Tropical Precipitation Response to Anthropogenic Climate Change in Recent Decades

This study investigates tropical precipitation responses to anthropogenic climate change during 1979-2024 using ERA5 reanalysis, CMIP6 simulations, and targeted sensitivity experiments. While future projections often assume the direct effect of CO₂ forcing, “Wet Get Wetter” or “Warm Get Wetter” frameworks, their validity for explaining recent observed rainfall trends remains uncertain. Clausius-Clapeyron scaling and a moisture budget analysis indicate that dynamic processes dominate recent tropical rainfall responses. Observations reveal a northward precipitation shift with wetting in the western and north equatorial Pacific, northern Indian region, and drying south of the equator in the Pacific and in South America. These trends coincide with a La Niña-like SST pattern, strengthened Walker circulation, Southern Ocean cooling, enhanced land-sea and inter-hemispheric thermal gradients, and intensification of the Indo-Pacific warm pool. CMIP6 models largely miss the first three features, projecting El Niño–like SST trends, but capture thermal gradients and Indo-Pacific warm pool intensification. Regression analysis shows that amplifying land-sea and inter-hemispheric thermal contrasts, and Indo-Pacific warm pool intensification, reproduces very well the observed circulation and rainfall changes. However, coupled sensitivity experiments highlight land warming as an active driver of tropical hydroclimate changes, challenging ocean-centric assumptions in current climate models.