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Now available in PDF format: Abstract Book [7.4 Mb] (posted 10 November 2005)

Abstracts for Speakers: Session 4

Air Quality Management: Application of Climate Science (AQ)

Sub-Theme 1: Climate Change, Air Quality and Human Health

AQ1.1

Review of the Health Effects Potentially Associated with Projected Changes
in Concentrations of Air Pollutants and Aeroallergens

Kristie Ebi, Exponent Health Sciences Group, kebi@exponent.com

Introduction:

Because weather affects the development, transport, dispersion, and deposition of air pollutants, there is concern that climate change could affect the burden of illness and mortality associated with these gases and fine particles. Climate change can affect air quality directly through changes in chemical reaction rates, boundary layer heights that affect vertical mixing of pollutants, and changes in synoptic airflow patterns that govern pollutant transport, or indirectly through changes in biogenic emissions. Unraveling the relationships among weather/climate, air pollution, and health is
complex. More is known about the potential impact of climate change on ground-level ozone than other air pollutants.

Methods:

Literature was evaluated on the associations between weather and adverse health outcomes from exposure to air pollutants and aeroallergens, and on how the burden of these disease are projected to change under a changing climate.

Results:

Climate change could impact local to regional air quality through shifting regional weather patterns and their associated statistics, increasing or decreasing anthropogenic emissions via changes in human behavior, and altering the levels of biogenic emissions as a result of higher temperatures and land cover change. However, establishing the scale and direction of change is challenging. Future air quality, especially at the local to regional level, will be moderated by background levels of a range of pollutants at the global scale. For example, background ozone levels have risen since pre-industrial times and this trend is expected to continue over the next 50 years. Assuming no change in the levels of ozone precursor emissions, the future occurrence of the requisite meteorological conditions will determine the frequency of "ozone episodes." When the necessary conditions occur, current air quality standards are projected to be exceeded. As many major cities reduce vehicle-based pollutant emissions, it is expected that urban levels of ozone will approach rural levels.

Increased concentrations of carbon dioxide and increases in temperature are projected to increase the growth rate of allergen-producing plants, the production and transport of pollen, and the length of the pollen season. Changes have been observed in some regions that are attributed to climate change. Air pollution may facilitate the penetration of allergens into the lungs, as well as increase the depth of allergen penetration; both of which could increase the risk of allergic diseases and asthma.

[Presentation: PDF | PPT]

AQ1.2

Impact of Climate Change on Air Pollution Episodes in the United States

L.J. Mickley, Harvard University

D.J. Jacob, Harvard University

B.D. Field, Harvard University

D. Rind, Goddard Institute for Space Studies

J.S. Fu, University of Tennesee

J.H. Seinfeld, Caltech

D.G. Streets, Argonne

One issue often overlooked in climate change discussions is the probable impact of climate change on air pollution episodes. It is well known, however, that weather is a key variable controlling the severity and duration of these episodes. Concentrations of pollutants are highly sensitive to winds, temperature, humidity, and other weather variables. For example, the anomalously hot and stagnant conditions in the summer of 1988 led to the highest ozone year on record in the northeastern United States. Concentrations of particulate matter (P.M.) are also strongly tied to weather
conditions. As greenhouse gas concentrations increase and climate change takes place, the consequences for air quality and human health could be
significant, but the magnitude of this effect is not known.

To provide policymakers with valuable information on this issue, we have launched a multi-institutional project called GCAP: Global Climate and Air Pollution. The goal of GCAP is to quantify the effects of 2000-2050 climate change on air quality in the United States. We will compare these effects to those of changing manmade emissions. Our approach is to apply present-day and future meteorological fields calculated by the Goddard Institute for Space Studies general circulation model (GISS GCM III) to the Harvard global chemistry-aerosol transport model (GEOS-CHEM). For a more accurate simulation of regional air pollution, we will also apply initial and boundary conditions from the global models to the CMAQ regional model.

As a first step in the GCAP investigation, we implemented tracers of manmade pollution (carbon monoxide and soot) into the GISS GCM and performed a climate simulation from the present-day to 2050. Our results show that the severity and duration of summertime pollution episodes in the Midwest and Northeast United States increase significantly by 2050 relative to the present-day. Pollutant concentrations during episodes increase by 5-10%, and the average episode duration increases from 2 to 3-4 days. These increases in pollution severity and duration are due solely to climate change in the model; they appear linked to a decline in the frequency of low pressure systems crossing southeastern Canada. These systems, and the cold fronts that accompany them, ventilate the Midwest and Northeast. With fewer cold fronts in the future model atmosphere, stagnation episodes last longer and pollutant levels build to higher values.

