Nor is anyone sure whether the phenomenon helps make strong storms even stronger.
But each side has evidence to bolster its case. Take Kert Davies, the research director for Greenpeace USA. He tells RFE/RL there are compelling signs that global warming is contributing to the severity of hurricanes in the Atlantic Ocean and typhoons in the western Pacific and Indian oceans.
Davies cites as one example new research by the prestigious Massachusetts Institute of Technology concluding cyclonic storms have steadily grown in size and strength since the 1970s.
"They are on average 50 to 80 percent stronger in the past 30 years. Heat is the fuel for a hurricane, and the planet is no doubt warming up. And there have been a number of studies showing that the oceans are holding that heat, acting as a battery, holding that charge, and the charge is released through hurricanes," Davies says.
Davies says he believes some of the most convincing evidence of global warming is the greater depth of warm water on the surface of oceans, seas, and major gulfs.
He says Hurricane Rita -- which slammed into the U.S. Gulf Coast on 24 September -- is a good example of how this deeper top layer of warm water makes storms stronger.
"Normally, the sea surface is warm just a couple feet down, or even 20 feet [7 meters] down. But below that, there's 50-degree [Fahrenheit -- 10-degree Celsius] water. And so, as a hurricane rolls along, it kicks up cool water, churning the water around with 30 to 40 foot [9 to 12 meter] waves in there, and it cools itself off. In the Gulf [of Mexico] this year, the warm water goes deep, that fuel [warm water] doesn't run out. It's just kicking up more fuel and more heat," Davies says.
Some scientists suggest storms are not only stronger, but more frequent. Rita was the 17th major storm of the Atlantic Ocean hurricane season -- already higher than the average of 11 tropical storms or hurricanes.
Davies says nobody was able to forecast how many hurricanes would form so far in the North Atlantic this year, or how severe they would be. He says it's time for meteorologists to acknowledge global warming -- and its apparent contribution to more violent storms -- before a busy, destructive storm season again catches them by surprise.
But Michael Crichton says the issue is not evidence, but the lack of it. Crichton, a physician, is the author of many science fiction novels, including the best-seller "Jurassic Park," which was made into a widely distributed film.
Crichton also is the author of the 2004 novel "State of Fear," in which he argues that alarmist environmentalists, using questionable science, could impose a form of what he calls ecological "totalitarianism" on the world.
Yeserday, Crichton made his case before the U.S. Senate Environment and Public Works Committee, which was seeking guidance in helping set environmental policy in the wake of Katrina and Rita.
Crichton told the committee about the rigors of medical research. He said findings cannot be legitimately published without strict "peer review," in which medical researchers must submit their findings to other medical researchers. This new group of researchers then conducts the same tests and compares its results with the original.
The protocols of climate science, Crichton said, "appear considerably more relaxed:"
"In climate science, it's permitted for raw data to be touched or modified by many hands. Gaps in temperature and proxy records are filled in. Suspect values are deleted because a scientist deems them erroneous. A researcher may elect to use parts of existing records, ignoring other parts. But the fact that the data has been modified in so many ways inevitably raises the question of whether the results of a given study are wholly or partially caused by the modifications themselves," Crichton said.
Crichton said he was not trying to disparage climate scientists' motives or fair-mindedness. Instead, he said, these researchers should take some steps to lend credibility to their findings.
"What is at issue is whether the methodology of climate science is sufficiently rigorous to yield a reliable result. At the very least, we should want the reassurance of an independent verification by another lab in which they would make their own decisions about how to handle the data and yet arrive at a similar result," Crichton said.
But the debate over global warming seems likely to continue for some time. Yesterday, a team of American climate experts suggest global warming is at least partially to blame for the steady shrinking of the Arctic Ocean ice cap.