Final Report: Impacts of Climate Change and Global Emissions on US Air Quality: Development of an Integrated Modeling Framework and Sensitivity Assessment

EPA Grant Number: R830961
Title: Impacts of Climate Change and Global Emissions on US Air Quality: Development of an Integrated Modeling Framework and Sensitivity Assessment
Investigators: Adams, Peter , Pandis, Spyros N.
Institution: Carnegie Mellon University
EPA Project Officer: Chung, Serena
Project Period: March 23, 2003 through March 22, 2006 (Extended to March 22, 2007)
Project Amount: $900,000
RFA: Assessing the Consequences of Global Change for Air Quality: Sensitivity of U.S. Air Quality to Climate Change and Future Global Impacts (2002) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air , Global Climate Change

Objective:

The objectives of this project are as follows:

  1. Develop a comprehensive modeling system for the description of the interactions between climate and local/regional air quality. This system will use a global climate-chemistry model, a regional meteorological model, and a regional air quality model to describe the relevant timescales (hours to decades) and length-scales (kilometers to global scales). It will also include an emissions processing system that will estimate climate-dependent emissions.
  2. Determine the sensitivity of ozone, particulate matter (PM), acid deposition, and visibility to individual meteorological parameters by performing a set of sensitivity experiments in the context of regional chemical transport models (Particulate Matter Comprehensive Air-Quality Model with Extensions [PMCAMx] and Community Multiscale Air Quality [CMAQ]).
  3. Evaluate the ability of the modeling system to describe current air quality in the United States, including annual average pollutant concentrations, their probability distributions, and the frequency of extreme air pollution episodes.
  4. Develop a set of future (year 2050) scenarios (meteorological fields, emissions, and chemical boundary conditions). These scenarios will include climate change and/or global emissions changes and will bound the space of system responses (best-, mean-, and worst-case scenarios).
  5. Use the comprehensive modeling system and these scenarios to assess air quality in the year 2050 with and without climate change and with and without changes in global emissions.
  6. Investigate reduced-form models and methodologies for incorporating the effects of climate change and global emission changes in future planning and assessment.

Summary/Accomplishments (Outputs/Outcomes):

Over the course of the project, a variety of research tasks were performed to achieve the goals listed above.

A. Regional Chemical Transport Model (CTM) Simulations of Sensitivity to Climate Parameters

A number of sensitivity simulations have been performed and analyzed to evaluate the impact of climate change on annual average PM2.5 concentrations, daily maximum 8-hour average (MDA8) ozone concentrations, and ozone exceedances. Four 10-day periods have been modeled so that all 4 seasons can be examined: 12–21 July 2001, 1–10 October 2001, 6–15 January 2002, and 1–10 April 2002. The first 3 days from each period were used as model initialization days and are excluded from the analysis. For each season, a base case and a suite of sensitivity simulations are performed. Each sensitivity simulation tests a single meteorological variable by perturbing it a given amount. The perturbed variables include temperature, wind speed, absolute humidity, mixing height, cloud liquid water content (LWC) and optical depth (OD), cloudy area, precipitation rate, and precipitating area. Except for cloud, precipitation, and mixing height changes, all perturbations are imposed uniformly in space and time on the modeling domain.

This activity has resulted in two peer-reviewed publications (Dawson, et al., 2007a; Dawson, et al., 2007b). The meteorological factor that had the largest impact on ozone was temperature, which increased MDA8 ozone on average by 0.34 ppb K-1. Other factors of some importance for ozone included absolute humidity, wind speed, and mixing height. For PM2.5, temperature was found to decrease average concentrations in January by -170 ng m-3 K-1 on average due to evaporation of ammonium nitrate and organic aerosol. In July, temperature led to increases in sulfate concentrations that largely offset this decrease. Other meteorological factors with significant impacts on PM2.5 levels included mixing height, wind speed, absolute humidity, and precipitation. This activity elucidates important physical and chemical processes that link climate change to air quality, eliminates minor sensitivities from consideration, and is useful for understanding later simulations in which meteorological parameters change simultaneously.

B. Results From Global Climate-Chemistry Simulations

A “unified” global model of climate, ozone photochemistry, and aerosols was used to predict the effect of climate change on future ozone and PM levels globally. Emissions were held at constant (present) levels to isolate the effect of climate change. A future climate was imposed on the global model by changing the sea-surface temperatures and associated ocean boundary conditions, which resulted in a mean increase of 1.7°C in global surface air temperatures, an increase in lower tropospheric specific humidity of 0.9 g H2O per kg air, and a mean increase in precipitation of 0.15 mm d-1. Impacts on annual-average PM2.5, annual-average ozone, and ozone episodes were analyzed across the globe but with a focus on the eastern United States as well. This activity has resulted in two peer-reviewed publications and contributes significantly to a third (Racherla and Adams, 2006; Racherla and Adams, 2007a; Racherla and Adams, 2007c).

