Chapter 1Introduction

1INTRODUCTION

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

1.1

Introduction

Chapter 1Contents
1 INTRODUCTION
1.1 DEVELOPMENT OF THE PROGRAMME ........................................................................................1.3
1.2 QUANTIFYING UNCERTAINTIES IN ANNUAL INVENTORIES AND TRENDS .......................1.3
1.3 ROLE OF GOOD PRACTICE IN MANAGING UNCERTAINTIES .................................................1.4
1.4 POLICY RELEVANCE ........................................................................................................................1.6

FigureFigure 1.1

1.2

Example-Decision Tree for CH4 Emissions from Solid Waste Disposal Sites ................1.5

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 111.1

Introduction

INTRODUCTION
DEVELOPMENT OF THE PROGRAMMEAt its 8th session in June 1998, the Subsidiary Body for Scientific and Technological Advice (SBSTA-8) of theUnited Nations Framework Convention on Climate Change (UNFCCC), encouraged the IPCC-OECD-IEA
Inventories Programme to give high priority to completing its work on uncertainty, as well as to prepare areport on good practices in inventory management and to submit a report on these issues for consideration bythe SBSTA, if possible by COP5. This report is the IPCC’s (Intergovernmental Panel on Climate Change)
response to the SBSTA.
To prepare for the work required, the IPCC held an Expert Meeting in Paris in October 1998. The Paris meeting
treated good practice as a way to manage uncertainties, as these would remain associated with greenhouse gas
emissions inventories for the foreseeable future. Good practice guidance assists countries in producing
inventories that are accurate in the sense of being neither over nor underestimates so far as can be judged, and inwhich uncertainties are reduced as far as practicable. Good practice guidance further supports the developmentof inventories that are transparent, documented, consistent over time, complete, comparable, assessed for
uncertainties, subject to quality control and assurance, efficient in the use of the resources available to inventory
agencies, and in which uncertainties are gradually reduced as better information becomes available.
The Paris meeting planned a series of four sectoral Expert Meetings to define good practice by sector and source
category. These meetings covered, respectively, (i) industrial process emissions 1 and emissions of new
greenhouse gases i.e., hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6), (ii)emissions associated with energy production and consumption, (iii) agricultural emissions and (iv) emissions
from waste.
The four sectoral meetings were followed by a meeting on quantifying uncertainties and cross-cutting issues ininventory management, and a concluding meeting to finalise the work. Emissions and removals associated withcarbon stocks in land use, land-use change and forestry were not addressed in this phase of work because of theparallel IPCC activity to produce a Special Report on this Sector. The Paris meeting anticipated the need todefine good practice in this area also, once the Special Report is complete and the Parties have had time toconsider it. Currently, good practice guidance covers emissions of the direct greenhouse gases: carbon dioxide(CO2), methane (CH4), nitrous oxide (N2O), HFCs, PFCs, and SF6. Emissions of the precursor gases carbon
monoxide (CO), nitrogen oxides (NOx), and non-methane volatile organic compounds (NMVOCs) were notcovered in this phase of good practice but could form part of the future work programme. Emissions associatedwith Solvents and Other Product Use are not covered in this report as the main gases emitted in this sector fall
into the class of NMVOCs.
It soon became clear that the programme initiated in Paris could not be completed by the fifth Conference of theParties to the UNFCCC (COP5), especially given the need for the report to go through the process ofgovernment and expert review. Also, with regard to the UNFCCC, the timetable for methodological work agreed
at COP4 required substantive outputs by COP6. Therefore, the timetable was extended, so that the IPCC’s reporton Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories could beavailable to the Parties at COP6 rather than COP5.

1.2

QUANTIFYING UNCERTAINTIES IN
ANNUAL INVENTORIES AND TRENDS

The IPCC Guidelines contain some quantitative advice on uncertainties,2 although so far relatively few countries
have reported on uncertainties in a systematic way.

1 Good practice guidance complementary to the IPCC Guidelines has not been developed for some categories of industrialemissions that are identified at the beginning of Chapter 3, Industrial Processes.
2 Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories, Vol. 1, Annex 1, Managing Uncertainties (IPCC,1996).

