A common warming-dependent decline emerges from divergent projections of tropical cyclone frequency

RESUMO

How global tropical cyclone frequency will respond to climate warming remains uncertain, with projections spanning both increases and decreases. Here we drive an environment-dependent probabilistic tropical cyclone model with 14 Coupled Model Intercomparison Project Phase 6 (CMIP6) models under intermediate- and high-emissions scenarios. Initially weak global changes evolve into a clearer late-century decline, driven by a strengthening Southern Hemisphere decline and a diminishing Northern Hemisphere increase, and stronger under higher emissions. Counterfactual decomposition shows that this stronger decline is not explained by individual environmental predictors, whose contributions largely offset, but by negative nonlinear interactions among absolute vorticity, vertical wind shear, relative humidity and potential intensity. Across 28 model-scenario projections the frequency trend scales linearly with global warming; conditioning on 2 degrees C narrows the 95% confidence interval from [-20.6%, +9.9%] to [-8.2%, -2.1%]. These results reconcile divergent projections through a common warming-dependent decline.