Atmospheric Sciences & Global Change
The Future of Clean Air
Century-scale scenarios connect clean air with prosperity
2004 urban air pollution (PM10 Air Pollution) was plotted by country as a function of Gross Domestic Product (GDP Per Capita) showing that as per capita income rises, air pollution falls. Two exceptions in the graph are Kuwait and the United Arab Emirates which have high income levels, but high pollutant levels, which may be influenced by windblown dust in that region. (Sources: World Health Organization, Annual mean concentration of particulate matter of less than 10 microns diameter (PM10) [ug/m3] and World Bank, GDP per capita.) Enlarge Image
Results: Affluent communities demand certain perks. And one of them is breathing clean air. After comparing historical data on regional air pollution and the affluence level of communities, scientists at Pacific Northwest National Laboratory and the University of North Carolina have projected air pollution scenarios into the end of the 21st century. They combined an integrated energy-economic model with a detailed atmospheric chemistry model to assure that higher projected regional income translates to lower regional air pollutant levels. Their century-scale scenario results were published in Climatic Change.
Why it matters: Emphysema, asthma, and lung cancer. These are just a few of the respiratory illnesses that are associated with exposure to ozone and air pollution particles. In most affluent regions of the world, air pollution is regulated to reduce the risk to human health and natural ecosystems caused by these airborne toxins. These air pollutants also alter present and future climate patterns, so making realistic scenarios of these emissions is important for making realistic projections of future climate change. Understanding the many factors that influence a region's air pollution levels helps scientists project future levels and climate change.
"This work was a foundational reference case for the recently released RCP4.5 model scenario, one of four scenarios that will be used by modeling groups around the globe to make realistic projections of future climate change," said Dr. Steven J. Smith, scientist at the Joint Global Change Research Institute, a partnership between PNNL and the University of Maryland, and lead research author. The four Representative Concentration Pathway scenarios are described in a special issue of Climatic Change.
Methods: Researchers combined two types of climate models for their analysis. The first was the PNNL-developed Global Change Assessment Model, or GCAM, which combines economic, energy, and land-use information accounting for energy supplies, agriculture, and land to track numerous pollution emissions. The second is the Model for OZone and Related chemical Tracers, or MOZART, a three-dimensional atmospheric chemical transport model.
The research team constructed a reference scenario with surface pollutant concentrations that tracked regional income over the 21st century. Historical analyses showed that high-income regional populations rarely tolerate high levels of pollution. The scientists used this analysis to guide their assumptions for the next century. Where simulated future pollution levels were not consistent with historical data because of factors such as weather, population, geographic location, or growth in industry, they increased the assumed level of air pollution control to improve consistency between regional pollution levels and economic income through time. They were able to project scenarios with a greater consistency between the income assumptions and simulated surface pollutant levels as compared to previous approaches. Surface air pollution concentrations in the scenarios were consistent between projected regional incomes and surface particulate levels. Consistency for surface ozone levels was more difficult to achieve due to the influence of emissions from up-wind regions.
What's next: Researchers are working on evaluating the co-benefit of climate policy in terms of reduced pollutant levels.
Acknowledgments: This work was funded by the Department of Energy's Office of Science and the Environmental Protection Agency. The work was performed by Dr. Steven J. Smith and Page Kyle of JGCRI, and Dr. J. Jason West of the University of North Carolina.
References: Smith SJ, JJ West and P Kyle. 2011. "Economically Consistent Long-Term Scenarios for Air Pollutant Emissions." Climatic Change, 108: 619-627. DOI: 10.1007/s10584-011-0219-1.