As the world's fifth-largest economic entity, California (CA) is vulnerable to climate changes, and in particular, the magnitude of winter (wet season) precipitation that is closely linked to regional drought severity, vegetation growth, and wildfire activities. However, future CA precipitation remains highly uncertain.
In this work, we applied the Pareto optimality concept and used novel metrics of observed teleconnection patterns to mechanistically constrain CMIP6 projected CA precipitation.
We estimated that precipitation will increase by the end of the 21st century by 0.4-1.3 mm d-1 (10% - 34%) over northern CA and by 0.1-0.5 mm d-1 (7% - 32%) over central and southern CA. Up to 71% of Earth System Model projection uncertainties were reduced mainly due to the strong and consistent causal relationships between North American west coast sea level pressures and CA precipitation in both observations and CMIP6 models. Our results indicate that teleconnection patterns are powerful mechanistic constraints that can help explain and reduce uncertainties in ESM projections.