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When It Comes To Recent Powerful Storms, Hurricane Dorian Is 1 Of Many

AILSA CHANG, HOST:

As we've just been hearing, Hurricane Dorian is an incredibly powerful storm. And in recent years, Dorian's had a lot of company. Hurricanes Maria, Irma, Matthew and Florence were all Category 4 or 5 storms, to name a few. So for more now on intense storms like these, we're joined now by meteorologist Jeff Berardelli. Welcome.

JEFF BERARDELLI: Glad to be here.

CHANG: So let me ask you, are hurricanes becoming more intense and more destructive in general, because it certainly feels like that? I mean, is it normal to have a new Category 5 storm every year?

BERARDELLI: It's not normal. In fact, the chance any one year of a Category 5 is about 20%. We've seen five Category 5s in four years.

CHANG: Yeah.

BERARDELLI: And your other question was, are we seeing an increase? Yes, we are - in the strongest of storms. There was a study done, and since 1975, they said there was a substantial and observable increase in the proportion of Category 4s and 5s - in fact, an increase of about 25% to 30% per degree Celsius of global warming, so that's 1.8 degrees Fahrenheit. So, yes, there is a substantial increase in global Cat 4s and Cat 5s because of a warmer climate.

CHANG: OK. And how does that work? How does climate change affect the severity of a hurricane?

BERARDELLI: Every single year, we set new records for ocean heat content. So although the global temperatures may go up-and-down every year, the ocean does not go up-and-down. It just only goes up, and that's because 93% of the excess heat that we are trapping because of greenhouse gases is stored in the ocean - 93%. Well, that has to come out somehow, and that is high-octane fuel for hurricanes. So the more heat that there is in the ocean, especially near the surface of the ocean, the stronger these systems tend to get. And that's what we're seeing.

CHANG: I see. So with Dorian, it's basically been hovering over the Bahamas for a while now. The storm's moving really slowly. It's dropping a ton of rain. Are we seeing slower, wetter storms now?

BERARDELLI: Yeah, it does seem like the latest research shows that storms are, in fact, slowing down, especially close to the coast. And the slower they move, the more rain they drop and the more destruction they cause.

CHANG: Let me ask you, what about - are we just seeing more hurricanes overall in the Atlantic?

BERARDELLI: No, it doesn't look like that. In fact, globally speaking, there does not seem to be a trend in the number of hurricanes. And we are not sure that there is going to be. There might actually be a cap in tropical activity in terms of energy per year. And so if the intensity goes up, the number may have to go down. That's just a theory, but it's a possibility.

CHANG: But as the intensity of storms is ramping up over the years, is this a reversible pattern at all if some sort of action is taken, or are we stuck dealing with more intense hurricanes going forward?

BERARDELLI: So the answer is both. We are stuck because there's a lag time. We release all this carbon dioxide, other greenhouse gases into the atmosphere, so we have at least another 1 degree Fahrenheit of warming that is going to happen regardless of what we do. And so hurricanes will continue to get stronger.

But the other answer to your question is, yes, if we reduce and eventually eliminate the use of fossil fuels, we start sucking carbon dioxide out of the atmosphere, then later in the century, there is the chance that we could reverse this trend. But as it stands right now, we're certainly not on a good track to reduce our fossil fuel consumption.

CHANG: That's meteorologist Jeff Berardelli. He contributes to CBS. Thank you very much.

BERARDELLI: You're welcome. Transcript provided by NPR, Copyright NPR.