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   dcterms:identifier "key-message-8-2";
   gcis:findingNumber "8.2"^^xsd:string;
   gcis:findingStatement "Inverse model analyses of atmospheric CO<sub>2</sub> data suggest substantial interannual variability in net carbon uptake over North America. Over the period 2004 to 2013, North American fossil fuel emissions from inventories average 1,774 ± 24 teragrams of carbon (Tg C) per year, partially offset by the land carbon sink of 699 ± 82 Tg C year. Additionally, inversion models suggest a trend toward an increasing sink during the period 2004 to 2013. These results contrast with the U.S. land sink estimates reported to the United Nations Framework Convention on Climate Change, which are smaller and show very little trend or interannual variability."^^xsd:string;
   gcis:isFindingOf <>;
   gcis:isFindingOf <>;

## Properties of the finding:
   gcis:descriptionOfEvidenceBase "Fossil fuel emissions are from Carbon Dioxide Information Analysis Center (CDIAC) estimates (available from the U.S. Department of Energy’s Environmental Systems Science Data Infrastructure for a Virtual Ecosystem [ESS-DIVE] data archive, The land carbon sink is based on the 10-year average of North American annual fluxes from four global inverse models, specified in the text. The error reported is twice the standard error of the mean of the 10 years and for the four models and mostly represents the amount of interannual variability. The evidence for a trend is based on a linear least-squares regression. The comparison of variability with the U.S. Environmental Protection Agency’s (EPA) estimate of the U.S. land sink is based on EPA data accessed at"^^xsd:string;
   gcis:assessmentOfConfidenceBasedOnEvidence "Fossil fuel uncertainty at the national, annual scale has the smallest uncertainty because it can be constrained by highly accurate information on imports and exports and internal usage. Inverse model-based estimates of CO<sub>2</sub> sources and sinks contain numerous random and systematic errors including biases associated with wind fields and parameterization of vertical mixing. Because models exhibit different mean atmospheric transport, their long-term average fluxes can differ significantly. However, the interannual variability of fluxes among inverse models is much more similar, meaning that the difference between the inverse model and EPA flux variability is likely to be robust."^^xsd:string;
   gcis:newInformationAndRemainingUncertainties "Fossil fuel emissions uncertainty is very low (see Appendix E: Fossil Fuel Emissions Estimates for North America). Long-term means of CO<sub>2</sub> sources and sinks derived from a given inverse model are highly uncertain. However, the interannual variability of fluxes from different models tends to agree well, suggesting lower uncertainty. EPA land flux estimates may not exhibit enough variability due to the U.S. Forest Service methodology, upon which EPA’s estimates are largely based."^^xsd:string;

   a gcis:Finding .

## This finding cites the following entities:

   prov:wasDerivedFrom <>.