MOCA møte Oslo/Kjeller 29.10 2013Stig B. Dalsøren

Reproducing methane distribution over the last decades with Oslo CTM3

Overall objective “Explain the recent increase in atmospheric methane and quantify the effect of realistic future methane levels”

WP 1: Analysis of the historic level and development of methane

WP 2: Assessment of the recent development and current level of methane

WP 3: Future development of methane levels and corresponding climate impact

Global Chemical Transport model OsloCTM3

Figure from (Seinfeld and Pandis, 1998).

Vertical: 60 layersHorizontal:

T42: 2.8 x 2.8 degrees

(T159: 1.125 x 1.125 degrees)

Processes

Chemistry

Gas phase chemistry 90 species18 tracers, one for each methane emission sector

AerosolsSulphateSea saltNitrate(Black/organic carbon)(Mineral dust)(SOA) (not included in these simulations)

Anthropogenic methane emissions 1970-2008 from Edgar 4.2 database

19841985

19861987

19881989

19901991

19921993

19941995

19961997

19981999

20002001

20022003

20042005

20062007

20082009

0

50

100

150

200

250

WetlandsOceans+TermitesBBURTg

/yea

rNatural methane emissions 1984-2009 from Philippe Bousquet (Based on Bousquet et al. 2011)

Total methane emissions 1970-2012

Test runs using observed surface methane concentrations, comparing loss and emissions:

Year Emissions Loss (Tg)

2000 534.8 580

Assuming equilibrium between emissions and loss in 2000 results in the following scalingfactors of methane emissions:

Bousquet (biomass burning+natural): 1.1041Edgar 4.2 (anthropogenic): 1.0677:

-> New emissions used in model runs:

Year Emissions Loss (Tg)

2000 580 580

Scaling approach on methane emissions

Anthropogenic: 1970-2008 Edgar 4.2

Biomass burning: 1997-2011 GFED, all other years use GFED 2000

Natural: 2000 Megan, all other years use MEGAN 2000

Meteorology: 1997-2012, all other years use year 2000

Stratospheric concentrations ozone depleting substances: Strat 2d data introduced in runs from 1980 and onwards.

Non-methane emssions and other input data in simualtion

3 rather distinct periods in the level of sophitication of model runs

1970-1984: Kind of test/spinup. Only changes in anthropogenic emissions taken into account. Few methane measurements/no global network to compare with.

1984-1997: Variation also in methane emissions from biomass burning and natural sources. More methane observations to compare with

1997-2008: Variation also in non-methane biomass burning emissions and meteorology. Numerous methane observations to compare with.

Methane budget 1970-2012 in OsloCTM3

19701971

19721973

19741975

19761977

19781979

19801981

19821983

19841985

19861987

19881989

19901991

19921993

19941995

19961997

19981999

20002001

20022003

20042005

20062007

20082009

20102011

20121400

1450

1500

1550

1600

1650

1700

1750

1800

CTM3 Surface mean

Khalil et al. 1989

Blake and Rowland 1986

CTM3 surface mean BP

AGAGE

ppbv

Global average surface level from observations and OsloCTM3

Comparison observationsAvailable surface stations at WDCGG

" • " denotes that the data from the station has been updated in the last 365 days

Jan 2008

Jul 2008

Methane (ppbv) in lowest model layer in CTM3 compared to observations (circles)

Examples: Portion of comparisons for stations for the period 2003-2012

Stations: 30-90 S

Stations: 0-30 S

Stations: 0-30 N

Stations: 30-90 N

Months

ppbv

Days

ppbv

In line with isotope studies for selected periods during 2008 and 2009 (Fischer et al. (2011))

Arctic summer CH4 source in 2008 and 2009 was from wetlands. During winter time fossil gas emissions dominated the CH4 input. Submarine emissions along the West Spitsbergen slope was found to have negligible CH4 input to the atmosphere in summer, despite the fact that it was possible to identify methane bubbles in the sea from the sea floor. GAME project isotope instrument installed and measurements available since beginning of 2012.

Jan 2001- Oct 2012pp

bv ppbv

Days

OH influence on methane loss

Possible reasons that the model simulation has a larger growth rate for recent years than the observations:

Bergamschi et al 2013, inversion study:

“For all inversions, the derived overall trend of the anthropogenic emissions is smaller than the trend in the EDGARv4.2 emission inventory”

“Bousquet et al. 2011 attribute the increase in total emissionslargely to wetlands while in our study, a substantial fraction of the total increase is attributed to anthropogenic emissions»

Remaining work/future plans• A lot of material for further analysis .

- Further comparison surface observations- Further studies on methane tracers from the different emission sectors- Comparison satellites (IASI, Sciamachy,…) and vertical profiles ?

- Isotopes in OsloCTM3 ??

• More tests with different emissions for the period 2006/2009-2013 ??

- Test more assumptions on development natural and anthropogenic emissions after 2009 (period of lacking emission data in current simulations)

- Test further with hydrate emissions from ESS.

• Complete the «constant methane» simulation to reveal the effect of CO, NOx, NMVOC, Strat O3,...... changes on methane oxidation through OH.

• Setup and simulations with future realistic emission scenario(s) (WP 3 in GAME)

Solid fuels

Gas

OilWetlands

EnergyRice/soil

Enteric fermentation Biomass burning

Surface methane change (ppbv) 2006-2007