white clouds above silhouette of clouds at day

Aviation Environmental Policy and Issues of Timescale, Chapter 3

Wolfe, Philip. (2015). Aviation environmental policy and issues of timescale. PhD dissertation, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA.


Every operational, technological, and policy decision affecting aviation represents a potential tradeoff among economic efficiency and impacts to climate, air quality, and community noise. Furthermore, effects in these domains occur over different temporal and spatial scales and with different aleatoric and epistemic uncertainty. Thus, robust, fast, and flexible tools that value these impacts on a common scale such as monetized changes in net welfare are needed along with methodologically sound and appropriate analysis frameworks to inform decisionmaking. The objectives of this thesis are threefold: 1) to advance the modeling tools used to calculate and value aviation’s impact on the environment; 2) to analyze realworld aviation environmental policies and advance policy decision-making support; and 3) to explore the underlying issues of timescales in policy modeling, to develop and make explicit the treatment of these timescales, and thereby to improve policy support best-practices. In support of the first objective, a model is presented for calculating the health impacts of aviation noise, particularly hypertension, myocardial infarction, and stroke to complement current modeling approaches of the willingness-to-pay for noise abatement. Also, advances are made to an existing simplified climate model for aviation by improving the representation of uncertainty, updating modeling components for both long- and short-lived forcing agents, and developing a module to consistently model the life-cycle impacts of alternative fuels. Finally, a method for modeling the social costs of aviation lead emissions is developed. In support of the second thesis objective, three policy case studies are presented: aircraft noise certification, residential soundproofing and land acquisition, and general aviation lead emissions. The costs and benefits of different policies are evaluated for each case. Results are calculated with explicit accounting for scientific, modeling, and economic uncertainty and are presented considering a range of policy-maker preferences for near- or long-term benefits. The thesis finds that aircraft certification stringency increases up to -5 dB from prior noise limits are cost-beneficial for all discount rates and for the entire range of scientific and economic assumptions and that a -7 dB stringency is cost beneficial when environmental costs are high or are discounted at a lower rate than market costs. The benefits of these policies are less than $5 billion USD over the lifetime of the policy. Further, this thesis finds that noise impacts on health cause an additional 40%-60% of welfare damages compared to considering annoyance costs alone. Noise insulation projects for homes in the vicinity of an airport are found to be on average cost beneficial only when aircraft related noise levels are above 75dB Day-Night Level, and that residential land acquisition projects are not cost-beneficial when considering environmental benefits alone. Finally, the work estimates the average environmental cost of leaded fuel emissions from general aviation at $1.06 billion USD per annum, with the environmental costs of aviation lead being sensitive to background atmospheric lead concentrations. To support the third thesis objective, a framework is introduced for explicitly considering appropriate timescales in environmental policy analysis. This thesis identifies a modeling framework consisting of three timescales: the policy influence period, the environmental lifetime, and valuation timescale. Focusing on the policy influence period, this framework is tested using the noise stringency certification policy as a test case. Failure to account for the full policy lifetime leads to an undercounting of environmental benefits. Furthermore, not considering the full timescale of policy costs or the impact of exogenous technological improvement on cost projections can impact the apparent appropriateness of a potential policy. In the case of noise stringency certification, a -7 EPNdB stringency increase appears to have net costs when a static policy time period from 2006 to 2036 is considered, but is cost beneficial over a more appropriate timescale that covers the full costs and benefits of the policy.