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AIR QUALITY AND CLIMATE TOPICS FOR TODAY 1. What are we worried about when we talk about “air quality” 2. Global air quality 3. Background & interhemispheric transport 4. Local/regional air quality O2 hn STRATOSPHERE 8-18 km CLIMATE CHANGE AND TROPOSPHERIC OZONE O3 TROPOSPHERE transport hn O3 NO2 NO OH HO2 hn, H2O Deposition CO, VOC Nitrogen oxide radicals; NOx = NO + NO2 generally limiting combustion, soils, lightning Tropospheric ozone precursors H2O2 Methane wetlands, livestock, natural gas Nonmethane volatile organic compounds (NMVOCs) vegetation, combustion, industry CO (carbon monoxide) combustion, VOC oxidation SENSITIVITY OF SURFACE AIR QUALITY TO METEOROLOGICAL VARIABLES Insights into the effect of climate change on air quality Effect of climate change Ozone PM (aerosol) Stagnation Temperature ? ? ? ? Mixing depth Precipitation = = Cloud cover Humidity = (relative) [Jacob and Winner, 2008] PREDICTIONS OF TEMPERATURE AND PRECIPITATION CHANGES IN THE NH Warmer everywhere, but precipitation (humidity, cloudiness, convection) trickier. [Jacob and Winner, 2008] EFFECT OF CLIMATE CHANGE ON OZONE AIR QUALITY Probability of max 8-h O3 > 84 ppbv vs. daily max. T Ozone exceedances of 90 ppbv, summer 2003 Lin et al. [2001] Correlation of high ozone with temperature is driven by (1) stagnation, (2) biogenic hydrocarbon emissions, (3) chemistry EFFECT OF CLIMATE CHANGE ON REGIONAL STAGNATION GISS GCM simulations for 2050 vs. present-day climate using pollution tracers with constant emissions weather map illustrating cyclonic ventilation of the eastern U.S. 2045-2052 summer 1995-2002 Pollution episodes double in duration in 2050 due to decreasing frequency of cyclones ventilating the eastern U.S; expected result of greenhouse warming. Mickley et al. [2004] TOPICS FOR TODAY 1. What are we worried about when we talk about “air quality” 2. Global air quality 3. Background & interhemispheric transport 4. Local/regional air quality EFFECT OF 2000-2050 CLIMATE CHANGE (A1B) ON GLOBAL TROPOSPHERIC OZONE Tropospheric ozone in year 2000 (ppb) 2050/2000 ratio Zonal annual mean concentrations Ozone increases in tropical upper troposphere because of increased lightning; but decreases in background surface air because of higher water vapor [Wu et al., 2008b] EFFECT OF 2000-2050 CLIMATE CHANGE (A1B) ON GLOBAL AFTERNOON SURFACE OZONE Ozone is predicted to increase over polluted continental regions (complex meteorological factors + natural emission changes) and decrease over the ocean (due to enhanced water vapour) [Wu et al., 2008b] CLIMATE CHANGE ALONE DEGRADES “MEAN” AQ IN THE US Climate change causes a 2–5 ppb positive offset over the Midwest and northeastern United States, partly driven by decreased ventilation from convection and frontal passages. [Wu et al., 2008a] …DUE TO AN INCREASE IN POLLUTION EPISODES Maximum JJA 8-h avg ozone 99th percentile 2050s 2000s Midwest Cumulative probability (%) Max. 8-hr-avg ozone Daily maximum temperature (K) Maximum JJA temperatures 2050s climate 2000s climate 40% decrease in NOx 2050s climate + DNOx Cumulative probability (%) Increased maximum temperatures during heat waves leads to increased ozone Amplification of temperatures at extreme due to • soil moisture feedbacks • 17% decreased cyclone frequency. [Wu et al., 2008] TOPICS FOR TODAY 1. What are we worried about when we talk about “air quality” 2. Global air quality 3. Background & interhemispheric transport 4. Local/regional air quality OBSERVED TREND IN OZONE BACKGROUND OVER CALIFORNIA IN SPRING SUGGESTS 10-15 ppbv INCREASE OVER PAST 20 