Different uncertainty in tropical oceanic and land precipitation sensitivities under global warming

The change in precipitation (P) under global warming has far-reaching implications for society. However, the high degree of intermodel uncertainty in future projections undermines the reliability of the multi-model mean. The present study investigates the sources of intermodel uncertainty in tropical-mean oceanic and land P sensitivities under global warming, based on an analysis of 28 models from CMIP6. Results show that the uncertainty in tropical-mean P sensitivity is greater over ocean compared to that over land, and both are closely tied to uncertainties in tropical-mean circulation sensitivity. Nevertheless, the underlying drivers of the uncertainty in tropical-mean circulation sensitivity vary between ocean and land. For the tropical-mean oceanic part, the tropical sea surface temperature (SST) warming pattern, particularly the SST warming over the western equatorial Pacific, plays a crucial role by modifying the atmospheric stability over the tropical Pacific. On the other hand, for the tropical-mean land part, the combined impacts of changes in land sea level pressure, relative humidity and SST warming over the equatorial Pacific contribute to the intermodel uncertainty in circulation sensitivity. The results highlight the importance of improving the simulation of these factors to reduce the discrepancies in tropical-mean oceanic and land circulation sensitivities among climate models, ultimately leading to a more accurate depiction of P sensitivities under global warming.

Automated summary

This study investigates the sources of intermodel uncertainty in tropical-mean oceanic and land precipitation sensitivities under global warming based on an analysis of 28 models from CMIP6. The results show that the uncertainty in tropical-mean precipitation sensitivity is greater over ocean compared to land, and both are closely tied to uncertainties in tropical-mean circulation sensitivity. However, the underlying drivers of the uncertainty vary between ocean and land.