Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
H 2 O-The increase in H 2 O is calculated to be a maximum of 0.4-0.7 ppmv in the Northern Hemisphere mid-to high-latitude LS for a fleet of 500 aircraft, compared to a
background of 3-4 ppmv.
Total Active Nitrogen (NOy)-The increase in NOy is calculated to be a maximum of 0.6-1.0 ppbv in the Northern Hemisphere mid-to high-latitude LS for a fleet of 500
aircraft, compared to a background of 3-10 ppbv.
SO2-Emission and conversion of SO2 to sulfate particles in the plume are still very uncertain for supersonic aircraft; thus, we summarize a range of scenarios. The
SAD would increase 20-100% between 15 and 20 km in the 30-90°N latitude band for EI(SO2 )=0.4 and a range of assumptions about gas to particle conversion in the
plume.
O3-Each model shows different distributions of O3 depletion and enhancement that probably reflect different methodologies of transport and chemistry incorporated in
individual models. The results summarized below are from different models over a range of scenarios.
● The calculated range for Northern Hemisphere annual average total O3 change is-1 .3 to 0.0% for a fleet of 500 aircraft with an EI(NOx )=5 in 2015 flying in a low
background sulfate SAD stratosphere. The O3 change is computed to be more positive in a higher background sulfate SAD stratosphere.
● The calculated range for Northern Hemisphere annual average total O3 change is-1 .4 to -0.1% for a fleet of 1,000 aircraft with an EI(NOx )=5 in 2050.
● Model simulations show that O3 depletion occurs throughout most of the stratosphere, except in the tropical LS. Some models calculate an O3 increase in the lowest
part of the mid-latitude stratosphere.
Carry-Through Computations to Chapters 5 and 6
Most Likely Values
For each scenario, a single model was used to propagate changes in constituents in Chapters 5 and 6.
Uncertainties
The various model computations exhibit a range of results that to some degree reflects uncertainties. However, this range does not define the uncertainties and,
indeed, it is very difficult at this time to quantify them. Factors that contribute include the following:
● Deficiencies in model representation of transport processes
● Deficiencies in model representation of chemical processes
● Unknown or missing chemical and physical processes
● Limited knowledge about the chemical composition of the future atmosphere and subsequent changes in atmospheric temperatures and winds resulting from climate
change effects
● Limitations in model resolution and dimensionality.
Uncertainties in the computations were estimated as follows:
http://www.ipcc.ch/ipccreports/sres/aviation/045.htm (3 von 4)08.05.2008 02:42:16