Environmental Engineering Reference
In-Depth Information
Source: IPCC SPM, 1999, and Deutschen Zentrum für Luft- und Raumfahrt (DLR) website at
www.dlr.de/ipa
Figure 5.3 Global annual mean radiative forcings from aircraft emissions for 1992 (a)
and 2050, scenario Fa1 (b) (Wm -2 )
Having set the scene with the overall influences on climate and radiative forcing, we
move on to illustrate the effects of subsonic aviation in 1992 and 2050, as estimated
by the IPCC (1999), shown in Figure 5.3. Here, we see an overall forcing of 0.05Wm -2
in 1992, approximately 3.5 per cent of the overall radiative forcing (as estimated in
the IPCC's second assessment report; IPCC, 1996), and an overall forcing of 0.19Wm -2
in 2050, 5 per cent of all climate forcings for a central scenario. The full range of
2050 scenarios studied imply forcings of 0.13 to 0.56Wm -2 (ie 2.6 to 11 times the
value in 1992).
Figure 5.3 shows the large uncertainties associated with contrail and cirrus effects
(the two being linked): as is quite clear, the contrail and cirrus effects are relatively
large and rather uncertain, the latter having no best estimate associated with it.
E MISSIONS FROM CURRENT AND FUTURE AVIATION
A number of attempts at estimating global aviation emissions have been made and
are conveniently summarized by Henderson et al (1999). For present-day emissions
(actually, early 1990s), three data sets are in common use: the ANCAT/EC2 data set
(Gardner et al, 1998); the DLR-2 data set (Schmitt and Brunner, 1997); and the
NASA data set (Baughcum et al, 1996). Furthermore, there are emission forecasts avail-
able for 2015 (Gardner et al, 1998; Baughcum et al, 1998) and scenarios for 2050
(FESG, 1998; Newton and Falk, 1997). Here, we focus upon the ANCAT/EC2 data
sets and derivatives, and the FESG 2050 scenarios.
These aforementioned emission data sets all provide three-dimensional (3D) grid-
ded data and have simplifying assumptions. The essential components include an air-
craft movements database; a representation of the global fleet in terms of aircraft and
engines; a fuel-flow model; calculation of emissions at altitude from fuel flow; and
landing and take-off (LTO) emissions data.
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