Application of a unified aerosol-chemistry-climate GCM to understand the effects of changing climate and global anthropogenic emissions on U.S. air quality PI: Daniel J. Jacob, Harvard University Co-Is: Joshua S. Fu, Univ. of Tennessee Loretta J. Mickley, Harvard University David Rind, GISS John H. Seinfeld, Caltech David J. Streets, Argonne How will a changing climate affect surface concentrations of O 3 and PM in the United States?

GCMs are the necessary tools to predict the response of air quality to future climate change Past model studies of the effects of climate change on AQ have focused on partial-derivative perturbations to meteorological variables, e.g., But the perturbations to different meteorological variables are inherently correlated, and the most important perturbation for AQ is likely to be the change in circulation. Only a GCM can make predictions of the effects of climate change on AQ (partial-derivative studies are useful as diagnostic) GCMs have never been applied to investigate the effects of climate change on air pollution meteorology. We are in uncharted territory!

MAJOR CHALLENGE IN APPLYING GCM TO AQ TRENDS: separating climate change from interannual variability in weather equilibrium climate  T = 0.3 o C  F = 0.46 W m -2 Mickley et al. [2003] present-day ozone Preindustrial ozone Illustration: change in global surface T in GISS GCM climate equilibrium simulations with present vs. preindustrial tropospheric ozone Need: time-dependent GCM calculation At least a 5-year sample of any climate regime

Interannual variability is even more of a problem at regional scales  T (mean +1.4 o C)  lowcloud (mean –2%)  precip (mean -0.5 mm/h) GCM interannual variability: Jun-Aug  T,  cloud,  precip over N. Mexico GISS GCM equilibrium Jun-Aug  T due to change in tropospheric ozone over past century (  F = 0.46 W m -2 ) How many years of simulation are needed? TBD, but get guidance from present-day AQ statistics

CHARACTERIZING AQ CLIMATOLOGY WITH NORMAL MODES (PRINCIPAL COMPONENTS OR EOFs) OBS (AIRS)MAQSIP (36 km 2 ) Fiore et al., in press, JGR r 2 = 0.60 Slope = 0.9 r 2 = 0.57 Slope = 0.8 r 2 = 0.68 Slope = 0.7 EOF 1: East-west EOF 2: Midwest- Northeast EOF 3: Southeast r 2 = 0.86 Slope = 1.0 r 2 = 0.76 Slope = 1.0 r 2 = 0.80 Slope = 1.0 EOFs for surface 1-5 pm ozone in eastern U.S., Jun-Aug 1995

SAME FUNDAMENTAL SYNOPTIC PROCESSES DRIVE OZONE VARIABILITY IN GLOBAL MODEL EOF 1: East-west EOF 2: Midwest- Northeast EOF 3: Southeast OBS (AIRS)GEOS-CHEM 2°x2.5° Fiore et al., in press, JGR r 2 = 0.74 Slope = 1.2 r 2 = 0.27 Slope = 1.0 r 2 = 0.90 Slope = 1.0 r 2 = 0.68 Slope = 1.0 r 2 = 0.54 Slope = 0.8 r 2 = 0.78 Slope = 1.0 EOFs for surface 1-5 pm ozone, Jun-Aug 1995

North America Europe Asia INTERCONTINENTAL TRANSPORT OF POLLUTION Surface ozone enhancements from anthropogenic emissions in northern midlatitudes continents (GEOS-CHEM, JJA 1997) Li et al., JGR 2002 Asian influence likely to increase in future; what will be the effect of climate change?

North Atlantic Oscillation (NAO) Index North American ozone pollution enhancement at Mace Head, Ireland (GEOS-CHEM) r = 0.57 NAOI: normalized surface pressure anomaly between Iceland and Azores TRANSATLANTIC TRANSPORT OF POLLUTION: correlation with North Atlantic Oscillation Index Greenhouse warming  NAO index shift  change in transatlantic transport of pollution

PROJECT OBJECTIVES To quantify the effect of expected climate change on AQ in the U.S., independent of changes in anthropogenic emissions; To quantify the combined effect of changes in climate and anthropogenic emissions on AQ in the U.S.; To examine how climate change will affect intercontinental transport of pollution to the U.S.; To define the normal modes (EOFs) of ozone and PM over the U.S., and examine whether the effect of climate change can be expressed as a perturbation to the structure and frequency of these modes; To nest CMAQ within a unified aerosol-chemistry-climate GCM for more accurate simulation of regional air pollution in future climate.

