Effects of 2000 2050 global change on u s ozone air quality
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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. Probability of max 8-h O 3 > 84 ppbv.

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

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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

Probability of max 8-h O3 > 84 ppbv

Background - We are facing rapid global change

1. Anthropogenic emissions of ozone precursors

2. Climate change

IPCC [2001]

Ozone air quality correlates strongly with temperature

Lin, et al. [Atm. Env. 2001]

IPCC [2001]


23 vertical layers extending to 85 km

Horizontal resolution of 4º x 5º


detailed ozone-NOx-VOC-aerosol chemistry

Anthropogenic emissions (IPCC A1B scenario)

Radiative forcing


Air pollutants & their precursors

Natural emissions

Chemistry, transport, deposition, etc

Climate Change

Models and future scenarios

Simulated 2000-2050 changes in global annual mean surface temperature = + 1.7oC

Growth factors for NOx emissions (future / present)

Biomass burning

fossil fuel

A1B 2000-2050 changes in NOx emissions

4 groups of simulations

Present-day conditions

Effects from climate change

Combined effects

Effects from emission change

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

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

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.

Change of convective mass flux at 850 hPa (future/present)

Change of afternoon PBL

(future / present)

Factors causing worse O3 AQ with the future climate

Change of surface Temp. (future – present)

Max. 8-hr-avg ozone

Cumulative probability (%)

Cumulative probability (%)




Cumulative probability (%)

Cumulative probability distributions of max 8-hr ozone (JJA)

global change has more effect on the pollution events than on the means

Max. 8-hr-avg ozone




Future climate

Future emissions

Future climate & emis

Cumulative probability (%)

Max. 8-hr-avg ozone

No effects from climate change?


Isoprene + OH RO2(OH sink)


RO + NO2 (O3 formation)

Isoprene + O3 M (O3 sink)

Why is SE U.S. ozone insensitive to climate change?

Competing effects of isoprene on ozone

RO2 + NO

RONO2 (sink for NOx)


Isoprene emissions

Isoprene emis +30%  Δ(O3)


future / present

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

Present emissions

Future emissions


Mitigation of climate penalty by emission reductions in ozone precursors

“climate penalty” for ozone air quality = 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.

Regional average summer max-8h ozone (ppb)

Mitigation of climate penalty by emission reductions - continued

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 from climate change

Effects from emission change

Combined effects

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.

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.


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

Effects of climate change on global ozone

Increase of ozone in the upper tropical troposphere due to increase of lightning

Annual zonal mean ozone

Surface afternoon ozone (JJA)

Changes of OH

Surface - summer

Global – zonal - annual

Changes of CO

Surface - July

Global – zonal - annual

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