Aviation impact on air quality present day and mid-century simulated in the Community Atmosphere Model (CAM)

The projected increase in global air traffic raises concerns about the potential impact aviation emissions have on climate and air quality. Previous studies have shown that aircraft non-landing and take-off (non-LTO) emissions (emitted above 1 km) can affect surface air quality by increasing concentrations of ozone (O₃) and fine particles (PM_2.5). Here, we examine the global impacts of aviation non-LTO emissions on surface air quality for present day and mid-century (2050) using the Community Atmosphere Model with Chemistry, version 5 (CAM5). An important update in CAM5 over previous versions is the modal aerosol module (MAM), which provides a more accurate aerosol representation. Additionally we evaluate of the aviation impact at mid-century with two fuel scenarios, a fossil fuel (SC1) and a biofuel (Alt). Monthly-mean results from the present day simulations show a northern hemisphere (NH) mean surface O₃ increase of 1.3 ppb (2.7% of the background) and a NH maximum surface PM_2.5 increase of 1.4 μg/m³ in January. Mid-century simulations show slightly greater surface O₃ increases (mean of 1.9 ppb (4.2%) for both scenarios) and greater PM_2.5 increases (maximum of 3.5 μg/m³ for SC1 and 2.2 μg/m³ for Alt). While these perturbations do not significantly increase the frequency of extreme air quality events (increase is less than 1.5%), they do contribute to the background concentrations of O₃ and PM_2.5, making it easier for urban areas to surpass these standards.