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

1.3

Introduction

Chapter 1

Nevertheless, evidence considered by the Paris meeting indicated that for a developed country the overall
uncertainty in emissions weighted by global warming potentials (GWPs) in a single year could be of the order of20%, mainly due to uncertainties in non-CO2 gases.3
Analysis also indicated that the uncertainty in the trend in emissions may be less than the uncertainty in theabsolute value of emissions in any year. This is because a method that over or underestimates emissions from asource category in one year may similarly over or underestimate emissions in subsequent years. The preliminary
evidence available to the Paris meeting suggested that, when this compensation is taken into account, theuncertainty on the trend in emissions between years could fall to a few percent for industrialised countries.4
Chapter 6, Quantifying Uncertainties in Practice, of this report describes methods to determine the uncertainty ineach source category. These methods use a combination of empirical data and expert judgement according toavailability. They estimate the relative contribution that the source category makes to the overall uncertainty ofnational inventory estimates, in terms of the trend as well as absolute level. These methods are consistent withthe conceptual guidance on uncertainties in Annex 1, Conceptual Basis for Uncertainty Analysis. They will
enable countries to report on uncertainties in a consistent manner, and provide valuable input to national
inventory research and development activities. The methods are capable of allowing for relationships inuncertainties between different inventory components, and are supplemented by an extensive set of default
uncertainties developed through the sector workshops.

1.3

ROLE OF GOOD PRACTICE IN
MANAGING UNCERTAINTIESTo be consistent with good practice as defined in this report, inventories should contain neither over nor
underestimates so far as can be judged, and the uncertainties in these estimates should be reduced as far aspracticable.
These requirements are to ensure that emissions estimates, even if uncertain, are bona fide estimates, in the senseof not containing any biases that could have been identified and eliminated, and that uncertainties have beenminimised as far as practicable given national circumstances. Estimates of this type would presumably be thebest attainable, given current scientific knowledge and available resources.
Good practice aims to deliver these requirements by providing guidance on:•Choice of estimation method within the context of the IPCC Guidelines;•Quality assurance and quality control procedures to provide cross-checks during inventory compilation;•

Data and information to be documented, archived and reported to facilitate review and assessment ofemission estimates;•Quantification of uncertainties at the source category level and for the inventory as a whole, so that theresources available for research can be directed toward reducing uncertainties over time, and theimprovement can be tracked.

Chapters 2 to 5 set out good practice guidance on the choice of estimation method at the source category levelby means of decision trees of the type illustrated in Figure 1.1, Example-Decision Tree for CH4 Emissions from
Solid Waste Disposal Sites. The decision trees formalise the choice of the estimation method most suited tonational circumstances. The source category guidance linked to the decision trees also provides information on
the choice of emission factors and activity data, and on the associated uncertainty ranges needed to support theuncertainty estimation procedures described in Chapter 6, Quantifying Uncertainties in Practice. The mostappropriate choice of estimation method (or tier) will depend on national circumstances, including theavailability of resources and can be determined according to the methods set out in Chapter 7, Methodological
Choice and Recalculation.
Inventory development is a resource intensive enterprise which means firstly that inventory agencies may needto prioritise among source categories and estimation methods, and secondly that data quality may improve overtime. Guidance applicable to all source categories is given in Chapter 7, regarding how to identify the key source

3 Based on an analysis of the UK inventory presented to the Paris meeting (Eggleston et al., 1998) and which is described in

more detail in Chapter 6, Quantifying Uncertainties in Practice, Section 6.3.1, Comparison between Tiers and Choice ofMethod.
4 See footnote 3

