The Role of Global Emission Inventory of Carbonaceous Emissions

Aerosols - liquid or solid particles suspended in the air - are important constituents of the global atmosphere. They have a direct effect on climate by scattering and/or absorbing solar radiation modifying the radiative balance of the atmosphere and indirect effect by acting as condensation nuclei, their increase in number concentration may give rise to increased number of cloud condensation nuclei, which might increase the droplet concentration with relatively smaller size droplets for fixed liquid water content, making clouds more reflective (Twomey, 1977). Recent measurements show that atmospheric black carbon (BC) and organic carbon (OC) aerosol particles frequently contribute significantly to the total aerosol mass (Novakov et al. 1997). BC is emitted as primary particles from incomplete combustion process, such as fossil fuel and biomass burning, and therefore much atmospheric BC is of anthropogenic origin. OC is emitted as both primary particles and by secondary production from gaseous compounds via condensation or gas phase oxidation of hydrocarbons. Primary organic aerosols come from both anthropogenic sources (fossil fuel and biomass burning) and from natural sources (such as debris, pollen, spores, and algae). Carbonaceous aerosols make up a large but highly variable fraction of the atmospheric aerosol. Black carbon aerosols absorb the solar radiation and induce positive forcing whereas organic matter aerosols reflect solar radiation and produce negative forcing. Various emission inventories have been developed for carbonaceous aerosols. Detailed emission inventories for both BC and OC have been developed (e.g., Penner et al., 1993; Cooke and Wilson, 1996; Liousse et al., 1996; Cooke et al., 1999, Bond et al. 2004) that consider both fossil fuel and biomass components. The inventories of biomass- burning BC and OC particles are more difficult to constrain than fossil fuel emissions, owing to the paucity of data. In the present study we have compared the direct radiative forcing of carbonaceous aerosols using two inventories i.e. Global Emission Inventory Activity (GEIA) and Bond et al. (2004) with the help of Laboratoire de Meteorologie Dynamique general circulation model. There is difference of around a factor of ~3 between the emissions of two inventories. Black carbon emissions are high by a factor of 2 and organic matter emissions by a factor of ~3. TOA direct radiative forcing from these two inventories for black carbon and organic matter aerosols differ by a factor of ~3 and by a factor of ~4 respectively. For total carbonaceous aerosols GEIA inventory gives net negative forcing and Bond inventory gives net positive forcing. There is a clear distinction between negative and positive forcing dominant areas for carbonaceous aerosols.