Emission projection and uncertainty analysis of exhaust emissions from global and Asian on-road vehicles

Two of the most notable impacts from emissions of air pollutants are climate change and hemispheric or intercontinental transport. Global emission projections are identified as critical elements in understanding these large-scale impacts. Such projections are required to understand the net response of climate to combined emissions of greenhouse gases, aerosols, and other trace species in the next 30 to 50 years. Emissions from vehicles vary with introduction of advanced technology and implementation of stringent environmental regulations. We present global emission projections of primary particulate matter emissions including the aerosol components black and organic carbon, from on-road vehicles from 2010 to 2050. These projections are based on a new model of technology that responds to socioeconomic conditions in different economic and mitigation scenarios. The model contains detail about technology stock, such as vintage, and applies exogenous data from economic scenarios to choose new technologies and retire old ones. The driving factors involved in the transitions of technology decision-making include consumption growth rates, retirement rates, timing of emission standards, and generation of superemitters. Asia is a significant contributor to global emissions and its growth rate is expected to be high, so we emphasize the trajectories in this region. Before 2030, the tradeoff between decreasing emission intensity and increasing fuel consumption results in relatively lower rates of increase of PM emissions, although emissions are still increasing. After 2030, we expect that standards will have cleaned up normal vehicles, so emission projections are highly dependent on the behavior of “superemitters.” Changes of technology and policy in the future are uncertain, and their relationship with socioeconomic variables is not well known. This lack of knowledge raises the question: What can be known about future emissions and air quality? We also present sensitivity analyses and Monte Carlo simulations to explore the impacts of these uncertainties on emission projection. We identify the most critical factors affecting our knowledge of emission pathways; these are targets for future research on the interaction between social and economic conditions and technological response