Summary:

Research in my group uses science to contribute to the formation of far-sighted environmental policy. Our work uses computer models of regional and global atmospheric chemistry and transport to quantify the magnitude of air pollution, examine its transport around the country and around the world, quantify its impacts on health, agriculture and climate, and examine how new energy technologies can simultaneously reduce the emission of air pollutants and greenhouse gases. My research program addresses the following central questions: 

1)      What are present and potential future regional and global levels of air pollution? 

2)      What are/will be the impacts of air pollution to human health and welfare including climate change? 

3)      What are appropriate energy and air pollution policy responses?  

I seek to answer these questions through research projects on both national and global scales. To address the first question, my group uses regional and global computer models to simulate the emissions of air pollutants, their chemical transformation and movement around the world. We address the second question using tools drawn from agronomy, epidemiology, engineering and economics. Answers to the first two questions facilitate our identification of appropriate energy and air pollution policy responses.

Our recent research has analyzed the impacts of air pollution in both the largest rapidly industrializing country (China) and in the largest developed country ( US). On a global scale we are investigating the inter-continental transport of air pollutants with an emphasis on transport from Asia to the US, and the effect of emissions of certain air pollutants (ozone precursors and aerosols) on public health and climate change. These issues are interlinked, globally pervasive and addressing one provides opportunities for leveraging solutions to others.

Current projects and future goals are described below.

China Research: Impacts of Air Pollution on Agriculture and Public Health

China is at a cross-road. It has emphasized economic development with little regard for environmental protection. Using atmospheric modeling, agricultural and health effects assessment, and economics, we have evaluated the impacts of present and potential future levels of air pollution in China on agriculture and public health. We demonstrate that unless the Chinese government takes action now by requiring widespread use of pollution control devices and/or cleaner advanced energy technologies, in 2020 China will suffer enormous reductions in agricultural yields and large increases in premature mortalities resulting from increasing levels of air pollution.

United States Research: Implications for Air Pollution Policy

Current “cap-and-trade” regulations in the US limit total nitrogen oxide (NOx) emissions in order to control ozone concentrations. These regulations implicitly assume that the damage caused by the emission of a unit of NOx is independent of when (during the summer ozone season) and where it is emitted. We used regional atmospheric modeling to demonstrate that when and where NOx is emitted, in fact, has a large impact on the quantity of ozone produced. Using epidemiological concentration-response relationships we also showed that ozone-related premature mortalities and morbidities vary with the size of the exposed population. Thus a shift of a unit of NOx emissions from one place or time to another could result in large changes in resulting health effects due to ozone formation and exposure. As a policy alternative to a cap on emissions, we propose charging emitters fees that are commensurate with the damage their emissions cause. This would create an incentive for emitters to reduce emissions at times and in locations where they cause the largest damage.

Global Research

Inter-continental Transport of Air Pollutants

As Asia industrializes there is growing concern that its emissions will increasingly affect air quality in the northern hemisphere including the US. A key question is whether concentrations of Asian pollutants will consistently rise in the US due to increasing background concentrations in the northern hemisphere or will vary seasonally or inter-annually. We have simulated seasonal and inter-annual variability in transport of continental tracers using a global atmospheric model. Our work confirms earlier findings that April is the month of strongest mid-latitude transport but also shows that April is a time of low inter-annual meteorological variability. In addition, we estimated the average trans-Pacific transport time in spring to be approximately 3-weeks. Our results are important because they provide insight into transport characteristics which determine how significant and how variable the impact of Asian emissions will be on US air quality. We are presently estimating the health impacts that occur in the US, Europe and Asia from aerosols transported to these regions from other continents.

Linkages between Air Pollution and Climate Change Science and Policy

Net Radiative Forcing Due to Changes in Regional Emissions of Ozone Precursors

Air pollution impacts human health and welfare; it can also influence climate. From a policy perspective it would be advantageous to be able to credit countries for reducing their emissions of air pollutants that contribute to climate warming thus securing both local and global benefits. We have extensively analyzed the influence that emissions of ozone precursors (NOx, carbon monoxide and non-methane hydrocarbons) have on climate change depending on the continent from which they are emitted. We found that radiative forcing (change in the balance between incoming solar and outgoing infrared radiation) depends strongly on the geographical location of the emission reduction, with reductions in the tropics having the largest effect. Our key finding is that simultaneous reductions of CO, NMHCs, and NOx reduce radiative forcing resulting from emission of tropospheric O₃ precursors while reductions in NOx emissions alone do not. With NOx emission reductions alone, there is no net climate benefit because the cooling effect of decreasing ozone is offset by the warming effect of increasing methane. Our work provides a critical scientific step in developing a new policy mechanism to potentially include air pollutant emissions in a climate agreement.

Mitigating ozone pollution with methane emission controls: Global health benefits

Reductions in methane emissions decrease greenhouse warming; we show that they also decrease surface ozone concentrations globally, and consequently, reduce premature mortalities due to ozone exposure. By combining global atmospheric modeling, health effects assessment, and economics, our work quantifies the previously unrecognized co-benefits of methane mitigation for air quality and human mortality at ~$240 per ton methane (~$12 per ton carbon dioxide equivalent). Methane mitigation is cost-effective for air quality management, and because it affects ozone globally, methane provides a first means of directly managing global air quality. Our research is uniquely interdisciplinary, with broad relevance for air quality, climate, public health, and environmental policy.

Effective Policy Implementation: Sustainable Development

Complementing courses I’ve taught on sustainable development is a research project examining the efficacy of partnerships between governments, industry and non-governmental organizations in furthering the goals of sustainable development.

Summary  

Future Goals:

My past work has addressed critical questions at the intersection of atmospheric science and environmental policy both in the US, Asia and globally. Although these issues may seem overwhelming in their complexity, advances in computational modeling have made attempts to study and to identify scientifically supportable policy options both feasible and realistic. Establishing limits and confidence levels on these predictions is important. Linking the findings with policy development is vital.

I wish to build on our unusual ability to use sophisticated models of regional and global air pollution to evaluate the benefits to human health and welfare of various policy options. Future research in my group should contribute to identification of policies which lead to both local and global benefits through the strategic reduction of the emission of reactive air pollutants and greenhouse gases. Future research goals are described below.

Asia 

Implementation of China’s new “Energy Development Plan in the Middle and Long Term (2004-2020)” will affect carbon dioxide and air pollution emissions and as a result public health. I wish to identify the influence the plan will have and where changes to the plan would have clear local and global benefits.

I also wish to extend our analysis of air pollution impacts to India. Like China, India has severe and worsening air pollution and increasing emission of greenhouse gases. A recent international meeting of the Asian Brown Cloud experiment focused on methods to improve our understanding of the impact of air pollution on rural health and agriculture in Asia.

United States

In addition to ozone production, NOx contributes to the formation of fine particulate matter (PM) which is also regulated due to its adverse impact on human health. I wish to quantify the impacts of PM formed from NOx emissions from large stationary sources on public health in order to include it in our proposed “damage minimizing” modification of the current cap-and-trade program. In addition, I wish to examine how chemical weather (pollution) forecasting, which is being developed within the atmospheric science community, can be used to predict the damage specific NOx emissions will cause. In a regulatory system where damages rather than emissions were limited, chemical weather forecasting could help industry plan whether to operate additional pollution control devices during times and in locations where environmental damages were likely to be greatest, or to purchase power or site generating facilities elsewhere.

Global  

Animations:

Examine animations of the present and possible future transport of air pollutants from one region of the world to another!