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Climate Change and Methane Emissions: Using Integrated Analysis Tools to Advise Policy

Marcus C. Sarofim



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Overview

• Climate Change Background– The Science– The Politics

• The Role of Methane– Conventional Wisdom– Research results (political, economic, and

scientific)– Policy recommendation: decouple CO2 from

CH4 policy


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The Earth’s Radiative Balance

Emitted by Atmosphere

Absorbed byAtmosphere67

165

Incoming Solar Radiation

342 Wm-2

AtmosphericWindow

40

30

235342

OutgoingLongwaveRadiation235 Wm-2

Greenhouse Gases

324 BackRadiation

40350

390 SurfaceRadiation

Absorbed by Surface

324Evapo-

transpiration

ThermalsAbsorbed by Surface

168 24 78

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Reflected Solar

107 Wm-2 107

Reflected byClouds, andAtmosphere

77

77

2478

Reflected by Surface

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Radiation

Latent Heat

Figure by MIT OCW, based on Kiehl and Trenberth 1997.

Radiative Forcing ComponentsRF Terms

Long-lived

greenhouse gases

Ozone Stratospheric

Land use Black carbonon snow

Tropospheric

Halocarbons

CO2

CH4

N2O

RF values (Wm-2) Spatial scale LOSU

High

High

Med

Low

Low

Low

LowGlobal

Global

Global

Global1.66 [1.49 to 1.83]

0.48 [0.43 to 0.53]0.16 [0.14 to 0.18]0.34 [0.31 to 0.37]

-0.05 [-0.15 to 0.05]0.35 [0.25 to 0.65]

0.07 [0.02 to 0.12]

-0.2 [-0.4 to 0.0]

-0.5 [-0.9 to -0.1]

-0.7 [-1.8 to -0.3]

0.01 [0.003 to 0.03]

0.12 [0.06 to 0.30]

0.1 [0.0 to 0.2]

Continental

Continentalto global



Local toContinental

Med- Low

Med- Low

Stratospheric waterVapour from CH4

Surface albedo

Direct effectTotal

Aerosol Cloud albedoeffect

Linear contrails

Solar irradiance

Total netanthropogenic

Nat

ural

Ant

hrop

ogen

ic

Radiative Forcing Wm-2-2 -1 0 1 2

{

{

1.6 [0.6 to 2.4]1.6 [0.6 to 2.4]

Figure by MIT OCW, based on IPCC.



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Politics

• UN Framework Convention on Climate Change– Stabilization of Greenhouse Gases at a level avoiding

dangerous anthropogenic interference– No binding commitment

• Kyoto Protocol– “Annex B” nations have commitments in 2008-2012– Multiple gases: CO2, CH4, N2O, HFCs, PFCs, SF6

• Cap and trade: using Global Warming Potentials



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Global Warming Potentials (GWPs)

∫∫=

dttCOa

dttxaxGWP

CO

x

)]([*

)]([*)(

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EPPA, Kyoto, and US inventories all use IPCC 1996 100 year GWPs

IPCC TAR 20 year 100 year 500 year IPCC 1996 (100 year)

CO2 1 1 1 1

CH4 62 23 7 21

N2O 275 296 156 310



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Anthropogenic Emissions by GWP weight

GHG emissions, 2000Total: 10.3 GtC eq.

CO2

CH4

N2O

(emissions data from the MIT EPPA model)



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Methane: Arguments against GWP based Trading• Conventional Wisdom

– Capture “What” flexibility by trading among GHGs• Results of this study

– CO2 constraints have negative interactions with economic distortions

– Methane is undervalued for reasons of chemistry and timing

– Methane emission inventories are much less accurate than fossil CO2 emission inventories

– Methane constraints are politically more palatable to developing nations



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The MIT Integrated Global Systems Model



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Anthropogenic Methane SourcesBiological Sources:

Anaerobic decomposition

Fossil Sources

Total: 300 to 400 Tg/year (2 to 3 GtCeq)

Data Source: US EPA bottom-up inventoryExploded slices indicate methane capture potential

CO2 Sources:

Fossil Fuels: 7 GtC/yr (85% of energy in 2000 is from fossil fuels)

Cement: 0.3 GtC/yr

Land-Use Change: 0.5 – 2.7 GtC/year

Agriculture(rice, livestock)

GasCoal

Landfills

Manure

Oil

Other(Combustion,w astew ater)



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Global Marginal Abatement Curves (2010)

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

CE Reduction (MMT) (single gas)

Mar

gina

l con

sum

ptio

n lo

ss (1

997$

/ton)

CH4

CO2

1) Many low cost methane abatement opportunities are available (Kyoto Protocol in 2010 even including the US would have required ~ 500 MMT carbon equivalent reduction)

2) Because of CO2 constraint interactions with tax distortions, GWP based inter-gas trading leads to non-optimal solutions

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

Carbon Equivalent Reduction (MMT)

Car

bon

Equi

vale

nt P

rice

(199

7$/to

n)

CO2

CH4



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Non-CO2 gas reductions: Impacts on climate

