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FROM AIR POLLUTION TO GLOBAL CHANGE AND BACK: Towards an integrated international policy for air pollution and climate change Daniel J. Jacob Harvard University NUMBER OF PEOPLE LIVING IN U.S. COUNTIES VIOLATING NATIONAL AIR QUALITY STANDARDS, 1999 Carbon monoxide (CO) EPA [2001] Lead Nitrogen dioxide Ozone (O3) Particles < 10 mm (PM10) Particles < 2.5 mm (PM2.5) Sulfur dioxide (SO2) Any pollutant 124 ppbv 84 ppbv 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 ASIAN DUST CLOUD OVER THE WESTERN U.S. (APRIL-MAY 1998) GOES Satellite Image PM10 West Coast R. Husar, Washington U. 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/ GOOD vs. BAD OZONE (O3) 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. OZONE AIR QUALITY STANDARD (84 ppbv, 8-hour average) EPA/AIRS data [Lin et al., 2001] THE TROPOSPHERIC OZONE BACKGROUND AT NORTHERN MIDLATITUDES HAS INCREASED SHARPLY OVER PAST 100 YEARS Ozone trend from European mountain observations [Marenco et al., 1994] 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) 0 preindustrial 20 40 present background U.S. (8-h avg.) 60 80 U.S. (1-h avg.) 100 120 ppbv SURFACE OZONE ENHANCEMENTS CAUSED BY ANTHROPOGENIC EMISSIONS FROM DIFFERENT CONTINENTS GEOS-CHEM model, July 1997 North America Europe Asia Li et al. [2002] 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 TREND IN NORTHERN HEMISPHERIC SURFACE TEMPERATURE OVER PAST 1000 YEARS IPCC [2001] EFFECTS OF GREENHOUSE GASES AND AEROSOLS ON CLIMATE Solar radiation reflected to space (cooling) Greenhouse gas layer (transparent to solar, absorbs in IR) Aerosol layer (scatters solar, transparent in IR) Greenhouse effect (warming) Terrestrial emission (IR) EARTH SURFACE HISTORICAL TRENDS OF GREENHOUSE GASES AND AEROSOLS Greenhouse gases Carbon dioxide Methane Aerosols Nitrous oxide Sulfur IPCC [2001] LINK BETWEEN AIR POLLUTION AND CLIMATE FORCING GLOBAL RADIATIVE FORCING OF CLIMATE, 1750-present [IPCC, 2001] POLLUTANT-RELATED OH 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] NOx: ozone precursor A1, A2, B1, B2: four different socioeconomic story lines SO2: aerosol precursor Methane EFFECTS OF FUTURE CHANGES IN GLOBAL ANTHROPOGENIC EMISSIONS High-ozone days over U.S. Standard 50% 50% NMVOC CH4 Fiore et al. [2002] 50% A1 NOx 2020 Radiative forcing Standard 50% 50% NMVOC CH4 B1 2020 50% A1 NOx 2020 IPCC scenario Fossil fuel NOx emissions (2020 vs. present) Global U.S. Methane concentration (2020 vs. present) A1 +80% -30% +35% B1 +10% -60% +20% B1 2020