methane sources and sinks

CO2 fertilization (increased water use efficiency). Plants take in carbon dioxide and lose water vapor through small pores in their leaves called stomata. Under elevated carbon dioxide levels the pores become smaller and the plant loses less water. This makes photosynthesis more efficient, and the plants can assimilate carbon more rapidly.

Methane sources and sinks

(Lowe 2006)

(Mt CH4 yr-1)

Known sources and sinks of atmospheric CH4 1990 – 2000

Atmospheric life time ~ 9 years

wetlandstermitesOcean hydrates

Total~ 600 Tg(CH4/y)

Biomass burning

Natural sources

EnergyDomestic waste

Ruminants

Rice paddies

Transport to stratosphere

Oxidation in soils

Tropospheric OH

Sources [Tg/yr] Sinks [Tg/yr]


(Lowe 2006)

(Mt CH4 yr-1)

(present relative to 1750)

Greenhouse gas global warming potentials(100 year time horizon)

Greenhouse gases GWP

Carbon dioxide (CO2) 1Methane (CH4) 21Nitrous Oxide (N2O) 310Hydrofluorocarbons (e.g., HFC 134a) 1300Perfluorcarbon (e.g., CF4) 6500Sulfur Hexafluoride (SF6) 23,900


(Lowe 2006)

(Mt CH4 yr-1)

Source Flux (MtCyr-1) Flux (GtCequivalentyr-1)

microbes in wetlands 92-237 (IPCC 2001) 2.12-5.45

ruminants and termites 100-135 (IPCC 2001) 2.30-3.11

anthropogenic 170-340 (IPCC 2001) 3.91-7.82

Methane (CH4) production:CH4 has 23 times the greenhouse potential of CO2

Anthropogenic carbon dioxide emissions about 7GtC/yr

Measured methane emissions (Frankenberg et al. 2005)

Methane emissions (Tg CH4) per source category as used in the TM3 model for the period August through November 2003 and for the whole year (between brackets). Frankenberg et al. 2005

Simulated methane emissions (Frankenberg et al. 2005)

Difference between measured and simulated methane emissions (Frankenberg et al. 2005)

Emissions from living plants

Plant litter

0

0,5

1

1,5

2

2,5

3

3,5

20 30 40 50 60 70 80

Temperature (°C)

CH

4 (n

g g-1

dw

h-1

)

Ash

Beech

Exclude biological activity

0

1

2

3

4

20 30 40 50 60 70 80

Temperature (°C)

CH

4 (n

g g-1

dw

h-1

)

Ash

Ash sterilised

Summary living plants

• 9 plant species (C3 and C4) • 18 l volume incubation chambers• dependence on sunlight• typical emission rates: 12 to 370 ng g(dw)-1 h-1

• grown on soil and hydroponically

Global extrapolationLiving biomass

Vegetation type/ Biome

Season lengtha (days)

NPPb

(Pg C yr-1)

Sunshine Hoursc (h d-1)

Annual CH4 productiond low / mean / highe

(Tg yr-1)

Tropical forests 365 21.9 8 33.2 / 78.2 / 123

Temperate forests 250 8.1 6 7.1 / 17.7/ 28.4

Boreal forests 150 2.6 4 1.1 / 3 / 4.1

Mediterranean shrublands 200 1.4 8 1.2 / 2.7 / 4.3

Tropical savannas and grasslands 200 14.9 8 12.4 / 29.2 / 45.9

Temperate grasslands 150 5.6 6 2.9 / 7.4 / 11.8

Deserts 100 3.5 10 1.7 / 3.8 / 5.9

Crops 200 4.1 8 2.9 / 7.2 / 11.5

Total 62.1 62.3 / 149 / 236

Leaf litterf

Periodg (days)

Tropical forests 365 21.9 8 0.23 / 1.53/ 3.2

Temperate forests 90 8.1 6 0.02 / 0.12 / 0.25

Boreal forests 60 2.6 4 0.01 / 0.02 / 0.05

Mediterranean shrublands 180 1.4 8 0.01 / 0.05 / 0.1

Tropical savannas and grasslands 365 14.9 8 0.16/ 1 / 2.1

Temperate grasslands 90 5.6 6 0.01 / 0.08 / 0.18 Deserts 365 3.5 10 0.04 / 0.28 / 0.56 Crops 90 4.1 8 0.01 / 0.07 / 0.15

Total 62.1 0.49 / 3.2 / 6.6


plants 63-243 (Keppler et al 2006)

1.45-5.59




Methane (CH4) production:CH4 has 23 times the greenhouse potential of CO2

Sources of atmospheric carbon• Respiration (autotrophic and heterotrophic)• Burning of fossil fuels

– over past 2 centuries, source of 480-500 Gt (Pg) C (IPCC 2001)• comparable in size to terrestrial plant pool

– current rate: 5.3 GtCyr-1 (IPCC 2001)• Natural fires• Outgassing of CO2:

– from fresh water: 0.9 GtCyr-1 (Richey et al 2002)– from ocean– from soils

• Methane (CH4) production:– CH4 has 23 times the greenhouse potential of CO2


plants 63-243 (Keppler et al 2006) 1.45-5.59




CH4 trend NOAA

Source: NOAA/CMDL [http://www.cmdl.noaa.gov]

12.3% reduction in tropical forests between 1990 and 2000

6-20 Tg CH4 yr-1

Source-sink imbalance 14 Tg yr-1

(IPCC)

methane sources and sinks

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