Global warming is not the cause of increased hurricane activity, researchers said, but many more busy -- and costly -- seasons are ahead.

We're in a busy period of hurricane activity that will inflict unimaginable damage, but global warming is not the cause, leading researchers told the nation's foremost forecasters and other experts Friday.

Chris Landsea, a respected researcher and the National Hurricane Center's science officer, told those at the National Hurricane Conference that there is no conclusive evidence that global warming has significantly enhanced or otherwise affected the number or intensity of hurricanes.

''Any trend we see due to global warming has very little impact, has caused very tiny changes, and might actually be slightly reducing the activity we see in the Atlantic,'' Landsea told the group, which numbered 2,100 earlier in the week, although some left before the global warming session began.

But overall, hurricane seasons will remain relatively active and they will become increasingly costly, researchers said.

Insurance experts warned Friday that the nation soon will absorb a hurricane that causes more than $100 billion in damage, and Landsea has estimated that a Category 5 hurricane could produce at least $140 billion in damage to South Florida.

But that, he and others said, has virtually nothing to do with global warming.


Landsea noted that former Vice President Al Gore's award-winning An Inconvenient Truth, which has galvanized attention to global warming, is promoted by a book cover and movie poster that show a hurricane emerging from a smokestack -- and spinning in the wrong direction, at least for residents of the Northern Hemisphere.

''So you might conclude that the hurricane science depicted in Mr. Gore's book just might have some inaccuracies,'' Landsea said.

William Gray of Colorado State University, another leading hurricane researcher, called any link between global warming and hurricanes ''an absolutely phony thing.''

The issue has divided much of the hurricane research community, with one group of scientists reporting strong relationships between global warming and recent storm activity.

That contingent asserts that hurricanes have been forming twice as often as they did a century ago and are growing stronger, mostly because of global warming caused, at least partially, by humans.

''When you look at the numbers and the strong relationship to sea surface temperatures and the reality of global warming, you end up with a causal link that can't be denied,'' Greg Holland, a scientist at the National Center for Atmospheric Research in Boulder, Colo., said last year.


Another group -- largely led by Landsea -- refutes those assertions, saying they are based on faulty data. Like Census takers who work only one side of the street, these critics say, Holland and his colleagues simply missed many storms of the past.

Many far-from-land storms escaped detection before hurricane hunter flights began in the 1940s and satellite observations began in the 1970s, this contingent says, so historical comparisons cannot be trusted.

''Our ability to monitor the Atlantic was much more limited than it is now,'' Thomas Knutson, a research meteorologist at a National Oceanic and Atmospheric Administration laboratory in Princeton, N.J., told the group Friday.

The dispute has become so noteworthy and occasionally toxic that some are making fun of it.

Earlier this week, Jeff Masters, a former federal hurricane researcher who now serves as chief meteorologist of the Weather Underground, published a blog item that began:

''A stunning new breakthrough in hurricane research has conclusively settled the matter: global warming is making Atlantic hurricanes and tropical storms more frequent.''

He said the research was accepted for publication ''later this millennium in The Journal of Irreproducible Results.'' Masters' lengthy satire was published Tuesday -- April Fools' Day.

On Friday, Landsea said he was omitting from his presentation ''all the four-letter words for those with sensitive ears and eyes.''

It is important to note, however, that almost everyone involved in this debate agrees that the planet's seas and atmosphere have been warming.


''What we are seeing is consistent with what the global warming models are predicting,'' Knutson said.

In fact, a study published Friday concludes that climate models showing a warming trend of up to seven degrees during the next 100 years seem to be accurate. The research by University of Utah scientists appears in the Bulletin of the American Meteorological Society.

Virtually all experts also agree that we are in the middle of an active hurricane period, even as more people flock to the coast.

The argument among hurricane researchers focuses narrowly on the effect, if any, global warming has had and will have on hurricane development and intensity.

''Global warming is real and hurricanes are a heat engine,'' Landsea said. ''The question is how much is global warming going to influence hurricanes?''

The answer, Landsea and other skeptics say, is not much. They attribute the upswing in hurricane activity during the past 13 years primarily to natural cycles that tend to ebb and flow over the decades.

Those cycles reach back long before a warming atmosphere became an issue, will continue in the future, and have left us in the middle of a natural upswing in activity, Landsea said.

''We're liable to see some very busy years in coming decades, not due to global warming but due to natural oscillations,'' he said. ''And the populations near the coast are still going to be a big issue.''