Mexico City Document: Three "Future Stories" for the MCMA

Improving air quality in the Mexico City Metropolitan Area (MCMA) is a daunting task. To help local decision makers achieve this goal, the Mexico City Program’s mix of Boston- and Mexico-based researchers have redefined the approach and scope of “integrated assessments” commonly used to provide such guidance.

For the last decade, climate researchers have been touting integrated assessments as a way to determine the costs and benefits associated with alternative ways to address climate change. By comparing the cost to reduce (mitigate) greenhouse gases, as well as the cost to adapt to climatic changes, against the anticipated damages that climate change may bring, they hope to inform governments, industry, and the public about what society should do. Both complexity and controversy apply to the determination of those costs and impacts. And, the level of guidance that can be provided under those circumstances remains suspect. Due to the size and complexity of the effort, computational models tend to be global in nature, and treat the economic and societal aspects in a top-down, aggregated manner. More sophisticated models group nations and regions into economic zones, and with luck look at the positive and negative feedbacks among greenhouse gases, atmospheric aerosols, terrestrial ecosystems, oceans, and economic activity.

How much guidance can such approaches offer local decision-makers regarding what “to do?” Furthermore, how high on the priority list of things needing attention is air quality in general, and climate change, given all the other challenges facing the MCMA? These are tough questions. The Mexico City Program has turned integrated assessment approach on its head, defining it from the decision-maker’s perspective, rather than the modeler’s. This means looking at issues from a local and regional perspective first, and doing the analysis on a bottom-up, versus top-down basis. The goal is to be “prescriptive,” taking into account that the future is very uncertain, and that local decision-makers often have numerous and competing goals.

To be informative, both the analysis and discussion of “assessment” results must address three levels of “feasibility,” the first two primarily computational, and the third process oriented. These three “feasibility screens” are:

1. Technical Feasibility

To realize an improvement in air quality, measures must achieve sufficient reductions in the “right” emissions. Depending on whether the issue is ozone or particulate concentrations, this might mean the right pollutant reductions at the right time and location in the city. How effective in improving air quality are the arsenal of PROAIRE measures? Are the improvements short-term, or can they be sustained over many years or decades?

2. Economic Feasibility

Second, of those measures that are “effective,” which are “affordable?” Are they “cost-effective” on a narrow accounting basis, or in a broader economic, social and environmental context? What direct and indirect “policy options” promote the “technology options” via technical analysis? How might such policy options be designed to be even more effective? Which are more amenable to market-based versus command-and-control approaches?

3. Political and Institutional Feasibility

Just because quantitative analysis indicates that certain measures are effective from the perspective of economics or emissions reduction, does not mean than politicians can back them or that the business community and the public will accept them. Nor does it mean that the current structure of the MCMA’s environmental, transportation, urban planning, and economic development agencies can easily implement them. As we look at longer-term solutions, greater coordination among these agencies will likely be needed. How can they act in the near and long-term to implement the most technically and economically feasible options, including monitoring, enforcement and refinement of those options?

With all these factors in mind, the Mexico City Program has combined several methodological approaches to address these needs. Using the best available information and models, the program has combined Royal Dutch Shell’s top-down scenario approach with MIT’s fact-finding, scenario-based tradeoff analysis. This synthesis allows researchers to retain the prescriptive capabilities of bottom-up tradeoff analysis of transportation, industry and other end-use focused emissions reduction options, and couple it with the alternative long-term changes in the MCMA’s population and economy—including level of affluence and motorization, and urban form. This approach allows the Mexico City Program research team to identify robust, long-term, cost-effective, and, hopefully, implementable combinations of options.

Research to date has focused on the technical and economic feasibility of the various measures. In order to refine and make the analysis more useful, the dialogue phase—to further inform decision makers and vet the better solutions—needs to be further pursued. As the Program advances, improved linkages among the bottom-up emissions modeling, the calculation of changes in pollutant concentrations, and their associated exposure and health impacts are being developed. At the Sixth Workshop on Mexico City Air Quality in January 2003, the MIT Scenarios Team will present the current research, and invites all attendees to make suggestions on how to refine and improve the integrated assessment.