Regional and global impacts of transport on air quality and climate

Abstract

Transport emissions affect atmospheric composition, resulting in significant impacts on air quality and climate. In addition to long-lived greenhouse gases, several short-lived pollutants are emitted during the fuel combustion process. We use a global chemistry-climate model to quantify the effects of transport on air quality and climate on the global scale. Results are shown focusing on the effects of transport-induced aerosol particles, given the limited information to date about their impact. Although transport emissions occur all over the world, mitigation measures to reduce their climate impact are frequently applied on regional or national scales only, especially in case of land-based transport. To characterize the global effect of such small-scale measures, we develop a new method to estimate the impact of such local regulations on global climate. An application to the German transport system is presented and the resulting climate impacts are compared with those of the global study. We find that the impact of globally-emitted short-lived pollutants on climate is relevant and comparable to the one of CO2. The climate impact of the German transport system, on the other hand, is mostly CO2-driven and the effect of short-lived species is only small. Short-lived pollutants, however, are still harmful for air quality at all scales, hence mitigation policies shall continue to address them.