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62 This handbook presents airport practitioners and decision makers, who may face signifi- cant adverse impacts from uncertain future climate change events, a methodology that can be used with currently available climate projections to simulate a full range of potential future outcomes. While the methodology itself is sound, as with any quantitative analysis, the outputs will only be as good as the inputs used. Climate science is progressing rapidly, and new and better climate models are constantly being developed and updated. Consequently, future research could be conducted using the latest projections as they become available, and it is suggested that analysts who want to use up-to-date climate forecasts should keep abreast of the latest CMIP5 projections available from the IPCC, which is the UN-sponsored entity charged with assessing scientific, technical, and socioeconomic information concerning climate change. The analysis and methodologies presented focus on two specific aspects of climate change likely to affect airports: sea level rise and rising temperatures. While these impacts are readily measur- able, other potential impacts of climate change may also be relevant for certain airportsâfor example, the increased occurrence of localized thunderstorms or air turbulence. Research could focus on advances in climate science to assess whether and how accurately these (or other) types of localized events could be forecast as the science improves. At a more detailed level, there are important aspects of the sea level rise and high-temperature analyses presented here and in the accompanying Microsoft Excel files that could be improved if better data become available. In the case of sea level rise, the modeling is based on estimates of historical flooding probabilities and future sea level rise that may not be particularly accurate for a given airport. By necessity, the estimated historical probabilities often rely on small numbers of actual flood- ing events and so may be subject to significant change as new events occur. Additionally, the future sea level rise estimates used in the Monte Carlo simulations rely heavily on a single table of probabilities for global mean sea level rise produced in a NOAA technical report (Exhibit D-4 in Appendix D). The climate science supporting the probabilities shown there is changing rapidly. Moreover, in order to employ the suggested methodology, one must interpolate between these probabilities; thus, the projections themselves may be subject to uncertainty across a wide range of outcomes. Again, as better or more complete estimates of sea level rise become available, better predictions from the Monte Carlo simulation methodology could be obtained. In addition, the flood modeling as presented is limited because it cannot take account of any variations in terrain that may exist between the reporting stations and the airport itself. Nor can it account for any existing mitigations (such as levies or stormwater systems) that may be C H A P T E R 8 Study Limitations and Recommendations for Future Research
Study Limitations and Recommendations for Future Research 63 operational. However, knowledgeable users of the software can overcome these shortcomings by adjusting their critical infrastructure elevations to take account of existing mitigations. Similarly, in the case of high temperatures, one expects that future research will be able to use better and more accurate localized forecasts. Specifically, the localized constructed analogs (LOCAs) referenced in Appendix D are themselves the result of a specific statistical downscaling technique that potentially could be improved in the future. Finally, the weight restriction calculations used in the Excel file for high temperatures are estimates only; analysts may want to confirm performance parameters with aircraft manufacturers when evaluating actual payload penalties. Overall, the use of better and more current localized data projections would be extremely valuable for future research efforts relating to potential climate change impacts on airports. It should also be noted that the Monte Carlo simulation technique could be more broadly appli- cable to other factors that affect airport risk assessments if these factors can be characterized probabilistically.
