![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20081106061749im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Final Report: Application of a Unified Aerosol-Chemistry-Climate GCM to Understand the Effects of Changing Climate and Global Anthropogenic Emissions on U.S. Air Quality
EPA Grant Number: R830959Title: Application of a Unified Aerosol-Chemistry-Climate GCM to Understand the Effects of Changing Climate and Global Anthropogenic Emissions on U.S. Air Quality
Investigators: Jacob, Daniel J. , Fu, Joshua , Mickley, Loretta J. , Rind, David , Seinfeld, John , Streets, David G.
Institution: Harvard University , Argonne National Laboratory , California Institute of Technology , NASA Goddard Institute for Space Studies (GISS) , University of Tennessee - Knoxville
EPA Project Officer: Winner, Darrell
Project Period: January 1, 2003 through January 1, 2005 (Extended to January 1, 2006)
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)
Research Category: Air Quality and Air Toxics , Global Climate Change
Description:
Objective:Our EPA-STAR project had five main objectives:
- To quantify the effect of expected 2000-2050 climate change on air quality in the United States, independent of changes in anthropogenic emissions;
- To quantify the combined effect of 2000-2050 changes in climate and anthropogenic emissions on air quality in the United States;
- To examine how climate change will affect the intercontinental transport of pollution to the United States;
- To define the normal modes of variability (EOFs) of ozone and PM over the United States, and examine whether the effect of climate change can be expressed as a perturbation in the structure and frequency of these modes;
- To nest the CMAQ regional model within the unified aerosol-chemistry-climate GCM for a more accurate simulation of regional air pollution in future climate.
To meet these goals, we launched GCAP (Global Change and Air Pollution), a multi-institutional project involving the complementary expertise of research groups at Harvard (Jacob, Mickley), Caltech (Seinfeld), NASA/GISS (Rind), DOE/ANL (Streets), and U. Tennessee (Fu). The basic scheme of GCAP involves simulating 2000-2050 climate change using the Goddard Institute for Space Studies general circulation model (GISS GCM) and then applying the GISS meteorology to the Harvard GEOS-Chem global model of atmospheric composition and to the EPA MM5/CMAQ regional model of air quality. In this way, the response of air quality to climate change can be calculated on global to regional scales. This report summarizes our results from Phase 1 of GCAP (2003-2007). Work on this project is ongoing through EPA-STAR grant R833370 (“Global Change and Air Pollution (GCAP) Phase 2: Implications for U.S. Air Quality and Mercury Deposition of Multiple Climate and Global Emission Scenarios for 2000-2050”, again with Daniel Jacob as PI.)
Summary/Accomplishments (Outputs/Outcomes):Overview. We calculate that by the 2050s the severity and duration of summertime regional pollution episodes in the midwestern and northeastern United States will increase significantly relative to present. This trend in the model appears due to a decline in the frequency of mid-latitude cyclones tracking across southern Canada. Cold fronts associated with these cyclones are known to provide the main mechanism for ventilation of the midwestern and northeastern United States. Using the full-chemistry GCAP model, we also predict that 2000-2050 changes in anthropogenic emissions will reduce the U.S. summer daily maximum 8-hour ozone by 2-15 ppb, but climate change will cause a 2-5 ppb positive offset over the Midwest and Northeast. The offset is partly driven by increased surface temperatures and by decreased ventilation from convection and frontal passages. Ozone pollution episodes in the model are far more affected by climate change than mean values, with effects exceeding 10 ppb in the Midwest and Northeast. We also find that ozone air quality in the Southeast is insensitive to climate change, reflecting compensating effects from changes in isoprene emission and air pollution meteorology.
