Large historical changes of fossil-fuel black carbon aerosols
Anthropogenic emissions of fine black carbon (BC) particles, the principal light absorbing atmospheric aerosol, have varied during the past century in response to changes of fossil-fuel utilization, technology developments, and emission controls. We estimate historical trends of fossil-fuel BC emissions in six regions that represent about two-thirds of present day emissions and extrapolate these to global emissions from 1875 onward. Qualitative features in these trends show rapid increase in the latter part of the 1800s, the leveling off in the first half of the 1900s, and the re-acceleration in the past 50 years as China and India developed. We find that historical changes of fuel utilization have caused large temporal change in aerosol absorption, and thus substantial change of aerosol single scatter albedo in some regions, which suggests that BC may have contributed to global temperature changes in the past century. This implies that the BC history needs to be represented realistically in climate change assessments. Records of BC deposition in ice, lake and swamp cores are needed to verify emission histories. Reducing global BC emissions could help to reduce the global warming "bounce?" that is expected to accompany controls on sulfur emissions, while also benefiting human health. Our estimates suggest that global diesel emissions are growing and could become the dominant issue if uncontrolled household use of coal and biofuels in developing countries declines in the future.