Executive Summary
2017_executive_summary
2017_executive_summary
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In addition to quantitative uncertainty assessments provided in accordance with UNFCCC reporting guidelines, a<br />
qualitative discussion of uncertainty is presented for all source and sink categories. Within the discussion of each<br />
emission source, specific factors affecting the uncertainty surrounding the estimates are discussed.<br />
Box ES-4: Recalculations of Inventory Estimates<br />
Each year, emission and sink estimates are recalculated and revised for all years in the Inventory of U.S. Greenhouse<br />
Gas Emissions and Sinks, as attempts are made to improve both the analyses themselves, through the use of better<br />
methods or data, and the overall usefulness of the report. In this effort, the United States follows the 2006 IPCC<br />
Guidelines (IPCC 2006), which states, “Both methodological changes and refinements over time are an essential<br />
part of improving inventory quality. It is good practice to change or refine methods when: available data have<br />
changed; the previously used method is not consistent with the IPCC guidelines for that category; a category has<br />
become key; the previously used method is insufficient to reflect mitigation activities in a transparent manner; the<br />
capacity for inventory preparation has increased; new inventory methods become available; and for correction of<br />
errors.” In general, recalculations are made to the U.S. greenhouse gas emission estimates either to incorporate new<br />
methodologies or, most commonly, to update recent historical data.<br />
In each Inventory report, the results of all methodology changes and historical data updates are presented in the<br />
Recalculations and Improvements chapter; detailed descriptions of each recalculation are contained within each<br />
source's description contained in the report, if applicable. In general, when methodological changes have been<br />
implemented, the entire time series (in the case of the most recent Inventory report, 1990 through 2014) has been<br />
recalculated to reflect the change, per the 2006 IPCC Guidelines (IPCC 2006). Changes in historical data are<br />
generally the result of changes in statistical data supplied by other agencies. References for the data are provided for<br />
additional information.<br />
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28 DRAFT Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2015