Detailed findings, in chronological order:
1. We constructed model-based forecasts of future emissions of the primary carbonaceous aerosols, black carbon (BC) and organic carbon (OC). These forecasts built on a recent 1996 inventory of emissions that contains detailed fuel, technology, sector, and world-region specifications. The forecasts were driven by four IPCC scenarios, A1B, A2, B1, and B2, out to 2030 and 2050, incorporating not only changing patterns of fuel use but also technology development. We projected that global black carbon (BC) emissions will decline from 8.0 Tg in 1996 to 4.3–6.1 Tg by 2050, across the range of scenarios. We also projected that organic carbon (OC) emissions will decline from 34 Tg in 1996 to 21–28 Tg by 2050. The introduction of advanced technology with lower emission rates, as well as a shift away from the use of traditional solid fuels in the residential sector, more than offset the increased combustion of fossil fuels worldwide. Although emissions of BC and OC will for the most part decline around the world, some regions in the developing world showed increasing emissions. Particularly difficult to control are BC emissions from the transport sector. Streets et al. 2004.
2. We examined the impact of future climate change on regional air pollution meteorology in the United States by conducting a transient climate change (1950 –2052) simulation in the GISS GCM 2’. We included in the GCM two tracers of anthropogenic pollution, combustion carbon monoxide (COt) and black carbon (BCt). We found that the severity and duration of summertime regional pollution episodes in the midwestern and northeastern United States increased significantly relative to present. Pollutant concentrations during these episodes increased by 5–10% and the mean episode duration increases from 2 to 3–4 days. These increases appeared to be driven by a decline in the frequency of mid-latitude cyclones tracking across southern Canada. The cold fronts associated with these cyclones are known to provide the main mechanism for ventilation of the midwestern and northeastern United States. The GISS GCM Model 3, which we use to drive the chemical transport model GEOS-Chem, captures transport of long-lived tracers reasonably well. Mickley et al., 2004.
3. We applied the unified tropospheric chemistry-aerosol model within the GISS GCM 2’ to simulate an equilibrium CO2-forced climate in the year 2100. Our goal was to examine the effects of climate change on global distributions of tropospheric ozone and aerosols. CO2 concentrations as well as the anthropogenic emissions of ozone precursors and aerosols/aerosol precursors were based on the IPCC A2 scenario. We found that 2100 global ozone and aerosol burdens predicted with changes in both climate and emissions were generally 5–20% lower than those simulated with changes in emissions alone. Two exceptions were that the nitrate burden was 38% lower in 2100, and the secondary organic aerosol burden was 17% higher. Although the CO2-driven climate change alone reduced the global ozone burden as a result of faster removal of ozone in a warmer climate, it also increased surface layer ozone concentrations near populated and biomass burning areas because of slower transport, enhanced biogenic hydrocarbon emissions, and faster chemistry. The warmer climate influenced aerosol burdens by increasing aerosol wet deposition, altering climate-sensitive emissions, and shifting aerosol thermodynamic equilibrium. We also calculated the impact of climate change on the 2100 direct radiative forcings of tropospheric ozone and aerosol. Liao et al., 2006.
4. As part of GCM model development, we explored the dependency of GCM tracer transports on model physics and horizontal and vertical resolution. We used the GISS Model E at 4° x 5° with 20 and 23 layers and the GISS Model 3 at 4° x 5° with 23 and 53 layers and at 2° x 2.5° with 53 and 102 layers. The online tracers employed were CO2, CH4, N2O, CFC-11, SF6, 222Rn, bomb 14C, and ozone. Model experiments were done two ways: with specified stratospheric ozone or with the stratospheric ozone tracer used for atmospheric radiation calculations. We showed that when GCM physics produced greater precipitation over land in the Northern Hemisphere summer monsoon region, as occurred in the GISS Model 3, the associated dynamics (stronger Hadley cell) and subgrid-scale transports led to faster and more realistic interhemispheric transport. Increased vertical resolution increased the vertical mixing between the boundary layer and upper troposphere, due to both convective and synoptic-scale influences. Rind et al., 2007.
