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Tropospheric Ozone: What are the links with climate and how well are we modeling them?

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Title: Tropospheric Ozone: What are the links with climate and how well are we modeling them?


1
Tropospheric Ozone What are the links with
climate and how well are we modeling them?
  • Drew Shindell

2
Tropospheric ozone is
  • a climate gas
  • the only source of hydroxyl
  • a governor of other reactive climate gases (e.g.
    methane, stratospheric ozone)
  • a factor in aerosol chemistry (e.g. in-cloud
    oxidation of sulfate)
  • a gas affecting local meteorology

3
Atmospheric Evolution
  • Great Oxidation Event 2.1-2.4 Ga
  • Onset of oxidized iron in sediments
  • Disappearance of pyrite (reduced sulfur)
  • Sulfide inclusions in diamonds brought to surface
    by volcanism show mass-independent isotopic
    variations in sulfur prior to 2.4 Ga (Farquhar et
    al., Science, 2002). Only known process is UV
    photolysis (190-220 nm)
  • Cyanobacteria
  • 2.7-2.8 Ga (Brocks et al., Science, 1999)

4
Archean (3.8 - 2.5 Ga)
  • Reducing atmosphere
  • Plenty of carbonate rocks
  • Sulfate low (based on 34S depletion)
  • So sulfate-processing bacteria not processing
    organic carbon
  • Methanogenic bacteria?
  • Methane lifetime 10,000 years (Kasting
    Siefert, Science, 2002)
  • Methane greenhouse answer to Faint sun paradox?
  • Increased oxygen at G.O.E. -gt less CH4 -gt first
    known glaciation

5
Paleocene/Eocene Thermal Maximum(55.5 Ma)
  • High latitudes warmed 5-7 C
  • Tropics warmed 2-3 C
  • Methane from gas hydrates (1500 GT C)
  • If oxidized to CO2, radiative forcing not large
    enough to give estimated warming
  • Methane lifetime increase by 50-100
  • Combined radiative forcing gives reasonable
    warming
  • Historical doubled CO2 analog
  • (Schmidt and Shindell, Paleoceanography, 2003)

6
O3
h?, H2O
h?, O2
OH HC,CO
NO2
NO HO2
7
Links with Climate
  • Chemistry
  • Temperature
  • Water vapor
  • Heterogeneous surfaces
  • Radiation
  • Photolysis rates
  • Sources
  • Stratospheric inflow
  • Surface emissions
  • In-situ (lightning)
  • Sinks
  • Wet deposition
  • Dry deposition

8
Chemistry
  • Temperature
  • reaction rates O3 h? ? O(1D)
  • Water vapor
  • O(1D) H2O ? 2OH
  • Heterogeneous surfaces
  • Oxidation of sulfate
  • Photochemical formation from VOCs
  • Mineral dust O3 chemistry budget -20 Tg/yr,
  • burden -8 Tg (Martin et al., JGR, 2002)
  • Ice particles

9
Water vapor
Response to volcanism demonstrates water vapor
sensitivity to surface temperature change (Soden
et al., Science, 2002)
10
Climate Sensitivity
  • 1.7 - 4.2 C for 2xCO2 (IPCC TAR)
  • 0.5 - 1.0 C per W/m2
  • Cloud feedbacks

11
Radiation
  • Overhead ozone changes
  • 1 in 2040 global annual average column
    positive in upper strat, negative in tropical and
    high latitude lower strat (Rosenfield et al.,
    JGR, 2002)
  • -3 column from dT and dH2O in 2040 positive in
    upper strat, negative in lower (Shindell Grewe,
    JGR, 2002)
  • Impacts on photolysis rates/OH formation
  • 1979-1992 3.1 OH, -1.0 O3, -2.3 CO
    (De Winter-Sorkina, Atm. Env., 2001)
  • 2.8 OH 1979-1990 (4 dO3 Strat)
    (Bekki et al., Nature, 1994)
  • 2 OH 1979-1992 (Krol et al., JGR, 1998)
  • Sensitivity of OH inversely proportional to NOx

12
Sources
  • Stratospheric inflow (ozone and NOx)
  • Circulation increase or decrease?
  • Stratospheric abundance changes?
  • Surface emissions
  • Methane from wetlands
  • NMHCs from forests
  • NOx from soils
  • Biomass burning (CO, NOx, CH4, NMHCs)
  • In-situ (lightning NOx)

13
Lightning Ozone
  • Lightning sensitivity to warming
  • Ionospheric potential 10/K
  • Flash vs. cloud height 10/K
  • Schumann resonance 250/K
  • Seasonal variations 50-800/K
  • OTD data vs land temperatures 40/K
  • No correlation in tropics!