Several conclusions result from this work. The tropospheric ozone burden decreased by 5%, primarily as a result of faster ozone loss rates via photolysis in the presence of water vapor. Ozone mixing ratios at the surface in remote areas decreased between 1 and 3 ppbv. Global burdens of PM2.5 species decreased between 2 and 18% because of increased wet deposition with increased precipitation. However, regional precipitation decreases and increases in chemical production of sulfate led to increased PM2.5 concentrations in some areas. Despite the fact that the global and annual average ozone burden decreases with the increasing humidity in our future climate simulations, a more complex response occurs in polluted regions. Summertime ozone increases occur over Europe and North America, but the increase is larger over North America. The different responses can largely be attributed to isoprene in the southeastern United States. Temperature-sensitive isoprene emissions increase in the model in this area leading to stronger ozone increases than seen in other polluted areas. Second, the frequency of ozone episodes (defined as any time step in which a grid cell exceeds 80 ppbv ozone) increases in our future simulations. An analysis of 5 present and 5 future years indicates that the increased episode frequency is statistically significant with respect to interannual variability. Finally, an analysis of interannual variability with the global model indicates that 3–5 present and future years must be simulated with the fully coupled global-regional system (see Section C) to separate the climate change response from simple interannual variability.

C. Development of a Coupled Global to Regional Climate and Air Quality Modeling System

A fully coupled global to regional scale model of climate change and air quality has been developed (Figure 1). In this Global-Regional Climate Air Pollution Modeling System (GRE-CAPS), present and future climates are simulated by the Goddard Institute for Space Studies version II' General Circulation Model (GISS-II' GCM), which is coupled to a gas-phase and aerosol chemistry model. Meteorology generated by the GCM is downscaled to the regional modeling domain using the Mesoscale Model (MM5) regional climate model. The downscaled meteorology is passed on to the regional chemical transport model, Particulate Matter Comprehensive Air Quality Model with Extensions (PMCAMx+). In addition to the downscaled meteorology, the chemical boundary conditions for the regional model are derived from the cells in the global model that correspond to the boundaries of the regional domain, simulating transport into the domain.

Figure 1. Schematic Illustration of the Coupling of Global and Regional Models to Develop the Global-Regional Climate Air Pollution Modeling System (GRE-CAPS)

Figure 1. Schematic Illustration of the Coupling of Global and Regional Models to Develop the Global-Regional Climate Air Pollution Modeling System (GRE-CAPS)

D. Evaluation of the GRE-CAPS Modeling System for the Present

The GRE-CAPS modeling system was evaluated for the present day, with comparisons between model-predicted and measured ozone and speciated PM2.5 concentrations. Comparisons between model-predicted temperatures and precipitation were also made. The model was used to simulate five present-day Januaries and six present-day Julys. The biases and errors in GRE-CAPS-predicted ozone concentrations were similar to those of PMCAMx when used for standard retrospective modeling. The fractional biases in mean daily peak ozone concentration and mean daily maximum 8-hour average ozone concentration are both less than 10%. The model-predicted distribution of peak hourly and daily maximum 8-hour average values agreed rather well with the measured distribution. There is less agreement between the model and measurements in the number of hours with ozone mixing ratios greater than 70 or 80 ppb, though this is also the case with standard PMCAMx modeling. The predictions of PM2.5 concentrations by GRE-CAPS were also of similar quality to those of PMCAMx driven by historical meteorology. The fractional biases in the predictions of total PM2.5, sulfate, ammonium, and nitrate were all less than 25% in both January and July. The model agrees well with organic PM2.5 measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, though there is less agreement with measurements from the Speciation Trends Network (STN). The GRE-CAPS system is shown to adequately reproduce ozone and PM2.5 concentrations for the present day, with model performance similar to that of PMCAMx for standard retrospective episode modeling.

