A comprehensive source apportionment of global CO2 using GEOS-Chem

Since the Industrial Revolution, rapid industrialization and fossil fuel consumption have driven a sustained increase in global CO 2 emissions, fundamentally altering Earth’s climate system and exacerbating the impacts of climate change. However, accurately quantifying the contributions of different sources to atmospheric CO 2 remains challenging because of its long atmospheric lifetime, strong transport-driven mixing, and uncertainties in existing emission inventories and observational constraints. Although recent advances in high-resolution emission inventories have improved representation of anthropogenic emissions, most studies remain emission-centered and do not fully account for atmospheric redistribution processes, leaving a critical gap in linking emissions to observed CO 2 concentrations. To address these limitations, this study develops an integrated source apportionment framework based on the GEOS-Chem model and a source shut-off approach to quantify the contributions of different sectors to atmospheric CO 2 . Our results show that electricity and heat production (40%) is the dominant contributor to global anthropogenic CO 2 , followed by industry and construction (27%), transport (23%), and residential sectors (10%). The power sector contribution shows an overall upward tendency, broadly associated with increasing electricity demand. Regional analyses indicate substantial spatial heterogeneity in source contributions, underscoring the importance of tailored mitigation strategies. In addition, terrestrial carbon sinks in high-latitude ecosystems and tropical forests provide a significant buffering capacity, although its relative contribution varies regionally.