Evaluating the Regional Impact of Aircraft Emissions on Climate

Unlike other transportation sectors where pollutant emissions usually occur only near the Earth’s surface, aviation emissions happen primarily at altitudes of 8-12 km above the surface, impacting the upper troposphere and the lower stratosphere (UTLS). At these altitudes, the pollutants can contribute significantly to greenhouse gas (GHGs) concentration and to the formation of secondary aerosols, which can have an impact on climate change. Most previous studies have focused on aviation effects on climate using globally-averaged metric values, which do not give information about the spatial variability of the effects. While aviation emissions have significant spatial variability in the sign and magnitude of response, the strength of regional effects is hidden due to the global averaging of climate change effects. Previous studies examine regional climate effect from aircraft using the metric radiative forcing, while this study will go to the next step of the cause-effect chain to quantify the aviation-induced effects using temperature change, with specific focus on selected regions such as the United States, Europe and East Asia. The chemistry-climate Community Atmosphere Model (CAM-chem6) is used in analyses to examine the regional climate effects based on 4 different latitude bands (90^oS-28^oS, 28^oS-28^oN, 28^oN-60^oN, 60^oN-90^oN) and 3 regions (contiguous United States, Europe and East Asia). The most regionally important aviation emissions are short-lived species, such as black carbon (BC) and sulfates, emitted from aircraft directly, and O₃-short induced by NOx emission indirectly as well as the aviation-induced clouds. The regional heterogeneity of these short-lived impacts will be explored and compared to the globally-averaged effects.