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 EPA [2001] 124 ppbv 84 ppbv Carbon monoxide (CO) Lead Nitrogen dioxide Ozone (O 3 ) Particles < 10  m (PM 10 ) Particles < 2.5  m (PM 2.5 ) Sulfur dioxide (SO 2 ) Any pollutant

ANNUAL MEAN PARTICULATE MATTER (PM) CONCENTRATIONS AT U.S. SITES, NARSTO PM Assessment (draft), 2002 PM10 (particles > 10  m)PM2.5 (particles > 2.5  m) Red circles indicate violations of national air quality standard: 50  g m -3 for PM10 15  g 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 Acadia National Park clean day moderately polluted day Places new emphasis for understanding long-range transport

GOOD vs. BAD OZONE (O 3 ) NO x = NO + NO 2 : nitrogen oxide radicals VOC (volatile organic carbon) = light hydrocarbons and substituted organic compounds

MEAN NUMBER OF SUMMER DAYS ( ) 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!) ppbv Europe (seasonal) U.S. (8-h avg.) U.S. (1-h avg.) preindustrial present background Europe (8-h avg.)

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 atoms N cm -2 s -1 Anthropogenic NO x emissions [IPCC, 2001] “Optimistic” IPCC scenario: OECD, U.S.  20%, Asia  50%

TREND IN NORTHERN HEMISPHERIC SURFACE TEMPERATURE OVER PAST 1000 YEARS IPCC [2001]

EFFECTS OF GREENHOUSE GASES AND AEROSOLS ON CLIMATE Greenhouse gas layer (transparent to solar, absorbs in IR) Greenhouse effect (warming) Terrestrial emission (IR) Aerosol layer (scatters solar, transparent in IR) Solar radiation reflected to space (cooling) EARTH SURFACE

HISTORICAL TRENDS OF GREENHOUSE GASES AND AEROSOLS Greenhouse gases Aerosols IPCC [2001] Carbon dioxide Methane Nitrous oxide Sulfur

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 Chin et al. [2000] DIESEL DOMESTIC COAL BURNING BIOMASS BURNING

WHAT DOES THE FUTURE HOLD? Future emission scenarios from IPCC [2001] A1, A2, B1, B2: four different socioeconomic story lines NO x : ozone precursor SO 2 : aerosol precursor Methane

EFFECTS OF FUTURE CHANGES IN GLOBAL ANTHROPOGENIC EMISSIONS High-ozone days over U.S.Radiative forcing Standard 50% 50% 50% A1 B1 NMVOC CH 4 NO x Standard 50% 50% 50% A1 B1 NMVOC CH 4 NO x IPCC scenario Fossil fuel NO x emissions (2020 vs. present) Global U.S. Methane concentration (2020 vs. present) A1+80%-30%+35% B1+10%-60%+20% Fiore et al. [2002]