Effect of 2000-2050 global change on U.S. ozone air quality

1. GCAP Effect of 2000-2050 global change on U.S. ozone air quality Shiliang Wu Loretta J. Mickley Daniel J. Jacob Eric M. Leibensperger David Rind (NASA/GISS) David G. Streets (ANL) GEOS-Chem users’ meeting, 2007/04 work supported by the EPA-STAR program

2. Background - We are facing rapid global change 2050 IPCC A1B scenario 2000 2000 2050 (-40%) (+90%) IPCC [2007]

3. 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) Radiative forcing GHG Air pollutants & their precursors Natural emissions Chemistry, transport, deposition, etc Climate Change Models and future scenarios

4. (annual zonal mean) Effects of 2000-2050 global change on tropospheric ozone +3% +20% +17%

5. Effects of 2000-2050 global change on U.S. ozone air quality Daily max 8h-avg ozone averaged over JJA (ppb) 2000 conditions 2050 climate – 2000 Increase of summer max-8h-avg ozone by 1-5 ppb in large areas of U.S. due to 2000-2050 climate change. 2050 – 2000 2050 emission – 2000 Less effects in western U.S. because (1) anthro. emissions there are low (2) increase of ozone from intercontinental transport.

6. Mixing depth (2050 / 2000) Convective mass flux (2050-2000) Factors causing worse O3 AQ with the future climate Summer surface T. (2050 – 2000)

7. What’s more: decrease of cyclone frequency 2000 climate 2050 climate 2049-2051 1999-2001 Eric M. Leibensperger, Harvard

8. Cumulative probability (%) Climate change has most effects on pollution events 2000s condition 2050s climate 2050s emissions 2050s climate & emis Max. 8-hr-avg ozone 99th percentile median

9. Mitigation of climate penalty by emission reductions in ozone precursors “climate change penalty” for ozone AQ = Δ[O3] from climate change Change of summer average max-8h ozone due to climate change (a) 2000 emissions (b) 2050 emissions Reductions of anthropogenic emissions significantly mitigate the “climate penalty” and can even turn it into a “climate benefit” in southeast and northwest U.S.

10. Conclusions Climate change is expected to worsen ozone air quality in the United States; the summer average daily max-8h ozone is projected to increase by 2-5 ppb over large areas due to the 2000-2050 climate change with the IPCC A1B scenario. Climate change has more effects on air pollution episodes than on the means; it tends to increase the 90th percentile ozone by 5-10 ppb. Factors causing worse ozone air quality associated with the future climate include: higher temperature, less convection and lower mixing depth, higher natural emissions as well as less frequent cyclones. Preliminary analysis suggests that the climate change penalty corresponds to a need for some 10% further reductions in NOx emissions to meet our goals for clean air. 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 the United States by 1-3 ppb for most areas while the changes in global anthropogenic emissions would increase the PRB ozone by 2-5 ppb. 2000–2050 global change would make fresh air more luxury in the United States.

11. Effects on annual mean afternoon surface O3