Discriminating the Roles of Anthropogenic GHGs and Aerosols on Tropical Cyclone Frequency from Downscaling CMIP6 Models

Tropical cyclones (TCs) are among the most devastating natural disasters, yet projections of TC activity remain highly uncertain. To better understand the impacts of different anthropogenic forcings – specifically greenhouse gases (GHG) and aerosols – on TCs, we downscaled the single forcing experiments of 11 CMIP6 models using the Columbia HAZard Model (CHAZ) to investigate the contribution of anthropogenic forcings on tropical cyclone variations. Our analysis focused on changes in the distribution of TCs in the North Atlantic (NAT) and Western North Pacific (WNP) basins, while elucidating the corresponding changes in the environmental variables that drive them. We then used the formulation of the Genesis Potential Indices (GPI) and tropical cyclone genesis index (TCGI) as a constraint to quantify the relative contribution of each environmental variable to each forcing. Our findings indicate that TC frequency has increased in the WNP and decreased in the NAT. GHGs have increased TC risk in the WNP but reduced it in the NAT, particularly within the Gulf of Mexico. Conversely, aerosols have had the opposite effect. The most significant contributors to changes in the WNP are wind shear and humidity, while changes in the NAT are primarily driven by differences in wind shear and potential intensity