CO2ONLY scenario: CO2emissions from 550 ppmscenario, all other gases as reference

US Climate Change Science Program Level 2 scenario: 550 ppm CO2stabilization, separate emissions paths for other Kyoto gases (CH4, N2O, HFCs, PFCs, SF6), meeting an overall radiative forcing target

0

0.5

1

1.5

2

2.5

3

3.5

4

2000 2020 2040 2060 2080 2100

Year

T C

hang

e Si

nce

2000

(°C

) Reference

CO2ONLY

OtherGases

550 ppm

Other Gases scenario: CO2emissions from reference, all other gases from 550 ppmscenario



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Climate Impacts of CH4 reductionResults in 2100 Constraining CH4

emissions to be constant at 2005 levels

A GWP equivalent scenario, constraining CO2 only

% reduction in T rise 14.9% 4.0%

Global ozone conc. (ppb) 36.8 40.1

CH4 lifetime (years) 9.0 10.8

• Methane reductions alone can reduce temperature rise by 15% overthe century

• 100 year Global Warming Potentials seriously undervalue CH4 for century scale temperature reduction– Chemistry: ozone and lifetime feedbacks

– Emission timing effects



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Methane ChemistryCH4

OH ·

CH3· + H2O

O2

CH3O2 · NO

O2

CH3OOH

OH ·

HO2 ·

OH ·

CH3O ·

HCHO

OH · or hv

CO + (H2, HO2 ·,H2O)

OH ·, O2

CO2 + HO2·

Deposition

NO2

NO2

NO2 + hv -> NO + OO + O2 -> O3

HO2· + NO -> NO2 + OH·

Net: CH4 + 8O2 + hv ->

CO2 + 4O3 + 2H2O

Methane Inventories: Bottom upEQUATION 10.19

ENTERIC FERMENTATION EMISSIONS FROM A LIVESTOCK CATEGORY

Emissions = EF(T)N(T)

106 ]]Where:

CH4 Rice = annual methane emissions from rice cultivation, Gg CH4 yr-1

EFijk = a daily emission factor for i, j, and k conditions, Kg CH4 ha-1 day-1

Aijk = annual harvested area of rice for i, j, and k conditions, ha yr-1

i, j, and k = represent different ecosystems, water regimes, type and amount of organic amendments, and other conditions under which CH4 emissions from rice may vary

tijk = cultivation period of rice for i, j, and k conditions, day

Where:

Emissions = methane emissions from Enteric Fermentation, Gg CH4 yr-1

EF(T) = emission factor for the defined livestock population, Kg CH4 head-1 yr-1

N(T) = the number of head of livestock species/category T in the country

T = species/category of livestock

EQUATION 5.1CH4 EMISSIONS FROM RICE CULTIVATION

CH4 Rice = (EFi.j.k ti.j.k Ai.j.k 10-6) i.j.k∑

Image by MIT OCW.



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Methane Inventories: Inverse Modeling

• 92 Methane monitoring sites• Observed winds• Chemistry model• Estimates of OH sink



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Methane InventoriesInverse

Modeling Results

Bottom-up methodologies

EPA (2006)

30

22

156

75

3

287

Anthro.CH4emissions in 2000 Chen & Prinn

(2006)EDGAR 32FT2000

Rice 112 39

Biomass burning

48 22

Animals + waste

185 147

Energy 48 94

Other 37 19

Total 430 321

IPCC Guidelines for GHG inventories are based on bottom-up approaches.

But if bottom-up inventories are inaccurate, their use in trading regimes is questionable

Contrast: Fossil CO2

Similar Problems: N2O, land use change CO2

Therefore: until methodology is improved, regulatory methods other than economic instruments (tax, cap & trade) should be used for methane control.



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Political Analysis• Kyoto Protocol

– All Gases: CO2, N2O, industrial gases by 100 year GWPs– Limited Nations: EU, Japan, NZ, Canada, Russia

• ~20% of global CH4 emissions• CDM extension to non-Annex B

• Methane to Markets Initiative– Methane only– Non-Kyoto participants: US, China, India, Brazil, Mexico, and

Australia• M2M nations emit ~60% of global CH4

– Drawbacks• “Voluntary”, “non-binding”: depends on “public-private partnerships”• Target is only 50 MMT Carbon equivalent reduction

• Evidence of OECD historical CH4 reductions



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Different Strategies?• Methane

– Short lifetime– Cheap abatement– Most emissions are hard to quantify– Recommend

• Command and Control instruments like best practices• Near term implementation

• Carbon Dioxide– Long lifetime– Long term zero emission target– Capital intensive– Fossil emissions are well quantified– Recommend

• Near term price signals• Long term research initiatives



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Cautions

• Possible delay of CO2 abatement• Potential increased policy complexity• Loss of “what” flexibility



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Conclusions

• Policy Advice– Uncouple methane policy and CO2 policy– Implement methane policies immediately

• Using a mix of policy instruments– Use a different strategy for CO2

• Methodology– Importance of integrated approach: science,

economics, and policy evaluated together