Reversed and comparable climate impacts from historical anthropogenic aerosol and GHG on global-scale tropical cyclone genesis potential

Abstract

Emissions of anthropogenic aerosol and greenhouse gases (GHG) have significantly altered various aspects of the climate extremes in recent decades, yet, the observed global tropical cyclone frequency (TCF) shows no significant trend. Untangling this puzzle requires a better understanding of the precise contributions of the individual anthropogenic forcing to global TCF changes. Here, we quantify the relative contributions of anthropogenic aerosol and GHG to global TCF, represented by genesis potential index (GPI), using the single anthropogenic forcing experiments from the 14 Coupled Model Intercomparison Project phase 6 (CMIP6) models. We find that the two forcings have comparable but opposite impacts on GPIs due to their influences on the TC environment, leading to an insignificant change in GPIs in the historical period (1850–2014). Notably, the aerosol radiative forcing’s intensity is only about one-third of that of GHG, suggesting a more effective modulation of aerosol forcing on GPIs. The stable global TC frequency during the past decades could be attributable to the similar pace of the two anthropogenic emissions. The results highlight that a reliable global TC projection depends on both the aerosol and GHG emission policies.