From an article on a new study:
Global warming could reduce how many hurricanes hit the United States, according to a new federal study that clashes with other research. The new study is the latest in a contentious scientific debate over how man-made global warming may affect the intensity and number of hurricanes.
In it, researchers link warming waters, especially in the Indian and Pacific oceans, to increased vertical wind shear in the Atlantic Ocean near the United States. Wind shear - a change in wind speed or direction - makes it hard for hurricanes to form, strengthen and stay alive.
So that means "global warming may decrease the likelihood of hurricanes making landfall in the United States," according to researchers at the National Oceanic and Atmospheric Administration's Miami Lab and the University of Miami.
The piece goes on to nicely outline the debate about the effects of warming on hurricane frequency:
One group of climate scientists has linked increases in the strongest hurricanes - just those with winds greater than 130 mph - in the past 35 years to global warming. The Intergovernmental Panel on Climate Change has said "more likely than not," manmade global warming has already increased the frequency of the most intense storms.
But hurricane researchers, especially scientists at NOAA's Miami Lab, have argued that the long-term data for all hurricanes show no such trend. . . . The Miami faction points to a statement by an international workshop on tropical cyclones that says "no firm conclusion can be made on this point."