Transcript Document

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
IPCC [2001]
Probability of max
8-h O3 > 84 ppbv
Ozone air quality
correlates strongly
with temperature
Lin, et al. [Atm.
Env. 2001]
IPCC [2001]
Models and future scenarios
GISS GCM III
GEOS-Chem
23 vertical layers extending to 85 km
detailed ozone-NOx-VOC-aerosol chemistry
Horizontal resolution of 4º x 5º
Anthropogenic emissions
(IPCC A1B scenario)
GHG
Radiative forcing
Climate Change
Simulated 2000-2050 changes in
global annual mean surface
temperature = + 1.7oC
Natural
emissions
Air
pollutants
& their
precursors
Chemistry, transport,
deposition, etc
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%
Growth factors for NOx emissions (future / present)
4 groups of simulations
fossil fuel
Biomass burning
Anthropogenic
emissions
Climate
Present
Present
Present
Future
Future
Present
Future
Future
Effects of 2000-2050 global change on U.S. ozone air quality
Daily max 8h-avg ozone averaged over JJA (ppb)
Present-day conditions
Effects from climate change
Effects from emission change
Combined effects
Increase of
summer
max-8havg 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 intercontinental
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 surface Temp.
(future – present)
Change of convective mass
flux at 850 hPa (future/present)
Change of afternoon PBL
(future / present)
Cumulative probability distributions of max 8-hr ozone (JJA)
Max. 8-hr-avg ozone
Midwest
Present
Future climate
Future emissions
Future climate & emis
Cumulative
probability
(%)
Cumulative
probability
(%)
Midwest
Northeast
Southeast
Northeast
Cumulative probability (%)
Max. 8-hr-avg ozone
Max. 8-hr-avg ozone
global change has more effect on the pollution events than on the means
Southeast
No effects from
climate change?
Cumulative probability (%)
Why is SE U.S. ozone insensitive to climate change?
Competing effects of isoprene on ozone
Isoprene + OH
RO2
(OH sink)
RO + NO2 (O3 formation)
O3
RO2 + NO
RONO2
Isoprene + O3
M
(sink for NOx)
(O3 sink)
Isoprene emissions
present
future / present
O3
Isoprene emis +30%  Δ(O3)
Mitigation of climate penalty by emission reductions
in ozone precursors
“climate penalty” for ozone air quality = Δ[O3] from climate change
Change of summer average max-8h ozone due to climate change
Present emissions
Future emissions
(ppb)
Reductions of anthropogenic emissions significantly mitigate the
“climate penalty” and can even turn it into a “climate benefit” in
southeast and northwest U.S.
Mitigation of climate penalty by emission reductions - continued
Regional average summer max-8h ozone (ppb)
75
“climate
penalty”
75
Northeast
70
present
climate
Southeast
70
65
Climate
penalty is
mitigated by
emission
reductions
future
climate
65
60
60
present
climate
future
climate
Climate
penalty is
turned into
climate
benefit by
emission
reductions
55
50
55
present
future
emissions emissions
present
future
emissions emissions
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 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
Fossil fuel and
biofuel emissions
over North America
are turned off.
Increase of bkgd
ozone, especially
in western U.S.,
mainly due to
increased intercontinental
transport from
Asia; increase of
biomass burning
over NA also
contributes.
Decrease of background ozone in response to
climate change except in the middle U.S.
where NOx emissions from soil increases.
Present-day
Effects from emission change
Effects from climate change
Combined effects
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%
1760
2400
36%
1760
2400
36%
Methane abundance, ppb
Effects of climate change on global ozone
Increase of
ozone in the
upper tropical
troposphere due
to increase of
lightning
Presentday
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%)
Annual zonal mean ozone
Surface afternoon ozone (JJA)
Changes of OH
Surface - summer
Presentday
Future
climate
Future
emissions
1.10
1.19 (+8%)
1.10 (--0%)
Global – zonal - annual
Changes of CO
Surface - July
Global – zonal - annual