Present-day warm pool constrains future tropical precipitation

Abstract

Future changes in tropical precipitation affect the livelihood of the world’s human population and ecosystems. Climate models project an increased rainfall intensification under anthropogenic warming, but uncertainties in the distribution and magnitude of the changes remain large. Here, we identify a strong positive relationship between the present-day Indo-Pacific warm pool size and projected precipitation changes in the central-to-eastern tropical Pacific using multi-model simulations. Models with larger present-day warm pool size project excessive future warming in the eastern tropical Pacific due to intensified ocean stratification which reduces the zonal sea surface temperature gradient of the tropical Pacific, resulting in the weakening of Walker circulation and precipitation increases in the central-to-eastern tropical Pacific. Based on this relationship, uncertainty in the projected precipitation in the central-to-eastern tropical Pacific can be reduced by approximately 25%, which demonstrates that an improved simulation of present-day Indo-Pacific warm pool size is important for reliable tropical precipitation projections.