UC Irvine

Abstract The Energy Exascale Earth System Model version 3 (E3SMv3) represents the latest advancement in Earth system modeling developed by the U.S. Department of Energy (DOE). Building upon previous versions, E3SMv3 introduces significant updates across its coupled components to enhance capability and improve fidelity. The atmosphere component incorporates advancements in chemistry, aerosol‐cloud interactions, convection, and microphysics. The ocean features a new time‐stepping scheme and a higher‐resolution unstructured mesh with sub‐ice‐shelf cavities, while the sea ice model integrates advanced snow and ice physics for more realistic cryospheric simulations. The land model introduces prognostic vegetation dynamics and a new sub‐grid topographic treatment of solar radiation. A new tri‐grid configuration harmonizes the horizontal grids of the land and river components for improved process coupling. It is enabled by a new non‐linear remapping between the atmosphere and land. E3SMv3 underwent extensive testing through a comprehensive simulation campaign, including pre‐industrial control, idealized experiments, and historical simulations spanning 1850–2024. The model demonstrates significant improvements in simulating the evolution of the historical surface temperature, particularly addressing the “pothole cooling” bias in earlier versions. Reduced aerosol‐related forcing contributes to more realistic radiative forcing and better alignment with the observational record. Ocean heat content (OHC) and sea ice trends are also improved as a result. Plain Language Summary The Energy Exascale Earth System Model version 3 (E3SMv3), developed by the U.S. Department of Energy, is a state‐of‐the‐science tool designed to advance our understanding of the Earth and energy systems. This model simulates interactions between the atmosphere, land, rivers, oceans, and sea ice to predict Earth system changes and their impacts. E3SMv3 includes major improvements, such as enhanced representations of atmospheric chemistry, clouds, aerosols, sea ice, and vegetation dynamics. It also introduces refined marine and land grids to improve the accuracy of how these components interact. E3SMv3 was evaluated through simulations of past and historical conditions, totaling over 5,000 years. The model successfully resolved a major issue leading to unrealistic cooling trends during the mid‐20th century. E3SMv3 now provides more accurate predictions of surface temperatures, ocean heat content, and sea ice changes, closely matching observed data. Key Points E3SMv3 introduces major updates to the atmosphere, sea ice, and land components, enhancing capability and improving fidelity E3SMv3 increases resolution in the ocean‐sea ice mesh and unifies land and river grids for tighter coupling within and between components Reduced aerosol forcing in E3SMv3 resolves mid‐20th century cooling biases, aligning historical temperature trends with observations