MIAMI – Studies that link global warming to an increase in hurricane ferocity might be full of hot air, according to a research paper that will be published Friday in a major scientific journal.

The paper, co-written by Chris Landsea of the National Hurricane Center, challenges earlier findings that hurricanes have grown more powerful in the last 30 years.

It says those studies failed to account for technological improvements that now produce more accurate – and often higher – estimates of a storm’s power than were available in the past.

“If you say, ‘Hey, the number of Category 4 and 5 storms has doubled since 1970,’ you have to ask where is that coming from and can we accept that as true,” said Landsea, one of the nation’s leading hurricane researchers, who now serves as science and operations officer at the hurricane center.

His answer: Probably not, because the databases used for historical studies are so skewed.

Set for publication in Friday’s edition of the journal Science, the study extends a multifaceted scientific debate that grows more heated every few months.

On one side are scientists who say they have found statistical evidence that the accumulated power of hurricanes around the world has dramatically increased in the past 30 years, largely because of global warming.

On the other side are Landsea and other scientists who say, yes, global warming is real, but its effect on hurricanes is not at all clear.

“It’s the data sets that are faulty,” Landsea said.

This branch of the debate began last August when Kerry Emanuel, a reputable climatologist at the Massachusetts Institute of Technology, analyzed historical wind-speed reports by the hurricane center and concluded that the accumulated power of hurricanes in the Atlantic, Caribbean and Gulf of Mexico more than doubled since 1970.

A particularly steep increase began in 1995, according to that study.

“The large upswing in the last decade is unprecedented and probably reflects the effect of global warming,” Emanuel wrote in his report, which was published in the journal Nature.

Several other reports have pointed in the same direction, but it is important to note that all such studies focus on the power of hurricanes.

No connection has been found between global warming and the number of hurricanes. Many scientists believe that the current period of hyperactivity is caused mostly by long-term natural cycles unrelated to global warming.

Landsea agreed that the accumulated power of Atlantic hurricanes has increased, but said that was largely because the natural cycle has produced more storms. He said the accumulated power of hurricanes has remained constant elsewhere in the world, casting doubt on global warming as a cause in the Atlantic.

He and his team also agreed that global warming might be enhancing hurricane winds, but only by 1 or 2 percent, which is nearly impossible to measure and represents a much lower rate than Emanuel suggested.

More to the point, Landsea said, scientists who do not account for vast improvements in technology since the 1970s can produce flawed studies.

One example cited by Landsea focuses on a 1970 storm that killed more than 300,000 people in Bangladesh. Using the technology available at that time and place, forecasters were unable to estimate that storm’s intensity. Now, with improved technology, that storm likely would be rated as the equivalent of a Category 4 or 5 hurricane.

“It’s not even being counted as a hurricane,” Landsea said. “If you miss that one, it shouldn’t be shocking if you’re missing a whole bunch of others that didn’t even hit land.”

In 1975, only two geostationary satellites monitored hurricanes. Now, eight more powerful satellites serve in that capacity, often prompting forecasters to produce higher wind estimates than might have been reported for a similar storm in the past.

“More satellites with improved imagery mean that you get “stronger’ hurricanes without the hurricanes changing at all,” Landsea said.

(c) 2006, The Miami Herald.

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Distributed by McClatchy-Tribune Information Services.

AP-NY-07-27-06 1721EDT

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