THURSDAY, Sept. 15 (HealthDay News) — An increase in the ferocity of hurricanes around the globe over the last 35 years may be attributable to global warming, a new report states.

The study, which appears in the Sept. 16 issue of the journal Science, is perhaps one of the strongest scientific statements yet on a connection between hurricane activity and global warming.

“I’m heading towards being a little less cautious,” study lead author Peter J. Webster, professor at the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology in Atlanta, said at a news conference Wednesday. “I think [rising] sea surface temperature is a global-warming effect and I think the change in [hurricane] intensity, which is a universal thing, is following sea surface temperature.”

Webster was referring to a demonstrated increase in the sea surface temperature (SST) of about half a degree centigrade since 1970. Scientists have hypothesized that higher sea surface temperatures result in greater hurricane intensity.

Not everyone is convinced by the new findings, however.

“The question is, is [the increase in intensity] real?” said Chris Landsea, a meteorologist with the National Hurricane Center in Miami. “Are we seeing a big increase the last 15 years or is it an artifact of the data? I’m afraid it’s probably not a real change that’s going on.”

Even one of Webster’s co-authors, Greg Holland, director of the Mesoscale and Microscale Meteorology Division of the National Center for Atmospheric Research in Boulder, Colo., hedged his bets a little. “There is a reasonable chance that this is consistent with global change but one can never say for sure with this amount of data,” he said.

All of which reflects the ongoing debate in the scientific community as to whether changes in hurricane tempers are due to natural variability or to the effects of global warming.

The Science article comes as U.S. rescue efforts continue in the Gulf Coast areas devastated by Katrina, a category 5 hurricane that battered parts of Louisiana — most notably New Orleans — and Mississippi and Alabama earlier this month. The authors of the study said the fury of Katrina on its own, however, cannot specifically be pinned on global warming.

“Katrina was one of those we’ve seen increasing in intensity but we can’t say Katrina by itself was part of this factor,” Holland said. “There is a substantial amount of natural variability.”

The study authors analyzed the frequency, duration and intensity (maximum wind speed) of hurricanes over the past 35 years in the five major ocean basins. The time period 1970 to 2005 was chosen because equivalent data was available for all years.

The number and frequency of hurricanes grew until 1995, then fell after that, leaving the overall rate steady.

The largest increases in intensity occurred in the North Pacific, Indian and Southwest Pacific Oceans, while the smallest percentage increase occurred in the North Atlantic.

“In all basins including the Atlantic, category 4 and 5 hurricanes have increased enormously, almost by a factor of two,” Webster said. “It’s not too far from the imagination to be able to ascribe changes in hurricane intensity to SST [sea surface temperatures].”

Hurricanes are rated on a scale of one to five, based on the Saffir/Simpson Hurricane Scale. A category 1 storm has winds ranging from 74 to 95 mph; a category 5 hurricane has winds exceeding 155 mph.

The number of category 1 hurricanes remained about the same, the study found, while the most severe hurricanes have not become any more intense.

Landsea contested some of the data and some of the findings.

“At the start of the study, in 1970, there was no way to even estimate what the winds were of hurric