Abstract. The global commercial aircraft fleet in 2006 flew 31.26 million flights, burned 188.20 million metric tons of fuel, and covered 38.68 billion kilometers. This activity emitted substantial amounts of fossil-fuel combustion products within the upper troposphere and lower stratosphere that affect atmospheric composition and climate. The emissions products, such as carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur compounds, and particulate matter, are not emitted uniformly over the Earth, so understanding the temporal and spatial distributions is important for modeling aviation's climate impacts.

Abstract. The global commercial aircraft fleet in 2006 flew more than 31 million flights, burned nearly 190 million metric tons of fuel, and covered 38 billion kilometers. This activity emitted substantial amounts of fossil-fuel combustion products within the upper troposphere and lower stratosphere that affect atmospheric composition and climate. The emissions products, such as carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur compounds, and particulate matter, are not emitted uniformly over the Earth, so understanding the temporal and spatial distributions is an important component for modeling aviation climate impacts. Here, we analyze global commercial aircraft emission data for 2004 and 2006. Data, provided by the Volpe National Transportation Systems Center, were computed using the Federal Aviation Administration's Aviation Environmental Design Tool. For both years, analysis of flight data shows 93 percent of fuel was burned in the Northern Hemisphere, 69 percent between 30 N and 60 N latitudes; 77 (75) percent was burned above 7 km in 2004 (2006). This activity led to 177 (162) Tg of carbon from CO2 globally in 2004 (2006), with half being emitted over three dominant regions: United States, Europe, East Asia. The difference between 2004 and 2006 is a result of fewer flights in 2006 and the methodology used to compute fuel burn and emissions from those flights. We also show that despite receiving only a few percent of global emissions, the Arctic receives a concentration of emissions of the same order of magnitude as the global average. The following is a summary of this data which illustrates the global and regional aviation emissions footprints for 2004 and 2006, and provides temporal and spatial distribution statistics of several emissions constituents. Finally, we show that 87 (85) percent of all flights in 2004 (2006) are short-haul missions, yet those flights are responsible for only 38 (39) percent of total emissions.

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This study examines the 20-year impacts of emissions from all commercial aircraft flights worldwide on climate, cloudiness, and atmospheric composition. Aircraft emissions from each individual flight worldwide were modeled to evolve from the subgrid to grid scale with the global model described and evaluated in Part I of this study. Simulations with and without aircraft emissions were run for 20 years. Aircraft emissions were found to be responsible for -6% of Arctic surface global warming to date, -1.3% of total surface global warming, and -4% of global upper tropospheric warming. Arctic warming due to aircraft slightly decreased Arctic sea ice area. Longer simulations should result in more warming due to the further increase in CO2. Aircraft increased atmospheric stability below cruise altitude and decreased it above cruise altitude. The increase in stability decreased cumulus convection in favor of increased stratiform cloudiness. Aircraft increased total cloud fraction on average. Aircraft increased surface and upper tropospheric ozone by -0.4% and -2.5%, respectively and surface and upper-tropospheric peroxyacetyl nitrate (PAN) by -0.1% and -5%, respectively. Aircraft emissions increased tropospheric OH, decreasing column CO and CH4 by -1.7% and -0.9%, respectively. Aircraft emissions increased human mortality worldwide by -620 (-240 to 4770) deaths per year, with half due to ozone and the rest to particulate matter less than 2.5 micrometers in diameter (PM2.5).

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