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State and Local Climate and Energy Program

Air Quality

Air Quality Impacts Associated with Climate Change

Air pollution levels are directly influenced by changes in weather, such as heat waves. Changes in weather that might result from climate change, such as warmer temperatures and more frequent episodes of stagnant air, therefore, also have the potential to affect air pollution. In addition, increases in heat-related mortality and morbidity are expected due to warmer temperatures.

EPA's Assessment of the Impacts of Global Change on Regional U.S. Air Quality: A Synthesis of Climate Change Impacts on Ground-Level Ozone (2009) evaluated the potential impact of global change on U.S. air quality (assuming no additional air pollutant emission reductions).

  • Ozone. The assessment indicates that climate change has the potential to significantly increase ground-level ozone concentrations in many regions over the next 40 years, although specific regional patterns are uncertain.
  • Particulate Matter. The analysis is less definitive about particle pollution impacts, but indicates that future climate conditions might result in a range of impacts—both increases and decreases—in particle pollution concentrations in different regions. Climate change may also affect different components of particle pollution differently.

Numerous scientific studies have linked ozone and particle air pollution to a variety of health problems, including increased susceptibility to respiratory infections and premature death.

Information about estimating the costs, benefits, and economic impacts of air quality improvements is available from EPA's Air Benefits and Costs Group and in the Report to Congress on the Benefits and Costs of the Clean Air Act. More details on assessing the air quality benefits of clean energy initiatives are available in Chapter 4 of Assessing the Multiple Benefits of Clean Energy: A Resource for States.

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Air Quality Contributions to Climate Change

In addition to changes in ozone and particle pollution due to climate change, these pollutants also contribute to climate change. Different types of pollutants affect the climate in different ways, depending on their specific properties and the amount of time they stay in the atmosphere. For example, particles influence the climate by scattering and absorbing incoming solar radiation and interacting with various cloud processes. Particles can also have important indirect effects on climate through impacts on clouds and precipitation.

Some pollutants absorb energy and lead to climate warming.

  • Ozone air pollution, according to the Intergovernmental Panel on Climate Change Exit EPA disclaimer, is the third most significant GHG after carbon dioxide and methane in terms of global warming.
  • Black carbon (BC), which is a component of particle pollution, directly absorbs incoming solar radiation and reduces reflection of sunlight off of snow and ice. In both of these ways, black carbon contributes to increased absorption of energy at the earth's surface and warming of the atmosphere. Recent studies suggest that black carbon may be having a significant impact on the earth's climate.

Other pollutants reflect the sun's rays and prevent that energy from reaching the Earth's surface, leading to climate cooling.

  • Some types of particles—particularly sulfates, nitrates, and some types of directly emitted organic carbon—are largely reflective and therefore have a net cooling impact on the atmosphere.

For more information about air quality interactions with climate change, see EPA's National Air Quality Status and Trends (2008).

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Air Quality Benefits of Climate Change Mitigation

Because of the links between climate and air quality, the National Academy of Sciences (2005) recommends that air pollution and climate change policies be developed through an integrated approach, as discussed in Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties Exit EPA disclaimer. A number of strategies that are used to reduce greenhouse gases for climate change mitigation will reduce air emissions that contribute to multiple air quality concerns such as ozone and particle pollution, toxic air pollutants, atmospheric deposition, and visibility. These kinds of approaches are "win-win," providing benefits for both air quality and climate change mitigation simultaneously.

Specifically, clean energy offers a cost-effective way to meet growing demand for electricity and natural gas while reducing emissions of air pollutants and greenhouse gases, improving public health, lowering energy costs, and improving the reliability and security of the energy system.

Energy efficiency can reduce electricity consumption, and renewable energy can supply energy from non- or less-polluting sources, resulting in fewer air emissions from electric generating power plants and improved air quality.

Many of the pages on this website provide detailed information and resources on clean energy opportunities for state and local decision makers, including:

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Assessing the Multiple Benefits of Clean Energy

Assessing the Multiple Benefits of Clean Energy: A Resource for States provides an overview of the multiple benefits of clean energy and their importance. It includes information on:

  • The importance of and approaches to calculating or estimating energy savings as the foundation for deriving multiple benefits
  • A range of tools and approaches to estimating energy systems, environmental, and economic benefits across varying levels of rigor
  • How states have supported the use of clean energy through the estimation of multiple benefits

Clean Energy Options for High Electric Demand Days

Clean Energy Options for Addressing High Electric Demand Days (PDF) (73 pp., 956K, About PDF) summarizes best practices for cross-cutting policies that promote the adoption of clean energy technologies that can reduce the air emissions from electric generators in High Electric Demand Days. The report provides detailed information on targeted policies and programs that promote energy efficiency, demand response, and clean DG technologies that could be employed to deliver significant reductions in air emissions, especially NOx, from electric generators on high electric demand days.

