On the role of atmospheric chemistry in the global CO 2 budget

International audience[1] A global 3D-chemistry-transport model is applied to study the magnitude and geographical distribution of the in situ photochemical CO 2 production in the atmosphere. In the model 1823 TgC/y of reactive carbon compounds (RCC) are emitted at the surface on global and annual average. 46% of the RCC source is released by the vegetation, 27% from biomass burning, and 27% from fossil fuel incomplete combustion. Of these, 1213 TgC/y are oxidized to produce CO 2. Physical removal of the emitted species represents a loss of 154 TgC/y; wet and dry deposition of intermediate oxidation products account for approximately 360 TgC/y. The relative importance of different reaction pathways is assessed. Sensitivity experiments indicate that only 30% to 45% of the RCC emitted are oxidized to CO 2. Interhemispheric gradients of CO 2 at the Earth's surface produced from RCC, including photochemistry and physical removal, are compared to CO 2 gradients from RCC assuming that 100% of the RCC are released as CO 2 , common in CO 2 inverse models. A maximum difference of 0.3 ppmv in the CO 2 gradients is revealed, a result of potential significance for carbon cycle studies. Citation: Folberth, G., D. A. Hauglustaine, P. Ciais, and J. Lathière (2005), On the role of atmospheric chemistry in the global CO 2 budget, Geophys. Res. Lett., 32, L08801