Are Hurricanes and Climate Change Connected? Researchers from the American Meteorological Society are meeting in January in New Orleans, the site of the hurricane Katrina disaster in 2005. Guest host Joe Palca talks with a hurricane scientist about whether there is a clear link between climate change and hurricanes and tropical cyclones.
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Are Hurricanes and Climate Change Connected?

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Are Hurricanes and Climate Change Connected?

Are Hurricanes and Climate Change Connected?

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JOE PALCA, host:

Up next, the connection between climate change and hurricanes. That's a topic that hurricane researchers have been debating in recent years. Scientists on one side say global warming is causing more frequent and stronger storms, while scientists on the other say there's no evidence that the uptake in hurricanes is anything more than the natural cycle of storm activity. Researchers gathered this week in New Orleans at a meeting of the American Meteorological Society to share new data and state their cases.

Joining us now is one of those scientists Thomas Knutson is a research meteorologist in the Geophysical Fluid Dynamics Laboratory at the National Oceanic and Atmospheric Administration in Princeton, New Jersey. He joins me by phone today from his office there.

Welcome to the program, Dr. Knutson.

Doctor THOMAS KNUTSON (Research Meteorologist, National Oceanic and Atmospheric Administration): Thank you.

PALCA: And if you'd like to join us with our discussion about hurricanes and also we'll be talking later about a new NASA satellite that's going to be measuring the Earth's carbon production, give us a call. The number is 800-989-8255. That's 800-989-TALK, and you can also check out our Web site for more details about what we're talking about.

So, Dr. Knutson, I take it that everybody is now on the same page and they all agree on something.

(Soundbite of laughter)

PALCA: About climate change, it's all finished, the shouting's over, right?

Dr. KNUTSON: Well, hardly based on the panel discussion that we had in New Orleans, there's still quite a bit of disagreement on this issue.

PALCA: Why is it such a hard issue to resolve?

Dr. KNUTSON: Well, we're - saying something about this issue depends on having long reliable records of hurricane activity. Another, they are hard to come by because our measurement techniques have changed so much over the years. And also, it's just a very, it's a very difficult problem, even from a modeling standpoint because we're trying to model the storms with climate models and these storms are - have very small-scale structure that's difficult to model. It's very expensive to model. You need very high-resolution models, so there are a lot problems that make this a very, a very difficult problem to tackle.

PALCA: Okay. Dr. Knutson, hold that thought. We have to take a quick break, but we'll come back and we'll be taking your calls at 800-989-8255. We're talking with Thomas Knutson of NOAA about whether or not there's a signal that can be detected off climate change on the strength and frequency of hurricanes. Stay with us.

(Soundbite of music)

PALCA: I'm Joe Palca and this is TALK OF THE NATION from NPR News.

(Soundbite of music)

From NPR News, this is TALK OF THE NATION: SCIENCE FRIDAY. I'm Joe Palca.

We're talking about climate change news this week and we're starting off with Dr. Thomas Knutson. He's at Princeton. Are you at the University of Princeton or does NOAA have an outpost to Princeton that I'm not aware of?

Dr. KNUTSON: No, this is not Princeton University. This is a NOAA laboratory, the Geophysical Fluid Dynamics Laboratory.

PALCA: I got it. Okay, all right. So he's with NOAA's Geophysical Fluid Dynamics Laboratory, which happens to be in Princeton - at Princeton, New Jersey.

And we're talking about some new data or some discussion that took place this week about hurricanes and whether or not you can detect a signal from a -well, from climate change. And I guess then, of course, by inference from the human activity that is affecting climate.

What's the value of resolving this debate? Is it simply a scientific question or are there practical implications of understanding whether hurricanes are getting more powerful because of climate change?

Dr. KNUTSON: Oh, there's definitely a practical implication of this because the - most of the damage caused by hurricanes is caused by very intense hurricanes, the major hurricanes.