State Implementation Plan (SIP) Credits for Emission Reductions

Guidance on SIP Credits for Emission Reductions from Electric-Sector Energy Efficiency and Renewable Energy Measures (PDF) (39 pp., 830K, About PDF) can help states in quantifying and including emission reductions from energy efficiency and renewable energy measures in State Implementation Plans. The guide describes four primary steps that states should take:

  • Estimate energy savings or the amount of energy generation that will be displaced by the new generator.
  • Convert the energy impacts of a project or initiative into an estimated emissions reduction.
  • Determine the impacts on air quality from estimated emission reductions.
  • Provide a mechanism to validate or evaluate the effectiveness of the project or measure.

Output-Based Environmental Regulations

EPA'sClean Energy-Environment Guide to Action Chapter, Output-Based Environmental Regulations to Support Clean Energy Supply (PDF) (11 pp, 809K, About PDF) describes how states can develop output-based environmental regulations (OBRs), which relate emissions limits to the productive output of a process. Because overall efficiency is rewarded, OBR is a powerful mechanism to encourage a range of energy efficiency equipment (e.g., combined heat and power) and process improvements, as well as the use of a host of renewable fuels.

Public Health Benefits of Reducing Air Pollution

In Public Health Benefits of Reducing Ground Level Ozone & Fine Particle Matter in the NorthEast U.S. Exit EPA disclaimer, the Northeast States for Coordinated Air Use Management (NESCAUM) examines the public health and monetary benefits of several potential emission control programs, which include an electric generating unit control strategy for nitrogen oxides and sulfur dioxide.

State Technical Forum Webcasts

The State Technical Forum is a monthly webcast series that explores analytical questions and key issues surrounding state climate change and clean energy efforts. Each forum is a facilitated discussion among state energy, environmental, and public utility commission officials, featuring peer exchanges, expert presentations, and targeted background documents.

EPA has held Technical Forum calls on the following topics:

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Clean Air and Climate Protection Software Tool (CACPS)

CACPS Exit EPA disclaimer calculates and tracks emissions and reductions of greenhouse gases (carbon dioxide, methane, nitrous oxide) and criteria air pollutants (NOX, SOX, carbon monoxide, volatile organic compounds, PM10, PM2.5) associated with electricity, fuel use, and waste disposal.

Co-Benefits Risk Assessment (COBRA) Screening Model

COBRA is a screening tool that enables users to:

  • Roughly estimate the impact of emission changes on ambient air pollution
  • Further translate this into health effect impacts
  • Monetize the value of those impacts

View the estimated county-level results in tables and maps

Emissions & Generation Resource Integrated Database (eGRID)

eGRID contains a comprehensive inventory of environmental attributes of electric power systems including air emissions data for nitrogen oxides, sulfur dioxide, carbon dioxide, and mercury. The data are organized in a series of Microsoft Excel files that state governments can use to find data on emissions from electricity generation within their state.

Environmental Benefits Mapping and Analysis Program (BenMAP)

BenMAP is a tool for estimating the health and economic benefits of air pollution reduction strategies. It combines air pollution monitoring data, air quality modeling data, census information, and population projections to calculate a population's potential exposure to ambient air pollution. BenMAP is used primarily to estimate benefits from changes in particulate matter and ozone concentrations, but it can also be adapted for other pollutants. Most Windows-based computers run BenMAP.

Particulate Matter (PM) 2.5 Benefit Per Ton Estimates

EPA's PM2.5 benefit per ton estimates allow users to:

  • Quickly estimate the monetized benefit of PM2.5 emission precursors.
  • Estimate the benefits of scenarios affecting emission sources located in one of nine urban areas or nationwide.
  • Estimate the benefits of scenarios that affect directly emitted PM2.5, nitrogen oxide (NOX), sulfur oxides (SOX), ammonia (NH3), or volatile organic compounds (VOCs) from emission generating units, stationary sources, mobile sources, and area sources.

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