5. Using GEOS-Chem chemical transport model driven by GISS GCM winds, we tackled the question, Why are there large differences between models in global budgets of tropospheric ozone? Global 3-D tropospheric chemistry models in the literature show large differences in global budget terms for tropospheric ozone. The ozone production rate in the troposphere, P(Ox), varies from 2300 to 5300 Tg yr-1 across models describing the present-day atmosphere. The ensemble mean of P(Ox) in models from the post-2000 literature is 35% higher than that compiled in the IPCC Third Assessment Report. Examination of the evolution of P(Ox) over the GEOS-Chem model history showed major effects from changes in heterogeneous chemistry, the lightning NOx source, and the yield of organic nitrates from isoprene oxidation. Multivariate statistical analysis of model budgets in the literature indicated that 74% of the variance in P(Ox) across models can be explained by differences in NOx emissions, inclusion of nonmethane volatile organic compounds (NMVOCs, mostly biogenic isoprene), and ozone influx from stratosphere-troposphere exchange (STE). Wu et al., 2007a.
6. We compared the results from CMAQ driven by GEOS-Chem boundary conditions with the results from other models in simulations for July 2001 over east Asia.. Our model captured the day-to-day and spatial variability of the observations at 4 ozonesonde sites. Statistics of both monthly and daily means showed that our model had skill in reproducing ozone and SO2 with small to moderate root mean square errors. NO2 gas concentrations were simulated less well. Fu et al., 2007.
7. We investigated the effects on U.S. ozone air quality from 2000-2050 global changes in climate and anthropogenic emissions of ozone precursors by using the GCAP model driven by meteorological fields from GISS. We followed the IPCC A1B scenario and separated the effects from changes in climate and anthropogenic emissions through sensitivity simulations. We found that the 2000-2050 changes in anthropogenic emissions reduced the U.S. summer daily maximum 8-hour ozone by 2-15 ppb, but climate change caused a 2-5 ppb positive offset over the Midwest and Northeast, partly driven by decreased ventilation from convection and frontal passages. Ozone pollution episodes were far more affected by climate change than mean values, with effects exceeding 10 ppb in the Midwest and Northeast. We found that ozone air quality in the Southeast was insensitive to climate change, reflecting compensating effects from changes in isoprene emission and air pollution meteorology. We defined a “climate change penalty” as the additional emission controls necessary to meet a given ozone air quality target. We found that a 50% reduction in U.S. NOx emissions was needed in the 2050 climate to reach the same target in the Midwest as a 40% reduction in the 2000 climate. Emission controls reduced the magnitude of this climate change penalty and even turned it into a climate benefit in some regions. Wu et al., 2007b.
8. We evaluated GCAP model predictions of aerosols using surface measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. Our work indicated that GCAP is a suitable tool for simulating aerosols over the United States in the present climate. The model reproduced fairly well the concentrations of sulfate black carbon, organic carbon (both primary and secondary components), and PM2.5. Nitrate concentrations were overestimated in the western United States with a normalized mean bias (NMB) of +75.6% and were underestimated in the eastern United States with a NMB of -54.4%. Special attention was paid to biogenic secondary organic aerosol (SOA). The highest predicted seasonal mean SOA concentrations of 1–2 mg m-3 and 0.5–1.5 mg m-3 were predicted over the northwestern and southeastern United States, respectively, in the months of June–July–August. Isoprene was predicted to contribute about half of the biogenic SOA burden over the United States. Predicted biogenic SOA concentrations were in reasonable agreement with those from observations. On an annual basis, SOA was predicted to contribute 10–20% of PM2.5 mass in the southeastern United States and as high as 38% in the northwest, indicating the important role of SOA in understanding air quality and visibility over the United States. Liao et al., 2007.