E. Development of Future Climate/Emissions Scenarios

A total of nine model simulations were performed with GRE-CAPS (see Table 1). The “Run duration” column in Table 1 refers to the length of time simulated by the global model component only; shorter time periods are down-scaled with PMCAMx. These simulations have been designed to explore the relative effects of the changes in future climate, U.S. and global anthropogenic emissions (increase/decrease), climate-sensitive emissions, CH4 abundance, and long-range transport on air pollution over the United States. So as to be useful to near-term air quality policy, we consider global change scenarios corresponding to the 2050s. As the projected 2050s climate change for most Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (IPCC SRES) is nearly the same (IPCC, 2001), we use the A2 2050s climate as a representative future climate. However, the scenarios diverge significantly with regards to their projected regional distributions of emissions, which will impact U.S. O3 and PM2.5 concentrations differently. Therefore, to examine the sensitivity of U.S. O3/PM2.5 to regional emissions increases (decreases), the A2 and B1 scenarios, which have overall higher and lower emissions for the United States, respectively, have been chosen.

Table 1. Summary of the Runs Performed. The first 6 months for runs 1–8 are considered as model initialization; run 9 utilizes 2 months of initialization time per summer. Climate-sensitive biogenic emissions are allowed to vary with the simulated climate in all runs except 9; please see Racherla and Adams (2007b) for further details.

Run

Climate

Anthropogenic emissions

Run duration

1

1990s

1990s

10.5 years

2

A2 2050s

1990s

10.5 years

3

1990s

A2 2050s

10.5 years

4

A2 2050s

A2 2050s

10.5 years

5

1990s

B1 2050s

10.5 years

6

A2 2050s

B1 2050s

10.5 years

7

1990s

1990s; A2 2050s for CH4

1.5 years

8

1990s

1990s North America; A2 2050s Rest of world

1.5 years

9

A2 2050s

1990s;1990s biogenic emissions

5 summers (JJA)

F. Assessment of Global Change Impact on Future Air Quality

We have performed a number of analyses to assess the relative impacts of climate change, climate-sensitive emissions, global methane, intercontinental transport, and domestic emissions on both average and peak ozone and PM2.5. This has been done for longer time periods (those listed in Table 1) with the global model alone and for more focused time periods with the full GRE-CAPS modeling system. In some cases, we are in the final stages of analysis and results are being finalized. In all cases, the conclusions need to carry caveats specific to the strengths/weaknesses of the specific modeling system used. Rather than attempt a complete synthesis of results, the reader is referred to the following papers: Dawson, et al., 2007d; Dawson, et al., 2007e; Racherla and Adams, 2007b; and Racherla and Adams, 2007c. In the list of references in this report, manuscripts listed as “in preparation” are expected to be submitted within a few months of the date of this report.

Conclusions:

The effects of global change on U.S. air quality have been assessed with a combination of a global climate and chemistry model (GISS GCM/CTM), a regional meteorological model (MM5), and a regional air quality model (PMCAMx). These have been integrated into a comprehensive modeling system known as the GRE-CAPS. The ability of GRE-CAPS to predict present-day ozone and PM2.5 levels has been evaluated and shown to be similar to that of PMCAMx (Dawson, et al., 2007c). Sensitivity studies of ozone and PM2.5 to changes in individual meteorological parameters have been performed (Dawson, et al., 2007a; Dawson, et al., 2007b) to assess and quantify where major sensitivities to climate/meteorology lie. The GISS GCM/CTM has been used to assess changes in background levels of ozone and PM2.5 (Racherla and Adams, 2006)resulting from climate change alone. The GISS GCM/CTM has also been used to assess ozone and PM2.5 changes in the U.S. with longer simulations than feasible with GRE-CAPS and to separate the effects of interannual variability from climate change per se (Racherla and Adams, 2007a; Racherla and Adams, 2007c). A suite of future climate and emissions scenarios has been developed to assess the relative impacts of climate change, domestic emissions, intercontinental transport, climate-sensitive emissions, and global methane on U.S. air quality (Racherla and Adams, 2007b), and these scenarios have been simulated in the GRE-CAPS model (Dawson, et al., 2007d; Dawson, et al., 2007e).

Effectiveness and Societal Benefits

A primary societal benefit is an improved understanding of how and to what extent global climate change, global emissions, domestic emissions, background levels of pollution, climate-sensitive emissions, and global methane impact U.S. air quality (ozone and PM2.5 levels). It has been demonstrated, in particular, that climate change will have significant impacts on U.S. air quality. A comprehensive modeling system, GRE-CAPS, has been developed to predict global change impacts on U.S. air quality from global to regional scales.

Computer Modeling

The GISS GCM/CTM model used in this study is described in detail in Liao, et al., 2003 and Liao, et al., 2004). It consists of three major components: (1) the GISS GCM II’ (Hansen, et al., 1983; Rind and Lerner, 1996; Rind, et al., 1999); (2) the Harvard tropospheric O3 NOx-hydrocarbon chemical model (Mickley, et al., 1999); and, (3) an aerosol model (Adams, et al., 1999; Chung and Seinfeld, 2002; Liao, et al., 2003; Liao, et al., 2004). The MM5 regional-scale meteorological model is described in Grell, et al. (1994) with detailed configuration described in Dawson, et al., 2007c. The PMCAMx model (Gaydos, et al., 2007) is the regional-scale air quality modeling tool used in this study.

