heat content below the surface means that they can be sustained and remain stronger, more intense than they otherwise would.
JOYCE: Global warming - well, there were huge hurricanes and brutal seasons before climate change, but scientists say now the oceans are warmer.
TRENBERTH: So these storms were indeed exactly what we've been worrying about with regard to climate change - that the storms are bigger, longer lasting and more intense.
JOYCE: Bigger, as in several Category 4 storms - more intense because when you add up the wind energy from the 10 hurricanes, it's unusually high - and longer lasting, as when Harvey hit Texas. Hurricanes normally die on land. Harvey didn't. Instead, it dropped a record rain. And that's another sign of climate change. A warmer ocean means more water vapor rises into the atmosphere, which makes for wetter storms.
Now, there are other factors at work besides warming. A global weather pattern called El Nino was absent this year. That often means a stormier Atlantic Ocean. Atmospheric scientist Kerry Emanuel at MIT notes that there's also a rather mysterious cycle for Atlantic hurricanes. It seems to repeat about every decade.
KERRY EMANUEL: We don't really understand it. It's there.
JOYCE: Sure enough, 12 years ago in 2005, the hurricane season was also a record breaker. Emanuel says scientists are not clear whether hurricanes are becoming more common. Some aspects of warming could actually decrease their frequency. But the hurricanes will likely be nastier.
EMANUEL: Insofar as the storms were intense and produced a lot of rain, they're a window into our long-term future.
JOYCE: And a costly future, Emanuel says, as people continue to build along coastlines. Damages this year from hurricanes are now assessed at well over $200 billion. That's another record. Christopher Joyce, NPR News.
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