Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
total fossil carbon emissions for a similar economic scenario (IS92a). Note the logarithmic scale
in Figure 6-6. For scenario F1a, fuel use parallels that of IS92a, but for Eab it grows faster than
total fossil fuel use. In converting aviation fuel to CO 2 emissions, we adopt a carbon fraction by
weight of 86%. Aviation fuel use prior to 1992 is based on International Energy Agency data
(IEA, 1991; for table, see Sausen and Schumann, 1999). To account for systematic
underestimation of fuel use (see Chapter 9), we have increased NASA-1992 and NASA-2015
emissions by 15% and 5%, respectively, to form the inventories NASA-1992* and NASA-2015*.
Figure 6-7 gives an expanded linear scale of aviation fuel use from 1990 to 2050 for scenarios
Fc1, Fa1, Fa1H, Fe1, Eab, and Edh, in order of increasing fuel use by 2050.
Chapter 4 studies the impact of a fleet of high-speed civil transport (HSCT, i.e., supersonic)
aircraft using a range of 3-D emission scenarios with atmospheric chemistry models. These
calculations form a parametric range that covers changes in fleet size, NO x emissions, cruise
altitude, sulfate aerosol formation, and future atmospheres. The present chapter combines those
results into a continuous scenario for the HSCT fleet, designated Fa1H: On top of the Fa1
scenario it assumes that HSCT aircraft come into service in 2015, grow at 40 planes per year to
a final capacity of 1,000 aircraft by 2040, continue operation to 2050, and displace equivalent air
traffic from the subsonic fleet (~11% of Fa1 in 2050). This Mach 2.4 HSCT fleet cruises at 18-20
km altitude and deposits most of its emissions in the stratosphere. It has new combustor
technology that produces very low emissions of 5 g NO2 per kg fuel. Table 6-1 gives the
breakdown of RF from two specific HSCT studies in Chapter 4: 500 HSCTs in a 2015
background atmosphere and 1,000 HSCTs in a 2050 background atmosphere (e.g., chlorine
loading, methane, nitrous oxide). The likely interval for the RF here combines the uncertainty in
calculating the ozone or water vapor perturbation with that from calculating the radiative
imbalance.
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Figure 6-6: Fossil fuel use (Gt C yr -1 ) shown for
historical aviation use (1950-92, solid line) and for
projected aviation scenarios Fa1 and Eab. Total
historical fossil fuel use and the projection according
to scenario IS92a are also shown.