『Abstract
　International policy makers and climate researchers use greenhouse gas emissions inventory estimates in a variety of ways. Because of the varied uses of the inventory data, as well as the high uncertainty surrounding some of the source category estimates, considerable effort has been devoted to understanding the causes and magnitude of uncertainty in national emissions inventories. In this paper, we focus on two aspects of the rationale for quantifying uncertainty: (1) the possible uses of the quantified uncertainty estimates for policy (e.g., gas a means of adjusting inventories used to determine compliance with international commitments); and (2) the direct benefits of the process of investigating uncertainties in terms of improving inventory quality. We find that there are particular characteristics that an inventory uncertainty estimate should have if it is to be used for policy purposes: (1) it should be comparable across countries; (2) it should be relatively objective, or at least subject to review and verification; (3) it should not be subject to gaming by countries acting in their own self-interest; (4) it should be administratively feasible to estimate and use; (5) the quality of the uncertainty estimate should be high enough to warrant the additional compliance costs that its use in an adjustment factor may impose on countries; and (6) it should attempt to address all types of inventory uncertainty. Currently, inventory uncertainty estimates for national greenhouse gas inventories do not have these characteristics. For example, the information used to develop quantitative uncertainty estimates for national inventories is often based on expert judgments, which are, by definition, subjective rather than objective, and therefore difficult to review and compare. further, the practical design of a potential factor to adjust inventory estimates using uncertainty estimates would require policy makers to (1) identify clear environmental goals; (2) define these goals precisely in terms of relationships among important variables (such as emissions estimate, commitment level, or statistical confidence); and (3) develop a quantifiable adjustment mechanism that reflects these environmental goals. We recommend that countries implement an investigation-focused (i.e., qualitative) uncertainty analysis that will (1) provide the type of information necessary to develop more substantive, and potentially useful, quantitative uncertainty estimates-regardless of whether those quantitative estimates are used for policy purposes; and (2) provide information needed to understand the likely causes of uncertainty in inventory data and thereby point to ways to improve inventory quality (i.e., accuracy, transparency, completeness, and consistency).

Keywords: adjustment; data quality; emissions; greenhouse gas; inventory; Kyoto Protocol; trading ratio; uncertainty; uncertainty analysis; UNFCCC』

1. Introduction
2. Using uncertainty estimates to adjust inventories
　2.1. Two possible adjustment mechanisms
　2.2. Characteristics of the adjustment factor and implications for the uncertainty analysis
3. Adjustments to emissions trading ratios based on the uncertainty of emissions
　3.1. Trading ratios: Upper bound emissions are unchanged
　3.2. Trading ratios: Probabilities of exceeding emissions commitments are unchanged
　3.3. Characteristics of the trading ratio and uncertainty analysis
　　3.3.1. Fulfilling environmental goals: The impacts of trading on environmental quality
　　3.3.2. Administrative complexity
　　3.3.3. Implications for trading ratios in practice
4. Uncertainty analysis as a tool for inventory improvement
5. Conclusions
Acknowledgement
References