Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
aircraft themselves, with consequences for emissions, are discussed in Chapter 7.
Alternative fuels to aviation kerosene are being investigated, and some of these fuels have some attractive environmental characteristics. For instance, hydrogen offers
the potential for eliminating direct CO 2 emissions, though at the expense of increased H 2 O production. None of the alternatives appear capable of eliminating both
CO 2 and H 2 O emissions. The use of such fuels also would require the development and implementation of new technology and infrastructure, and many factors would
need to be considered, including overall energy use, energy density, availability, cost, indirect impacts through production, and environmental benefits. These issues
are also discussed in Chapter 7.
Future emissions from aviation will also be influenced by the manner in which aircraft are operated. At present, there is non-optimum use of airspace and ground
infrastructure. However, advances in digital communications technology and satellite systems should allow new flight management procedures involving greater use of
computerized air traffic control systems. In principle, such systems could lead to reductions in the lengths of routes between certain cities and higher traffic volumes in
heavily flown corridors. More efficient routing would directly reduce fuel use and emissions. Economic and environmental benefits also might be enhanced through
greater use of meteorological information. Changes in flight altitudes and speeds could occur as a result of new aircraft designs and operating procedures; these
changes would result in aircraft emissions occurring at different altitudes. These factors are described in Chapter 8.
The framework within which technical and operational changes occur is influenced by government and industry, with aircraft safety the most important objective.
Operator fleet decisions are influenced primarily by aircraft mission, performance, and operating cost, though aircraft technology and regulatory acceptance are
significant parameters. Economic instruments such as fuel taxes and emissions charges affect an aircraft's operating costs. Aircraft operating limitations such as
emission caps could directly affect capital investment as well as operating costs. On the other hand, new and emerging market mechanisms such as aircraft emissions
trading are policy instruments that could introduce flexibility into regulatory compliance schemes. Such issues are discussed in Chapter 10.
When evaluating possible options for limiting certain emissions in the future, it is important to keep a proper perspective. This report is the first detailed assessment of
the global environmental effects of a single industrial sector. Air transport is only one of a number of transport modes that use fossil fuel, either directly or indirectly.
Each of these modes may have specific advantages, globally or nationally. Other sources of greenhouse gases and other emissions also contribute to the composition
of the global atmosphere and are likely to change with time. The environmental consequences of all emissions (transport and non-transport) and the economic impacts
associated with different policy options will need to be balanced.
In this report, the relative importance of various aircraft emissions are assessed according to the best available knowledge of atmospheric effects and in the light of
current knowledge of future technological options. Economic analyses will be required to investigate the consequences of possible mitigation strategies. Ideally, these
analyses would take into account the wide range of activities in the aeronautics and aviation industries and assign monetary value to emissions and their effects. The
current state of such economic analysis is discussed in Chapter 10.
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