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Study Links Extreme Weather And Climate Change

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Study Links Extreme Weather And Climate Change

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Study Links Extreme Weather And Climate Change

Study Links Extreme Weather And Climate Change

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In 2000, England and Wales experienced the wettest autumn since record keeping began in 1766. An Oxford University study says the likely cause was human-driven climate change — the first time scientists have linked climate change to an extreme weather event.

NEAL CONAN, host:

In October and November of 2000, England and Wales experienced the wettest autumn since they started to keep records back in 1766. Some blame the deluge on the effects of global warming, but there was no proof. Today, scientists from Oxford University published a study in the journal, Nature, that claims to explain the link between climate change and a specific extreme weather event for the first time.

If you have questions about links between climate change and specific weather events, give us a call: 800-989-8255. Email us: talk@npr.org. You can also join the conversation on our website. That's at npr.org, click on TALK OF THE NATION.

NPR science correspondent Richard Harris joins us here in Studio 3A. You may have heard his story about this last night. Richard, always nice to have you with us today.

RICHARD HARRIS: Nice to be here, Neal.

CONAN: And how do you establish a link between climate change and a very wet couple of months a decade ago?

HARRIS: Well, it - the answer is, not easily. And they don't claim that they've done it with 100 percent certainty, but basically, what they've said was they basically are pretty confident that there's - the weather was much worse than it would have been otherwise. And here's how they went about doing that. They -of course, a lot of climate research is based on computer simulations of the environment. And they ran thousands and thousands of simulations on, actually, people's computers, personal computers scattered all over the world, who volunteered to be part of a distributed computing experiment, essentially, where basically if you aren't using your computer, you can say, somebody else can use it over the network and crunch some numbers for me.

CONAN: Some people do this for the search for extraterrestrial intelligence and - at this stage.

HARRIS: Weather, exactly. So, yes, that's - so - and so thousands of these computers were put into action. Some of them were calculating what, you know -how likely this would have been under the current climate, as we know it. And other - were essentially saying, what if there had been no human component of global warming? What if the planet had not had a bunch of extra carbon dioxide in the atmosphere, which we know it does have as a result of the Industrial Revolution, burning fossil fuels, and how likely would this have been under that scenario? And the answer was, quite strongly, that this would be highly unlikely under that scenario. And it came up pretty often under the scenario, the real world as we see it today.

So these guys said, it's not absolute proof, but basically, it's about as good as we're going to get for the time being and sort of attributing a specific set of incidents - these floods and this prolonged period of excessive rain - to human activity.

CONAN: Why is it so difficult to prove? Everybody says, we see so many more extreme storms that we seemed to see before. Clearly there's a link.

HARRIS: Well, this gets into the fact that, of course, the weather system and climate is inherently chaotic. And you remember the butterfly effect, where a butterfly flaps its wings and creates some little stirring of air currents that can get multiplied over, you know, over periods of weeks or months or so on and create a typhoon half a continent away - or a continent away. I mean, these are sort of fanciful ways of thinking about the climate.

But, in fact, little perturbations can blow up like that and create things. It makes it very, very hard to go back to the - and say this was caused by this because - any particular incident was caused by any particular thing. So that makes it really hard to do. What you can, with more confidence, say is that, basically, extreme events like this are more common. And there's actually another study that actually says, yes, extreme downpours, certainly in the Northern Hemisphere, have become more common, or they've become more extreme since the '50s and '60s.

There's - but basically, you're sort of left saying, we know that carbon dioxide goes into the air. More water vapor goes into the air. When the air is warmer, it can hold more water. And so when there's a downpour, more of that water comes out of the air. And that's a - that's pretty basic physics, to start with. And so you have some confidence that the basic principles are quite understandable and they make sense. But actually pinpointing it on one specific event is always just problematic.

CONAN: How do you define extreme weather as opposed to, well, I mean, every year we get some hurricanes, for example?

HARRIS: That's right. And, in fact, there's always been bad weather, and there always will be bad weather. And that's - you point out very nicely another part of the problem here, which is that you're going to get some bad weather anyway. The question is, people sort of tear it apart by looking at the worst of the worst, and they say how many category five hurricanes are there?

For example, the you know, big, big, big hurricanes. Or how many really severe downpours, like these downpours that were unprecedented in centuries of climate data gathered in England and Wales?

So if you look at the extreme of the extreme, you actually get a much better picture in some ways of longtime - long period time changes. The trick is, of course, the more extremes you look at, the more rare the events are. And then you're dealing with a smaller sample, so then all of a sudden it's like (unintelligible) then all of a sudden you run into problems about, well, maybe it's just due to bad luck again. So...

CONAN: And there seem to be cycles of these things, a pattern of four or five years where you get a whole bunch of really bad hurricanes, another pattern of another four of five years - not so bad.

HARRIS: That's true also. So yup, it's - there's no doubt that there's natural variability in the system, and so you're really looking for a signal for some evidence of something above and beyond that natural variability. Tricky, tricky problem.

CONAN: We're talking with NPR's science correspondent Richard Harris about the extreme weather and its link, maybe, probably - it depends on who you listen to - to global climate change.

