Quality assurance of calculations for ”Reference approach”

In the Swedish greenhouse gas inventory submitted to the UNFCCC in 2012, there were systematic differences between the amounts of energy and carbon dioxide calculated with the Sectoral (bottom-up) approach (SA) and Reference (top-down) approach (RA), as shown in CRF Table 1AC. For most years, fuel consumption and emissions according to RA were lower, which could indicate that the Swedish emissions reported to UNFCCC according to SA were overestimated. For several years, the difference exceeds two percent, and according to IPCC Guidelines explanations are required for such large differences.

Possible explanations have been investigated earlier[1] and these explanations fall into two main groups; some differences are related to the choice of calorific values and emission factors for refined and primary fuels, respectively, and others are related to the choice of activity data used in the Reference Approach. For the earliest part of the time series, the documentation on both activity data and emission factors used in RA is scarce.

The result of the comparison between RA and SA is also dependent on the amounts of fuels reported under non-energy use of fuels (CRF 1AD). At present, several data sources are used for this category and there is a need for documentation and quality check of these data as well.