References:

Adams PJ, Seinfeld JH, Koch DM. Global concentrations of tropospheric sulfate, nitrate, and ammonium aerosol simulated in a general circulation model. Journal of Geophysical Research-Atmospheres 1999;104(D11):13791-13823.

Chung SH, Seinfeld JH. Global distribution and climate forcing of carbonaceous aerosols. Journal of Geophysical Research 2002;107(D19):4407, doi:10.1029/2001JD001397.

Dawson JP, Adams PJ, Pandis SN. Sensitivity of ozone to summertime climate in the eastern USA: a modeling case study. Atmospheric Environment 2007a;41(7):1494-1511.

Dawson JP, Adams PJ, Pandis SN. Sensitivity of PM2.5 to climate in the Eastern US: a modeling case study. Atmospheric Chemistry and Physics 2007b;7:4295-4309.

Dawson JP, Racherla PN, Lynn BH, Adams PJ, Pandis SN. Simulating present-day and future air quality as climate changes: model evaluation. Atmospheric Environment (submitted, 2007c).

Dawson JP, Racherla PN, Pandis SN, Adams PJ. Emissions policy ramifications of the impacts of climate change on air quality in the Eastern US (in preparation, 2007d).

Dawson JP, Racherla PN, Pandis SN, Adams PJ. Impacts of climate change on regional and urban air quality in the Eastern US: the role of meteorology (in preparation, 2007e).

Gaydos TM, Pinder R, Koo B, Fahey KM, Yarwood G, Pandis SN. Development and application of a three-dimensional aerosol chemical transport model, PMCAMx. Atmospheric Environment 2007;41(12):2594-2611.

Grell GA, Dudhia J, Stauffer D. A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5). NCAR, Boulder, CO, 1994.

Hansen J, Russell G, Rind D, Stone P, Lacis A, Lebedeff S, Ruedy R, Travis L. Efficient 3-dimensional global-models for climate studies–Model-I and Model-Ii. Monthly Weather Review 1983;111(4):609-662.

Intergovernmental Panel on Climate Change (IPCC). In: Climate Change 2001: The Scientific Basis, Cambridge University Press, Cambridge, 2001.

Liao H, Adams PJ, Chung SH, Seinfeld JH, Mickley LJ, Jacob DJ. Interactions between tropospheric chemistry and aerosols in a unified general circulation model. Journal of Geophysical Research-Atmospheres 2003;108(D1).

Liao H, Seinfeld JH, Adams PJ, Mickley LJ. Global radiative forcing of coupled tropospheric ozone and aerosols in a unified general circulation model. Journal of Geophysical Research-Atmospheres 2004;109(D16).

Mickley LJ, Murti PP, Jacob DJ, Logan JA, Koch DM, Rind D. Radiative forcing from tropospheric ozone calculated with a unified chemistry-climate model. Journal of Geophysical Research-Atmospheres 1999;104(D23):30153-30172.

Racherla PN, Adams PJ. Sensitivity of global tropospheric ozone and fine particulate matter concentrations to climate change. Journal of Geophysical Research-Atmospheres 2006;111(D24).

Racherla PN, Adams PJ. The response of surface ozone to climate change over the eastern United States. Atmospheric Chemistry and Physics (submitted, 2007a).

Racherla PN, Adams PJ. The sensitivity of regional air pollution over the United States to future global climate and anthropogenic emissions changes: 1. Ozone. Atmospheric Chemistry and Physics (in preparation, 2007b).

Racherla PN, Adams PJ. The sensitivity of regional air pollution over the United States to future global climate and anthropogenic emissions changes: Part 2. Particulate matter. Atmospheric Chemistry and Physics (in preparation, 2007c).

Rind D, Lerner J. Use of on-line tracers as a diagnostic tool in general circulation model development. 1. Horizontal and vertical transport in the troposphere. Journal of Geophysical Research-Atmospheres 1996;101(D7):12667-12683.

Rind D, Lerner J, Shah K, Suozzo R. Use of on-line tracers as a diagnostic tool in general circulation model development 2. Transport between the troposphere and stratosphere. Journal of Geophysical Research-Atmospheres 1999;104(D8):9151-9167.


