Identifying the ozone-neutral aircraft cruise altitude

Depletion of stratospheric ozone, and the associated increase in population exposure to UV radiation, is an environmental consequence high-altitude, supersonic aviation. Assessments impacts emissions from subsonic aircraft – which fly at lower altitudes have instead shown that they produce a net increase, rather than decrease, global suggesting existence intermediate “column ozone neutral” cruise altitude. Knowing this altitude its variation with factors such as latitude, season, fuel composition could provide pathway towards reducing aviation, but would require prohibitive number atmospheric simulations. We use newly developed GEOS-Chem tropospheric-stratospheric adjoint identify location column ozone-neutral function these factors. show that, although mean neutral 13.5 km globally, varies 14.6 12.5 between equator 60°N. This by less kilometer seasons, depletion resulting flying greater factor two. also find eliminating sulfur result 0.5–1.0 when conventional jet burned. Our results imply low Mach burning low-sulfur (e.g. biofuels) may be able achieve zero change. However, for fleet neutrality will careful consideration non-linear sensitivity latitude.