Model projected impact of Anthropogenic warming on late 21st century intense Atlantic hurricane activity

Understanding the relative impacts of human-induced and natural climate changes on the intensity and frequency of the strongest Atlantic hurricanes is a topic of great significance. Although some recent dynamic model studies have suggested that anthropogenic climate change could produce a decrease in Atlantic tropical cyclone frequency during the 21st century, these models were unable to reproduce storms of major hurricane intensity, leaving unaddressed the crucial question of a possible global warming influence on these most destructive storms. In this paper results will be presented which show the influence of future global warming on the frequency of the strongest Atlantic hurricanes using the operational GFDL and GFDN hurricane prediction models which produces a realistic distribution of intense hurricane activity for present day conditions. Results will be presented for a late 21st century climate warming scenario which show that despite a decrease in overall numbers of tropical cyclones, the number of category 4 and 5 hurricanes will increase significantly by the end of the century for the warmer climate conditions as derived from an ensemble of 18 Coupled Model Intercomparison Project 3 (CMIP3) climate models. In further sensitivity tests, substantial increases were also simulated for conditions from three out of four individual CMIP3 models examined. The largest increase of very intense hurricane activity was simulated in the western Atlantic, north of the Main Development Region (MDR, 10o-20oN, 80o-20oW). This region corresponds fairly well with a region of increase potential intensity, reduced vertical wind shear, and increased SSTs. Results for each of the various climate realizations will be shown and compared with each other.