CCQM-GAWG Task Group on GHG Scale Comparisons (CCQM-GAWG-TG-GHG)

Terms of reference

The task group was established during the 43rd meeting of the CCQM Gas Analysis Working Group, 20-21 April 2021, with the following goals:

1. To document procedures for CO₂ in air scale establishment, maintenance and value transfer, validated by measurements performed by members of the Task Group;
2. To develop a comparison protocol to enable the mathematical relationship between independently held sets of primary CO₂ in air standards to be developed, targeting the dissemination of standards on related scales with consistency at the 0.02 μmol/mol level;
3. To develop a protocol for an on-going comparison that will demonstrate the maintenance or divergence of the relationship between scales based on different sets of primary CO₂ in air standards over decadal time periods;
4. To document best practices for the characteristics and quality criteria for CO₂ in air standards and scale ensembles relating to their suitability for GHG scale development. This includes evaluation of gas matrix effects, other potential cross sensitivities, and the number of standards required per scale ensemble and their impact on measurement uncertainty.
5. Propose data management strategies that ensure long term data integrity and allow retroactive scale revisions to be unambiguously applied.