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Annex 6: Quality assurance and quality control

During preparation of the New Zealand 2003 national greenhouse gas inventory, work continued on the implementation of the New Zealand National Greenhouse Gas Inventory Quality Control and Quality Assurance Plan. Specific checks have been completed as time and resources have allowed.

A6.1 QC procedures implemented in preparation of the 2003 inventory

Tier 1 quality control (QC) checks for key sources (as identified in the level and trend analysis of the 2002 national inventory) and a selection of non key sources were completed on the 2003 data. Two of these checklists, with the results, are included as examples in this Annex. The checks incorporated in the CRF Reporter software (time-series consistency, recalculation and completeness checks) were undertaken to identify any outliers and inconsistencies in the trends from 1990-2003.

In addition to the QC checks undertaken with the Tier 1 QC checklists, a Tier 2 quality check was carried out on solid waste disposal (a key source category).

Some specific findings and improvements included:

  • SF6 data for 1998 and 1999 reported in the 2002 inventory was about twice as high as that of all other years in the time-series. This was traced to an inconsistency in the method used to estimate emissions for those years compared to the rest of the time-series. This was corrected for the 2003 inventory.
  • Rounding errors were found in a table used to enter data for total emissions of HFC-134a for mobile air conditioning in the 2002 inventory. This was fixed in the 2003 inventory as separate entries were made for first-fill, operation and disposal emissions with the CRF software correctly summing these sub-sources to give total emissions.
  • CH4 emissions from ammonia production for the years 2002 and 2003 were around half of that in previous years even though production levels were similar to previous years. This was traced to incorrect emission factors and activity data being used. This was corrected in the 2003 inventory.
  • SO2 emissions from aluminium production for the years 2000 and 2001 were found to be missing. Values were interpolated. Emissions for NOx and CO for the entire time-series were back calculated using emission factors provided by the smelter for the 2003 data.
  • Activity data for asphalt roofing in 1994 were entered as 0.4 kt in the 2002 inventory which was almost 10 times higher than activity data for the years around it. After consultation with the external consultant who gathered the data, it was decided to change the figure to 0.05 (the same value as previous years) as it is likely to have been a transcription error.
  • A transcription error in the SF6 estimates from Mg foundries prior to the year 2000 was found in the previous inventory. This was fixed for the 2003 inventory.
  • Potential emissions for the consumption of halocarbons and SF6 were calculated for the whole time-series for the first time. Potential emissions for SF6 for the years 1990, 1998 and 1999 were interpolated as data was missing for those years.

A6.2 QA procedures implemented

A checklist of recent reviews of specific sectors (including emission factors) undertaken as part of the quality assurance of the New Zealand national inventory is included in this Annex. It shows that during 2004, a peer review was undertaken of emissions from substitutes for ozone-depleting substances (as part of the industrial processes sector). New Zealand has taken note of the recommendations and will implement these as time and resources allow (the recommendation that potential emissions be calculated and included in future inventories has been addressed and included in this inventory submission). A review of New Zealand's Quality Assurance/Quality Control programme was also undertaken in late 2004. New Zealand has noted these recommendations and is working to address the issues raised.

Documentation and archiving of important reports and resources have continued including email correspondence related to clarification of methodologies used by external agencies.

Procedures scheduled in New Zealand's QA/QC plan for 2004/05 that have been implemented include:

  • Tier 1 quality control checks extended to include a selection of non key sources for the 2003 data in the inventory.
  • Tier 1 quality control checklists updated to include relevant checks on New Zealand data.
  • Tier 2 quality control checks on solid waste disposal (key source category).
  • Holding copies of CVs of people from external agencies who undertake expert reviews of parts of the national inventory.

A6.3 Future development of the QA/QC system

New Zealand will aim to implement the recommendations from the quality management review report during 2005 as time and resources allow. This will lead to a more structured QA/QC programme and a timetable for completing Tier 1 quality checks on all source categories and Tier 2 quality control checks for key source categories.

A6.4: Example worksheets for QC procedures in 2003

Example worksheets for QC procedures in 2003 [PDF, 31 KB]

A6.5: QA summary worksheet

QA summary worksheet [PDF, 20 KB]