It is possible to use the IEA CO2 estimates for comparison with the greenhouse-gas inventories reported by countries to the UNFCCC Secretariat. In this way, problems in methods, input data or emission factors may become apparent. However, care should be used in interpreting the results of any comparison since the IEA estimates may differ from a country's official submission for many reasons.
A recent comparison of the IEA estimates with the inventories submitted to the UNFCCC showed that for most Annex II countries, the two calculations were within 5%. For some EIT and non-Annex I countries, differences between the IEA estimates and national inventories were larger. In some of the countries the underlying energy data were different; suggesting that more work is needed on the collecting and reporting of energy statistics for those countries.
Some countries have incorrectly defined bunkers as fuel used abroad by their own ships and planes. Still other countries have made calculation errors for carbon oxidation or have included international bunkers in their totals. Since all of the above will affect the national totals of CO2 emissions from fuel combustion, a systematic comparison with the IEA estimates would allow countries to verify their calculations and produce more internationally comparable inventories.
In addition, the main bias in the energy data and emission factors will probably be systematic and not random. This means that the emission trends will usually be more reliable than the absolute emission levels. By comparing trends in the IEA estimates with trends in emissions as reported to the UNFCCC, it should be possible to identify definition problems or changes in the calculations, which were not reflected in the base year.
For many reasons the IEA estimates may differ from the numbers that a country submits to the UNFCCC, even if a country has accounted for all of its energy use and correctly applied the IPCC Guidelines. No attempt has been made to quantify the effects of these differences. In most cases these differences will be relatively small. Some of the reasons for these differences are:
The IEA uses a Tier 1 Sectoral Approach based on the 1996 IPCC Guidelines. Countries may be using a Tier 2 or Tier 3 method that takes into account different technologies.
• The IEA is using the 1996 IPCC Guidelines.
The IEA is still using the 1996 IPCC Guidelines. Some countries may have already started using the 2006 IPCC Guidelines.
• Energy activity data are extracted from the IEA energy balances and may differ from those used for the UNFCCC calculations.
Countries often have several "official" sources of data such as a Ministry, a Central Bureau of Statistics, a nationalised electricity company, etc. Data can also be collected from the energy suppliers, the energy consumers or customs statistics. The IEA Secretariat tries to collect the most accurate data, but does not necessarily have access to the complete data set that may be available to national experts calculating emission inventories for the UNFCCC. In addition to different sources, the methodology used by the national bodies providing the data to the IEA and to the UNFCCC may differ. For example, general surveys, specific surveys, questionnaires, estimations, combined methods and classifications of data used in national statistics and in their subsequent reclassification according to international standards may result in different series.
• The IEA uses average net calorific values.
The IEA uses an average net calorific value (NCV) for each secondary oil product. These NCVs are region-specific and constant over time. Country-specific NCVs that can vary over time are used for NGL, refinery feedstocks and additives. Crude oil NCVs are further split into production, imports, exports and average. Different coal types have specific NCVs for production, imports, exports, inputs to main activity power plants and coal used in coke ovens, blast furnaces and industry, and can vary over time for each country.
Country experts may have the possibility of going into much more detail when calculating the heat content of the fuels. This in turn could produce different values than the IEA.
• The IEA uses average emission factors.
The IEA uses the default emission factors which are given in the 1996 IPCC Guidelines. Country experts may have better information available.
• The IEA does not have detailed information for the stored carbon calculation.
The IEA does not have complete information on the non-energy use of fuels. The amount of carbon stored is estimated using the default values given in the 1996 IPCC Guidelines. For "other products" in the stored carbon calculation, the IEA assumes that 100% of kerosene, white spirit and petroleum coke that is reported as non-energy use in the energy balance is also stored. Country experts calculating the inventories may have more detailed information.
• The IEA cannot allocate emissions from auto-producers into the end-use sectors.
The 1996 IPCC Guidelines recommend that emissions from autoproduction should be included with emissions from other fuel use by end-consumers. At the same time, the emissions from the autoproduction of electricity and heat should be excluded from the energy transformation source category to avoid double counting. The IEA is not able to allocate the fuel use from autoproducers between the industrial and "other" sectors. Therefore, this publication shows a category called "Unallocated autoproducers". However, this should not affect the total emissions for a country.
• Military emissions may be treated differently.
According to the 1996 IPCC Guidelines, military emissions should be reported in Source/Sink Category 1 A 5, Other (not elsewhere specified). Previously, the IEA questionnaires requested that warships be included in international marine bunkers and that the military use of aviation fuels be included in domestic air. All other military use should have been reported in non-specified other sector.
At the IEA/Eurostat/UNECE Energy Statistics Working Group meeting (Paris, November 2004), participants decided to harmonise the definitions used to collect energy data on the joint IEA/Eurostat/UNECE questionnaires with those used by the IPCC to report greenhouse-gas inventories. As a result, starting in the 2006 edition of this publication, all military consumption should be reported in non-specified other sectors. Sea-going versus coastal is no longer a criterion for splitting international and domestic navigation. For more information on the changes, please consult the Energy Statistics Working Group meeting report on our website at http://www.iea.org/Textbase/stats/ questionnaire/index.asp.
However, it is not clear whether countries are reporting on the new basis, and if they are, whether they will be able to revise their historical data. The IEA has found that in practice most countries consider information on military consumption as confidential and therefore either combine it with other information or do not include it at all.
• The IEA estimates include emissions from coke inputs into blast furnaces. Countries may have included these emissions in the IPCC category industrial processes.
National greenhouse-gas inventories submitted to the UNFCCC divide emissions according to source categories. Two of these IPCC Source/Sink Categories are energy and industrial processes. The IPCC Reference Approach estimates national emissions from fuel combustion based on the supply of fuel to a country and by implication includes emissions from coke inputs to blast furnaces in the energy sector. However, within detailed sectoral calculations certain non-energy processes can be distinguished. In the reduction of iron in a blast furnace through the combustion of coke, the primary purpose of coke oxidation is to produce pig iron and the emissions can be considered as an industrial process. Care must be taken not to double count these emissions in both energy and industrial processes. The IEA estimates of emissions from fuel combustion in this publication include the coke inputs to blast furnaces.
• The units may be different.
The 1996 IPCC Guidelines and the UNFCCC Reporting Guidelines on Annual Inventories both ask that CO2 emissions be reported in Gg of CO2. A million tonnes of CO2 is equal to 1 000 Gg of CO2, so to compare the numbers in this publication with national inventories expressed in Gg, the IEA emissions must be multiplied by 1 000.
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