YEARS Background: concentration that would be present in absence of local anthropogenic emissions Trend: 0.5-0.8 ppbv yr-1 Jaffe et al. [2003] Trend real? Driven by emission increases in Asia? RISING OZONE BACKGROUND IN EUROPE Hohenpeissenberg/ Payerne polluted 3-5 km Naja et al. [2003] background Changes in anthrop. NOx emissions Mace Head, 1987-2004 [Simmonds et al., 2004] HEMISPHERIC OZONE POLLUTION: IMPLICATIONS OF ENHANCED OZONE BACKGROUND FOR MEETING AIR QUALITY STANDARDS (AQS) Europe AQS (8-h avg.) Europe AQS (seasonal) U.S. AQS (8-h avg.) U.S. AQS (1-h avg.) Was here until 2008! 0 Preindustrial ozone background 20 40 60 Present-day ozone background at northern midlatitudes 80 100 120 ppbv EFFECT OF INCREASING SIBERIAN FOREST FIRES ON SUMMER SURFACE OZONE IN PACIFIC NORTHWEST Observations GEOS-CHEM ozone enhancements Siberian fires Ozone Mean summer 2003 enhancement of 5-9 ppbv (9-17 ppbv in events) Jaffe et al. [2004] SIMULTANEOUS CHANGES IN POLICY-RELEVANT SUMMERTIME BACKGROUND OZONE deeper PBL, drier soil NOx Climate change alone would diminish the impact of background ozone, however the background is expected to rise in the future (non-US emissions) [Wu et al., 2008b] CLIMATE CHANGE INCREASES SUMMERTIME OZONE Changes in summer 8-h avg. daily maximum ozone from 2000-2050 climate change Higher temperatures, stagnation ppb Increased water vapor sink • Models agree that 2000-2050 climate change will decrease background ozone but increase surface ozone. We find an increase of 3-5 ppb over large regions. • Most but not all models find maximum effect during pollution episodes (up to 10 ppb) due to increased stagnation and higher temperatures. • Most models find significant effects in Northeast/ Midwest. • Many models disagree in Southeast partly due to different mechanisms for oxidation of biogenic isoprene (the dominant VOC precursor) [Wu et al., 2008a] TOPICS FOR TODAY 1. What are we worried about when we talk about “air quality” 2. Global air quality 3. Background & interhemispheric transport 4. Local/regional air quality CHANGES IN AQ (SUMMER) OVER THE US (A2) mean 95th percentile Present Day O3 DO3 Climate only DO3 Emissions only Changes in O3 due to climate (driven primarily by cloud cover) are significantly smaller than impact of emission reductions in the mean, although a larger effect [Nolte et al., 2008] on extremes is predicted (similar to Wu et al.). LOOKING SPECIFICALLY IN TEXAS… Present-Day Future Climate Future Climate & Land Use 84 ppb Increases in exceedances in Houston area [Jiang et al., 2008] RIGHT DOWN TO THE URBAN SCALE… Days in summer with O3 > 84 ppb (NAAQS) 50 Chicago 2000 2100 Down-scaling experiments now possible… Summertime ozone in Chicago estimated to increase by 6-17 ppb [Holloway et al., 2008] EUROPEAN HEATWAVE OF 2003: A CLIMATE CHANGE TEST CASE? Daytime temperatures topped 38°C (over 100°F) for several days! EMEP Stations Substantial ozone increases were associated with these events, although O3 did high not get as high as in the late 1980s (due to the reduction of precursor emissions). Europe also experienced enhanced wildfire activity (warmer and drier climate). [Vautard et al., 2007] MANAGING AIR QUALITY IN CHINA “The key question is how soon developing nations will tip the balance in favor of the environment, so that they can help to improve the air quality for their citizens and relieve global climate change for themselves as well as the rest of the world. The upgrading of the national environmental protection agency to the ministry level is an indication of China’s determination to clean up its environment.” [Fang et al., 2009]