SCOTT SIMON, HOST:
Hurricane Irma's had winds of 185 miles per hour for 37 hours straight at one point. That's a record. Right behind Irma, of course, is another hurricane, Jose - not as big but still very dangerous, as Texas still dries out from its encounter last week with the enormous Hurricane Harvey, which makes a lot of people wonder, how unusual is this sequence of hurricanes? Is this our future? And is this climate change at work? Here to talk about that is NPR science correspondent Christopher Joyce. Chris, thanks so much for being with us.
CHRISTOPHER JOYCE, BYLINE: Good to be here, Scott.
SIMON: This does seem extraordinary - three huge hurricanes in a matter of weeks.
JOYCE: It's unusual, very unusual - not unprecedented. There have been occasions in the past in the Atlantic and the Pacific, where there have been two or three hurricanes swirling around somewhere. What makes them particularly noticeable, of course, is that they're hitting land. Often, these happen, but nobody knows because they never hit land.
SIMON: How does what we're seeing match up with the predictions that have been made over the years by climate scientists?
JOYCE: We have to remember that, though, of course, there have always been hurricanes, and there would be without climate change. But what the computer models that climate scientists use - what they tell us is that bigger storms are going to get bigger. Not necessarily more - there will be more of them, but they'll get bigger. And the reason for this is heat. Heat drives storms. The more heat you have, the bigger storms you have. What happens is hot water creates water vapor. You know, a cup of coffee - it's got vapor coming off it. So the water vapor rises. You get convection. It creates these circulating winds. And that's what creates the conditions for a hurricane. And what's happened is that, you know, hurricanes feed off of this fuel. And the hotter the oceans, the more fuel you'll get for the hurricane.
SIMON: Global warming can provide that heat from the ocean.
JOYCE: Yes. I mean, there's always heat. And there've always been hurricanes. But there's extra heat now. I mean, this summer, the Atlantic Ocean, where the hurricanes form, was close to two degrees Fahrenheit warmer than the normal. And that may not seem like a lot. But you're talking about tens of thousands of square miles, 150 feet deep. That's a lot of heat. We saw a similar situation in 2005 when Katrina hit in 2010 - a very warm ocean and lots of hurricanes. And we should note that it's not just power you get from the heat. More water vapor means more rain. And that's what happened with Harvey. A warmer atmosphere holds more rain. More of it comes out of the hotter ocean. So that's what happened with Harvey.
SIMON: So is this our future?
JOYCE: Very hard to predict. Natural things unrelated to climate change cause hurricanes to happen. You know, we saw this with Harvey. There was a high pressure system over the United States that made it stall and rain more over Houston. That's not related to climate change clearly. Some people think it is, but it's difficult to say. But at the same time, the heat is the essence here. And climate scientists are pretty sure that at least one thing is clear. We're going to ratchet things up the hotter it gets. The ocean absorbs that heat, and we'll get hurricanes that get ratcheted up a little bit. Some get ratcheted up a lot. But the more we heat up the oceans, the more we're going to get big, big storms.
SIMON: Same time as we've had these hurricanes, of course, there have been some huge wildfires that have been burning in the West. Do scientists believe climate change is at work there, too?
JOYCE: That's a tougher link. Again, so many things cause wildfires, not least of which is a hundred years of suppressing wildfires. The Forest Service, Smokey the Bear - has suppressed it, meaning a lot of fuel has grown up, a lot of underbrush. So when it does burn, it burns hotter and bigger. That said, again, heat makes a big difference. It's been hotter than normal. When you have heat, you suck more moisture out of the land. You suck more moisture out of the vegetation. It's drier. Poof. You get maybe not more fires, but you get big ones.
SIMON: NPR's Christopher Joyce, thanks so much.
JOYCE: You're welcome.
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