The ANCAT/EC global inventory of NOx emissions from aircraft

A three dimensional global emissions inventory for NO, from civil and military aviation has been formulated by a joint European Civil Aviation Conference/European Commission working group in support of the AERONOX project “The Impact of NOx Emissions from Aircraft Upon the Atmosphere at Flight Altitudes 8–15 km”. The inventory was compiled on a resolution of 2.8 by 2.8° by 1 km in altitude for a 12 month period spanning mid-1991 to mid-1992. Traffic movement data were compiled from Air Traffic Control recorded movements and timetables for January, April, July and October and combined with an airframe emissions performance model. The global emission of aircraft NOx was estimated to be 2.78 Tg NO2 yr−1 and the overall emission index for NOx in g NOx kg−1 fuel burnt was 16.8. The estimated NOx emissions are higher than the most comparable inventory (NASA, 1990) by a factor of almost 2. The vertical distribution shows that 60% of the global NOx is emitted at cruise altitudes of 10–12 km. There is a pronounced latitudinal bias with 93 % of the global emissions being in the Northern Hemisphere and 70% between 30 and 60°N The spatial distributions of NOx emissions show some seasonality. Emissions of CO2 H2O and SO2 have also been estimated at 528, 216 and 0.165 Tg yr−1, respectively. Although not quantified, the uncertainties in the emissions estimate of NOx from aircraft are discussed and a small overestimation in the traffic movement data base was identified. However, the uncertainties are probably smaller than those for natural sources of NOx which are injected into the top of the troposphere. More work is required to refine emission inventories from aircraft.