Global warming theory and complex computer climate models predict that a warming ocean will increase the intensity of hurricanes. Both of this year's hurricane to date have made landfall at Category 5 on the Safir-Simpson Scale, the first time that's ever been recorded in the Atlantic basin.

Is there a connection here? Maybe. But it's not as clear as you might think, says Chris Landsea, science and operations officer at the National Hurricane Center.

All the numerical models say we should see increased hurricane intensity as the oceans warm. But Landsea notes that the "sensitivity" of that response is not very impressive - on the order of two percent. In other words, for every one-degree increase in global ocean temperatures, we would expect to see a two-percent increase in hurricane intensity.

Since the tropical oceans are about 1 degree warmer now due to global warming, he said, that means a 160-mph hurricane - the hurricane center's estimate of Felix's top sustained winds at landfall - will instead strike land at 162 mph.

On the other hand, it seems to me, that's an average. Some storms will be more dramatically intensified by warmer oceans, some less so. It's the really bad ones that we worry most about. It's like rising temperatures. The global average is one thing, but the impact is expected to be - and already is - more dramatic in the Arctic and Antarctic. And a seemingly modest rise of a few degrees in the average temperature for Baltimore means some summer days (and some winter days) will be dramatically warmer. And the difference between 95 degrees and 105 degrees on a July afternoon can kill people.

In any case, Landsea said the "real driver" behind the busy hurricane seasons of recent years, and the more numerous Category 5 storms, is a long-term natural cycling of ocean surface temperatures and atmospheric conditions that began in 1995 and is expected to continue for another 10 to 30 years. It's a cycle that looks much like another that began in the 1920s and continued into the 1960s.

"In fact," Landsea said, "there is one year we may have had two Category 5's making landfall."

Those were Hurricane Hilda and Hurricane Janet, in 1955. Both followed the same paths Dean and Felix have this season. "Janet we know was a Category 5," he said. Hilda struck in a sparsely populated region of Central America where measurements were scarce. Hurricane hunter aircraft in those days didn't fly through storms that strong, and there were no satellites to estimate central winds. "We don't have any idea how strong it was," Landsea said. "It could have been a 3, 4 or 5."

We do know it crossed the Yucatan and reintensified in the Gulf of Mexico, becoming a borderline Cat. 3 or 4.

We also know that seasons like this one, in the middle of a multi-decadal upswing in hurricane frequency, and La Nina conditions, the season is "not only busy, but long-lasting," Landsea said. "October and November are quite active as well."