Agriculture remains central to Ghana’s economy, providing food, employment, and income for most rural households. Yet recent intensification through mechanization and high input use has accelerated soil degradation, particularly the decline of soil organic carbon (SOC), a key indicator of soil fertility and climate regulation. This study applied the Rothamsted Carbon Model (RothC) to quantify and project SOC dynamics in Ghanaian croplands from 2001 to 2024 and to simulate trajectories to 2074 under baseline, optimistic, and pessimistic climate and vegetation productivity trends. Harmonized datasets on SOC, clay content, NDVI, and climate variables were processed at 250 m resolution in Google Earth Engine. Model outputs correlated strongly with observed SOC (r = 0.91) but yielded a negative Nash–Sutcliffe efficiency (–1.16), reflecting systematic underestimation relative to SoilGrids while remaining consistent with field measurements. National mean SOC declined from 23.79 t ha -1 in 2001 to 22.94 t ha -1 in 2024 (–3.6%), with the steepest reductions in southern high-SOC zones and slight gains in northern low-SOC areas. Across agroecological zones, losses ranged from 27–31% (p < 0.0001), primarily due to humus pool depletion, whereas inert organic matter remained stable. Lag analyses indicated immediate SOC reductions following temperature increases and delayed effects under moisture stress. Projections suggest further SOC declines of 17–35% by 2074, underscoring the need for climate-responsive and agroecologically differentiated soil carbon management strategies in Ghana. Integrating SOC monitoring into national climate and land restoration policies would enable more targeted interventions to sustain soil productivity and carbon resilience.