1. Geophysical Fluid Dynamics Laboratory Review
June 30 - July 2, 2009

2. Climate and Air Quality
Presented by
Arlene Fiore

3. Methane emission reduction potential (Mton CH4 yr-1)
Addressing air quality and climate via methane emission controls: A viable option?
Cost-saving
Cost-effective
All identified
(industrialized nations)
METHANE CONTROL OPTIONS
10% of anth.
emissions
20% of anth.
emissions
Methane emission reduction potential (Mton CH4 yr-1)
IEA [2003] for 5 industrial sectors
~25% of global anthropogenic emissions at cost-savings / low-cost
(West and Fiore, 2005) 3

4. Decreasing methane lowers global surface O3 background
Range across 18 models
 Robust result across models
N. Amer. Europe E. Asia S. Asia
N. Amer. Europe E. Asia S. Asia
Intercontinental emission controls: CH4 ≈ NOx+NMVOC+CO
 Domestic emission controls: NOx+NMVOC+CO more effective
-20% Foreign Anthrop. Emissions
-20% Domestic Anthrop. Emissions
(Results from TF HTAP model intercomparison; Fiore et al., 2009) 4

5. Benefits from CH4 controls to climate and air quality: Decreased radiative forcing and high-O3 events
Methane emission reductions are applied to BASE emission scenario
(2005 to 2030 full-chemistry transient simulations in MOZART-2)
CLIMATE
AIR QUALITY
Net Forcing
Percentage of model grid-cell days
where surface ozone (MDA8) > 70 ppbv
BASE 2005
BASE 2030
CH4
CONTROL
CH4=700 ppb
(W m-2)
OZONE
METHANE
Cost-effective controls
prevent increase in
O3 > 70 ppbv in 2030
relative to 2005 in Europe
BASE
CH4=700 ppb
CH4 CONTROL
(Fiore et al., 2008) 5

6. Climate sensitivity: Small increases in temp
Climate sensitivity: Small increases in temp. and OH shorten the methane lifetime
Contributions to change in methane lifetime from to in BASE
Global mean surface
methane (ppb)
DT(+0.3K) + =
DOH(+1.2%)
BASE
Decrease in methane lifetime (years)
OBSERVED
BASE (constant emis.)
ANTH (time-varying)
ANTH+BIO (time-varying)
(Fiore et al., 2006) 6

7. Summary: Connecting climate and air quality via O3 & CH4
CLIMATE AND AIR QUALITY BENEFITS FROM CH4 CONTROL
Decreased hemispheric background O3 (robust across models)
Complementary to NOx, NMVOC controls
Independent of reduction location (but depends on NOx)
IMPACT OF CHANGING CLIMATE ON METHANE TRENDS ?
1990 to 2004 model trend driven by increasing T, OH
Trends in global lightning activity?
Other potential climate feedbacks (on sources and sinks)
(Fiore et al., 2002, 2006; West and Fiore, 2005; Fiore et al., 2008, 2009) 7

8. NEW DIRECTION: Impact of Future Changes in Climate on Air Quality
20-year AM3 simulations with annually-invariant emissions of ozone and aerosol precursors (except for lightning NOx), to isolate role of climate change
Present Day Simulation (“1990s”): observed SSTs and sea ice ( mean)
Future Simulation (“A1B 2090s”): observed SSTs and sea ice + average
changes from 19 IPCC AR-4 models
CHANGES IN SUMMER (JJA) MEAN DAILY MAX 8-HOUR OZONE 8