Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Two HSCT cases with detailed 3-D emission scenarios-one with 500 aircraft and the other with 1,000 aircraft-were used to calculate RF from stratospheric O3 and
H2O perturbations (see Table 6-1). Most of the ozone change occurs above the tropopause; thus, there is poorer agreement among RF models and a greater
difference in RF values after stratospheric temperatures adjust. The ozone perturbation calculated for 500 supersonic aircraft with the 2015 background atmosphere is
substantially different in nature from that calculated for 1,000 aircraft with the 2050 atmosphere, in part because of specified changes in chlorine and methane contents
of the stratosphere (see Chapter 4). Nevertheless, the best RF values are about the same: -0.01 W m-2. The uncertainty range in these values is large and changes
sign (-0.04 to +0.01 W m-2), reflecting not only the range in O3 perturbations given by Chapter 4 but also the large uncertainty in deriving RF for stratospheric
perturbations. This ozone-related RF for the HSCT fleet is based only on the stratospheric ozone perturbation calculated by the models in Chapter 4; the tropospheric
changes are discarded, and a correction for the displacement of about 11% of the subsonic traffic is included, as shown in Table 6-1 (scenario Fa1H).
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