Conclusions:Our work has expanded understanding of the effects of global change on tropospheric chemistry and, especially, on regional air quality. We have identified the meteorological changes associated with climate change that would most greatly degrade regional air quality by 2050: higher temperatures, reduced boundary layer ventilation, and longer stagnation periods. In particular, our work has shown that the frequency and severity of pollution episodes in the eastern U.S. would increase in the future climate due to weakening of the northern mid-latitude cyclone tracks. (The cold fronts associated with these cyclones are responsible for sweeping away pollution in this region.) We have calculated the climate change penalty on regional air quality in the United States, and found that a 50% reduction in U.S. NOx emissions is needed in the 2050 climate to reach the same target in the Midwest as a 40% reduction in the 2000 climate. We predict that emission controls will reduce the magnitude of the climate change penalty and even turn it into a climate benefit in some regions.
Journal Articles on this Report: 7 Displayed | Download in RIS Format
| Other project views: | All 18 publications | 7 publications in selected types | All 7 journal articles |
| Type | Citation | ||
|---|---|---|---|
|
|
Fu JS, Jang CJ, Streets DG, Li Z, Kwok R, Park R, Han Z. MICS-Asia II: modeling gaseous pollutants and evaluating an advanced modeling system over East Asia. Atmospheric Environment 2007 Aug 7 [Epub ahead of print] doi:10.1016/j.atmosenv.2007.07.058. |
R830959 (Final) |
|
|
|
Liao H, Chen W-T, Seinfeld JH. Role of climate change in global predictions of future tropospheric ozone and aerosols. Journal of Geophysical Research 2006;111:D12304, doi:10.1029/2005JD006852. |
R830959 (2005) R830959 (Final) |
|
|
|
Liao H, Henze DK, Seinfeld JH, Wu S, Mickley LJ. Biogenic secondary organic aerosol over the United States: comparison of climatological simulations with observations. Journal of Geophysical Research 2007;112:D06201, doi:10.1029/2006JD007813. |
R830959 (Final) R833370 (2007) |
|
|
|
Mickley LJ, Jacob DJ, Field BD, Rind D. Effects of future climate change on regional air pollution episodes in the United States. Geophysical Research Letters 2004;31:L24103, doi:10.1029/2004GL021216. |
R830959 (2004) R830959 (Final) |
|
|
|
Rind D, Lerner J, Jonas J, McLinden C. Effects of resolution and model physics on tracer transports in the NASA Goddard Institute for Space Studies general circulation models. Journal of Geophysical Research 2007;112:D09315, doi:10.1029/2006JD007476. |
R830959 (Final) |
|
|
|
Streets DG, Bond TC, Lee T, Jang C. On the future of carbonaceous aerosol emissions. Journal of Geophysical Research 2004;109:D24212, doi:10.1029/2004JD004902. |
R830959 (2004) R830959 (Final) |
|
|
|
Wu S, Mickley LJ, Jacob DJ, Logan JA, Yantosca RM, Rind D. Why are there large differences between models in global budgets of tropospheric ozone? Journal of Geophysical Research 2007;112:D05302, doi:10.1029/2006JD007801. |
R830959 (Final) |
|
chemical transport, volatile organic compounds (VOCs), nitrogen oxides, sulfates, organics, pollution prevention, environmental chemistry, modeling, climate models, tropospheric ozone, tropospheric aerosol,
,
Ecosystem Protection/Environmental Exposure & Risk, Air, Scientific Discipline, RFA, climate change, Chemistry, Atmospheric Sciences, Environmental Engineering, particulate matter, Monitoring/Modeling, aerosols, meteorology, climate model, Global Climate Change, atmospheric models, airborne aerosols, air quality, ozone, atmospheric dispersion models, greenhouse gas, climatic influence, air quality models, environmental monitoring, climate models, aerosol formation, atmospheric chemistry, climate variability, environmental measurement, environmental stress, global change, atmospheric particulate matter, ambient air pollution, anthropogenic stress, atmospheric aerosol particles, ecological models, ambient aerosol, atmospheric transport, greenhouse gases
Relevant Websites:
http://www.as.harvard.edu/chemistry/trop/
Progress and Final Reports:
2003 Progress Report
2004 Progress Report
2005 Progress Report
Original Abstract