Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us?

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dc.contributor.authorLassey, KRen_AU
dc.contributor.authorEtheridge, DMen_AU
dc.contributor.authorLowe, DCen_AU
dc.contributor.authorSmith, AMen_AU
dc.contributor.authorFerretti, DFen_AU
dc.date.accessioned2008-04-11T06:48:31Zen_AU
dc.date.accessioned2010-04-30T05:03:30Zen_AU
dc.date.available2008-04-11T06:48:31Zen_AU
dc.date.available2010-04-30T05:03:30Zen_AU
dc.date.issued2007-05-02en_AU
dc.date.statistics2007-05en_AU
dc.description.abstractLittle is known about how the methane source inventory and sinks have evolved over recent centuries. New and detailed records of methane mixing ratio and isotopic composition ((CH4)-C-12, (CH4)-C-13 and (CH4)-C-14) from analyses of air trapped in polar ice and firn can enhance this knowledge. We use existing bottom-up constructions of the source history, including "EDGAR"- based constructions, as inputs to a model of the evolving global budget for methane and for its carbon isotope composition through the 20th century. By matching such budgets to atmospheric data, we examine the constraints imposed by isotope information on those budget evolutions. Reconciling both (CH4)-C-12 and (CH4)-C-13 budgets with EDGAR-based source histories requires a combination of: a greater proportion of emissions from biomass burning and/or of fossil methane than EDGAR constructions suggest; a greater contribution from natural such emissions than is commonly supposed; and/or a significant role for active chlorine or other highly-fractionating tropospheric sink as has been independently proposed. Examining a companion budget evolution for (CH4)-C-14 exposes uncertainties in inferring the fossil-methane source from atmospheric (CH4)-C-14 data. Specifically, methane evolution during the nuclear era is sensitive to the cycling dynamics of "bomb C-14" ( originating from atmospheric weapons tests) through the biosphere. In addition, since ca. 1970, direct production and release of (CH4)-C-14 from nuclear-power facilities is influential but poorly quantified. Atmospheric (CH4)-C-14 determinations in the nuclear era have the potential to better characterize both biospheric carbon cycling, from photosynthesis to methane synthesis, and the nuclear-power source. © Author(s) 2007en_AU
dc.identifier.citationLassey, K. R., Etheridge, D. M., Lowe, D. C., Smith, A. M., & Ferretti, D. F. (2007). Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us? Atmospheric Chemistry and Physics, 7(8), 2119-2139. doi:0.5194/acp-7-2119-2007en_AU
dc.identifier.govdoc1227en_AU
dc.identifier.issn1680-7316en_AU
dc.identifier.issue8en_AU
dc.identifier.journaltitleAtmospheric Chemistry and Physicsen_AU
dc.identifier.pagination2119-2139en_AU
dc.identifier.urihttp://dx.doi.org/10.5194/acp-7-2119-2007en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/1062en_AU
dc.identifier.volume7en_AU
dc.language.isoenen_AU
dc.publisherEuropean Geosciences Unionen_AU
dc.subjectEvolutionen_AU
dc.subjectAtmospheresen_AU
dc.subjectCarbon isotopesen_AU
dc.subjectMethaneen_AU
dc.subjectBudgetsen_AU
dc.subjectEmissionen_AU
dc.titleCentennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us?en_AU
dc.typeJournal Articleen_AU
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