Global Warming and Atlantic Hurricane Intensity
Vecchi, G.A., Swanson, K.L. and Soden, B.J. 2008. Whither hurricane activity? Science 322: 687-689.
Based on pertinent data obtained between 1946 and 2007, Vecchi et al. plotted Atlantic hurricane power dissipation index (PDI) anomalies calculated from both the absolute SST values of the Atlantic Basin and the relative SST values derived from all tropical ocean basins as a function time, extending them throughout most of the current century based on projections of the two parameters obtained from 24 different climate models; and comparing the results they obtained between1946 and 2007 with the measured PDI anomalies.
"Between 1946 and 2007," in the words of the three researchers, the relative SST "is as well correlated with Atlantic hurricane activity as the absolute SST." However, they report that the "relative SST does not experience a substantial trend in 21st-century projections," and, therefore, they say that "a future where relative SST controls Atlantic hurricane activity is a future similar to the recent past, with periods of higher and lower hurricane activity relative to present-day conditions due to natural climate variability, but with little long-term trend."
This result, as Vecchi et al. describe it, "suggests that we are presently at an impasse," and that "many years of data will be required to reject one hypothesis in favor of the other," as the projections derived from the absolute and relative SST parameters "do not diverge completely until the mid-2020s." Consequently, if the absolute SST ultimately proves to be the proper forcing factor, the scare stories of Al Gore and James Hansen relative to this topic would have some validity. But if the relative SST proves to be the controlling factor, the researchers say that "an attribution of the recent increase in hurricane activity to human activities is not appropriate, because the recent changes in relative SST in the Atlantic are not yet distinct from natural climate variability."