Table C1. Reliability of Emissions Estimates in This Report
| Greenhouse Gas and Source of Emissions |
Share of Source in U.S. Emissions Total (Percent) |
Estimated Errors in Activity Data (Percent of Total for Source) |
Estimated Errors in Emissions Factors (Percent of Total for Source) |
Weighted Uncertainty (Percent of Total Emissions) | |||||
| Bias | Random | Bias | Random | Low | High | ||||
| Low | High | Low | High | ||||||
| Carbon Dioxide | |||||||||
| Petroleum | 35.2 | 2.1 | 2.4 | 0.5 | 1.7 | 1.7 | 0.5 | 1.0 | 1.1 |
| Coal | 29.9 | 0.6 | 4.3 | 0.6 | 1.0 | 1.0 | 0.5 | 0.4 | 1.4 |
| Natural Gas | 17.2 | 0.5 | 2.8 | 0.5 | 0.0 | 0.0 | 0.4 | 0.1 | 0.5 |
| Other | 0.6 | -9.3 | 7.8 | 11.1 | 23.3 | 23.3 | 4.4 | 0.2 | 0.2 |
| Missing Sources | 0.0 | 0.0 | 0.7 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.4 |
| Total | 82.9 | 1.1 | 3.7 | 0.6 | 1.2 | 1.2 | 0.5 | 1.7 | 3.5 |
| Methane | |||||||||
| Energy-Related | 3.2 | 13.2 | 14.0 | 4.9 | 20.8 | 25.0 | 4.5 | 0.8 | 0.9 |
| Agricultural | 2.8 | 3.1 | 5.0 | 3.0 | 36.4 | 36.4 | 10.6 | 1.1 | 1.1 |
| Industrial and Waste | 3.2 | 9.7 | 29.4 | 5.0 | 50.5 | 13.8 | 10.1 | 1.6 | 1.1 |
| Missing Sources | 0.0 | 0.0 | 4.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Total | 9.2 | 8.9 | 20.6 | 4.3 | 35.9 | 24.6 | 8.3 | 3.5 | 3.1 |
| Nitrous Oxide | |||||||||
| Energy-Related | 1.3 | 0.5 | 2.8 | 0.5 | 55.0 | 200.0 | 10.0 | 0.7 | 2.5 |
| Agricultural | 4.1 | 4.0 | 5.0 | 4.5 | 90.0 | 100.0 | 10.0 | 3.7 | 4.1 |
| Industrial and Waste | 0.4 | 2.8 | 5.0 | 3.5 | 55.0 | 200.0 | 10.0 | 0.1 | 0.5 |
| Missing Sources | 0.0 | 0.0 | 15.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 2.5 |
| Total | 5.7 | 3.1 | 19.5 | 3.5 | 80.0 | 128.5 | 10.0 | 6.5 | 7.5 |
| Other Gases | |||||||||
| HFCs, PFCs, SF6 | 2.2 | 4.5 | 2.4 | 0.9 | 13.8 | 15.5 | 2.5 | 0.5 | 0.6 |
| Missing Sources | 0.0 | 0.0 | 10.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.2 |
| Total | 2.2 | 4.5 | 12.4 | 0.9 | 13.8 | 15.5 | 2.5 | 0.5 | 0.6 |
| Total: All Sources | 100.0 | 2.0 | 6.4 | 1.1 | 9.2 | 11.0 | 1.8 | 13.2 | 12.9 |
|
Notes: The "low" and "high" bias errors provide a subjective estimate of the largest bias error lower or higher than the current
point estimate that would be consistent with current understanding of the nature of the activity or emissions mechanism. Each
value is calculated as the weighted average of the uncertainties associated with a group of sources in each category. It is
calculated as a percentage of the point estimate of emissions from that source. "Random error" is a subjective estimate of the
largest random error that is consistent with current understanding of the nature of the activity or emissions estimate. "Weighted
uncertainty" is calculated as the square root of the sum of the squared activity factor and emissions factor errors and then
multiplied by the point estimate of the share of total emissions for the source. It is calculated as a percentage of the point
estimate of total 1997 U.S. emissions. |
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Back to Appendix C: Uncertainty in Emissions Estimates