If the past three decades are any indication, we might be seeing many more powerful hurricanes like Katrina in the years to come.

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That's according to a new study released today in the journal Science, which supports claims made after Katrina that warmer ocean temperatures are giving hurricanes more power.

"Odds are that in the next 20 years, [the intensity of hurricanes] is going to stay high, if not increase," said study co-author Judy Curry, chairwoman of Georgia Tech's School of Earth and Atmospheric Sciences. "We may be looking at more and more Katrina-like storms."

Curry, lead author Peter J. Webster and colleagues tracked the wind speeds of hurricanes around the world since 1970 using data from satellites and reconnaissance airplanes.

They found that while the total number of hurricanes has dropped over the past decade, the number of Category 4 and 5 hurricanes has doubled. They now average about 18 per year.

In the North Atlantic alone, 25 Category 4 and 5 hurricanes occurred between 1990 and 2004, compared with 15 of that strength between 1975 and 1989.

The winds of Category 4 hurricanes are between 131 and 155 mph; Category 5 storms have winds of 156 mph or higher.

Warm ocean temperatures evaporate water vapor into the atmosphere, which condenses and then heats the air, fueling a hurricane, Curry said. Even a small amount of heat makes a big difference in a hurricane's strength.

Tropical ocean surface temperatures increased by almost 1 degree Fahrenheit between 1970 and 2004.

Scientists are divided about how to stop ocean temperatures from increasing.

Some, like Brenda Ekwurzel, at the Union of Concerned Scientists, say that high levels of carbon dioxide in the atmosphere trap heat, making the oceans warmer.

While it's not just global warming that causes higher ocean temperatures, "these daily decisions that we make to drive a car that may be getting only 15 to 20 miles per gallon are really the decisions that affect our grandchildren," she said.

But even if we stop burning fossil fuels, it's hard to tell what would happen, said Curry. She thinks the data suggest the United States needs better disaster management plans and evacuation policies, rather than another debate about global warming.

The idea that global warming is contributing to warmer ocean temperatures, in turn helping hurricanes gain strength, caused controversy after Hurricane Katrina.

When the German minister for the environment said he hoped the hurricane would make the United States wise up to its misguided energy policies, he was criticized by European news media outlets.

This past August, a study published in Nature by Massachusetts Institute of Technology climatologist Kerry Emmanuel said that the strength of hurricanes in regions of the Atlantic and Pacific oceans has been increasing since the 1970s.

Emanuel was quick to point out that most people are concerned only about hurricanes that make landfall within the United States, which account for about one in 500 of the storms measured by these studies.

"The landfall of intense hurricanes is such a rare event that there's absolutely no way that you could see trends unless you waited a hundred years," he said.

He and many other climate scientists want to focus now on preventing people from building on coasts. The damage from hurricanes has gone up exponentially in the United States in the past few decades, he said.