Assessment of the Impacts of Different Carbon Sources and Sinks on Atmospheric CO2 Concentrations Based on GEOS-Chem

Global atmospheric CO2 concentrations, driven by anthropogenic emissions and natural carbon cycle dynamics, have emerged as a critical accelerator of climate change. However, due to the spatiotemporal heterogeneity of carbon sources and sinks, estimating CO2 flux remains highly uncertain. Accurately quantifying the contribution of various carbon sources and sinks to atmospheric CO2 concentration is essential for understanding the carbon cycle and global carbon balance. In this study, GEOS-Chem (version 13.2.1), driven by MERRA-2 meteorological data, was used to simulate monthly global CO2 concentrations from 2006 to 2010. The model was configured with a horizontal resolution of 2.5° longitude × 2.0° latitude and 47 vertical hybrid-sigma layers up to 0.01 hPa. To evaluate the impact of different emission sources and sinks, the “Inventory switching and replacing” approach was applied, designing a series of numerical experiments in which individual emission sources were selectively disabled. The contributions of eight major CO2 flux components, including fossil fuel combustion, biomass burning, balanced biosphere, net land exchange, aviation, shipping, ocean exchange, and chemical sources, were quantified by comparing the baseline simulation (BASE) with source-specific perturbation experiments (no_X). The results show that global CO2 concentration exhibits a spatial pattern with higher concentrations in the Northern Hemisphere and land areas, with East Asia, Southeast Asia, and eastern North America being high-concentration regions. The global average CO2 concentration increased by 1.8 ppm year−1 from 2006 to 2010, with China’s eastern region experiencing the highest growth rate of 3.0 ppm year−1. Fossil fuel combustion is identified as the largest CO2 emission source, followed by biomass burning, while oceans and land serve as significant CO2 sinks. The impact of carbon flux on atmospheric CO2 concentration is primarily determined by the spatial distribution of emissions, with higher flux intensities in industrialized and biomass-burning regions leading to more pronounced local concentration increases. Conversely, areas with strong carbon sinks, such as forests and oceans, exhibit lower net CO2 accumulation.