14
  • Ozone response
  • (Flash vs cloud height parameterization of
    Price and Rind)
  • 27 Tg 8 for 3 TgN (GEOS-CHEM - Martin)
  • Chemistry budget 190 Tg/yr
  • 18 Tg 6 for 2.2 TgN (GISS GCM - Shindell)
  • Chemistry budget 63 Tg/yr
  • 23 for 0.5 TgN (1D/2D model -
    Toumi)
  • Radiative forcing
  • 0.1 W/m2 for 2.2 Tg, 0.03 W/m2 for 0.8 Tg
    (GISS)
  • 0.34 W/m2 (1D/2D)

15
Lightning Change
Radiative Forcing dTs/dO3
200
500
750
0.8 TgN/yr36
1000
16
Lightning NOx travels via stratosphere(Grewe et
al., Chemosphere, 2002)
17
VOC emissions
  • Biosphere model T, precipitation, CO2,
    vegetation redistribution (no atmospheric
    chemistry)
  • (Constable et al, Global Change Biology
    1999)
  • 80 US isoprene emissions with 2xCO2
  • vegetation redistribution alone causes decrease
  • CTM linked to a vegetation model
  • (Sanderson et al, IGAC Symposium, 2002).
  • Global annual average isoprene from 549 to 697
    Tg/yr
  • Without redistribution, from 549 to 736 Tg/yr
    (34)
  • Tropical forest dieoff
  • GCM with isoprene parameterization (Bell et al,
    GISS)
  • Without redistribution from 350 to 473 Tg/yr
    (35)

18
Isoprene climate
  • Red oak doubled isoprene emissions with elevated
    CO2 (Sharkey et al., Plant Cell Env., 1991)
  • Aspen showed 40 decrease (Sharkey et al., Plant
    Cell Env., 1991)
  • Cottonwood showed 21 decrease for 800 ppm CO2
    (Rosenstiel et al., Nature, 2003)
  • Including 2xNPP, all increases (20-400)
  • Effect on ozone dependent upon NOx background

19
Wetland Emissions
Range 100-260 Tg/yr Function
of temperature, soil moisture, area
20
Wetlands and climate
  • Sensitivity gauged by interannual variation
    during past 15 years (e.g. Walter et al., JGR,
    2001 Dentener et al., ACP, 2003)
  • Especially negative methane growth rate anomaly
    following Pinatubo
  • GCM simulation with parameterization of
    emissions 103 Tg/yr for 2xCO2

21
Other emissions
  • Bromine from sea ice (Roscoe et al., GRL, 2001)
  • Leads to tropospheric ozone loss
  • Small positive feedback from warming

22
Sinks
  • Wet deposition
  • Hydrological cycle changes
  • Changes in pH of droplets
  • Dry deposition
  • Surface wind velocities (turbulent processes)
  • Surface temperature and pressure (boundary layer
    height)
  • Surface radiation (includes cloud changes)
  • Surface type (snow, ice, etc.)

23
Models show
Model dO3 dOH
UKMO -10 13
IMAGES/NCAR (2xCO2 dH2O) -5 (tropical upper troposphere) 7
ECHAM/CHEM (25 CO2) -3 to -10 (H2OT) up to 5 (NH) (H2OT) 10-20 (precip dynamics)
GISS -3 9
Cambridge 3
1D model, Callis et al., JGR, 1983 -4
24
Budgets of TAR CTMs
  • Chemistry -855 to 507
  • Dry deposition -533 to -1178
  • Stratospheric influx 391 to 1440
  • All give ozone fields in agreement with sonde
    observations

