Shifting seasonal cycles of surface ozone: the role of regional vs. global emission changes

Olivia Clifton

Fiore/McNeill Symposium July 17, 2013

Acknowledgments. Arlene Fiore (CU/LDEO), Gus Correa (CU/LDEO), Larry Horowitz (GFDL), Vaishali Naik (GFDL)

The GFDL CM3/AM3 chemistry-climate model

AM3 option to nudge to reanalysis winds

Donner et al., 2011, Golaz et al. 2011, Levy et al., 2013, Naik et al., revised

cubed sphere grid ~2°x2°; 48 levels

Atmospheric Dynamics & PhysicsRadiation, Convection (includes wet

deposition of tropospheric species), Clouds, Vertical diffusion, and Gravity wave

Atmospheric Dynamics & PhysicsRadiation, Convection (includes wet

deposition of tropospheric species), Clouds, Vertical diffusion, and Gravity wave

Chemistry of gaseous species (O3, CO, NOx, hydrocarbons) and aerosols

(sulfate, carbonaceous, mineral dust, sea salt, secondary organic)

Dry Deposition

Aerosol-Cloud Interactions

Chemistry of Ox, HOy, NOy, Cly, Bry, and Polar Clouds in the Stratosphere

ForcingSolar Radiation

Well-mixed Greenhouse Gas ConcentrationsVolcanic Emissions

ForcingSolar Radiation

Well-mixed Greenhouse Gas ConcentrationsVolcanic Emissions

Ozone–Depleting Substances (ODS)

Ozone–Depleting Substances (ODS)

Modular Ocean Model version 4 (MOM4)&

Sea Ice Model

Modular Ocean Model version 4 (MOM4)&

Sea Ice Model

Pollutant Emissions (anthropogenic, ships,

biomass burning, natural, & aircraft)

Pollutant Emissions (anthropogenic, ships,

biomass burning, natural, & aircraft)

Land Model version 3(soil physics, canopy physics, vegetation

dynamics, disturbance and land use)

Land Model version 3(soil physics, canopy physics, vegetation

dynamics, disturbance and land use)

Observed or CM3 SSTs/SIC for CMIP5 Simulations

Observed or CM3 SSTs/SIC for CMIP5 Simulations

GFDL-CM3GFDL-AM3

Atmospheric Chemistry 86km

A. Fiore

Year

CH4 Abundance (ppb) past 1000 years [Etheridge et al., 1998]

20001000

800

1200

1600

1400

1000

1500

Historical increase in atmospheric methane and ozone (#2 and #3 greenhouse gases after CO2 [IPCC, 2007])

Ozone at European mountain sites 1870-1990 [Marenco et al., 1994]

A. Fiore

Methane has an indirect influence on climate & increases background levels of surface ozone

Monthly mean surface O3 (ppb) Observed (1988-2009 mean) vs. CM3 model (1990-2005 mean)

Clean Air Status & Trends Network (CASTNet) sites: rural ground monitoring sites in the United States designed to capture background ozone levels, managed and operated by EPA

Changes in seasonal cycles in high-elevation mountaintop ozone: CM3 vs. observations from Parrish et al., 2013 at

Hohenpeissenberg (47º48’N/9º30’W, 1.0km)

Parrish et al., 2013

CM3

Wintertime bias in both earlier and later historical periods in CM3

Agreement between changes in seasonal cycle shapes

~ 30 years between 5 year periods

Seasonal cycles in high-elevation mountaintop ozone: CM3 vs. observations from Parrish et al., 2013 at Zugspitze

(47º25’N/10º59’E, 3.0km)

CM3

Parrish et al., 2013

Bias in both earlier and later historical periods in CM3

Agreement between changes in seasonal cycle shapes

Agreement between differences between periods in late spring through late summer

~ 20 years between 5 year periods

Well-mixed greenhouse gases (WMGGs) & Emissions of Short-Lived Climate Forcers (SLCFs)

under “RCPs”

Figures c/o V. Naik

Anthrop. NO (Tg yr-1)

Anthrop. BC (Tg yr-1)

Anthrop. SO2 (Tg yr-

1)

-50% -80%-50% -80%

2050 2100

-40% -60%-20% -60%

-25% -50%-35% -70%Methane

abundance (ppb)

CO2 abundance

(ppm)

