The Impact on the Ozone Layer of a Potential Fleet of Civil Hypersonic Aircraft

Abstract

The aeronautical community is currently researching technology that might lead to commercial hypersonic aircraft that would cruise at Mach 5-8 in the middle or upper stratosphere and would transfer passengers from London to New York or from Los Angeles to Tokyo in just a couple of hours. Depending on the engine technology to be adopted, these aircraft will potentially release substantial amounts of water vapor and nitrogen oxides around 30-40 km altitude. We show here that the operation of a large fleet of such aircraft could potentially deplete considerable amounts of ozone in the stratosphere, which would lead to a substantial increase in biologically damaging ultraviolet radiation reaching the Earth's surface. The calculations are based on a specific emission scenario, which carries large uncertainties but can easily be scaled to account for the type of aircraft engine to be eventually adopted, improved technology to be expected, and the size and operation conditions of the future aircraft fleet. Plain Language Summary Commercial hypersonic aircraft, if developed in the future, will be flying at Mach 5 to 8 in the middle to upper stratosphere (30 to 40 km altitude) to carry passengers in a couple of hours from London to New York or from Los Angeles to Tokyo. Depending on the adopted technology and fleet size, the powerful engines of such airplanes may release substantial amounts of water and nitrogen oxides in the stratosphere, which could potentially damage the protecting ozone layer and hence increase the level of biologically damaging ultraviolet radiation reaching the Earth surface. The paper uses an advanced global atmospheric model to assess the impact of a potential fleet of hypersonic aircraft.

Stratospheric Ozone and Climate Forcing Sensitivity to Cruise Altitudes for Fleets of Potential Supersonic Transport Aircraft

“…The difference between the NOy and H 2 O perturbations is that a much larger fraction of emitted H 2 O is transported southward across the tropics to the SH as well as transported upward to the stratopause into the mesosphere. This is due to the differences in their atmospheric lifetimes, with around 1 year and 3 months lifetime in the upper stratosphere for H 2 O and NOy, respectively (Kinnison et al., 2020). At cruise altitudes from 21 to 23 km, the maximum local H 2 O concentration increase reaches 1.5 ppmv at NH mid‐latitudes and the stratospheric column H 2 O increase by 4.45% in the NH average.…”

“…The distribution of ozone is determined by a complex balance between transport and chemical production and destruction (Brasseur, 2020;WMO, 2018). Transport processes influence ozone concentration both by transporting ozone itself and also by the transport of precursors that induce ozone chemical production and transport of other gases that lead to the destruction of ozone (e.g., NOx and H 2 O emitted from aircraft).…”

Potential Impacts of Supersonic Aircraft Emissions on Ozone and Resulting Forcing on Climate: An Update on Historical Analysis

“…NO x and H 2 O (after reaction to form hydrogen oxides; HO x ) are known to be important gases in the chemical production and destruction of stratospheric ozone. Both NO x and HO x can be directly involved in catalytic chemical reactions that destroy molecules of stratospheric ozone, both from natural and human-related sources like supersonic aircraft (e.g., Crutzen, 1972;Dessens et al, 2007;Johnston, 1971Johnston, , 1989Kawa et al, 1999;Kinnison & Wuebbles, 1994;Kinnison, Brasseur, Baughcum, et al, 2020;Penner et al, 1999). Emissions of NO x and HO x can interfere with each other's ozone-loss mechanisms and they can also interfere with other ozone-loss mechanisms (e.g., ClO x ).…”

Perspective on aircraft in the stratosphere: 50 years from COMESA through the ozone hole to climate

“…That drew on observations of emissions in the lower stratospheric wake of a Concorde, by the NASA ER‐2 (Fahey et al ., 1995). Grooβ et al ., (1998) and Kinnison et al ., (2020) also modelled these factors.…”

“…It is out of scope to review fully the rapid growth in laboratory results, observations and modelling over the half century that has led to the present worldwide efforts and understanding. That has been done by periodic reviews under the aegis of the World Meteorological Organisation, for example (Wahner and Geller, 1994;Lee et al, 2009;WMO, 2018;Kinnison et al, 2020). In the concluding perspective, the lessons of the last half century will be summarised and their implications for the future considered.…”