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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/understanding-urban-carbon-fluxes/finding/key-message-4-5> dcterms:identifier "key-message-4-5"; gcis:findingNumber "4.5"^^xsd:string; gcis:findingStatement "Urban methane (CH<sub>4</sub>) emissions have been poorly characterized, but the combination of improved instrumentation, modeling tools, and heightened interest in the problem is defining the range of emissions rates and source composition as well as highlighting infrastructure characteristics that affect CH<sub>4</sub> emissions (<em>high confidence</em>)."^^xsd:string; gcis:isFindingOf <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/understanding-urban-carbon-fluxes>; gcis:isFindingOf <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report>; ## Properties of the finding: gcis:descriptionOfEvidenceBase "For Key Finding 5, consistent and persistent evidence of under-reported CH<sub>4</sub> emissions was found in Los Angeles, Boston, and Indianapolis (Lamb et al., 2016; McKain et al., 2015; Wong et al., 2016). Other studies report inverted distributions of CH<sub>4</sub> emissions in Los Angeles (75% thermogenic, 20% biogenic; Hopkins et al., 2016) compared with San Francisco (17% thermogenic, 82% biogenic; Jeong et al., 2017). Intensive field surveys of urban natural gas systems in seven cities indicate large variations in CH<sub>4</sub> leakage rates from urban gas distribution infrastructure attributed to differences in pipeline material and age (Hopkins et al., 2016; Jackson et al., 2014; Phillips et al., 2013; von Fischer et al., 2017)."^^xsd:string; gcis:assessmentOfConfidenceBasedOnEvidence "The assessment of confidence is based on a small number of cities where emissions have been studied over a short period of time. The confidence level is based on the results of these studies, which are robust and agreed upon, but this confidence does not necessarily apply across the continent due to the limited number of studies conducted to date."^^xsd:string; gcis:newInformationAndRemainingUncertainties "The uncertainties in urban-scale CH<sub>4</sub> emissions estimates are not well established because the number of cities where these emissions have been studied is small and the temporal duration of the studies is very limited. While Key Finding 5 is of high confidence for the limited times and numbers of cities represented in the literature, this finding cannot yet be generalized across other North American cities."^^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/understanding-urban-carbon-fluxes/finding/key-message-4-5> prov:wasDerivedFrom <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/preface/figure/figurep-4>.