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)

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GEOS-Chem users’ meeting, 2007/04

work supported by the EPA-STAR program

Background - We are facing rapid global change

IPCC [2007]

2000

2050

2000

2050

IPCC

A1B

scenario

(-40%)

(+90%)

Models and future scenarios

Effects of 2000-2050 global change on tropospheric ozone

(annual zonal mean)

+3%

+17%

+20%

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

2000 conditions

2050 climate – 2000

2050 emission – 2000

2050 – 2000

Daily max 8h-avg ozone averaged over JJA (ppb)

Increase of summer max-8h-avg ozone by 1-5 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

Summer surface T. (2050 – 2000)

What’s more: decrease of cyclone frequency

2000 climate 2050 climate

1999-2001

2049-2051

Eric M. Leibensperger, Harvard

Climate change has most effects on pollution events

Max. 8-hr-avg ozone

2000s condition

2050s climate

2050s emissions

2050s climate & emis

median

99^th percentile

Mitigation of climate penalty by emission reductions in ozone precursors

“climate change penalty” for ozone AQ = Δ[O₃] from 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.

(a) 2000 emissions

(b) 2050 emissions

Change of summer average max-8h ozone due to climate change

Conclusions

1. 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.
2. 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.
3. Preliminary analysis suggests that the climate change penalty corresponds to a need for some 10% further reductions in NO_x emissions to meet our goals for clean air.
4. Reductions of anthropogenic emissions can significantly mitigate the “climate penalty” for ozone air quality, and even turn it into a “climate benefit”.
5. 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.

Effects on annual mean afternoon surface O₃