ENSO amplitude changes due to greenhouse warming in CMIP5: Role of mean tropical precipitation in the twentieth century

This study examines the relationship between the intermodel diversities of the present climate climatology and those of El Nino-Southern Oscillation (ENSO) amplitude change under global warming in the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. The models with increased ENSO amplitude under greenhouse warming (i.e., ENSO-amplified models) tend to simulate a twentieth century stronger climatological Intertropical Convergence Zone and South Pacific Convergence Zone over the central-eastern Pacific that are located farther away from the equator during boreal spring. Moisture budget analysis indicates that those climatological differences lead to stronger positive climatological precipitation change over the off-equatorial central-eastern Pacific under greenhouse warming. The stronger positive climatological precipitation change enhances the air-sea coupling strength over the central-eastern Pacific, which leads to increase the ENSO amplitude.