Anthropogenic warming projected to drive a decline in global tropical cyclone frequency in CMIP6 simulations

Changes in tropical cyclone (TC) frequency in a warming climate remain highly uncertain, with model simulations often yielding conflicting results. Here, through an analysis of 26 CMIP6 models under the SSP5-8.5 scenario, we project a decline in global TC frequency of 2–10% by the late 21st century. This decline is driven by an El Niño-like warming pattern, marked by amplified warming in the equatorial central-eastern Pacific, equatorial Atlantic, and North Indian Ocean. These non-uniform sea surface temperature (SST) trends weaken zonal SST gradients, suppressing the Walker circulation, and inducing Gill-type atmospheric responses to localized heating, in addition to an equatorward shift in the Intertropical Convergence Zone. These changes reduce upward motion across most basins, suppressing TC genesis. Additionally, radiative forcing reduces interhemispheric temperature contrasts, dampening the cross-equatorial Hadley circulation and further decreasing TC frequency, most notably in the South Indian Ocean. Our findings highlight the critical role of spatially heterogeneous SST warming in modulating TC activity and stress the need to reduce uncertainties in future SST projections. These insights advance the physical understanding of climate-driven TC projections and provide essential guidance for adaptation planning in vulnerable regions.