RCP8.5 “extreme”RCP6.0 RCP4.5 “moderate”RCP2.6

GFDL CM3 scenarios & sensitivity simulations

Each scenario in

GFDL CM3 includes

3 ensemble members

Sensitivity simulation CH4 chemistry CH4 radiation O3 precursors

RCP8.5_2005CH4 2005 2005 RCP8.5

RCP8.5_2005CH4_chem 2005 RCP8.5 RCP8.5

RCP8.5_2005CH4_rad RCP8.5 2005 RCP8.5

RCP4.5_WMGG 2005 RCP4.5 2005

Scenario Climate

RCP8.5 CH4 doubles by end of century, “extreme” scenario

RCP4.5 CH4 changes little “moderate” scenario

-100

-50

0

50

100

2005 to 2100 % change

CH4

Global NOx

EMISSION PROJECTIONS

CO2

NE US NOx

Mtn. W NOx

21st Century Scenarios

Global Mean Temperature (>500 hPa)

RCP4.5_WMGG Enables separation of roles of changing climate from changing air pollutant emissions

RCP8.5 extremeRCP4.5 moderateRCP4.5_WMGG

Future-Base NOx emiss. decreases

molecules/cm2/s

0

Changing seasonal cycles by end of 21st century in RCP8.5 vs. RCP4.5; in ppb, land only

2006-2015 2091-2100 RCP8.5

2006-2015 2091-2100 RCP4.5

NOx reductions decrease O3 in most months under RCP4.5

Higher O3 in RCP8.5 in cooler months despite NOx reductions

Changes from 2006-2015 to 2091-2100 in monthly mean surface O3 due to CH4 in RCP8.5; in ppb, land only

RCP8.5RCP8.5_2005CH4 RCP8.5_2005CH4_chemRCP8.5_2005CH4_rad

Difference between RCP8.5 and RCP8.5_2005CH4_chem (RCP8.5 but with CH4 held at 2005 levels) indicates that doubling CH4 in RCP8.5 increases surface O3 over NE & WUS by > 5-15 ppb

Increasing CH4 chemistry contributes to the high increase in O3 during winter & early spring and dampens decreasing effect of NOx emissions controls in the summer on O3

Higher CH4 from chemistry contribution in winter

How is CH4 from chemistry affecting end of 21st century seasonal cycle? in ppb, land only

2006-2015 2091-2100 RCP8.52091-2100 mean of RCP8.5_2005CH4 & 2005CH4_chem

Magnitude of the future seasonal cycle is governed by increasing CH4 chemistry and the shifting O3 seasonal cycle is governed by NOx emissions controls

Future seasonal cycles have similar shape in NE USA and Mountainous W

Which month holds the decadal monthly mean O3 maximum?

RCP8.5_2005CH4 2091-2100

DJF MAM JJA SON

RCP8.5 2091-2100 2006-2015

CH4 emissions stay

at 2005 levels

CH4 emissions

double

By end of 21st century regional NOx emissions controls shift the monthly mean maximum from summer months to winter & early spring

Doubling CH4 vs. leaving CH4 at 2005 levels doesn’t affect the month that the maximum monthly means occur

Shifting back to RCP4.5: Change in ozone seasonal cycles by the end of the 21st century in RCP4.5; in

ppb, land only

RCP4.5 demonstrates large impact of NOx emissions controls, showing decreases of surface O3 in the summer >10-15 ppb

RCP4.5_WMGG (O3 precursors remain at 2005 levels) suggests that climate warming will increase O3 by a few ppb in NE USA summer and Mtn. W USA in early spring and decrease it slightly in Mtn. W summer, with little change over the other seasons.

Conclusions

• Shifting balance of effect of regional-vs-global emissions sources on surface ozone– Present seasonal cycles governed in summer by

regional NOx emissions

– Future seasonal cycles governed by global CH4

emissions • Increasing CH4 from chemistry is most

important player in regards to CH4 in increasing surface ozone by the end of the 21st century

– Climate change may impact future surface O3, but can be offset by NOx reductions, which preferentially decrease highest O3 events (most evident in NE USA plots)

• Future questions: how is methane from radiation vs. methane from chemistry affecting strat-to-trop exchange of ozone?

RCP8.52005CH4_chem2005CH4_rad