MOCA møte Oslo/Kjeller Stig 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 degrees) Processes

Chemistry Gas phase chemistry 90 species 18 tracers, one for each methane emission sector Aerosols Sulphate Sea salt Nitrate ( Black/organic carbon) (Mineral dust) (SOA)(not included in these simulations)

Anthropogenic methane emissions from Edgar 4.2 database

Natural methane emissions from Philippe Bousquet (Based on Bousquet et al. 2011)

Total methane emissions

Test runs using observed surface methane concentrations, comparing loss and emissions: YearEmissionsLoss (Tg) Assuming equilibrium between emissions and loss in 2000 results in the following scalingfactors of methane emissions: Bousquet (biomass burning+natural): Edgar 4.2 (anthropogenic): : -> New emissions used in model runs: YearEmissionsLoss (Tg) Scaling approach on methane emissions

Anthropogenic: Edgar 4.2 Biomass burning: GFED, all other years use GFED 2000 Natural: 2000 Megan, all other years use MEGAN 2000 Meteorology: , 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 : Kind of test/spinup. Only changes in anthropogenic emissions taken into account. Few methane measurements/no global network to compare with : Variation also in methane emissions from biomass burning and natural sources. More methane observations to compare with : Variation also in non-methane biomass burning emissions and meteorology. Numerous methane observations to compare with.

Methane budget in OsloCTM3

Global average surface level from observations and OsloCTM3

Comparison observations Available 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

Stations: S

Stations: 0-30 S

Stations: 0-30 N

Stations: 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 Jan Oct 2012 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 attribute the increase in total emissions largely 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/ ?? - 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 O 3, changes on methane oxidation through OH. Setup and simulations with future realistic emission scenario(s) (WP 3 in GAME)

Solid fuels Gas Oil Wetlands Energy Rice/soil Enteric fermentation Biomass burning Surface methane change (ppbv)