The DOE E3SM Model Version 2: Overview of the Physical Model and Initial Model Evaluation

This work documents version two of the Department Energy's Energy Exascale Earth System Model (E3SM). E3SMv2 is a significant evolution from its predecessor E3SMv1, resulting in model that nearly twice as fast and with simulated climate improved many metrics. We describe physical lower horizontal resolution configuration consisting 110 km atmosphere, 165 land, 0.5° river routing model, an ocean sea ice mesh spacing varying between 60 mid-latitudes 30 at equator poles. The performance evaluated Coupled Intercomparison Project Phase 6 Diagnosis, Evaluation, Characterization Klima simulations augmented historical well to evaluate impacts different forcing agents. has realistic features system, notable improvements clouds precipitation compared E3SMv1. E3SMv1 suffered excessively high equilibrium sensitivity (ECS) 5.3 K. In E3SMv2, ECS reduced 4.0 K which now within plausible range based on recent World Climate Research Program assessment. However, number important biases remain including weak Atlantic Meridional Overturning Circulation, deficiencies characteristics spectral distribution tropical atmospheric variability, underestimation observed warming second half period. An analysis single-forcing indicates correcting temperature bias would require substantial reduction magnitude aerosol-related forcing.