ROBERT SIEGEL, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.
MICHELE NORRIS, host:
And I'm Michele Norris.
It's nearly hurricane season again, and today government forecasters said they are expecting a busy one. They predict seven to 10 hurricanes between June and November, and that forecast is likely to renew debate about whether global warming is to blame.
Here's NPR's Jon Hamilton.
JON HAMILTON: One factor is the temperature of the ocean - it's getting warmer. Roger Pielke Jr. of the University of Colorado at Boulder says scientists don't spend much time arguing about that.
Professor ROGER PIELKE JR. (Environmental Studies Program, University of Colorado): Yeah, there's a general agreement that around the world, sea surface temperature have increased over many decades in the 20th century.
HAMILTON: There's also growing evidence that the warming, at least in the part of the Atlantic where many hurricanes developed, is being cause by the build up of greenhouse gasses in the atmosphere.
And Pielke says it's pretty clear what that means for hurricanes heading toward the U.S.
Prof. PIELKE: Scientists are in very broad consensus that increasing sea surface temperatures, all else equal, would lead to stronger storms.
HAMILTON: They don't agree about whether that's already started to happen, or whether warmer water is also likely to increase the number of hurricanes. But scientists do agree on what people living along the coast should take away from the debate on climate change.
Dr. KEVIN E. TRENBERTH (Head, The Climate Analysis Section, National Center for Atmospheric Research): There are some real changes that are going on so look out.
HAMILTON: Kevin Trenberth is a climate scientist at the National Center for Atmospheric Research in Boulder. It's funded by federal money. Trenberth says one area of scientific agreement that doesn't get much attention involves the amount of rain coming from hurricanes and other storms. It's increasing because warmer water puts more water vapor in the air and more water vapor means more rain.
Dr. TRENBERTH: And so we are seeing that indeed when it rains init pours much more so now than it did a few years ago.
HAMILTON: So there's more flooding from rivers and storm drains. Scientists say this is likely to be compounded by more flooding from the ocean. The reason is that a hurricane causes tides to rise much higher than normal and Trenberth says there's no doubt that as the earth gets warmer even normal tides are getting higher.
Dr. TRENBERTH: We have good measurements of sea level over the global oceans now, so we've seen that there's been a rise in sea level of an inch and a half in the last, well, 13 years or so. So sea level is going up at a rate of about a foot a century at the current time.
HAMILTON: The factor that worries scientists most though doesn't have anything to do with global warming. It has to do with the dramatic increase in the number of people who live along the coast. Roger Pielke says Miami offers a good example of why this is s problem.
Prof. PIELKE: In 1926, there was a really major Category 4 or stronger hurricane to hit what is today downtown Miami. Well, in 1926, there was about 100,000 people that lived on the coast there.
HAMILTON: These days there are millions, and millions more have spread along the rest of the East Coast and the Gulf Coast. Pielke says that means there are fewer and fewer places where a hurricane can land without doing a lot of damage. And he says it also means there's likely to be more damage from any one storm.
Prof. PIELKE: The potential for loses is doubling every 10 years. So a storm like Hurricane Andrew in 1992 was about a $30 billion storm. Today, it might be $60 billion or $70 billion, 10 years from now it might be $120 billion, $140 billion.
HAMILTON: Which would make it more expensive than even Hurricane Katrina.
Jon Hamilton, NPR News.
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