E3SMv1 is the first version of DOE’s Energy Exascale Earth System Model. E3SMv1 started from CESM1 but has since undergone significant changes. E3SMv1 includes new ocean and sea ice components based on the Model for Prediction Across Scales (MPAS) framework as well as a new river model, the Model for Scale Adaptive River Transport (MOSART). In the atmosphere, the spectral-element (SE) dynamical core replaces the finite volume option and most of the physics has been enhanced or replaced. The atmosphere vertical resolution was also more than doubled (30 to 72 levels). CMIP6 simulations were run at the standard resolution of 100km atmosphere and 60-30 km ocean.

We present an overview of E3SMv1 performance at the standard resolution. Progress towards reducing systematic climate model biases (such as improved clouds and precipitation) has been made, but significant challenges remain. E3SMv1 is a high sensitivity model with a strong aerosol-cloud forcing. While E3SMv1 reproduces the amount of warming observed over the 20th Century, the temporal evolution of that warming is unrealistic. We present evidence to suggest that both sensitivity and aerosol forcing are at fault.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. It is supported by the Energy Exascale Earth System Model (E3SM) project, funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. IM Release LLNL-ABS-754811.