800-989-8255. Email us: TALK OF THE NATION - email us: talk@npr.org. Let's see if we can get Chris on the line. Chris with us from Littleton in Colorado.

CHRIS (Caller): Hi. I've been hearing about cold weather funnel(ph) clouds, pretty much tornadoes that happen in winter. And I was wondering why these are caused, especially in places that don't usually get tornadoes, like Idaho, Arkansas, places that don't get tornadoes in tornado season, but they're happening in January, February, March. I can take my question off the air.

CONAN: All right, Chris. I have to say that the first thing I learned is you can always get a tornado anywhere. But...

HARRIS: Yeah. And I can't answer this question more specifically than to say tornadoes happen when the atmosphere has got a lot of spin in it, and that can happen for quite a number of reasons. To my knowledge, there has not been any linkage between increase in tornadoes and global warming. That's been one area that is - there's always been spin in the atmosphere.

So that's an area where the - I think the linkage is less clear. But these specific studies are looking at precipitation, extreme precipitation events, really heavy downpours and hail and snow and so on.

CONAN: One thing I think a lot of people would be interested in is anybody researching whether one of those extreme weather events that might have been caused by human activity that increased global climate change, whether that was Hurricane Katrina.

HARRIS: That's true, and many, many people said Hurricane Katrina is - I mean, people sort of take one step back and they say, this is the kind of weather we would expect to see when - as a result of increasing changes to our climate. But again, pinpointing it specifically to Katrina, some people have done that rhetorically. They have not really done that very cleanly scientifically.

But there are - again, you can go back and say part of the power of a hurricane is how warm the sea surface temperatures are and the sea surface was quite warm, which is why Katrina was such a big storm. So you can make some logical steps, but you can't necessarily connect all those dots and said sea would not have been that warm without global warming particularly.

So that's tricky. But - and of course the other thing about hurricanes is it also depends where it hits. If that hurricane had hit somewhere else on the shore, it would have, you know, gone on to our long list of hurricanes that, you know, that we dodged. So Hurricanes aren't just a weather phenomenon. They're also weather versus human structures.

CONAN: Here's an email question from Kim in San Francisco: Can the recent record snowstorms be accurately characterized as the result of record moisture rather than record cold?

HARRIS: That's a little tricky. I think that there - people have been trying to untangle exactly what caused the record snowstorms on the Eastern Seaboard. I think one trouble you get into with snow is that a lot of snow is - you can have like a foot of snow and it doesn't really mean it's that much moisture in it. So...

CONAN: It depends on the character of the snow.

HARRIS: Absolutely does. So a lot of - so it's something I always struggle with, sort of trying to parse out, you know, how much is actually - you know, if you put that into a rain gauge, it turns out not to be that much precipitation.

CONAN: The rule of thumb I always thought was an inch of rain equals a foot of snow.

HARRIS: That sounds about right. It obviously depends on what the snow is, but yeah.

CONAN: All right. Kim's, by the way, other part of her email: I know science denialists believe that snow disproves global warming. If the recent snowpocalypse did not have this unusually low temperature, but instead resulted from unusually high moisture levels, this might help weaken some of the denial out there.

HARRIS: Yeah. Well, what we're seeing of course is many, many changes in the atmosphere. We're seeing cold air coming down in some places like that. You're getting - you know, you're getting strange things happen in the Arctic that then end up affecting us down here, the changing in the direction of the jet stream, moisture coming up the Eastern Seaboard.

It all adds together in a very chaotic way, which, again, makes it hard to -it's ridiculous to say, you know, a heavy snowfall disproves global warming. But it's also hard to say that that's a cause of global warming either.

CONAN: Yet this study, is this gonna be the slam dunk, the smoking gun, where those who say, yes, we can clearly see that extreme weather is the result of human activity which has caused more climate change, can say, look, here it is, here's your proof?

HARRIS: Unfortunately, no. I mean, this is the - because I think that there's still enough questions about - you can never get perfect on a study like this. And so they've gone further than other studies have gone. But they can't just stand up and say, see, global warming caused this extreme wetness. They can say it was a heck of a lot more likely to occur in the kind of climate conditions we've seen. But they can't absolutely put the nail in it and say proof positive, case closed.

CONAN: Let's see if we get another caller in. Let's go to Bob, Bob with us from Cleveland.

BOB (Caller): Yes. I had heard that because of the melting Arctic ice, you know, because of global warming, that the North Atlantic was being cooled to the point where the Gulf Stream, which brings all the heat up from the Tropics, was about half its previous strength And if that's true, you know, that seemingly would have led to the big freeze that happened in Europe this year. Hear anything about it?

CONAN: Very cold years in Europe this year and last year as well.

HARRIS: Yeah, there is...

BOB: And last year.

HARRIS: Yeah, there is a general concern about that. Because one of the possible effects of climate change and one reason that it's not very precise always to say global warming, is that you can, in fact, slow down the conveyor belt of cold water going that helps basically - actually, it's warm water that moves north, cold water that moves under the surface and helps keep Europe actually warmer than it should be. Europe is actually a pretty high latitude compared to where we are. And it's warmed because of this warm water that comes off the Atlantic.

