Climate impact of supersonic air traffic: an approach to optimize a potential future supersonic fleet – results from the EU-project SCENIC

Abstract

Abstract. The demand for intercontinental transportation is increasing and people are requesting short travel times, which supersonic air transportation would enable. However, besides noise and sonic boom issues, which we are not referring to in this investigation, emissions from supersonic aircraft are known to alter the atmospheric composition, in particular the ozone layer, and hence affect climate significantly more than subsonic aircraft. Here, we suggest a metric to quantitatively assess different options for supersonic transport with regard to the potential destruction of the ozone layer and climate impacts. Options for fleet size, engine technology (nitrogen oxide emission level), cruising speed, range, and cruising altitude, are analyzed, based on SCENIC emission scenarios for 2050, which underlay the requirements to be as realistic as possible in terms of e.g., economic markets and profitable market penetration. This methodology is based on a number of atmosphere-chemistry and climate models to reduce model dependencies. The model results differ significantly in terms of the response to a replacement of subsonic aircraft by supersonic aircraft, e.g., concerning the ozone impact. However, model differences are smaller when comparing the different options for a supersonic fleet. Those uncertainties were taken into account to make sure that our findings are robust. The base case scenario, where supersonic aircraft get in service in 2015, a first fleet fully operational in 2025 and a second in 2050, leads in our simulations to a near surface temperature increase in A reduced supersonic cruise altitude or speed (from Mach 2 to Mach 1.6) reduces both, climate impact and ozone destruction, by around 40%. An increase in the range of the supersonic aircraft leads to more emissions at lower latitudes since more routes to SE Asia are taken into account, which increases ozone depletion, but reduces climate impact compared to the base case.

Potential climate impact of black carbon emitted by rockets

“…Figure 2b shows the vertical distribution of the BC layer, with a peak enhancement of 8 ng per kg of air at 25 km, above the main part of the emission. In comparison, the BC loading of a fleet of future supersonic aircraft is predicted to reach 0.8 ng per kg of air at an altitude of 16 km [e. g. Grewe et al , 2007].…”

“…We estimate the globally averaged steady state direct radiative forcing (RF) from a uniformly distributed stratosphere black carbon layer from rockets as where σ m is the BC mass specific absorption efficiency, F s is mean solar SW flux, τ is stratospheric lifetime, A is Earth albedo, N is number of launches per year, P is propellant burned in the stratosphere per launch, EI BC is the rocket soot emission index, and S is Earth's surface area. For 0.1 μ m BC particles σ m equals 9 m 2 g −1 [ Zhang et al , 2008] and using values of EI BC , N, and P expected for the suborbital rocket fleet (discussed below), we find RF equals 43 mWm −2 , much larger than BC forcing from current aviation and comparable to BC forcing from the global road transport sector [ Balkanski et al , 2010] and net forcing associated with the global air transport [ Grewe et al , 2007]. The estimated rocket RF is large enough to motivate a more detailed look at the problem of rocket BC emissions using a detailed global climate model (GCM) to study changes in global patterns of circulation and climate and the distribution of important trace species, such as ozone.…”

Transport impacts on atmosphere and climate: Aviation

“…8 shows the lifetime of a local water vapour perturbation, which also serves as a good indicator for wet deposition. (Grewe and Stenke, 2007).…”

“…Additional studies are currently underway to better evaluate the differences to the results of the IPCC (1999 -see Isaksen et al, 1999) assessment of supersonic aircraft emissions. The study of Grewe et al (2007) proposes a metric for the quantitative assessment of different options for supersonic transport with regard to the potential destruction of the O 3 layer and climate impacts. Options for fleet size, engine technology (EINO x ), cruising altitude, range, and cruising height were analysed, based on SCENIC emissions scenarios for 2050, which were to be as realistic as possible in terms of e.g., economic markets and profitable market penetration.…”

Future impact of non-land based traffic emissions on atmospheric ozone and OH – an optimistic scenario and a possible mitigation strategy

“…Several other studies have also investigated how aircraft NO x emissions alter the chemical composition of the atmosphere (e.g. Hidalgo and Crutzen, 1977;Johnson et al, 1992;Brasseur et al, 1996;Schumann, 1997;Grewe et al, 1999Grewe et al, , 2007Schumann et al, 2000;Kraabøl et al, 2002;Stevenson et al, 2004;Gauss et al, 2006;Søvde et al, 2007). The studies dealing with impact from future subsonic aircraft NO x emissions project an increase in aircraft-induced ozone in 2050 compared to the present day atmosphere, but the effect depends on the emission scenario used.…”