Constraining the projections of tropical extreme precipitation with radiation–precipitation relationship

Abstract Over the tropics, a robust statistical relationship between outgoing longwave radiation ( R ) and precipitation ( P ) is observed, linked to the cloud-radiative effect (CRE). To quantify this R – P relation, we define the CRE parameter, which exhibits significant disparities across global climate models (GCMs), with most overestimating it relative to the observation. Given the strong correlation between the CRE parameter and both historical and future extreme precipitation, an emergent constraint on the hydrological cycle projection is constructed. It lowers the fractional increase in the 99.9th percentile of tropical precipitation by the end of the 21st century from 29% to 24% under the high-emission warming scenario, with a 58% reduction in uncertainty. Overall, GCMs tend to underestimate the intensity of tropical extreme precipitation while overestimating its fractional increase. These findings provide valuable insights for model evaluation, improvement, and climate adaptation strategies.