Identifying Chemistry-Climate-Air Quality
Connections To Inform Public Policy
Arlene M. Fiore
Acknowledgments. Jasmin John, Meiyun Lin, Vaishali Naik, Larry
Horowitz, D.J. Rasmussen, Alex Turner, GAMDT (GFDL); Oliver Wild
(U Lancaster): Mike Bauer (CU/GISS)
AAAS Meeting, Vancouver
February 19, 2012
Addressing air quality and climate via methane emission
controls: A viable option?
Ozone reduction (ppb)
Cost-saving
reductions
0.7
North America
Rest of Annex I
Rest of World
(industrialized nations)
1.4
<$10 / ton
CO2 eq.
All identified
reductions
00
1.9
10% of anth.
emissions
20% of anth.
emissions
20
40
60
80
100
120
20
40
60
80
100
120
-1
Methane
Methanereduction
reductionpotential
potential(Mton
(MtonCH
CH4 4yryr)-1)
IEA [2003] for 5 industrial sectors
~25% of global anthrop. emissions at cost-savings / low-cost
>1 ppb decrease in global surface ozone
West & Fiore, ES&T, 2005; Fiore et al., GRL, 2002
Benefits of ~25% decrease in global anthrop. CH4 emissions
OZONE AIR QUALITY
CLIMATE
Global mean
avoided warming in
2050 (°C)
Range over
18 models
 ~ 1 ppb, robust across models (factor of 2 range)
[Fiore et al., JGR, 2009; TF HTAP, 2007, 2010; Wild et al., ACPD, 2012]
 7700-400,000 annual avoided cardiopulmonary
premature mortalities in the N. Hemisphere
uncertainty in concentration-response relationship only
[Casper Anenberg et al., ES&T, 2009]
[WMO/UNEP, 2011]
Atmospheric CH4 and surface O3 over the next century?
Representative Concentration Pathways (RCPs)
ppb
METHANE
RCP8.5
RCP6.0
RCP4.5
RCP2.6
Tool: GFDL CM3 chemistryclimate model
• ~2°x2°; 48 levels
• Atm-ocean-sea ice-land GCM
• Fully coupled chemistry in
troposphere+stratosphere
• Aerosol – warm cloud interactions
c/o V. Naik
NOx Emissions
RCP4.5* WMGG
Tg N yr-1
RCP8.5
RCP4.5
c/o J. John
Donner et al., J. Climate, 2011;
Golaz et al., J. Climate, 2011;
Naik et al., in prep,
Horowitz et al., in prep
Multiple feedbacks complicate projections of atmospheric
CH4 and O3 abundances
tCH
Stratospheric O3
Troposphere
BCH 4
= tropopause
4
 k (T )[OH ][CH ]
4
surface
NOx
O3 + hν
O1D
+ H2 O
OH + CH4
k
CH3+H2O
T
T
NOx, CO, NMVOC, CH4
Anthropogenic sources
Biospheric sources
Negative feedback of warming climate on methane lifetime;
anthrop. emission trajectory can amplify or counteract
TROPOSPHERIC CH4 LIFETIME IN GFDL CM3 CHEMISTRY-CLIMATE MODEL
t
Years
RCP 8.5: CH4: +4%: Doubling CH4
offsets influence of warmer T (+4.5K)
RCP4.5*
WMGG only:
t
RCP4.5:
CH4: -13%
More warming (+2.3K; aerosol),
CO, CH4 decrease
J. John et al., in prep
tCH : -5%
4
Rising T(+1.4K),
OH (LNOx, H2O)
Percentage changes are (2081-2100) – (20062025)
How will O3 air quality evolve over North America?
RCP emissions: lower? Warmer climate: higher?
 Dramatic rise in CH4 in RCP8.5
opposes NOx-driven decreases
Observed O3-T
correlation implies
that changes in
climate will influence
air quality
July mean obs from U.S. EPA CASTNet site
Penn State, PA 41N, 78W, 378m
TEMP (C; 10am-5pm avg)
[Wild et al.,
revised for ACP]
MDA8 O3 (ppb)
Annual mean N. Amer.
Surface O3 changes (ppb)
NO CLIMATE CHANGE
O3 change estimated from sensitivities derived from TF HTAP model ensemble
Over NE USA, stagnation episodes are a major driver of
observed surface O3-T correlation: Future evolution?
Leibensperger et al. [2008]: strong anticorrelation in summer between
(a) number of migratory cyclones over Southern Canada/NE U.S. and
(b) number of stagnation events and associated NE US high-O3 events
Number of storms in region each summer (JJA) in RCP8.5, GFDL CM3 model
 Robust across models?
[e.g., Lang and Waugh, 2011]
 Can we evaluate modeled
relationships btw air
quality and climate?
Cylones diagnosed from 6-hourly SLP with MCMS
software from Mike Bauer, (Columbia U/GISS)
æ
ç -4
è
é exceedances ùö æ
ê
ú÷ × ç -6
ë cyclone ûø è
é cyclones ùö
êë
úû÷ = +24
summer ø
é exceedances ù
êë
ú
summer û
A. Turner et al., in prep
How well does a global chemistry-climate model simulate
regional O3-temperature relationships?
“Climatological” O3-T relationships:
Monthly means of daily max T and monthly means of MDA8 O3
AM3: 1981-2000
OBS: 1988-2009
r2=0.41, m=3.9
r2=0.28, m=3.7
July Monthly avg. daily max T
Slopes (ppb O3 K-1)
July Monthly avg. MDA8 O3
CASTNet sites,
NORTHEAST
USA
Month
 Model captures observed O3-T relationship in NE USA in July,
despite high O3 bias
 Broadly represents seasonal cycle Rasmussen et al., Atmos. Environ., 2012
What is the combined impact of climate + emission
on surface O3 over North America?
Annual mean N. American
surface O3 change (ppb)
EMISSIONS CHANGE ONLY
EMISSIONS + CLIMATE CHANGE
520
GFDL CM3 RCP8.5
RCP4.5 ens. mean
Individual members
015
-510
[Wild et al.,
revised for ACP]
-10 5
2005
2025
2045
2065
2085
Why does O3 increase in GFDL CM3 RCP8.5? Higher CH4 sensitivity?
Increased strat O3 influence? [e.g., Butchart et al., 2006; Hegglin & Shepherd,
2009; Kawase et al., 2011; Li et al., 2008; Shindell et al. 2006; Zeng et al., 2010]
 How well do models represent strat-to-trop O3 transport?
Western NA: Particularly active region for STE in present day,
a good test case for model evaluation
Upper level dynamics associated with a deep stratospheric ozone intrusion
(21:00UTC May 27, 2010)
Satellite observations
AM3 “nudged high-res” (~50km2 )
250 hPa simulations
potential vorticity
AIRS total column ozone
DU
GOES-West water vapor
250 hPa jet (color)
350 hPa geopotential height (contour)
Decreasing humidity 
 AM3 resolves features consistently with satellite perspective
M. Lin et al., in prep.
Identifying chemistry-climate-air quality connections to
inform public policy… some final thoughts
• Methane controls as “win-win” for climate and O3 air quality
 Cooling influence on climate (by lowering both methane and O3)
 Decrease baseline surface O3 (robust across models)
 Complex chemistry-climate feedbacks along future trajectories
• Analysis of long-term chemical and meteorological obs may
reveal key connections between climate and air pollution
 Crucial for testing models used to project future changes
 Need to maintain long-term observational networks
• Climate-driven influences on air quality
 Need better process understanding at regional scale;
new opportunities with chemistry-climate models
 Potential for shifts in relative importance of locally produced vs.
transported O3