Potential Impacts of High-speed Transport Emissions on Ozone and Resulting Forcing on Climate
Commercial aircraft flying at supersonic speeds in the lower stratosphere are being discussed once again after a hiatus of almost 20 years. Emissions from potential fleets of supersonic transport aircraft have raised concerns about potential effects on stratospheric ozone and climate. This study first, as an update on historical studies, evaluates the environmental effects from supersonic aircraft and compares the new analyses with previous assessments using emission inventories from 20 years ago. Then a series of sensitivity studies of possible future cruise altitudes have been conducted to evaluate the potential atmospheric response for a fleet of supersonic aircraft assumed to be fully operational in 2050. In the historical study, we show that the resulting ozone effects largely depend on the NOx emission levels and the net changes in stratospheric ozone are determined by the chemical interactions between different ozone production and depletion cycles. In the sensitivity study, we show that the effects on total column ozone and radiative forcing show a strong dependence on cruise altitude, especially for flights above 17 km. Impacts on stratospheric ozone can be reduced by either flying at lower cruise altitudes or by the development of low NOx emitting combustors. Water vapor emissions have a larger impact on climate radiative forcing than ozone, with stronger forcing associated with higher cruise altitude. This study can potentially help facilitate technological development and optimize aircraft operations towards making supersonic travel environmentally friendly.