So one of the concerns - and there's not much evidence that this is happening -but there's concern that it could in the centuries to come, is that if you disrupt the way that that ocean water overturns, you actually could actually end up cooling off Europe. And cooling is not good if you're trying to grow crops and things like that. So that's a big concern. A theoretical concern, it seemed more likely a couple of - a couple years ago, but people are saying, you know, it's not high on our list of worries but it's possible. And we need to keep an eye on effects like that.

CONAN: Bob, thanks very much for the call.

BOB: So you're saying there's no evidence of that happening right now?

HARRIS: In terms of the ocean temperature, I think that's correct.

BOB: Hmm.

CONAN: Thanks, Bob.

BOB: Okay.

CONAN: We're talking with NPR science correspondent Richard Harris. You're listening to TALK OF THE NATION from NPR News.

And this email from Peter in Franconia, Minnesota, where he notes it has been as cold as Hades this past winter: Weathermen have difficulty predicting the weather 24 hours in advance. Consequently I doubt the validity of these cause-and-effect theories regarding climate change. There are loads of terrible issues caused by our dependence on fossil fuels, including war, pollution, traffic jams, et cetera. I don't see the need to connect the dots between complex long-term theoretical problems.

HARRIS: Well, I think that many people have decided that we shouldn't just argue about climate change, you know, about all of our energy issues as a climate issue. That's - I think that is a point of view that I think many people have embraced. It is - a lot of the other things that the caller - the writer talks about. And I think that's a very fair point.

I think that in terms of predicting the weather, I think - actually, we don't do so terribly. I mean, yeah, you can't - they miss - they do miss on a day-to-day basis. But we're not looking at tiny changes like that when they're looking at global climate models; they're looking at broad patterns of how things change. And when you look at weather people, they actually doing a reasonably good job of predicting what the next season is gonna be like. Is it going to be an unusually wet - or a big drought coming up, stuff like that. They actually do reasonably well looking out. So don't be fooled by the weather forecaster being wrong one day about what's going to happen the next...

CONAN: Where the rain snowline is, for example. Let's see if we can - let's get Steven on the line, Steven with us from Jacksonville.

STEVEN (Caller): Yeah. Hi, Chris. Last year's Farmer's Almanac, I believe it was, or possibly the year before, had a nice article talking about solar activity and its effect on the Earth, that more solar activity theoretically hits the Earth and makes it warmer. But they're saying that the trend is going down, that we're in a down cycle, and theoretically that the Earth should be cooling down as opposed to warming up. So maybe all of this pollution is saving us from feeling that effect. What do you think?

HARRIS: Well, if you're talking about the 11-year solar cycle, it's true that we are - we just came out of the minimum of the solar cycle around a year or two ago, where basically there was very little solar activity, sunspots, which are sort of an index of how much more stuff the sun - how much more energy comes off of the sun. The variations are measurable but tiny in relation to the other kinds of effects that we see with our climate. So we are now beginning to climb out of this 11-year solar cycle and get back into a period of increasing solar activity. And that will be true over the next 11 years. And then we'll be going - then it'll be, you know, down again. So that's a very short term. The 11-year cycle is a very short term effect and it's not going to affect us in the long run. There is also a longer-term effect of solar output. But again, when you - those have been included in the projections of climate change and they're so small that basically everything else swamps them out.

CONAN: Some spectacular solar flares over the past couple of days, but I'm not sure that affects the weather too much. Let's go to the email from Mary in Jamestown, Rhode Island: Why have we not heard anything about the effects of recent volcanoes around the world? Scientists still examining the effects of Krakatoa from the 1870s. Haven't the recent ones seen the same effect? I remember Pinatubo causing some global cooling.

HARRIS: Absolutely, and the Icelandic volcano this past year probably...

CONAN: I'm glad you're not trying to (unintelligible)...

(Soundbite of laughter)

HARRIS: I would never dare. But the main difference is where the volcano injects its ash and particles. And the big volcanoes that actually affect the Earth's climate have so much oomph, they actually put these particles up into the stratosphere and they - they're carried around the Earth, high up in the atmosphere, and particularly the sulfur particles can definitely cool the Earth. But the Icelandic volcanoes, other volcanoes that have been erupting, don't have that much oomph. The particles don't go into the stratosphere so they come out of the air pretty quickly, so they don't affect our climate - at least yeah, they might affect, you know, temperatures for a little while but they definitely don't affect the climate. They don't stick around long enough.

CONAN: Close airports in England when the wind's blowing in that direction, as it usually does, but not necessarily cool that climate down, and that's not necessarily responsible for what's happening, that very cold winter they're having in England this year.

HARRIS: Yeah.

CONAN: All right. Richard Harris, thank you very much.

HARRIS: My pleasure.

CONAN: NPR's science correspondent Richard Harris with us here in Studio 3A. Tomorrow it's SCIENCE FRIDAY. Ira Flatow will be here. We'll see you again on Monday. Have a good weekend, everybody.

It's the TALK OF THE NATION from NPR News. I'm Neal Conan in Washington.

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