Reference:Webster et al. 2005
From Global Warming ArtWebster, P. J., G. J. Holland, J. A. Curry, and H.-R. Chang (2005). "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment". Science 309 (5742): 1844-1846. DOI:10.1126/science.1116448.
"We examined the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years, in an environment of increasing sea surface temperature. A large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5. The largest increase occurred in the North Pacific, Indian, and Southwest Pacific Oceans, and the smallest percentage increase occurred in the North Atlantic Ocean. These increases have taken place while the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade."
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