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

Ozone air quality correlates strongly with temperature

Probability of max 8-h O3 > 84 ppbv

Lin, et al. [Atm. Env.

2001]IPCC [2001]

IPCC [2001]

Models and future scenarios

Chemistry, transport, deposition, etc

GHGAir

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

fossil fuel

Growth factors for NOx emissions (future / present)

Biomass burning

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%

Anthropogenic emissions

Climate

Present Present

Present Future

Future Present

Future Future

4 groups of simulations

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

Present-day conditions Effects from climate change

Effects from emission change Combined effects

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.

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 convective mass flux at 850 hPa (future/present)

Change of afternoon PBL (future / present)

Change of surface Temp. (future – present)

Cumulative probability (%)

Cumulative probability (%)

Midwest

Southeast

Northeast

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

o

zon

e

Cumulative probability (%)

Max

. 8-

hr-

avg

o

zon

e

PresentFuture climateFuture emissionsFuture climate & emis

Northeast

Southeast

Midwest

Max

. 8-

hr-

avg

o

zon

e

Cumulative probability (%)

No effects from climate change?

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

RO2 + NORONO2 (sink for NOx)

Competing effects of isoprene on ozone

Isoprene emis +30% Δ(O3) present future / present

Isoprene emissions

Isoprene + OH RO2 (OH sink)

Isoprene + O3 M (O3 sink)O3

RO + NO2 (O3 formation) O3

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.

(ppb)

Present emissions Future emissions

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

Northeast

55

60

65

70

75

presentemissions

futureemissions

presentclimate

futureclimate

Southeast

50

55

60

65

70

75

presentemissions

futureemissions

presentclimate

futureclimate

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 is mitigated by emission reductions

“climate penalty”

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)!

Present-day Effects from climate change

Effects from emission change Combined effects

Effects of 2000-2050 global change on Policy Relevant Background (PRB) ozone

Decrease of background ozone in response to climate change except in the middle U.S. where NOx emissions from soil increases.

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.

Fossil fuel and biofuel emissions over North America are turned off.

PRB ozone = Ozone levels that would exist in the absence of anthropogenic emissions from U.S., Canada and Mexico

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%

Methane abundance, ppb 1760 2400 36% 1760 2400 36%

Effects of climate change on global ozone

Annual zonal mean ozone

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%)

Surface afternoon ozone (JJA)

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

Changes of OH

Global – zonal - annual

Surface - summer Present-day

Future climate

Future emissions

1.10 1.19 (+8%) 1.10 (--0%)

Changes of CO

Global – zonal - annual

Surface - July