Journal Articles on this Report : 8 Displayed | Download in RIS Format

Other project views: All 13 publications 8 publications in selected types All 8 journal articles
Type Citation Project Document Sources
Journal Article Dawson JP, Adams PJ, Pandis SN. Sensitivity of PM2.5 to climate in the Eastern US: a modeling case study. Atmospheric Chemistry and Physics 2007;7(16):4295-4309. R830961 (Final)
R833374 (2007)
R833374 (2008)
R833374 (2010)
R833374 (Final)
  • Full-text: Atmospheric Chemistry and Physics-Full Text PDF
    Exit
  • Abstract: Atmospheric Chemistry and Physics-Abstract
    Exit
  • Journal Article Dawson JP, Adams PJ, Pandis SN. Sensitivity of ozone to summertime climate in the eastern USA: a modeling case study. Atmospheric Environment 2007;41(7):1494-1511. R830961 (Final)
  • Full-text: Science Direct
    Exit
  • Abstract: Science Direct
    Exit
  • Other: Science Direct PDF
    Exit
  • Journal Article Dawson JP, Racherla PN, Lynn BH, Adams PJ, Pandis SN. Simulating present-day and future air quality as climate changes: model evaluation. Atmospheric Environment 2008;42(19):4551-4566. R830961 (Final)
    R833374 (2007)
    R833374 (2008)
    R833374 (2010)
    R833374 (Final)
  • Full-text: ScienceDirect-Full Text HTML
    Exit
  • Abstract: ScienceDirect-Abstract
    Exit
  • Other: ScienceDirect-Full Text PDF
    Exit
  • Journal Article Lynn BH, Healy R, Druyan LM. An analysis of the potential for extreme temperature change based on observations and model simulations. Journal of Climate 2007;20(8):1539-1554. R830961 (Final)
  • Abstract: Journal of Climate Abstract
    Exit
  • Journal Article Pinder RW, Adams PJ, Pandis SN, Gilliland AB. Temporally resolved ammonia emission inventories: current estimates, evaluation tools, and measurement needs. Journal of Geophysical Research-Atmospheres 2006;111:D16310, doi:10.1029/2005JD006603. R830961 (2005)
    R830961 (Final)
  • Abstract: AGU Abstract
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  • Journal Article Pinder RW, Adams PJ, Pandis SN. Ammonia emission controls as a cost-effective strategy for reducing atmospheric particulate matter in the Eastern United States. Environmental Science & Technology 2007;41(2):380-386. R830961 (Final)
  • Abstract from PubMed
  • Full-text: ACS
    Exit
  • Other: ACS PDF
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  • Journal Article Racherla PN, Adams PJ. Sensitivity of global tropospheric ozone and fine particulate matter concentrations to climate change. Journal of Geophysical Research-Atmospheres 2006;111:D24103, doi:10.1029/2005JD006939. R830961 (2005)
    R830961 (Final)
  • Abstract: AGU Abstract
    Exit
  • Journal Article Racherla PN, Adams PJ. The response of surface ozone to climate change over the Eastern United States. Atmospheric Chemistry and Physics 2008;8(4):871-885. R830961 (Final)
    R833374 (2007)
    R833374 (2008)
    R833374 (2010)
    R833374 (Final)
  • Full-text: Atmospheric Chemistry and Physics-Full Text PDF
    Exit
  • Abstract: Atmospheric Chemistry and Physics-Abstract
    Exit
  • Supplemental Keywords:

    ambient air, atmosphere, ozone, particulates, visibility, acid deposition, global climate, tropospheric, chemical transport, oxidants, nitrogen oxides, sulfates, organics, modeling, general circulation models, climate models,, RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, particulate matter, Air Quality, Air Pollutants, climate change, Air Pollution Effects, Chemistry, Monitoring/Modeling, Environmental Monitoring, Atmospheric Sciences, Atmosphere, anthropogenic stress, aerosol formation, ambient aerosol, atmospheric particulate matter, atmospheric dispersion models, ecosystem models, environmental measurement, meteorology, climatic influence, emissions monitoring, global change, ozone, air quality models, climate, modeling, climate models, greenhouse gases, airborne aerosols, atmospheric aerosol particles, atmospheric transport, neural networks, environmental stress, regional emissions model, ecological models, climate model, greenhouse gas, aerosols, atmospheric models, Global Climate Change, atmospheric chemistry, ambient air pollution

    Relevant Websites:

    http://www.ce.cmu.edu/~adams/index.html exit EPA
    http://www.cheme.cmu.edu/who/faculty/pandis.html exit EPA

    Progress and Final Reports:

    Original Abstract
  • 2003 Progress Report
  • 2004 Progress Report
  • 2005 Progress Report