Grantee Research Project Results

2011 Progress Report: Impacts of Global Climate and Emissions Changes on U.S. Air Quality (Ozone, Particulate Matter, Mercury) and Projection Uncertainty

EPA Grant Number: R833373
Title: Impacts of Global Climate and Emissions Changes on U.S. Air Quality (Ozone, Particulate Matter, Mercury) and Projection Uncertainty
Investigators: Liang, Xin-Zhong , Wuebbles, Donald J. , Williams, Allen , Kunkel, Kenneth , Caughey, Michael
Current Investigators: Liang, Xin-Zhong , Wuebbles, Donald J. , Williams, Allen , Lei, Hang , He, Hao , Kunkel, Kenneth , Caughey, Michael , Su, Senjian
Institution: University of Maryland - College Park
EPA Project Officer: Chung, Serena
Project Period: April 15, 2007 through April 14, 2011 (Extended to April 14, 2013)
Project Period Covered by this Report: April 15, 2011 through April 14,2012
Project Amount: $900,000
RFA: Consequences of Global Change For Air Quality (2006) RFA Text | Recipients Lists
Research Category: Air , Climate Change

Objective:

The objective of this study is to quantify and understand the impacts and uncertainties of global climate and emission changes, from the present to 2050 and 2100, on U.S. air quality, focusing on ozone, particulate matter and mercury. The original contribution of this research will derive from the application of a unique, state-of-the-art, well-established ensemble modeling system that couples a global climate-chemical transport component with a mesoscale regional climate-air quality component over North America. Both components incorporate multiple alternative models representing the likely range of climate sensitivity and chemistry response under the conceivable emissions scenarios to rigorously assess the result uncertainty. Each will be enhanced to contain a fully coupled model to study climate-aerosol interactions, focusing on how they affect U.S. air quality at the present and in the future.

We propose to conduct three primary sets of experiments by the ensemble modeling system to achieve the proposed objective. Historical simulations of climate and air quality for the recent past will first be conducted for system validation and bias identification, and also used as the baseline reference for future projections. Future projections for 2050 and 2100 will then be made to quantify the individual and combined impacts of global climate and emissions changes on U.S. air quality. Finally, sensitivity experiments will refine understanding of relationships with major contributing source regions and types, and uncertainties associated with key conclusions. All experiments will focus on April-October when most air quality episodes occur (except for sensitivity studies on the PM and mercury annual cycle), and integrate for a period of 5-10 years to obtain reasonably robust statistics. Subsequent diagnostic studies will identify possible future changes, and their climate and emissions causes, in the frequency, duration, and extreme pollutant concentrations of adverse air quality episodes over the United States.

Through the proposed application of this unique ensemble modeling system, we will make a major contribution to a key goal of the EPA Global Change Research Program to quantify the effect and uncertainty of global changes on U.S. air quality. The advanced state of the system components will result in a more complete scientific understanding of complex interactions among global climate and emissions and U.S. air quality across a full range of spatial and temporal scales. We will build on recent achievements of our ozone study, including a developed modeling system, viable experiment design, effective modeling strategy and objective diagnostic approach, for ozone consolidation, aerosol elaboration and mercury exploration studies for use in designing future effective emission control strategies to meet the national standards.

Progress Summary:

We investigate the effects of projected global changes in climate and human-related emissions for the year 2050 relative to 2000 for trends in the potential risk of hazardous ozone pollution episodes using a global climate chemistry model, CAM-Chem (Community Atmospheric Model with Chemistry), driven by meteorology output from Community Climate System Model version 3. The projected changes in climate are likely to foster the risk of high ozone pollution episodes over many parts of the world. Our analysis under projected climate and emissions on the frequency of “hazardous ozone days“ in which the peak ozone concentration exceed the limit in the summer of 2050, based on 8 and 1-hour standards, show that the risk of hazardous ozone pollution episodes will likely increase in developing regions, but changes of risk in developed regions depend on scenarios. The relative change of high ozone days is relatively larger under the 1-hour than the 8-hour standard, which indicates that the changes of surface ozone level are more significantly presented on the high value part.

