How Credibly Do CMIP6 Simulations Capture Historical Mean and Extreme Precipitation Changes?

Future precipitation changes are typically estimated from climate model simulations, while the credibility of such projections needs to be assessed by their ability to capture observed precipitation changes. Here we evaluate how skillfully historical climate simulations contributing to the Coupled Model Intercomparison Project Phase 6 (CMIP6) capture observed changes in mean and extreme precipitation. We find that CMIP6 historical simulations skillfully represent observed precipitation changes over large parts of Europe, Asia, northeastern North America, parts of South America and western Australia, whereas a lack of skill is apparent in western North America and parts of Africa. In particular in regions with moderate skill the availability of very large ensembles can be beneficial to improve the simulation accuracy. CMIP6 simulations are regionally skillful where they capture observed (positive or negative) trends, whereas a lack of skill is found in regions characterized by negative observed precipitation trends where CMIP6 simulates increases.

Automated summary

In this study, the accuracy of historical climate simulations contributing to CMIP6 in capturing observed changes in mean and extreme precipitation is evaluated. The CMIP6 simulations skillfully represent observed precipitation changes in large parts of Europe, Asia, northeastern North America, parts of South America, and western Australia, but show a lack of skill in western North America and parts of Africa. Large ensembles can be beneficial to improve simulation accuracy in regions with moderate skill. CMIP6 simulations are regionally skillful in capturing observed trends, but lack skill in regions with negative observed precipitation trends where increases are simulated.