Recently, CMIP7 proposed conducting emission-driven simulations to address carbon cycle uncertainty and enhance policy-relevant climate projections. Unlike previous phases focused on GHG concentrations, emission-driven simulations aim to capture the full carbon cycle, including both human and natural processes and are relevant to mitigation policies based on emissions and land use strategies. This approach accurately represents carbon removal and sequestration impacts, provides real-time information on emissions reductions and near-term climate impacts, and supports comprehensive climate modeling while integrating advanced techniques like machine learning.

As part of the E3SM BGCv2 simulation campaign, we developed a land-atmosphere-interaction-focused configuration within the E3SM biogeochemistry (BGC) model. This new configuration prescribes anthropogenic GHG emissions and incorporates prognostic CO₂, accounting for its radiative properties in the atmosphere as well as active land BGC and the simulation of land-atmosphere CO₂ fluxes. By using prescribed oceanic CO₂ fluxes and sea surface temperature (SST), we substantially reduce computational requirements, making this configuration a valuable testbed for exploring interactions between land BGC and atmospheric processes.

Our set of simulations spanning spin-up, historical, and future scenarios will provide insights into present-day climate forcing to date and impacts from SSP370 scenario. Here we provide a detailed description of the new BGC land-atmosphere-interaction-focused configuration and evaluate the coupled BGC transient historical run using E3SM_Diags, ILAMB, and GDESS diagnostic packages. The coupled simulation exhibits performance comparable to E3SMv2 AMIP for atmospheric components and land offline transient historical simulations. Comparison with observed  CO₂ data demonstrates similar trends and seasonal cycles. These indicate successful coupling. This success lays a strong foundation for Human-Earth-System coupling, fully emission-driven coupled simulations, and other activities in E3SM phase 3.