  Recent US major landfalling hurricanes Katrina and Rita and last year's four
U.S. landfalling major hurricanes have spawned an abundance of questions
concerning the role that global warming might be playing in these events. This
idea has been given added credence by the September 2005 Science paper of
Webster, Holland, Curry and Chang (Vol. 304, pp. 1844-1846) showing that the
global number of Category 4-5 hurricanes have increased in the last 15 years
(1990-2004) in comparison with the prior 15-year period of 1975-1989. They
report 171 Category 4-5 hurricanes in the earlier 15-year period vs. 269 (56%
increase) in the later 15 year period. Global mean surface temperature in the
later period has been about 0.3C higher than in the earlier period. The
authors' imply that their measured rise in global Category 4-5 hurricanes is
likely related to these higher global temperatures.
  Having been involved with hurricane research and forecasting for nearly 50
years, I feel I have an obligation to offer comments on this paper's primary
finding on the recent rise of global Category 4-5 hurricanes. I do not agree
that global Category 4-5 tropical cyclone activity has been rising, except in
the Atlantic over the past 11 years. The recent Atlantic upsurge has
explanations other than global temperature rise.
