Atmospheric Impacts of a Near Future Supersonic Aircraft Fleet

Supersonic aircraft are once again being considered by manufacturers, airlines, and regulators, with the possibility of supersonic commercial flights within the next decade. This study quantifies the impacts that two possible supersonic aircraft fleets might have on both the global ozone layer and the climate, including the potential effects of sulfur and soot emissions when burning conventional jet fuel. Using a global, tropospheric-stratospheric chemistry-transport model (GEOS-Chem) to simulate the impacts of their emissions, we find that a fleet of Mach 2.2 aircraft flying at 18-20 km altitude will cause 17 times as much ozone destruction as a larger fleet of Mach 1.6 aircraft flying at 15-17 km, due to both the altitude of emission and the differences in estimated emissions of nitrogen oxides (NOx) per unit of fuel burned. We also find that the slower, lower Mach 1.6 fleet may have a net negative (non-CO2) radiative forcing, as the positive (warming) forcing from ozone and water vapor is exceeded by a negative (cooling) forcing from sulfate and black carbon aerosols. By contrast, the radiative forcing due to the faster, higher-altitude Mach 2.2 fleet is of uncertain sign but similar magnitude. Our results show that both interannual variability and aerosol-related forcing may significantly affect the estimated non-CO2 radiative forcing due to supersonic aircraft emissions.