And if the strongest hurricanes are getting stronger or do become stronger due to anthropogenic warming that could lead to larger impacts, hurricane impacts on society; more storm-surge flooding, greater levels of wind, wind damage.

Although there - aside from just being a very interesting question intellectually, it also has, I think, some important implications for society.

PALCA: Well, let's invite some of our callers to join the conversation and let's go first to Michael(ph) in Baton Rouge, Louisiana.

Michael, welcome to SCIENCE FRIDAY.

MICHAEL (Caller): Thank you. My question, you know, I live in Baton Rouge, Louisiana, and we're very, you know, prone to hurricanes here and I'm wondering, you know, with the, you know, historically, we heard about El Nino and all of these kind of weather cycle patterns that comes into play. And I'm wondering, you know, we hear about these weather cycle patterns all the time. I mean, historically, do we have any sort of conclusive evidence that this is a historical pattern that these hurricanes are progressively getting worse and then they'll tide - you know, they'll eventually get, you know, less in scale? Or is this something that can be directly attributed to global warming…

PALCA: Interesting. Well, that is the debate, Michael. But what do you think about that, Dr. Knutson?

Dr. KNUTSON: Well, first of all, we're not seeing evidence of - in the data of any increase in hurricane activity in terms of U.S. land falling activity. There is some evidence that perhaps based in wide activity has gone up in terms of numbers.

But we're trying to adjust the data sets for problems as you go back in time and after you do some adjustments, then there's much less evidence that there's been a basin-wide increase.

But one of - a paper, a very interesting study that was presented in New Orleans pointed toward increasing intensities just of the most intense hurricanes, they found that that seemed to be in their records, at least going back to 1980, that there seemed to be some increase showing up there in a number of different basins.

In fact, most of the basins - the question still is, that's a fairly short time period, so can that change be attributed to anthropogenic force in global warming and so forth?

PALCA: You know, there's been another take on this and I think there was even a paper that came out this week that suggests that if, you know, that that global warming and climate change may actually bring a reduction in the number and strength of hurricanes that will be striking the U.S. How is that possible?

Dr. KNUTSON: Yes. Well, if you look at the climate models and their projections of how the tropical climate is projected to change in the 21st century, those models on average show an increase in vertical wind shear in the tropical Atlantic.

And that is an effect, which should lead to reduced hurricane activity particularly in terms of numbers. So there is an interesting, one interesting aspect that comes out of the number of studies is the possibility that the total number of storms may go down, so we may have fewer tropical storms and fewer hurricanes.

But yet, the strongest, the frequency of the very strongest storms could still go up. I know that may sound confusing, but essentially they're saying you could have fewer storms, but the possible range of intensities becomes larger due to this, the warmer sea surfaces because this wind shear, which can disrupt development of storms is something, which sort of comes and goes with changes in weather patterns.

And during periods of low wind shear, then you may have a storm develop, which can then intensify to a greater level in a warmer climate than it could in a cooler climate.

PALCA: Do you sometimes wish when reporters like me ask you these questions that you were sitting and having this conversation 50 years from now and looking back on a 50-year data set or a 100-year data set and really be able to answer them definitively instead of this sort of difficult projection mode we seem to be in?

Dr. KNUTSON: Oh, certainly and it will be great to have much longer records to look at, much higher resolution models, but you know, if this is a difficult problem, but as scientists, we sort of have to play the hand that we're dealt. This is the information that we have to go on now and we think it's an important problem and we're pursuing it.

But because of all these difficulties of the data sets and limitations of models and so forth, we're - there really, there only limited things that we can say at this point about this issue. We cannot really give highly confident answers at this point, although we are working very hard on the problem.

PALCA: All right. We'll leave it there, Dr. Knutson. Thank you very much.

Dr. KNUTSON: You're welcome.

PALCA: Thomas Knutson is a research meteorologist at the Geophysical Fluid Dynamics Laboratory at the National Oceanic and Atmospheric Administration in Princeton, New Jersey.

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