Environmental Engineering Reference
In-Depth Information
Consequently, if emissions of GHG and radiative forcing from civil aviation are
to be reduced, the following options are available in the short and medium term:
•
influencing the development of demand for aviation services in terms of lower
frequency and shorter average distance of air travel;
•
increasing the technical efficiency of aircraft in use;
•
increasing the operational efficiency of air traffic; and
•
optimizing cruise altitude in a manner that reduces the effects of emissions on
the climate.
Deploying any of these options in isolation may result in partially counteracting or
rebound effects in the development of other variables (see Table 11.1). One might
expect, at least, reductions in demand to provide for unambiguous effects on GHG
emissions. However, reducing demand beyond what the aviation industry has planned
for may limit their capacity to achieve high load factors and may slow down the
take-up of more environmentally efficient technology.
Table 11.1
Likely rebound effects of options for reducing aviation's climate impact
Effect of
Reduced air
travel
frequency
Reduced air
travel
distance
Increased
technical
efficiency
Increased
operational
efficiency
Optimized
cruise altitude
on
Air travel frequency
+
+
+
ne
Air travel distance
+
++
++
ne
Technical efficiency
-
-
ne
ne
Operational efficiency
short term
-
- -
ne
-
Optimized altitude
ne
ne
ne
ne
Note:
The effects of deploying the options in the columns on those in the rows are indicated by the
abbreviations: (ne) no effect; (+) increase; (++) substantial increase; (-) decrease; (- -) substantial
decrease.
In so far as improvements in the mentioned determinants of energy intensity of avi-
ation go hand in hand with cost reductions that are passed on to customers, this will
result in induced demand, the volume of which depends upon price elasticity. Figure
11.1 shows for Swissair how technical and operational improvements have reduced
energy use per tonne kilometre of payload and how the influence on overall fuel use
was counteracted by increases in demand driven by the simultaneous effects of decreas-
ing ticket prices in real terms and growing incomes. Thus, additional efficiency gains
and cost savings induced by kerosene taxes or emission charges may leave the growth
trend in demand nearly unchanged (Brosthaus et al, 2001, p138). Estimates for effi-
ciency gains in air traffic management suggest that the overall effect on carbon emis-
sions, including demand induced by reduced travel times and lower ticket prices, may
be a negligible decrease in emissions or even higher emissions (Freire et al, 2000, p8).
