A More General Framework for Understanding Atlantic Hurricane Variability and Trends

1767 NOVEMBER 2007 AMERICAN METEOROLOGICAL SOCIETY | R ecent literature has been refocusing on the association between tropical North Atlantic Ocean sea surface temperature (SST) and Atlantic hurricane activity. Emanuel (2005) demonstrated this relationship using a power dissipation index (PDI), which depends on storm intensity and the lifetime of each storm over each hurricane season. Emanuel’s SST time series was calculated as an average over a large region (6°–18°N, 20°–60°W) of the tropical Atlantic. He found that the Atlantic SST and PDI time series are highly correlated on decadal time scales. A similar relationship was shown by Webster et al. (2005); they found that the number and percentage of the most intense storms is well correlated with large-scale tropical Atlantic SST variability on decadal time scales. The social and economic consequences of these relationships assume a heightened urgency when recent SST increases resulting from global warming are considered. Indeed, Atlantic hurricane activity appears to be increasing in concert with the marked increases in tropical Atlantic SST over the last 30–40 yr. However, while there is both substantial evidence and fairly broad agreement that the increase of tropical Atlantic SST within the secular record is largely attributable to anthropogenic forcing (e.g., Santer et al. 2006), there is presently less agreement regarding any associated increases in hurricane activity resulting from human activity (e.g., Henderson-Sellers et al. 1998; Landsea et al. 1998; Goldenberg et al. 2001; Emanuel 2005; Webster et al. 2005; Landsea 2005; Pielke et al. 2005; Trenberth 2005; Anthes et al. 2006; Elsner 2006; Elsner and Jagger 2006; Elsner et al. 2006a,c; Pielke et al. 2006; Trenberth and Shea 2006; Holland and Webster 2007). A More General Framework for Understanding Atlantic Hurricane Variability and Trends