[Presentation: PDF | PPT]

AQ1.3

Ozone Air Quality Management through Methane Emission Reductions: Global Health Benefits

J. Jason West, Princeton University, Atmospheric & Oceanic Sciences Program, and Woodrow Wilson School of Public and International Affairs, jwest@princeton.edu

Arlene M. Fiore, NOAA Geophysical Fluid Dynamics Laboratory

Larry W. Horowitz, NOAA Geophysical Fluid Dynamics Laboratory

Denise L. Mauzerall, Princeton University, Woodrow Wilson School of Public and International Affairs, and Geosciences Department

Methane and ozone are the second and third most important greenhouse gases after carbon dioxide. Tropospheric methane oxidation also contributes to the growing global background concentration of surface ozone, an air pollutant associated with premature human mortality. Mitigation of methane emissions therefore decreases surface ozone everywhere while slowing climate warming, yet methane mitigation has not been considered for air quality management.

Here we estimate the effects of methane mitigation on global surface ozone concentrations, and the consequent global decreases in premature
mortality. Relative to a baseline scenario from 2000 to 2030 (based on IPCC SRES A2), we apply a 20% reduction of global anthropogenic methane emissions (65 Mton CH₄ yr^-1) starting in 2010. Using the MOZART-2 global atmospheric chemistry-transport model, we estimate that this methane reduction would decrease 8-hr. surface ozone by ~1 ppbv (part per billion by volume) globally. The global reduction in premature human deaths resulting from these surface ozone decreases are then estimated using epidemiological relationships. We combine the simulated daily spatially-distributed decreases in surface ozone with estimates of future population, to estimate the global incidences of premature mortality prevented by the methane reduction. Results are expressed both as avoided premature mortalities and as monetized benefits per ton of methane reduced.

Our results indicate that methane emission control is a viable approach to long-term ozone management, with benefits that are shared globally. Methane mitigation therefore offers a unique opportunity to manage air quality globally, while slowing greenhouse warming, improving public health, and increasing energy supply.

Fiore, A. M., D. J. Jacob, B. D. Field, D. G. Streets, S. D. Fernandes, and C. Jang (2002), Linking ozone pollution and climate change: The case for controlling methane, Geophys. Res. Lett., 29(19), 1919.

West, J. J., and A. M. Fiore (2005) Management of tropospheric ozone by reducing methane emissions, Environ. Sci. & Technol., 39(13): 4685-4691, doi: 10.1021/es048629f.

West, J. J., A. M. Fiore, L. W. Horowitz, and D. L. Mauzerall (under review) Mitigating ozone pollution with methane emission controls: global health benefits, Proc. Nat. Acad. Sci.

[Presentation: PDF | PPT]

AQ1.4

EPRI Workshop on Interactions of Climate Change and Air Quality: Findings and Recommendations

Daniel J. Jacob, Harvard University, djacob@fas.harvard.edu

Better understanding of the interactions between climate change and regional air quality is an emerging priority for environmental policy. Aerosols and ozone, the two principal air pollutants in the developed world, also affect climate in important and complicated ways. In turn, changes in climate may have profound implications on air quality through perturbations to winds, mixing depths, temperatures, and other meteorological variables. Climate change will also affect emissions associated with fires, dust storms, lightning, and the biosphere, as well as the atmospheric deposition and ecosystem cycling of bio-accumulating pollutants such as mercury. Better understanding and assessment of the linkages between air quality and climate change is needed to develop joint mitigation approaches that are overall more effective. This will require accurate physical models that account for the interactions between atmospheric components and climate on global to regional scales. Presently, there are major gaps in scientific understanding that limit the development of such models. In order to identify the critical research priorities, the Electric Power Research Institute (EPRI) convened a workshop in April 2005 with participation of a broad range of scientific experts. We present here the key findings and recommendations from the workshop, including in particular the identification of specific gaps in knowledge where focused research programs would earn large dividends for improved decision making.