GISS GCM Atmospheric chemistry Aerosol microphysics  emissions  land use  climate forcing CACTUS model  climate  chemistry PROJECT HERITAGE #1: CHEMISTRY, AEROSOLS, AND CLIMATE: TROPOSPHERIC UNIFIED SIMULATION (CACTUS) NASA Interdisciplinary Science (IDS) investigation: Harvard (Jacob, Mickley), Caltech (Seinfeld), GISS (Rind), UCI (Prather), CMU (Adams), GIT (Nenes) Current version of CACTUS model incorporates coupled ozone-PM chemistry in GISS GCM (4 o x5 o, 9 layers); Liao et al., JGR PM microphysics developed separately (Adams and Seinfeld, JGR, in press).

PROJECT HERITAGE #2: INTERCONTINENTAL TRANSPORT OF AIR POLLUTION (ICAP) EPA/OAQPS and EPA/ORD project: among others Harvard (Jacob), Argonne (Streets), U. Houston (Byun) Phase I ( ): apply GEOS-CHEM CTM to simulate effects of future changes in emissions on U.S. ozone AQ with present climate Key result: double dividend of methane control for climate stabilization and air quality [Fiore et al., GRL 2002] Phase II ( ): 1.Develop coupled ozone-PM-mercury simulation in GEOS-CHEM to serve as outer nest for CMAQ Ozone-PM coupling completed [Martin et al., JGR 2003; Park et al., JGR in press], mercury in development GEOS-CHEM/CMAQ coupling in development (with D. Buyn) 2.Conduct preliminary investigation of effects of climate change on air pollution meteorology using 9-layer GISS GCM simulations of CO and soot tracers simulation is in progress

PROJECT APPROACH 1.Conduct climate change simulations in CACTUS GCM GISS GCM w/4 o x5 o horiz resolution, 23 layers in vertical, q-flux ocean Chemical tracers (CO and soot) transported in model IPCC scenarios A1 and B1 Analysis: Trends in air pollution meteorological variables (T, humidity, PBL height, clouds) Trends in ventilation, circulation, scavenging using chemical tracers as diagnostics Assessment of # n of simulation years needed for climate statistics 2. Conduct global ozone-PM simulations for present, 2030, and 2050 climates Use CACTUS GCM or GEOS-CHEM CTM (driven by GISS GCM meteorology) for n-year coupled ozone-PM simulations for the three climates. Conduct simulations with (1) present-day emissions, (2) modified climate-dependent natural emissions, (3) modified anthropogenic emissions Analysis: Evaluate present-day simulation with observations, including EOFs for ozone and PM Diagnose changes in ozone and PM through statistical analysis including EOFs Diagnose changes in intercontinental transport of pollution

PROJECT APPROACH (cont.) 3. Interface CACTUS GCM (or GEOS-CHEM CTM) with CMAQ for improved simulation of regional pollution including episodes Build model interface including GISS  MM5 meteorology Conduct a 1-year simulation for 2050 climate over scale of continental U.S. (36 km 2 resolution); choose polluted year Analysis: Diagnose regional pollution episodes and ozone/PM concentration statistics

PROJECT TEAM AND RESPONSIBILITIES Harvard (Jacob/Mickley): project leadership, GCM and ozone-PM simulations, EOF analysis Caltech (Seinfeld): integration of PM simulation into updated CACTUS model, analysis of PM results GISS (Rind): GCM support, analysis of climate-driven changes in air pollution meteorology Argonne (Streets): global and U.S. inventories of ozone and PM precursors, primary PM Tennessee (Fu): interface of CACTUS with CMAQ, CMAQ simulation for 2050 climate