We quantify the projected change in land carbon store (CLCS) for different socioeconomic scenarios (SSPs). Using factorial simulations of a land surface model, we estimate the CLCS uncertainties associated with land use change (LUC) and nitrogen (N) deposition trajectories. Our study highlights the need for delivering additional LUC and N deposition trajectories from integrated assessment models for each SSP in order to accurately assess their impacts on the carbon cycle and climate.