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 Chemistry, transport, deposition, etc GHG Air pollutants & their precursors Climate Change GISS GCM III 23 vertical layers extending to 85 km Horizontal resolution of 4º x 5º GEOS-Chem detailed ozone-NOx-VOC-aerosol chemistry Anthropogenic emissions (IPCC A1B scenario) Natural emissions Radiative forcing Simulated 2000-2050 changes in global annual mean surface temperature = + 1.7oC

A1B 2000-2050 changes in NOx emissions Global U.S. 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% fossil fuel Growth factors for NOx emissions (future / present) Biomass burning 4 groups of simulations Anthropogenic emissions Climate Present 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-8h-avg 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 inter-continental 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) global change has more effect on the pollution events than on the means Cumulative probability (%) Cumulative probability (%) Max. 8-hr-avg ozone Max. 8-hr-avg ozone Present Future climate Future emissions Future climate & emis Midwest Northeast Cumulative probability (%) Midwest Southeast Northeast Cumulative probability (%) Max. 8-hr-avg ozone No effects from climate change? Southeast

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 (sink for NOx) O3 Isoprene + O3 M (O3 sink) Isoprene emissions Isoprene emis +30%  Δ(O3) present future / present

Mitigation of climate penalty by emission reductions in ozone precursors “climate penalty” for ozone air quality = Δ[O3] from climate change (ppb) Present emissions Future emissions Change of summer average max-8h ozone due to climate change 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) Climate penalty is turned into climate benefit by emission reductions “climate penalty” Climate penalty is mitigated by emission reductions 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 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 climate change Effects from emission change Combined effects Fossil fuel and biofuel emissions over North America are turned off. Increase of bkgd ozone, especially in western U.S., mainly due to increased inter-continental transport from Asia; increase of biomass burning over NA also contributes.

Conclusions 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. 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. Reductions of anthropogenic emissions can significantly mitigate the “climate penalty” for ozone air quality, and even turn it into a “climate benefit”. 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 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% 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 CO from fossil fuel, Tg /yr 381 363 81 35 -57% 176 169 -4% 3 2.6 -13% 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 28 Acetone from vegetation , Tg C/yr 43 51 19% 2.7 23% Methane abundance, ppb 1760 2400 36%

Effects of climate change on global ozone Increase of ozone in the upper tropical troposphere due to increase of lightning Present-day 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 Global – zonal - annual Present-day Future climate Future emissions 1.10 1.19 (+8%) 1.10 (--0%) Global – zonal - annual

Changes of CO Surface - July Global – zonal - annual