Global warming tie to hurricanes unclear

By Michael Christie

MIAMI (Reuters) - Despite growing consensus that global warming may spawn stronger tropical cyclones, weather experts believe it is too soon to blame climate change for the unprecedented punch of back-to-back monster hurricanes.

Hurricane Felix, a top-ranked storm on forecasters' Saffir-Simpson scale of hurricane intensity, slammed into Central America on Tuesday. Hurricane Dean, also a Category 5, battered Mexico's Yucatan Peninsula on August 21.

It was the first time on record that two Atlantic hurricanes had made landfall as Category 5 storms in the same season, and only the fourth time since records began in 1851 that more than one Category 5 had formed in a year.

But climatologists, including those who believe global warming is having a dangerous impact on the ferocity of tropical cyclones, cautioned against making assumptions.

"My guess is that the high intensities of Dean and Felix had more to do with when and where they formed and tracked than with global warming per se," said Kerry Emanuel, a Massachusetts Institute of Technology professor of meteorology who has published ground-breaking research on the subject.

"But it is true that the theoretical (wind) speed limit in the tropical Atlantic is about 10 percent higher now than it was 15 years ago, and that may indeed be a contributing factor."

Weather experts said the similar paths taken by Dean and Felix was the result of a persistent high pressure weather system, usually located further northeast around Bermuda but now positioned over Florida and the Gulf of Mexico.

The high has been protecting the United States and steering the storms into parts of the Caribbean where sea surface temperatures are highest and atmospheric conditions are ideal for strengthening. Warm, deep water provides tropical cyclones with the fuel they need to grow.