Aviation and the Global Atmosphere

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. Although improvements in aircraft engine technology and air traffic management technology will bring environmental benefits, these benefits are not expected to be sufficient to fully offset the projected growth of aviation emissions arising from increased demand for air transportation services (as discussed in the scenarios in Chapter 9). These scenarios adopt simplifying assumptions of full implementation of communication, navigation, and surveillance/air traffic management (CNS/ATM) and no infrastructure constraints. As a result, they are thought to show unrealistically high projected growth of air traffic and emissions. Policy measures aimed at addressing the growth of aviation emissions will need to take this factor into account.

. The International Civil Aviation Organization (ICAO) is the United Nations (UN) specialized agency that has global responsibility for the establishment of standards, recommended practices, and guidance on various aspects of international civil aviation, including the environment. The Kyoto Protocol committed countries to work through ICAO in limiting or reducing emissions of greenhouse gases from aviation bunker fuels, but international aviation emissions are not covered by emissions reduction targets in the Kyoto Protocol.

. Policy measures have the potential to limit the growth of aircraft emissions by encouraging technological innovation, effecting greater operating efficiencies in the aviation industry, and affecting demand. Such measures include initiatives to ensure timely implementation of CNS/ATM; development of regulatory standards for aircraft emissions, operational measures, and avoidance of delay; and market-based instruments such as environmental levies and emissions trading. Voluntary and mandated policies to reduce emissions internalize to the producer or consumer many of the associated environmental costs.

. Cost-benefit analysis (CBA) has been used as a tool to conduct economic analysis of environmental mitigation measures across many areas of economic activity, but some difficulties have arisen in its application to aviation, primarily because of measurement and information problems. CBA provides a framework for balancing economic and environmental impacts associated with different policy options. The precautionary and "polluter pays" principles set out in the 1992 Rio Declaration are also relevant to economic analysis of policies aimed at limiting the growth of aviation emissions.

. In 1981, ICAO established aircraft engine emission standards for oxides of nitrogen (NOx). Since then, the NOx standard has been made more stringent (by 20% in 1993). A further 16% change to newly certified engines after 2003 was recommended in 1998. ICAO has established an approach that requires that any actions to mitigate the environmental effects of aviation show environmental need, technical feasibility, and economic reasonableness. The current method of regulating NOx based on the landing/take-off (LTO) cycle does not fully address emissions at altitude. ICAO is developing a new parameter for emissions certification during climb and at cruise altitude to complement the existing LTO cycle-based parameter.

. Timely implementation of CNS/ATM is important to success in leading to reduced fuel burn and emissions; CNS/ATM is critically dependent on the development of necessary institutional and financial arrangements.

. Existing studies indicate that levies on fuel and en route charges are viewed as the most environmentally effective levies. If passed through to consumers, environmental levies could reduce consumption of aviation fuel, hence aircraft emissions, by providing incentives to develop and use more energy-efficient aircraft, by optimizing operations, and by reducing the growth in demand for air transport. However, a practical difficulty is that most bilateral air service agreements exempt fuel used internationally from tax. Levies at a regional level may avoid this and other problems. There is concern, however, that this approach would not have sufficient environmental impact, in some cases could increase other emissions, and could lead to economic distortions.

. Emissions trading is a market-based approach that enables participants from all industries to cooperatively minimize the costs of reducing emissions. The role of governments would be to set a cap on emissions and rules for trading reductions under such a cap. Initial experience at the national and international levels in other industries suggests that emissions trading can provide an effective incentive for firms to innovate and achieve low-cost emissions reduction.

. Other potential mitigation measures are voluntary agreements to meet environmental targets and funding of research to better understand the environmental impact of aircraft emissions.

. There are uncertainties over future trends in traffic and emissions and the impact of mitigation measures.

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