Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Aviation and the Global Atmosphere
Table of contents | Previous page | Next page
6.5.2. Climate Signatures of Aircraft-Induced Ozone Perturbations
With uncertainty in relating RF to climate response noted above, it would be useful to compare
CGCM-modeled climate responses for aircraft perturbations. Less agreement is expected
between models because the magnitude of their feedback responses (i.e., climate sensitivity)
can be quite different from one another. A review of different model sensitivities has been given
in IPCC (1990, 1992, 1996); the values vary from a sensitivity of about 0.4 K/(Wm-2) to 1.2 K/
(Wm-2) for doubled CO 2 . How the sensitivity would vary for heterogeneous aircraft perturbations
is not known.
The most appropriate tool would be simulations in the transient mode using coupled atmosphereocean
GCMs. These simulations are computationally very expensive, and it would be very
difficult to separate signal from noise. To date, however, all known comprehensive model
simulations of aircraft induced climate change were made in the quasi-stationary mode using
either pure atmospheric GCMs (e.g., Sausen et al., 1997) or atmospheric GCMs coupled to
mixed layer ocean models (examples below). In other words, these simulations studied quasiequilibrium
response to a stationary or seasonally repeating perturbation. Pure atmospheric
models underestimate the response if, for instance, sea surface temperature is fixed to a
prescribed value. Equilibrium simulations with coupled models overestimate the aircraft effect in
absolute numbers relative to transient simulations (see discussion in Sausen and Schumann,
1999), and the spatial pattern of climate change can serve only as a first estimate (Kattenberg et
al., 1996). These simulations must be compared with analogous simulations for well-mixed
greenhouse gases (e.g., CO 2 doubling). Then the particular climate sensitivity to aircraft-induced
radiative forcing and aircraft signatures of climate changes may possibly be extracted.
Using the GISS 3-D climate/middle atmosphere model, Rind and Lonergan (1995) studied the
http://www.ipcc.ch/ipccreports/sres/aviation/082.htm (1 von 3)08.05.2008 02:43:10
Figure 6-11: Equilibrium change of annual, zonal
mean temperature (K) caused by ozone perturbation
due to NO x emissions of a projected sub- and
supersonic aircraft fleet for the year 2015, as
simulated with the GISS model (Rind and Lonergan,
1995). This calculation is not for any specific
scenarios assessed here.
Other reports in this collection