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@prefix dcterms: <http://purl.org/dc/terms/> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . @prefix gcis: <http://data.globalchange.gov/gcis.owl#> . @prefix cito: <http://purl.org/spar/cito/> . @prefix biro: <http://purl.org/spar/biro/> . <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/observations-of-atmospheric-carbon-dioxide-and-methane/finding/key-message-8-3> dcterms:identifier "key-message-8-3"; gcis:findingNumber "8.3"^^xsd:string; gcis:findingStatement "During most of the study period covered by the <em>Second State of the Carbon Cycle Report</em> (2004 to 2012), inverse model analyses of atmospheric CH<sub>4</sub> data show minimal interannual variability in emissions and no robust evidence of trends in either temperate or boreal regions. The absence of a trend in North American CH<sub>4</sub> emissions contrasts starkly with global emissions, which show significant growth since 2007. Methane emissions for North America over the period 2004 to 2009 estimated from six inverse models average 66 ± 2 Tg CH<sub>4</sub> per year. Over the same period, EPA-reported CH<sub>4</sub> emissions equate to a climate impact of 13% of CO<sub>2</sub> emissions, given a 100-year time horizon."^^xsd:string; gcis:isFindingOf <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/observations-of-atmospheric-carbon-dioxide-and-methane>; gcis:isFindingOf <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report>; ## Properties of the finding: gcis:descriptionOfEvidenceBase "The conclusions of minimal interannual variability (standard deviation), trend (slope and its uncertainty), and mean flux are all based on fluxes from 14 inverse models used in the global CH<sub>4</sub> budget analysis of the Global Carbon Project (Saunois et al., 2016). The 13% ratio of CH<sub>4</sub> to CO<sub>2</sub> warming impact is based on EPA CH<sub>4</sub> and CO<sub>2</sub> emission estimates using a 100-year global warming potential (GWP) value of 28."^^xsd:string; gcis:assessmentOfConfidenceBasedOnEvidence "Total emissions have a high uncertainty (not reflected in the variability value stated in the Key Finding); note that EPA does not provide an uncertainty for its estimate. The absence of any trend has higher confidence, because numerous models with different methodologies contributed to this finding. However, the models used in the comparison did not uniformly cover the 2000 to 2013 period, making the conclusion less robust than that for CO<sub>2</sub>. On the other hand, the smaller variability relative to CO<sub>2</sub> is consistent across models and is more robust. The 13% value is uncertain because of EPA’s CH<sub>4</sub> emissions estimate and, to a lesser extent, the GWP uncertainty."^^xsd:string; gcis:newInformationAndRemainingUncertainties "Total CH<sub>4</sub> emissions for North America include the inversely derived value of 60 Tg CH<sub>4</sub> per year and the EPA anthropogenic emissions estimate for the United States, which would impact the 13% ratio. Inverse models are subject to poorly known uncertainties stemming from the use of biased priors, imperfect models of atmospheric transport, and the sparse network of <em>in situ</em> measurements."^^xsd:string; a gcis:Finding . ## This finding cites the following entities: <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/observations-of-atmospheric-carbon-dioxide-and-methane/finding/key-message-8-3> prov:wasDerivedFrom <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/preface/figure/figurep-4>.