Air Date: Week of March 1, 2002

Droughts could become more common with global warming, but scientists aren't sure what that might mean for the current drought on the East Coast. Host Steve Curwood discusses the issue with Kevin Trenberth of the National Center for Atmospheric Research.

Transcript

TRENBERTH: This is the sort of thing we expect to see more of. And so, we can't actually blame this specifically on global warming. But it's consistent with the idea of what global warming will do to us.

CURWOOD: Kevin Trenberth is a climate expert with the National Center for Atmospheric Research in Boulder, Colorado. And he's been following these extreme weather patterns, and how they relate to climate change. Kevin Trenberth says, "It's hard to pinpoint the causes of the current East Coast drought." But, he says, "Global warming could lead to more droughts in the future."

TRENBERTH: There are a couple of effects that are really important that come into play here. First, the global warming warms up the atmosphere and the atmosphere, when it's warmer, can hold more water. Secondly, some of the global warming itself, some of the heating that's occurring, goes into evaporating moisture. That increased drying creates an increased risk of drought in general. But in addition, because there's more moisture in the atmosphere, it means that all of the weather systems that occur, whether they're thunderstorms or snowstorms, and so on, they just gather up all the moisture that's around. And as a result, it's apt to rain harder at the time when it does rain. And so, greater extremes is one of the prospects, and more risk of floods, and more risk of droughts. That's the sort of thing we expect to happen with global warming.

CURWOOD: At what point do you think we could say it was global warming?

TRENBERTH: Well it's always difficult on a day-to-day basis. Because there can be weather systems from one year to the next that are related to things like El Nino. And there are influences like that that have had an influence this year. But the degree of warmth that has occurred, especially from November through to about the current time, is certainly remarkable. And we're breaking records.

CURWOOD: Now, there might be what you weather and climate folks call an El Nino developing in the Pacific at this time. What effect might that have on the East Coast drought?

TRENBERTH: Certainly a change in the weather patterns, such as from El Nino, can turn that around. Although, it depends upon what I call the "particular flavor" of El Nino. Somewhere in the United States is apt to be wetter. And on the other hand, somewhere else is apt to be very dry. What we will be doing is tracking that and seeing how it goes. And we should get a better handle on that in about the next month or so. The spring is really the critical time when a lot of the rains occur, especially in the breadbasket of the United States, and across into the East. And, if I were a farmer, I would keep track of how this developing El Nino is occurring, and what the official forecasts are.

CURWOOD: Dr. Trenberth, for those of us who may have forgotten, I should say, at this point, the El Nino is a condition where there's quite a bit of warmer water on the surface of the Pacific. How am I doing with the accuracy of my description?

TRENBERTH: Well, that's correct. El Nino refers to a warming, especially east of the date line. But it's a huge area of the globe, all the way from the date line across to the coast of South America. It tends to produce very wet conditions in Peru and Ecuador. It tends to produce very dry conditions in Australia and Indonesia. And it has quite a profound effect on the United States. But the effects on the United States depend very much on exactly what time of year you're talking about, as well.

CURWOOD: Now, in the long run, Dr. Trenberth, how do you think we can prepare for longer periods of drought? For surviving these extremes in weather that you're predicting are likely to happen with climate change?

TRENBERTH: Well, if indeed this occurs, that we get too much water at certain times, and then not enough at other times, it means that water management becomes a key issue as we go into the future. It means, on an individual farm, having a little reservoir with water so that you can save it up when there are times of plenty. But, then you can use it at times when you've got a shortfall. I think that kind of thing. But also, on a much larger basis, it applies much more generally to large reservoirs, and dams, and management of hydroelectric power, and things like that. Water management is going to be a key issue as we move into the future.

CURWOOD: Kevin Trenberth is the head of the Climate Analysis Section of the National Center for Atmospheric Research. Thanks for speaking with us.

TRENBERTH: You're most welcome.

 

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