Co-Benefits of Black Carbon Mitigation for Climate and Air Quality

Abstract

Black carbon (BC) and organic carbon (OC) are two Short lived Climate Forcers (SLFCs) that have significant short-term effects on the earth’s energy budget through radiative forcing. Their emissions reduce air-quality and have damaging effects on public health. Recent studies on the impact of BC and OC on near- and long-term climate change show mixed results. This study is one of the first to quantify the co-benefits of BC/OC emission mitigation for climate and air quality policy in terms of policy costs. This assessment is performed using the integrated assessment model IMAGE 3.0. We found that in the short term BC/OC mitigation can contribute significantly to avoiding premature deaths caused by air pollution and to reducing global warming. It is estimated that 464 to 726 thousand deaths can potentially be avoided worldwide as a result of reduced air pollution and a maximum reduction in global average temperature of 0.02oC to 0.05oC can be achieved in 2030. This means that in our baseline scenario, the short-term temperature reduction from BC/OC reduction is similar to the temperature reduction resulting from standard (CO2) climate policy at roughly half the costs and with a significant additional societal health benefit (approximately 500 thousand deaths avoided). However, it should be noted that BC/OC mitigation cannot compensate for CO2 mitigation with regard to long term climate goals. In the long term (2100), the impacts of BC/OC mitigation are reduced for three reasons: 1) policies targeting longer-term climate forcers such as CO2 have a stronger impact on long-term climate change, 2) BC and OC emissions are expected to be reduced even without additional policies as a result of strengthening of air pollution policy and, 3) in the climate policy scenario, a shift to cleaner fuels will also reduce BC/OC emissions. Considering the short-term climate effect of BC/OC mitigation, the short- and long-term effect of avoided deaths, and the synergies and comparable policy costs for BC/OC climate and BC/OC air quality policy it generally seems attractive to aim for maximised air quality policy. Only if short term temperature change is the main policy goal, BC/OC climate policy has a clear advantage.