AIR POLLUTION AND GLOBAL CHANGE: TOWARDS AN INTEGRATED POLICY Daniel J. Jacob

NUMBER OF PEOPLE LIVING IN U. S NUMBER OF PEOPLE LIVING IN U.S. COUNTIES VIOLATING NATIONAL AIR QUALITY STANDARDS, 1999 Carbon monoxide (CO) EPA [2001] Lead Nitrogen dioxide 124 ppbv Ozone (O3) 84 ppbv Particles < 10 mm (PM10) Particles < 2.5 mm (PM2.5) Sulfur dioxide (SO2) Any pollutant

GOOD vs. BAD OZONE NOx = NO + NO2: nitrogen oxide radicals VOC (volatile organic carbon) = light hydrocarbons and substituted organic compounds

MEAN NUMBER OF SUMMER DAYS (1980-1998) EXCEEDING THE U. S MEAN NUMBER OF SUMMER DAYS (1980-1998) EXCEEDING THE U.S. OZONE AIR QUALITY STANDARD (84 ppbv, 8-hour average) EPA/AIRS data [Lin et al., 2001]

Historical records imply a large anthropogenic contribution to the present-day ozone background at northern midlatitudes Ozone trend from European mountain observations, 1870-1990 [Marenco et al.,1994] Preindustrial ozone models }

SURFACE OZONE IN U.S. INCLUDES A 20-40 ppbv BACKGROUND THAT HAS INCREASED BY ~3 ppbv OVER THE PAST 20 YEARS 8-h daily maximum ozone probability distribution at rural U.S. sites [Lin et al., 2000] 1980-1984 1994-1998

THIS OZONE BACKGROUND IS A SIZABLE INCREMENT TOWARDS VIOLATION OF U. S THIS OZONE BACKGROUND IS A SIZABLE INCREMENT TOWARDS VIOLATION OF U.S. AIR QUALITY STANDARDS (even more so in Europe!) Europe (8-h avg.) Europe (seasonal) U.S. (8-h avg.) U.S. (1-h avg.) 0 20 40 60 80 100 120 ppbv preindustrial present background

SURFACE OZONE ENHANCEMENTS CAUSED BY ANTHROPOGENIC EMISSIONS FROM DIFFERENT CONTINENTS GEOS-CHEM model, July 1997 North America Europe Asia Li et al. [2002]

RANGE OF ASIAN/EUROPEAN POLLUTION SURFACE OZONE ENHANCEMENTS OVER THE U.S. IN SUMMER as determined from a simulation with these emissions shut off Subsidence of Asian pollution + local production Max Asian/European pollution enhancements (up to 14 ppbv) occur at intermediate ozone levels (50-70 ppbv) stagnation tropical air MAJOR CONCERN IF OZONE STANDARD WERE TO DECREASE! Fiore et al. [2002]

EFFECT OF NORTH AMERICAN SOURCES ON PREDICTED EXCEEDANCES OF EUROPEAN AIR QUALITY STANDARD (55 ppbv, 8-h average) GEOS-CHEM model results, summer 1997 Number of exceedance days (out of 92) # of exceedance days that would not have been in absence of N.American emissions Li et al. [2002]

ANNUAL MEAN PARTICULATE MATTER (PM) CONCENTRATIONS AT U. S ANNUAL MEAN PARTICULATE MATTER (PM) CONCENTRATIONS AT U.S. SITES, 1995-2000 NARSTO PM Assessment (draft), 2002 PM10 (particles > 10 mm) PM2.5 (particles > 2.5 mm) Red circles indicate violations of national air quality standard: 50 mg m-3 for PM10 15 mg m-3 for PM2.5

COMPOSITION OF PM2.5 (NARSTO PM ASSESSMENT)

ASIAN DUST CLOUD OVER THE WESTERN U.S. (APRIL-MAY 1998) GOES Satellite Image PM10 West Coast R. Husar, Washington U.

moderately polluted day EPA REGIONAL HAZE RULE: FEDERAL CLASS I AREAS TO RETURN TO “NATURAL” VISIBILITY LEVELS BY 2064 Places new emphasis for understanding long-range transport clean day moderately polluted day Acadia National Park http://www.hazecam.net/

TROPOSPHERIC OZONE MAINTAINS THE OXIDIZING POWER OF THE ATMOSPHERE O2 + hn STRATOSPHERE Stratospheric ozone Tropopause (8-18 km) TROPOSPHERE ? Complex non-linear chemistry Lightning ? hn hn, H2O Nitrogen oxides (NOx) CO, Hydrocarbons ? Ozone (O3) Hydroxyl (OH) The Pacman of the atmosphere! Fires Biosphere Human activity physics chemistry biology Ocean

CLIMATE FORCING BY AIR POLLUTANTS GLOBAL RADIATIVE FORCING OF CLIMATE, 1750-present [IPCC, 2001] POLLUTANT-RELATED OH

1750-2000 radiative forcing from tropospheric ozone is less well constrained than implied by IPCC 2001 report Global simulation of late 19th century ozone observations with the GISS GCM Standard model: DF = 0.44 W m-2 “Adjusted” model (lightning and soil NOx decreased, biogenic hydrocarbons increased): DF = 0.80 W m-2 [Mickley et al., 2001]

BLACK CARBON: A MAJOR “GREENHOUSE” AEROSOL Its forcing is likely underestimated in IPCC 2001 report DIESEL DOMESTIC COAL BURNING BIOMASS BURNING Chin et al. [2000]

WHAT DOES THE FUTURE HOLD? Future emission scenarios from IPCC [2001] A1, A2, B1, B2: different socioeconomic story lines NOx A2: “dirty world” B2: “clean world” SO2

Growth of Asian emissions over the next decades will increase role of background for ozone air quality in U.S. Anthropogenic NOx emissions [IPCC, 2001] 2000 “Optimistic” IPCC scenario: OECD, U.S. m20%, Asia k 50% 2020 109 atoms N cm-2 s-1

FUTURE EMISSIONS MAY BE LESS THAN PRESENT FORECASTS IF PUSH IS MADE FOR ENERGY EFFICIENCY AND AIR QUALITY IN DEVELOPING WORLD Streets et al. [2001] LINK AIR QUALITY AND CLIMATE CHANGE MITIGATION OBJECTIVES!

GETTING A BIG BANG FOR THE BUCK: controlling methane emissions A 50% reduction in anthropogenic methane emissions would: yield a fast negative global radiation forcing of 0.37 W m-2 (-0.30 W m-2 from methane, -0.07 W m-2 from ozone) decrease the incidence of ozone > 80 ppbv in surface air over U.S. by more than 50% [A.M. Fiore, GEOS-CHEM model results, 2002] Recent methane trend Historical methane trend

IPCC PROJECTION OF FUTURE METHANE EMISSIONS Can we try to decrease methane emissions instead?