We investigate the relative contributions of changes in local anthropogenic emissions (LE) versus changes in remote anthropogenic emissions (RE) to global surface ozone air quality in 2050 through a global climate chemistry model CAM-Chem driven by the meteorology output from CCSM-3. We find that projected changes in anthropogenic emissions under the A1FI scenario lead to an increase of 5-14 ppb in summertime daily maximum 8-hour (DM8H) ozone concentration over the United States by 2050, of which 48% is contributed by LE changes and 52% is contributed by RE changes. However, under the A1B and B1 scenarios, contributions from LE changes are much larger than that from RE changes over all three regions except the Asia under the B1 scenario, in which the RE changes contribute 31% of total change. The results indicate that for the United States and Europe, pollution control is a local issue under global low emission situations, while it becomes an international issue when fossil fuel use is rapidly increasing. Due to the weak Euro-Asia transport, local emission increase seems to be the main force for Asia’s ozone air quality change under all cases except the low emission scenario B1. Therefore, the strategies for regional air quality control need to be based on the global emissions perspective.

A mechanistic representation of the atmospheric mercury cycle is developed for CAM-Chem. The model simulates the emission, transport, transformation and deposition of atmospheric mercury (Hg) in three forms: elemental mercury (Hg0), reactive mercury (HgII), and particulate mercury (HgP). The chemistry mechanism includes the oxidation of Hg0 in gaseous phase by ozone with temperature dependence, OH, H₂O₂ and chlorine. Aqueous chemistry includes both oxidation and reduction of Hg0. Simulated wet depositions of mercury over the continental United States are compared to observations on 26 Mercury Deposition Network stations to test the wet deposition simulations. Both the evaluations on gaseous concentration simulation and wet deposition simulation confirm the ability of the CAM-Chem mercury model in simulations of atmospheric mercury cycle. In addition, the simulated results also present the global mercury air quality, which indicate that mercury pollution in East Asia and Southern Africa is very serious with TGM concentrations above 3.0 ng/m³.

We have completed the evaluation of aerosol simulations from the CMM5-CMAQ model system for the present conditions (1995-1999). We found that the CMAQ simulations well captured the average ground-level PM_2.5 (particulate matter with size smaller than 2.5 microns) concentrations in the rural/suburban sites, but had substantial underestimation in the urban areas, especially megacities such as Los Angeles. These results suggest that the modeling approach applied provides high credibility for the future projections of regional PM_2.5 pollution, but higher spatial resolution is needed to resolve the emissions and meteorology in urban areas for better PM_2.5 pollution simulations in the future. We also conducted present-day CMAQ simulations with the CAM-Chem lateral boundary conditions (LBCs), and results show lower PM_2.5 ubiquitously over the United States, which suggests the CAM-Chem LBCs transport less air pollutants into the United States than the clean LBCs set default in the CMAQ model. The consequence of these present-day model behaviors on future U.S. air quality assessment will be addressed in the remaining period of the project.

We have completed the analysis on the PM_2.5 simulations projected for the future conditions under different climate and emissions scenarios (A1Fi and A1B). It is found that ground-level PM_2.5 concentrations decrease in the eastern United States under both A1Fi and A1B scenarios; however, the PM_2.5 levels increase in the western United Staes under these scenarios. We also investigated the future projections with only climate change (emissions were kept as present-day level), and results suggest that the effects of climate change on ground-level PM_2.5 pollution are one order of magnitude lower than the effects of emissions change.

Future Activities:

Diagnose outputs to quantify relative roles of global climate and emission changes.
Diagnose outputs to study the impacts of climate and emission changes on U.S air quality.
Publish the results in peer-reviewed journal articles.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views
Other project views:	All 21 publications	21 publications in selected types	All 21 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	Post ES, Grambsch A, Weaver C, Morefield P, Huang J, Leung LY, Nolte CG, Adams P, Liang XZ, Zhu JH, Mahoney H. Variation in estimated ozone-related health impacts of climate change due to modeling choices and assumptions. Environmental Health Perspectives 2012;120(11):1559-1564.	R833373 (2011) R833373 (Final)	Full-text from PubMed Abstract from PubMed Associated PubMed link Full-text: EHP-Full Text PDF Abstract: EHP-Abstract & Full Text HTML

Supplemental Keywords:

climate change, emission, uncertainty, pollutant transport, ozone, particulate matter, mercury, aerosol, dust, deposition, regional climate model, air quality model, RFA, Air, Atmosphere, Air Pollution Effects, climate change, air quality modeling, environmental monitoring, particulate matter

Relevant Websites:

http://cwrf.umd.edu/application.php?aqm Exit

Progress and Final Reports:

Original Abstract

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.