25
Ozone budgets (Tg/yr) 2xCO2
Model Chemistry Dry deposition Dry dep normalized to PD surface O3 Strat-Trop exchange Burden
UKMO present 507 -1237 705 366
UKMO change -132 85 (-38) 75 -39
GISS present 985 -1385 399 313
GISS change -195 101 151 (-55) 95 -12
Cambridge present 800 -1265 465 317
Cambridge change (2100 emissions) -394 28 (89) 368 16
26
Annual average dO3 ()2xCO2 vs control
200
500
750
1000
-10 -8 -6 -4 -1 1 4 6
8 10
27
Annual avg O3 chemistry change2xCO2 vs control
(kg/s)
100
200
500
750
1000
-18 -10 -7 -4 -1 1 4 7 10
18
28
Spatial pattern of surface chemistry changes
(1E-16 kg/s/m2)
-2 -1.4 -.9 -.6 -.3 -.1
.1 .3 .6 .9 1.4 2
29
Dry deposition
Total change 101 Tg O3/yr, Snow/ice cover
contributes 17
30
Annual avg O3 chemistry change2xCO2 vs control
(kg/s)
100
200
500
750
1000
-18 -10 -7 -4 -1 1 4 7 10
18
31
dNOx () dHNO3 wet (kg/s)2xCO2 vs
control
200
500
750
1000
-16 -13 -9 -6 -2 2 6 9 13 16
-8 -6 -5 -3 -1 1 3 5 6 8
32
Change in PANs
Increased temperatures lead to more thermal
dissociation Global reduction 23 31 Met
Office (Johnson et al., JGR, 1999)
33
Annual average dOH ()2xCO2 vs control
200
500
750
1000
-25 -19 -14 -8 -3 3 8 14 19 25
34
Ozone budgets (Tg/yr)
Model Chemistry Dry deposition Strat-Trop exchange Burden
GISS with climatological ozone in stratosphere -195 101 95 -12
GISS with interactive stratospheric O3 -175 33 146 -1
Dry deposition is sped up at high
latitudes Increased stratospheric ozone with
2xCO2 (and no other change!) 40 Tg/yr from
convective transport
35
O3 change including stratosphere
50
100
200
500
750
1000
-11 -8 -6 -4 -1 1 4 6 8 11
-11 -8 -6 -4 -1 1 4 6 8 11
36
Stratosphere-Troposphere exchange dependence
upon surface warming
(dO3 )
100
1000
-90 0 90 -90
0 90
-50 -20 -15 -10 -5 0 5
10 15 20 36
12
12
8
8
4
4
0
0
Rind et al., JGR, 2002
37
100
5
-5
-5
-10
1000
38
100
19
25
14
8
-8
1000
39
Radiative forcing 0.03 W/m22xCO2 vs control
-.24 -.2 -.15 -.11 -.07 -.02
.02 .07 .11 .15 .20 .24
40
0.08 W/m2
-.24 -.2 -.15 -.11 -.07 -.02
.02 .07 .11 .15 .20 .24
41
Meteorology changes
Preindustrial vs present, Mickley et al.,
2003 PI vs present, 10 radiative forcing and
-1 OH due to O3/met
42
Changes in context
dOH dO3
  • 2xCO2 climate 7
  • 2100 NOx 34
  • 2100 CH4 -22
  • 2100 CO -6
  • 2100 NMHCs -5
  • All 17
  • 2
  • 25
  • 21
  • 2
  • 2
  • 60

43
Conclusions
  • Chemistry Relatively good (global)
  • Climate sensitivity likely larger source of
    uncertainty than chemical response
  • However, still missing chemistry
    (chemistry-aerosols, NOx/HNO3 ratios, etc.)
  • Radiation Relatively good
  • Future stratospheric ozone uncertain
  • Response relatively well-known
  • Overall effect likely small

44
Conclusions Sources
Response Size Knowledge
Biogenic large poor Interactive vegetation, data on more species
Lightning medium medium Interactive stratosphere, validation with OTD
STE large poor Better understanding of GW generation propagation, convection
Fire ? none
45
Conclusions Sinks
  • Wet deposition Relatively poor
  • Cloud/hydrology response to climate change
  • Aerosol changes (e.g. CCN)
  • Dry deposition Relatively poor
  • Vegetation changes
  • Snow ice changes (Arctic, AO/NAO)
  • Turbulence sub-grid scale
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