1.4

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

Chapter 1

Introduction

categories that should be prioritised in the inventory development process, as well as when and how torecalculate previously prepared emissions estimates to ensure consistent emission trends. A key source category
is defined in Chapter 7, as one that has a significant influence on a country’s total inventory of direct greenhousegases in terms of the absolute level of emissions or the trend, or both. The outcome of the determination of thekey source category analysis is taken into account during inventory preparation as indicated in the decision trees.
Chapter 7, also addresses means to manage methodological changes and recalculations. For example, a change ina method may be due to the introduction of emissions’ abatement technology, the availability of more detailed
data, or the greater significance of a source category whose rapid variation over time substantially affects thetrend in total emissions. Guidance is provided for splicing time series in those cases where changes in methods
are consistent with good practice.
Good practice in quality assurance and quality control (QA/QC) procedures described in Chapter 8, Quality
Assurance and Quality Control, covers measurement standards, routine computational and completeness checks,
and documentation and data archiving procedures to be applied to the inventory at the compilation stage. Chapter
8, also describes a system of independent review and auditing that could be implemented by inventory agencies.
QA/QC as defined here covers only actions that inventory agencies could take in respect of their own
inventories. It does not include an international system of review, except insofar as the requirements fortransparency would be common between an international review process and internal reviews conductedroutinely by inventory agencies.
Figure 1.1 Example-Decision Tree for CH4 Emissions from Solid
Waste Disposal Sites
Box 1
Are waste
disposal activity
data obtainable for thecurrent inventory
year?

NoUse IPCC default
values, per capita orother methods toestimate activity data

Estimate CH4emissions using theIPCC default
methodYes

Are waste
disposal activity data
available for previousyears?
Yes

NoIs this akey source category?
(Note 1)

NoYes

Box 2
Estimate CH4emissions using theFirst Order Decay(FOD) method

Obtain or
estimate data on
historical changes insolid waste disposal

Note 1: A key source category is one that is prioritised within the national inventory system because its estimate has a significant
influence on a country’s total inventory of direct greenhouse gases in terms of the absolute level of emissions, the trend in emissions, orboth. (See Chapter 7, Methodological Choice and Recalculation, Section 7.2, Determining National Key Source Categories.)

Throughout this report, good practice refers to actions that could be undertaken by inventory agencies inproducing their greenhouse gas inventories. However, the request from the SBSTA is not restricted to nationalactions, and in the Annexes the report reflects the broader picture, both scientifically and internationally.

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

1.5

Introduction

Chapter 1Annex 1, Conceptual Basis for Uncertainty Analysis, deals with the concepts that underlie the practical advice
on uncertainties provided in Chapters 2 to 8 of the main report. Annex 2, Verification, discusses internationaland scientific aspects of inventory verification. Annex 3, the Glossary, defines the terms of particular interest in
the context of greenhouse gas inventories, and also summarises mathematical definitions of selected statisticalterms for convenient reference.

1.4

POLICY RELEVANCE

The report on Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories(Good Practice Report) does not revise or replace the IPCC Guidelines, but provides a reference thatcomplements and is consistent with these Guidelines. This is because the Conference of the Parties decided5 thatthese IPCC Guidelines would be used for reporting by Parties included in Annex I to the UNFCCC. For thepurposes of developing good practice guidance, consistency with the IPCC Guidelines is defined by threecriteria:(i)

Specific source categories addressed by good practice guidance have the same definitions as thecorresponding categories in the IPCC Guidelines.

(ii)

Good practice guidance uses the same functional forms for the equations used to estimate
emissions that are used in the IPCC Guidelines.

(iii)

Good practice guidance allows correction of any errors or deficiencies6 that have been identified in
the IPCC Guidelines.

Criterion (i) does not exclude identification of additional source categories that may be included in the Other
category in the IPCC Guidelines. Default emission factors or model parameter values have been updated where
they can be linked to particular national circumstances and documented.
The main development in the negotiations since the SBSTA-8’s request has been agreement on the revised
reporting guidelines for Annex I Parties’ greenhouse gas inventories.7 These UNFCCC guidelines contain crossreferences to the IPCC’s work on good practice concerning choice of methodology, emission factors, activity
data, uncertainties, quality assessment and quality control procedures, time series consistency, accuracy andverification.
It is through good practice guidance and uncertainty management that a sound basis can be provided to produce
more reliable estimates of the magnitude of absolute and trend uncertainties in greenhouse gas inventories thanhas been achieved previously. Whatever the level of complexity of the inventory, good practice provides
improved understanding of how uncertainties may be managed to produce emissions estimates that are
acceptable for the purposes of the UNFCCC, and for the scientific work associated with greenhouse gas
inventories.

5 Decision 2/CP.3 and the document FCCC/CP/1999/7 referred to in decision 3/CP.5.
6 For example, some of the equations in the IPCC Guidelines do not formally allow for emissions mitigation technologies ortechniques.
7 See Decision 3/CP.5.

1.6

IPCC Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories