Light Absorption by Organic Aerosol Emissions Rivals That of Black Carbon from Residential Biomass Fuels in South Asia

Solid-biomass-fuel residential cookstoves are the largest source of aerosol emissions in the Indian subcontinent. For assessing radiative forcing due to this pollutant source, laboratory-generated cookstove performance data sets are currently used, which have established black carbon (BC) as the dominant atmospheric-warming aerosol species. We report findings on the strong near-ultraviolet wavelength absorption characteristics of emitted organic carbon (OC) aerosols from household stove combustion of nationally representative biomass fuels. OC emissions from cookstoves have been conventionally parametrized in regional climate models to be nonlight-absorbing in the visible solar spectra. We conclude that light-absorbing OC contributes roughly as much as BC to total absorption cross sections, thereby enhancing the associated positive forcing estimates. Our findings underscore the importance of including light-absorbing OC within the subcontinent's air quality and climate impact assessment frameworks.