An important goal of IPCC inventory guidance is to support the development of national greenhouse gas inventories that can be readily assessed in terms of quality. It is good practice to implement quality assurance/quality control (QA/QC) and verification procedures in the development of national greenhouse gas inventories to accomplish this goal. The procedures as described in this chapter also serve to drive inventory improvement.

The guidance is designed to achieve practicality, acceptability, cost-effectiveness, incorporation of existing experience, and the potential for application on a world-wide basis. A QA/QC and verification system contributes to the objectives of good practice in inventory development, namely to improve transparency, consistency, comparability, completeness, and accuracy of national greenhouse gas inventories.

QA/QC and verification activities should be integral parts of the inventory process. The outcomes of QA/QC and verification may result in a reassessment of inventory or category uncertainty estimates and to subsequent improvements in the estimates of emissions or removals. For example, the results of the QA/QC process may point to particular variables within the estimation methodology for a certain category that should be the focus of improvement efforts.

The terms 'quality control', 'quality assurance', and 'verification' are often used in different ways. The definitions of QC, QA, and verification in Box 6.1 will be used for the purposes of this guidance.

Box 6.1

Definitions of QA/QC and verification

Quality Control (QC) is a system of routine technical activities to assess and maintain the quality of the inventory as it is being compiled. It is performed by personnel compiling the inventory. The QC system is designed to:

(i) Provide routine and consistent checks to ensure data integrity, correctness, and completeness;

(ii) Identify and address errors and omissions;

(iii) Document and archive inventory material and record all QC activities.

QC activities include general methods such as accuracy checks on data acquisition and calculations, and the use of approved standardised procedures for emission and removal calculations, measurements, estimating uncertainties, archiving information and reporting. QC activities also include technical reviews of categories, activity data, emission factors, other estimation parameters, and methods.

Quality Assurance (QA) is a planned system of review procedures conducted by personnel not directly involved in the inventory compilation/development process. Reviews, preferably by independent third parties, are performed upon a completed inventory following the implementation of QC procedures. Reviews verify that measurable objectives (data quality objectives, see Section 6.5, QA/QC Plan.) were met, ensure that the inventory represents the best possible estimates of emissions and removals given the current state of scientific knowledge and data availability, and support the effectiveness of the QC programme.

Verification refers to the collection of activities and procedures conducted during the planning and development, or after completion of an inventory that can help to establish its reliability for the intended applications of the inventory. For the purposes of this guidance, verification refers specifically to those methods that are external to the inventory and apply independent data, including comparisons with inventory estimates made by other bodies or through alternative methods. Verification activities may be constituents of both QA and QC, depending on the methods used and the stage at which independent information is used.

Before implementing QA/QC and verification activities, it is necessary to determine which techniques should be used, and where and when they will be applied. QC procedures may be general with a possible extension to category specific procedures. There are technical and practical considerations in making these decisions. The technical considerations related to the various QA/QC and verification techniques are discussed in general in this chapter, and specific applications to categories are described in the category-specific guidance in Volumes 2 to 5. The practical considerations involve assessing national circumstances such as available resources and expertise, and the particular characteristics of the inventory (e.g., whether or not a category is key).



In practice inventory compilers do not have unlimited resources. Quality control requirements, improved accuracy and reduced uncertainty need to be balanced against requirements for timeliness and cost effectiveness. A good practice system for QA/QC and verification seeks to achieve that balance, and also to enable continuous improvement of inventory estimates. Judgements to select the respective parameters will need to be made on the following:

• Resources allocated to QA/QC for different categories and the compilation process;

• Time allocated to conduct the checks and reviews of emissions and removal estimates;

• Frequency of QA/QC checks and reviews on different parts of the inventory;

• The level of QA/QC appropriate for each category;

• Availability and access to information on activity data, emission factors and other estimation parameters, including uncertainties and documentation;

• Acquisition of additional data specifically required, e.g., alternative data sets for comparisons and checks;

• Procedures to ensure confidentiality of inventory and category information, when required;

• Requirements for documenting and archiving information;

• Whether increased effort on QA/QC will result in improved estimates and reduced uncertainties;

• Whether sufficient independent data and expertise are available to conduct verification activities.

In order to prioritise QA/QC and verification efforts for certain categories, particularly in terms of activities requiring more intensive analysis and review, the following questions should be asked to identify where to focus such activities in a given inventory development cycle:

• Is this source/sink a key category according to the definition and methodologies presented in Chapter 4, Methodological Choice and Identification of Key Categories? Has the category been designated as key for qualitative reasons? For example:

- Is there considerable uncertainty associated with the estimates for this category?

- Have there been significant changes in the characteristics of this category, such as technology changes or management practices?

- Have significant changes occurred recently in the estimation methodology used for this category?

- Are there significant changes in the trends of emissions or removals for this category?

• Does the methodology use complex modelling steps or large inputs from outside databases?

• Are emission factors or other parameters associated with the estimation methodology significantly different to recognized IPCC defaults or data used in other inventories?

• Has a significant amount of time passed since emission factors or other parameters have been updated for this category?

• Has a significant amount of time passed since this category last underwent thorough QA/QC and verification procedures?

• Has there been a significant change in how data are processed or managed for this category, such as a database platform change or change in modelling software?

• Is there a potential overlap with estimates reported under other categories (for example because of common activity data) that can generate double counting or incomplete estimates?

Answering yes to the above questions should help identify those sources/sinks where category specific QA/QC and verification activity should be prioritised. Also, the timing of the QA/QC activity should coincide with changes in the category. One time changes in methodologies or data processing, for example, may only require intensified QA/QC within the inventory cycle where those changes occurred.

In terms of the implementation of QA/QC procedures, there should be no difference between confidential and publicly available data; both should carry descriptions of the measurement and calculation procedures and the steps taken to check and verify the values reported. These procedures may be carried out on the confidential data by either the provider of the information or by the inventory compiler and, in either case, confidential source data should be protected and archived accordingly. However, the QA/QC procedures that are implemented need to remain transparent and their description available for review. For example, when data are aggregated across categories at a national level to protect confidentiality, the report should contain a description of the relevant QA/QC procedures.

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