摘要：Intensification of El Nio-Southern Oscillation (ENSO)-rainfall variability in response to global warming is a robust feature across Coupled Model Intercomparison Project (CMIP) iterations, regardless of a lack of robust projected changes in ENSO-sea-surface temperature (SST) variability. Previous studies attributed this intensification to an increase in mean SST and moisture convergence over the central-to-eastern Pacific, without explicitly considering underlying nonlinear SST-rainfall relationship changes. Here, by analyzing changes of the tropical SST-rainfall relationship of CMIP6 models, we present a mechanism linking the mean SST rise to amplifying ENSO-rainfall variability. We show that the slope of the SST-rainfall function over Nio3 region becomes steeper in a warmer climate, ~42.1% increase in 2050-2099 relative to 1950-1999, due to the increase in Clausius-Clapeyron-driven moisture sensitivity, ~16.2%, and dynamic contributions, ~25.9%. A theoretical reconstruction of ENSO-rainfall variability further supports this mechanism. Our results imply ENSO's hydrological impacts increase nonlinearly in response to global warming. Tropical rainfall variability associated with El Nino-Southern Oscillation increases nonlinearly with rising sea-surface temperatures in a warming climate, through increased moisture sensitivity as well as dynamic contributions, suggest analyses of the CMIP6 climate model simulations.
