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

GCAP

Background - We are facing rapid global change

IPCC [2007]

0

5

10

15

20

25

30

35

40

45

50

U.S. Global

NO

x em

issi

on

fro

m f

oss

il fu

el (

Tg

N /

yr)

2000

2050

2000

2050

IPCC A1B scenario

(-40%) (+90%)

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

2000 2050 change

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%

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.

Mixing depth (2050 / 2000)

Factors causing worse O3 AQ with the future climate

Summer surface T. (2050 – 2000)

Convective mass flux (2050-2000)

What’s more: decrease of cyclone frequency

2000 climate 2050 climate

1999-2001 2049-2051

Eric M. Leibensperger, Harvard

Cumulative probability (%)

Climate change has most effects on pollution events

Max

. 8-

hr-

avg

o

zon

e

2000s condition2050s climate2050s emissions2050s climate & emis

median99th 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

Conclusions1. 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 NOx 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