Global Tropical Cyclones and Climate: Current Signal and Future Change

We investigate the adjustments of tropical cyclone frequency for both current and future climate using a combination of statistical downscaling and high-resolution climate simulations. The basis of the statistical downscaling is a new Cyclone Genesis Index (CGI, Bruyere et al submitted), an evolution from the GPI developed by Emanuel and Nolan. The dynamical simulations are provided by the Nested Regional Climate Model for high-resolution, and a range of GCMs together with NCEP/NCAR and ERA reanalyses for the statistical downscaling. Applying this process to the North Atlantic has demonstrated a role for both climate variability and change in current climate and future predictions. While there is uncertainty on the precise role of each, it is likely that climate change has the major role in the recent increase in frequency. Climate change is the dominant factor in future predictions, where we find consistent increases in annual frequency with a superimposed natural variability. The process is now being applied to all cyclone basins and the differing responses across these basins will be presented.