Chapter 4 - Methodological Choice and Identification of Key Categories

This chapter addresses how to identify key categories 1 in a national inventory. Methodological choice for individual source and sink categories is important in managing overall inventory uncertainty. Generally, inventory uncertainty is lower when emissions and removals are estimated using the most rigorous methods provided for each category or subcategory in the sectoral volumes of these Guidelines. However, these methods generally require more extensive resources for data collection, so it may not be feasible to use more rigorous method for every category of emissions and removals. It is therefore good practice to identify those categories that have the greatest contribution to overall inventory uncertainty in order to make the most efficient use of available resources. By identifying these key categories in the national inventory, inventory compilers can prioritise their efforts and improve their overall estimates. It is good practice for each country to identify its national key categories in a systematic and objective manner as presented in this chapter. Consequently, it is good practice to use results of key category analysis as a basis for methodological choice. Such a process will lead to improved inventory quality, as well as greater confidence in the estimates that are developed.