Executive Summary

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Figure ES-16: 2015 Key Categories (MMT CO2 Eq.)
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Note: For a complete discussion of the key category analysis, see Annex 1. Blue bars indicate either an Approach 1, or Approach
1 and Approach 2 level assessment key category. Gray bars indicate solely an Approach 2 level assessment key category.
Quality Assurance and Quality Control (QA/QC)
The United States seeks to continually improve the quality, transparency, and credibility of the Inventory of U.S.
Greenhouse Gas Emissions and Sinks. To assist in these efforts, the United States implemented a systematic
approach to QA/QC. The procedures followed for the Inventory have been formalized in accordance with the
Quality Assurance/Quality Control and Uncertainty Management Plan (QA/QC Management Plan) for the
Inventory and the UNFCCC reporting guidelines.
Uncertainty Analysis of Emission Estimates
Uncertainty estimates are an essential element of a complete inventory of greenhouse gas emissions and removals,
because they help to prioritize future work and improve overall quality. Some of the current estimates, such as those
for CO 2 emissions from energy-related activities, are considered to have low uncertainties because the amount of
CO 2 emitted is directly related to the amount of fuel consumed, the fraction of the fuel that is oxidized, and the
carbon content of the fuel. For some other categories of emissions, however, a lack of or missing data,
representativeness of data to real world conditions associated with the emissions/removal activities in United States,
sampling errors, and measurement errors are example factors that contribute to the uncertainty associated with the
estimates presented. Recognizing the benefit of conducting an uncertainty analysis, the UNFCCC reporting
guidelines follow the recommendations of the 2006 IPCC Guidelines (IPCC 2006), Volume 1, Chapter 3 and require
that countries provide single estimates of uncertainty for source and sink categories.
Executive Summary
ES-27