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PRI's Environmental News Magazine

Storm Brewing

Air Date: Week of June 9, 2006

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Hurricane forecasters agree we’re in for another busy storm season. But there's a debate about just why that is. The government's storm forecasters say it's mostly due to natural cycles in hurricane activity. A new study says it's really global warming at work. Living on Earth's Jeff Young reports.

Transcript

CURWOOD: Coming up: a lot of stormy weather, hurricane style, is predicted by many experts this year. But they can’t agree on why. Stay tuned to Living on Earth.

[MUSIC: Brian Eno “Fractal Zoom” from ‘Compounds + Elements’ (All Saints Records – 2006)]

CURWOOD: It’s Living on Earth, I’m Steve Curwood. Hurricane forecasters say we’re in for yet another busy storm season in the Atlantic. The government’s hurricane center expects between eight and ten hurricanes this year, with as many as six of them becoming major storms.

And along with these predictions come new scientific studies linking the intensity of hurricane activity to global warming. It’s a topic of fierce debate among hurricane scientists, and it’s a debate with major implications for public policy. Living on Earth’s Jeff Young reports on the emerging science, and why Washington is now listening.

YOUNG: In these anxious, early days of hurricane season, hurricane scientists are in high demand on Capitol Hill. Academics and officials from NOAA – the National Oceanic and Atmospheric Administration – are busy briefing lawmakers on yet another stormy summer. NOAA Hurricane Center Director, Max Mayfield, blames a combination of warm water, weak trade winds and areas of low pressure – hurricane-making conditions he says come around every couple of decades.

MAYFIELD: Many believe these favorable conditions, which came together around 1995, are part of a multi-decadal climate pattern, which last peaked in the 50s and 60s and could last another 10 to 20 years.

YOUNG: Charts of Atlantic storm activity show lots of hurricanes in the 50s and 60s, then quiet in the 70s and 80s. Now we’re in the midst of another busy period. Mayfield calls it a multi-decadal signal and says it’s a natural cycle in hurricanes.

And what about studies linking global warming to hurricane strength? Mayfield’s boss, Louis Uccellini, says that’s an important area of research at NOAA’s National Centers for Environmental Prediction. But Uccellini says the most important factor in hurricane activity is that natural cycle Mayfield described.

UCCELLINI: So we’re looking at this decadal oscillation as a key driver for what we’re seeing today in terms of the hurricane numbers and intensity in the Atlantic.

YOUNG: But some emerging science questions that underlying assumption of a “natural” hurricane cycle. MIT professor Kerry Emanuel just published his latest paper arguing that a rise in sea surface temperature, due to global warming, is really what’s at play. Emanuel says he even surprised himself with the findings. Not long ago he agreed with the theory of natural storm cycles.

EMANUEL: But further work on this suggests that we – collectively, massively – fooled ourselves into thinking that there is something cyclic about Atlantic variability.

YOUNG: At yet another Capitol Hill briefing, Emanuel argued that the quiet period in the 70s was due to pollution and volcanic activity blocking some sunlight, effectively countering global warming for a while. He showed a chart tracking sea surface temperatures and storm activity in the Atlantic over the years. The two lines match far more closely than anyone expected.

EMANUEL: There’s a really quite astounding correlation between the frequency of hurricanes in the Atlantic and the ocean temperature in the tropical Atlantic. The frequency, intensity and duration of the events are all going up with ocean temperature.

YOUNG: Emanuel’s findings are controversial. Hurricane center forecaster Chris Landsea challenged Emanuel at the same Hill briefing. Landsea says there are just too many gaps in the data to draw such a conclusion.

LANDSEA: Our ability to monitor hurricanes means we’re sensing these big changes and how strong they are, more than we could in the past, and this has led to artificial increases in the databases. Hurricanes are showing up stronger, but I think it’s an artifact of the data.

YOUNG: Emanuel agrees the historical data have flaws, but not enough to change his conclusion. And the implications of his conclusion are worrisome.

EMANUEL: If we’re right, and I think we probably are in this case, there’s no reason to expect a downturn again. We’ll certainly have quiet years. But I don’t think we’ll see a quiet decade again for a long time.

YOUNG: Other recent studies link climate change and the power of hurricanes around the world. A Purdue University paper found the total power produced by tropical cyclones has roughly doubled over the last 40 years, due to an increase in sea surface temperature. That reinforced earlier findings by Georgia Tech professor Peter Webster. Webster found the number of hurricanes that reached Category 4 and 5 worldwide nearly doubled since 1970.

These papers quickly became part of the global warming debate in Washington. Environmental groups are eager to use hurricanes as potent symbols for the danger of global warming. And industry-funded think tanks are just as eager to cast doubt. Climate scientist Peter Webster found himself the target of some sharp personal attacks.

WEBSTER: The sad thing now is that the debate we’re having is less than pleasant. I’m not sure why that is. I find that personally very disturbing.

YOUNG: Uccellini, at NOAA, says it’s now more important than ever for scientists to clearly communicate their findings about climate change and hurricanes and the level of uncertainty in that work.

UCCELLINI: I think the issue sort of gets magnified as to what happens after the science is done and how does that get translated into policy. The stakes are high, and that’s why I think everybody inside and outside of government dealing with these issues in a professional way have to be very careful how they proceed.

YOUNG: The study of hurricanes could be in for some stormy weather itself. For Living on Earth, I’m Jeff Young in Washington.

 

Links

NOAA hurricane predictions for 2006

Purdue University study linking global warming with rising cyclone intensity

Penn State press release on Emanuel/Mann study

Georgia Tech press release on Webster study

Emmanuel/Mann study

 

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