Effect of 2000-2050 global change on ozone air quality in the United States

Shiliang Wu, Loretta Mickley, Daniel Jacob, Eric Leibensperger, David Rind (GISS), David Streets (ANL)

Harvard UniversityOct. 12, 2007

work supported by the EPA-STAR program

Models and future scenario

Chemistry, transport, deposition, etc

GHGAir

pollutants & their

precursors

Climate Change

GISS GCM 3 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

GCAP (Global Change and Air Pollution) model

Trends of NOx emissions from fuel use (2050 / 2000)

(IPCC A1B scenario)

Global changes in anthropogenic emissions

- 40% +90%

+800%

+300%

4

2

1.5

1.1

0.9

0.8

0.7

0.6

0.5Global total NOx emissions: + 90%

A1B 2000-2050 changes in climate

Annual mean surface temperature +1.6 K

Temperature: 2050 – 2000

Humidity: 2050 / 2000

2000 2050 NOx-lightning, Tg N/yr 4.9 5.8 +18%

NOx - soil, Tg N/yr 6.1 6.6 +8%

Isoprene, Tg C/yr 430 537 +25%

+1.6%

+17% +18%

2050 climate / 2000

2050 emission / 2000

2000

2050 / 2000

Effects of 2000-2050 global change on tropospheric ozone(annual zonal mean)

Effects of 2000-2050 global change on tropospheric ozone (annual surface afternoon mean)

2050 climate – 2000

2050 emission – 2000

2000

2050 – 2000

Policy relevant background (PRB) ozone (summer afternoon)

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

2000 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) increase of ozone from intercontinental transport and (2) anthro. emissions are low there.

Changes in summertime air pollution meteorology due to climate change

Surface temperature (2050 – 2000) Convective mass flux (2050 - 2000)

Mixing depth (2050 / 2000) Soil moisture (2050 / 2000)

1.0

0.8

0.6

0.5

-0.5

-1.0

-1.5

-2.0[g/m2/s]

oC

What’s more: decrease of cyclone frequency

Eric M. Leibensperger, Harvard

1999-2001 2049-2051

Summertime cyclones decrease by 17% in the 2050 climate

Cumulative probability (%)

Cumulative probability (%)

Midwest

Southeast

Northeast

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

climate 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

2000 conditions2050 climate2050 emissions2050 climate & emis

Northeast

Southeast

Midwest

Max

. 8-

hr-

avg

o

zon

e

Cumulative probability (%)

median99th percentile

Cumulative probability (%)

Why climate change has the most effects on pollution events?

Max

. 8-

hr-

avg

ozo

ne

2000s conditions2050s climate2050s emissions2050s climate & emis

median99th percentileMidwest

Dai

ly m

axim

um te

mpe

ratu

re (

K)

Cumulative probability (%)

Mitigation of climate change penalty by reductions in anthropogenic emissions

“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 the Southeast and Northwest.

(a) 2000 emissions (b) 2050 emissions

Change of summer 90th percentile max-8h O3 due to climate change

Translating climate change penalty to emission control efforts

2000 conditions

NOx emission - 40% (2000 climate)

NOx emission - 40% (2050 climate)

NOx emissions - 50% (2050 climate) 2000–2050 climate

change implies an additional 25% effort in NOx emission controls to achieve the same ozone air quality.

Conclusions

1. Climate change is expected to worsen the U.S. ozone air quality; the summer average daily max-8h ozone is projected to increase by 2-5 ppb over large areas due to 2000-2050 climate change with the IPCC A1B scenario. Climate change has most effects on air pollution episodes than on the means; it increases the 90th percentile ozone by up to 10 ppb.

2. The 2000-2050 changes in anthropogenic emissions of ozone precursors outside of North America would increase the mean summer PRB ozone by 3-6 ppb in the western United States, and by 2-3 ppb in the East.

3. Factors causing worse ozone air quality associated with the future climate include: higher temperature, less convection, lower mixing depth, higher natural emissions as well as less frequent cyclones.

4. 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.

5. Emission reductions can greatly mitigate the “climate change penalty” for ozone air quality, and can even turn it into a “climate benefit”.