MnrAq
MnrAq
MnrAq
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60 Third IMO GHG Study 2014<br />
1.4 Quality assurance and control of top-down and bottom-up inventories<br />
The quality analysis is presented in three sections. The first section discusses QA/QC for the top-down<br />
emissions inventory. The second section summarizes the QA/QC elements of the bottom-up fuel and emissions<br />
inventory. The third section contains a comparison of the top-down and bottom-up emissions inventories.<br />
Sections 1.1 and 1.2 contain many detailed processes that constitute QA/QC effort; these sections therefore<br />
discuss QA/QC mainly in summary and provide context for the quantitative bottom-up uncertainty analysis<br />
in Section 1.5.<br />
1.4.1 Top-down QA/QC<br />
Top-down statistics were evaluated for transparency and any significant discrepancies that might reflect<br />
confidence in inventories based on fuel statistics.<br />
This section begins with a review of the Second IMO GHG Study 2009 and a brief discussion of data quality,<br />
confidence and uncertainty. It reviews relevant data quality information provided by IEA, including information<br />
about likely causes of potential under- or overestimation of marine fuel use (both domestic and international).<br />
Top-down method QA/QC efforts undertaken specifically for this study are described. Lastly, this section<br />
gives a QA/QC summary of the study.<br />
Second IMO GHG Study 2009: review of top-down data quality<br />
The Second IMO GHG Study 2009 performed qualitative analyses of errors and inconsistencies of IEA statistics<br />
to help explore how the top-down and bottom-up discrepancy may be explained by uncertainty in reported<br />
fuel statistics. That study identified the following potential issues with top-down data:<br />
• different data quality between OECD and non-OECD countries (fishing);<br />
• identical numbers from year to year for some countries;<br />
• big swings from year to year for other countries;<br />
• differences in EIA bunkers statistics.<br />
Although a number of challenges were recognized, mainly arising from the use of different data sources, the<br />
sources of uncertainty remained unexplored and potential corrections were not attempted.<br />
The Second IMO GHG Study 2009 explicitly quoted provisions in the IEA Agreement on an International<br />
Energy Program (IEP) that determined which fuels would be considered in national oil stocks and which were<br />
considered to be counted as international data. In particular, international marine bunkers were “treated as<br />
exports under a 1976 Governing Board decision incorporated into the Emergency Management Manual”<br />
(Scott, 1994). This information and subsequent discussion in the Second IMO GHG Study 2009 suggested that<br />
some degree of allocation error among international bunkers, exports and/or imports could be a factor in the<br />
accuracy of top-down fuel statistics for shipping.<br />
IEA statistics: review of top-down data quality<br />
IEA collects data from OECD countries that have agreed to report mandatory data through monthly and joint<br />
annual IEA/Eurostat/UNECE questionnaires. For non-OECD countries, IEA collects data through voluntary<br />
submissions (using no standard format) or through estimates made by IEA or its contractors. Figure 43 presents<br />
a map of OECD and non-OECD countries that provide energy data to IEA; not all of these countries have<br />
marine fuel sales to report (Morel, 2013).