Persistent Future North Atlantic Tropical Cyclone Risk in Two Contrasting CMIP6 Scenarios

Ratnaksha Lele, Adam H. Sobel, Chia-Ying Lee, Suzana Camargo, Patrick Kelly, Ted Amdur, Radovan Drinka

We analyze North Atlantic Tropical Cyclone (TC) activity using the Columbia HAZard (CHAZ) model to downscale 12 models from CMIP6 under the SSP1-2.6 and SSP5-8.5 scenarios --- those with the least and greatest anthropogenic forcing respectively. TC frequency increases along the Southeastern U.S. and declines along the Gulf under both SSPs. Greater TC frequency is not projected in the highest-warming scenario (SSP5-8.5) than in the lowest-warming scenario (SSP1-2.6) in the North Atlantic basin, even though it is in the global mean. These patterns remain broadly consistent over the 21st century, with stronger changes under higher-emission scenarios. The response appears driven primarily by El Niño-like shifts in the tropical Pacific mean state that influence Atlantic potential intensity and vertical wind shear. These results suggest that regional TC activity is more sensitive to the pattern of surface warming than to its global mean, and highlight the importance of the tropical Pacific in particular.