Improving the quality of national greenhouse gas inventories

Environmental Science & Policy 2 (1999) 335±346

Improving the quality of national greenhouse gas inventories B. Lim a,b,*, P. Boileau a,c, Y. Bonduki a,b, A.R. van Amstel d, L.H.J.M. Janssen e, J.G.J. Olivier e, C. Kroeze f a

IPCC Unit for Greenhouse Gas Inventories, 2 rue Andre Pascal, 75775 Paris, Cedex 16, France National Communications Support Programme, UNDP-GEF, 16th ¯oor, 304 East 45th Street, New York, NY 10017, USA c Global Air Issues Branch, Environment Canada, 351 St. Joseph Blvd, Hull, Quebec, Canada K1A 0H3 d Wageningen Agricultural University, P.O. Box 9101, HB NL-6700 Wageningen, Netherlands e RIMV National Institute of Public Health and the Environment, Laboratory for Waste Materials and Emissions, P.O. Box 1, NL-3720 BA Bilthoven, Netherlands f Wageningen Institute for Environment and Climate Research Wageningen Agricultural University P.O. Box 9101, 6700 HB Wageningen, Netherlands b

Abstract This paper summarises the ®ndings of an Intergovernmental Panel on Climate Change (IPCC) Expert Meeting on Methods for the Assessment of Inventory Data Quality held in Bilthoven, The Netherlands, 5±7 November 1997. Under the Kyoto Protocol of the Climate Convention, reliable inventories of national greenhouse gases (GHG) are needed for verifying compliance. Four approaches are suggested for assessing and improving the quality of greenhouse gas inventories: inventory quality assurance; inventory comparisons; model comparisons; and direct emission measurements. The paper presents recommendations for improving the quality of emission estimates of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). # 1999 Elsevier Science Ltd. All rights reserved.

1. Introduction In 1996, the IPCC identi®ed inventory quality as an emerging issue. The IPCC noted that the ``Guidelines should produce estimates that can be monitored and veri®ed with independent sources of information''. One year later, Annex-I Parties agreed to legally binding commitments under the Kyoto Protocol. Clearly, the quality of national GHG inventories has implications for monitoring and veri®cation of commitments under the Protocol. The quality of emission estimates may also signi®cantly in¯uence the design of an emission trading system and other emission reduction mechanisms of the Convention. Yet none of the technical issues on inventory quality have been resolved.

To address these issues, an IPCC Expert Meeting on Methods for the Assessment of Inventory Data Quality was held in Bilthoven (5±7 November 1997). The meeting brought together over 60 participants from 20 countries. It examined approaches for validating and verifying national GHG inventories, as well as for estimating and reporting uncertainty in national estimates. Several papers from the meeting are included in this Special Issue. The meeting also considered the direction of future work to improve inventory quality. This paper summarises discussions from that meeting.

2. Objectives The objectives of the meeting were:

* Corresponding author. Tel.: +1 212 906 5730; fax: +1 212 906568. E-mail address: [email protected] (B. Lim)

. to examine whether the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories

1462-9011/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 4 6 2 - 9 0 1 1 ( 9 9 ) 0 0 0 2 3 - 4

336

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

Table 1 Global totals for carbon dioxide Source

Number of countries

Total emissions (Tg/year)

Global budget (Tg/year)a

First National Communicationsb Country studiesc Global databased Total

34 31 124 189

13675 5081 6666 25422

± ± ± 28233

a

IPCC (1996) (7.7 GtC44/12). UNFCCC (1997). c Braatz et al. (1996). d Olivier et al. (1996). b

(Revised Guidelines) produce emission estimates which can be monitored and veri®ed; . to examine approaches for assessing and improving the quality of national GHG inventories; . to identify sources of uncertainty in national GHG inventories and to suggest ways of reducing them; . to recommend ways of improving the Revised Guidelines.

3. Verifying the e€ectiveness of the IPCC method The Revised Guidelines are applied by many Parties to estimate national GHG emissions. At the global scale, one way of checking their e€ectiveness is to aggregate national emissions and to compare the aggregated totals with IPCC global budgets (IPCC, 1996). While this comparison is simplistic, it does provide a crude evaluation of the Revised Guidelines. Three sources of data were used to compile global inventories of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These were: National Communications submitted to the United Nations Framework Convention on Climate Change (UNFCCC, 1997); country case studies (Braatz et al.,

1996); and global databases (e.g. Olivier et al., 1996; van Amstel et al., 1997). For CO2, the di€erence between the estimated global budget of fossil fuels and the sum of the available inventories is small (<10%) (Table 1). However, the IPCC global budget (1996) was obtained from a similar global database of emission estimates. Thus, the estimated global budget and the sum of inventory data are expected to be similar. This makes the comparison less meaningful. For CH4, the discrepancy between the global budget and the sum of national inventories is about 30% (Table 2). The global budget was derived from atmospheric measurements and is therefore independent of the inventory data. The agreement between the two budgets is within the expected level of uncertainty, which is also 30%, thus giving con®dence in the Revised Guidelines. For N2O, the sum of inventories is close to the range of the global budget (Table 3). The global budget was obtained from observed atmospheric increases and is independent of the inventory data. However, the estimates of total emissions in Table 3 were based on the previous IPCC method for N2O (IPCC, 1995). Using the current Revised Guidelines (IPCC, 1997), the global emission estimate is higher, around 11 Tg N2O/ year (Mosier et al., 1998). This is in the midrange of

