The impact of NOx emissions from subsonic aircraft on the atmosphere: a 3D model study of the changes in ozone and radiative forcing for the period 1990-2015

The model results indicate that NO_x emissions from aircraft cause an increase in the NO_x and ozone concentrations in the upper troposphere and lower stratosphere, and a positive radiative forcing. For 1990 aircraft emissions result in an increase in the NO_x concentration at 10-11 km of about 20 ppt in January and 50 ppt in July over the northern mid-latitudes, corresponding to a relative increase of about 50%. The maximum increase in the ozone concentrations due to the aircraft emissions at northern mid-latitudes is about 2.5% in January and 3-4% in July.

The aircraft-induced ozone changes cause a global average radiative forcing of 0.013 W/m² for January and 0.025 W/m² for July. The 2015 ANCAT projection, yield 90% higher aircraft NO_x emissions than in 1990. As a consequence of this, the calculated NO_x perturbation by aircraft emissions increases by about 100% between 1990 and 2015, and the ozone perturbation by about 50-70%. The global average radiative forcing due to the aircraft-induced ozone changes increases by about 50% between 1990 and 2015. The perturbation of ozone due to the aircraft NO_x emissions increases faster during this period than that due to NO_x surface sources from industry, electricity production and road traffic.