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Effects of 2000-2050 global change on U.S. ozone air quality Shiliang Wu (Harvard) Loretta J. Mickley (Harvard) Daniel J. Jacob (Harvard) David Rind (NASA/GISS) David G. Streets (ANL) AGU Fall meeting, 2006 work supported by the EPA-STAR program Background - We are facing rapid global change 1. Anthropogenic emissions of ozone precursors 2. Climate change IPCC [2001] Probability of max 8-h O3 > 84 ppbv Ozone air quality correlates strongly with temperature Lin, et al. [Atm. Env. 2001] IPCC [2001] Models and future scenarios GISS GCM III GEOS-Chem 23 vertical layers extending to 85 km detailed ozone-NOx-VOC-aerosol chemistry Horizontal resolution of 4º x 5º Anthropogenic emissions (IPCC A1B scenario) GHG Radiative forcing Climate Change Simulated 2000-2050 changes in global annual mean surface temperature = + 1.7oC Natural emissions Air pollutants & their precursors Chemistry, transport, deposition, etc A1B 2000-2050 changes in NOx emissions Global U.S. Present Future Change Present Future Change NOx (fossil fuel), Tg N/yr 24.6 47.3 92% 5.9 3.6 - 39% NOx (biomass burning), Tg N/yr 6.5 8.1 25% 0.03 0.06 100% NOx (lightning), Tg N/yr 4.9 5.8 18% 0.14 0.17 21% NOx (soil), Tg N/yr 6.1 6.6 8% 0.35 0.39 11% Growth factors for NOx emissions (future / present) 4 groups of simulations fossil fuel Biomass burning Anthropogenic emissions Climate Present Present Present Future Future Present Future Future Effects of 2000-2050 global change on U.S. ozone air quality Daily max 8h-avg ozone averaged over JJA (ppb) Present-day conditions Effects from climate change Effects from emission change Combined effects Increase of summer max-8havg ozone by 2-5 ppb in large areas of U.S. due to 2000-2050 climate change. Less effects in western U.S. because (1) anthro. emissions there are low (2) increase of ozone from intercontinental transport. Factors causing worse O3 AQ with the future climate Higher temperature More soil NOx emissions (+21%) Lower mixing depth More lightning NOx emissions (+11%) Less convection More isoprene emissions (some areas) Change of surface Temp. (future – present) Change of convective mass flux at 850 hPa (future/present) Change of afternoon PBL (future / present) Cumulative probability distributions of max 8-hr ozone (JJA) Max. 8-hr-avg ozone Midwest Present Future climate Future emissions Future climate & emis Cumulative probability (%) Cumulative probability (%) Midwest Northeast Southeast Northeast Cumulative probability (%) Max. 8-hr-avg ozone Max. 8-hr-avg ozone global change has more effect on the pollution events than on the means Southeast No effects from climate change? Cumulative probability (%) Why is SE U.S. ozone insensitive to climate change? Competing effects of isoprene on ozone Isoprene + OH RO2 (OH sink) RO + NO2 (O3 formation) O3 RO2 + NO RONO2 Isoprene + O3 M (sink for NOx) (O3 sink) Isoprene emissions present future / present O3 Isoprene emis +30% Δ(O3) Mitigation of climate penalty by emission reductions in ozone precursors “climate penalty” for ozone air quality = Δ[O3] from climate change Change of summer average max-8h ozone due to climate change Present emissions Future emissions (ppb) Reductions of anthropogenic emissions significantly mitigate the “climate penalty” and can even turn it into a “climate benefit” in southeast and northwest U.S. Mitigation of climate penalty by emission reductions - continued Regional average summer max-8h ozone (ppb) 75 “climate penalty” 75 Northeast Southeast 70 70 present climate 65 Climate penalty is mitigated by emission reductions future climate 65 60 60 present climate future climate Climate penalty is turned into climate benefit by emission reductions 55 50 55 present future emissions emissions present future emissions emissions Q: Is climate change bad for O3 AQ? A: That depends. With present-day anthropogenic emissions – BAD for most places. With the reduced anthropogenic emissions – Not that bad; or even GOOD for some regions (e.g. southeast and northwest)! Effects of 2000-2050 global change on Policy Relevant Background (PRB) ozone PRB ozone = Ozone levels that would exist in the absence of anthropogenic emissions from U.S., Canada and Mexico Fossil fuel and biofuel emissions over North America are turned off. Increase of bkgd ozone, especially in western U.S., mainly due to increased intercontinental transport from Asia; increase of biomass burning over NA also contributes. Decrease of background ozone in response to climate change except in the middle U.S. where NOx emissions from soil increases. Present-day Effects from emission change Effects from climate change Combined effects Conclusions 1. Climate change could worsen ozone air quality in U.S.; the summer average daily max-8-hr ozone is projected to increase by 2-5 ppb over large areas of U.S. due to the 2000-2050 climate change with the IPCC A1B scenario. 2. Factors causing worse ozone air quality associated with the future climate include: higher temperature, less convection and lower mixing depth as well as higher natural emissions. 3. Reductions of anthropogenic emissions can significantly mitigate the “climate penalty” for ozone air quality, and even turn it into a “climate benefit”. 4. The 2000-2050 climate change would reduce the PRB ozone in U.S. by 1-3 ppb for most areas while the changes in global anthropogenic emissions would increase the PRB ozone in U.S. by 2-5 ppb. Backup – some extra slides Changes in emissions of ozone precursors Global U.S. Present Future Change Present Future Change NOx from fossil fuel, Tg N/yr 24.6 47.3 92% 5.9 3.6 -39% NOx from biofuel, Tg N/yr 2.2 2.1 -5% 0.01 0.01 0% NOx from biomass burning 6.5 8.1 25% 0.03 0.06 100% NOx from fertilizer, Tg N/yr 0.46 0.87 89% 0.05 0.05 0% CO from fossil fuel, Tg /yr 381 363 -5% 81 35 -57% CO from fossil fuel, Tg /yr 176 169 -4% 3 2.6 -13% CO from fossil fuel, Tg /yr 459 750 63% 3.4 8.4 147% Ethane from fossil fuel, Tg C/yr 6.0 17 183% 1 0.3 -70% Propane from fossil fuel , Tg C/yr 10.1 31.6 213% 1.5 0.7 -53% NOx from lightning, Tg N/yr 4.9 5.8 18% 0.14 0.17 21% NOx from soil, Tg N/yr 6.1 6.6 8% 0.35 0.39 11% Isoprene from vegetation, Tg C/yr 430 537 25% 28 35 25% Acetone from vegetation , Tg C/yr 43 51 19% 2.2 2.7 23% 1760 2400 36% 1760 2400 36% Methane abundance, ppb Effects of climate change on global ozone Increase of ozone in the upper tropical troposphere due to increase of lightning Presentday Future climate Future emissions Future climate and emissions Burden, Tg 309 317 (+3%) 363 (+17%) 371 (+20%) Lifetime, days 22.4 21.0 (- 6%) 20.6 (- 8%) 19.5 (- 13%) Annual zonal mean ozone Surface afternoon ozone (JJA) Changes of OH Surface - summer Presentday Future climate Future emissions 1.10 1.19 (+8%) 1.10 (--0%) Global – zonal - annual Changes of CO Surface - July Global – zonal - annual