Table 2 Global totals for methane Source

Number of countries

Total emissions (Tg/year)

Global budget (Tg/year)a

First National Communicationsb Country studiesc Global database d Total

33 31 125 189

108 66 121 295

± ± ± 375

a

IPCC (1996). UNFCCC (1997). c Braatz et al. (1996). d Olivier et al. (1996). b

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

337

Table 3 Global totals for nitrous oxide Source

Number of countries

Total emissions (Tg N2O/year)

Global budget (Tg N2O/year)a

First national communicationsb Country studiesc Global databased Total

33 31 125 189

2.0 0.1 2.8 4.9

± ± ± 5±13

a

IPCC (1996) (3±8 Tg (N)/year44/28). UNFCCC (1997). c Braatz et al. (1996). d Olivier et al., 1996. b

the global budget, again giving con®dence in the Revised Guidelines.

4. Assessing the quality of national greenhouse gas inventories The meeting considered several approaches for assessing the quality of GHG inventories: . Approach 1: inventory quality assurance. Evaluation of the underlying data and algorithms of inventories according to a range of criteria. . Approach 2: inventory comparisons. Comparisons among national, regional and global inventories, including their estimation methodologies and input data. . Approach 3: model comparisons. Comparisons of national, regional and global inventories with atmospheric budgets derived from atmospheric concentrations and chemical transport models. . Approach 4: direct emission measurements. Comparisons of national or regional inventories with atmospheric measurements upwind or downwind from local, national or regional sources. As a ®fth approach, participants suggested the use of indicators of economic and other activities to verify emission trends in countries. Examples are Schipper and Haas (1997) for CO2 indicators and Bosseboeuf et al. (1997) for energy indicators. 4.1. Approach 1: inventory quality assurance 4.1.1. Background This approach evaluates the sources of underlying data and the methods used to prepare inventories. Evaluation may include: tracing the original sources of emission factors and testing the sample set for appropriateness, reproducibility, statistical variance, etc.; assessing the robustness of the survey techniques used

for collecting activity data; identifying and evaluating the reliability of national and international sources of emission factors and activity data, and comparing independent sources of these data; assessing the algorithms used to prepare emission estimates. This approach can help identify systematic di€erences in data, and quantify uncertainties in emission estimates. 4.1.2. Potential of the approach The potential of an approach for assessing the quality of inventories depends on our understanding of quality. Inventory quality can be de®ned according to several criteria. These include: accuracy, precision, uncertainty, error, reliability, completeness, comparability and transparency. Ranking their importance is dicult as this depends on the purpose of the inventory (e.g., scienti®c, policy). Most participants agreed that key criteria (unranked) were: completeness; consistency; transparency; comparability; and accuracy. Adequate quality depends on the purpose of the inventory. National representatives believed inventories had two main purposes: analysing trends of emissions and assessing the e€ects of policies and measures. The quality of GHG emission estimates should be adequate for both purposes. Participants considered that standard procedures for preparing national inventories should be developed, similar to ISO standards. However, atmospheric modellers felt that the quality of anthropogenic GHG inventories was adequate for their needs. Evaluating inventory data can also involve validation and veri®cation. The de®nitions of validation and veri®cation were debated. Some participants thought these de®nitions were clear. Validation is a procedure which provides, by reference to independent sources, evidence that an inquiry is free from bias or otherwise conforms to its declared purpose. Veri®cation is a procedure to test the internal agreement of data or procedures. Others argued that the terms validation and veri®cation were used interchangeably. Further clari®cation is needed.

338

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

4.2. Approach 2: inventory comparisons 4.2.1. Background Inventory comparisons are often a two-step process. The ®rst step is a comparison of national, regional or global emissions estimates at a sectoral level. This initial comparison identi®es gross inconsistencies, but does not provide reasons for discrepancies. Only a second comparison of emission factors, activity data, and algorithms, provides clues as to why the emission estimates di€er. Provided there is sucient transparency in the inventory documentation, these simple comparisons can prove to be useful. There are limitations to inventory comparisons. These relate to the de®nitions of sources/sinks of national inventories. The de®nitions often di€er, making direct comparisons between inventories less meaningful. For example, the IPCC de®nitions for veri®cation and validation di€er from those used by CORINAIR, the European emission inventory methodology (EEA, 1997). Thus, to carry out such comparisons, the reporting framework of the inventories must be harmonised and made comparable. Currently, the IPCC Overview and Summary Tables do not supply sucient detail for comparisons. Detailed worksheets are required. Examples of inventory comparisons can be found in Marland and Rotty (1984), IPCC (1992a, 1992b, 1994), Marland and Boden (1993), Graedel et al. (1993), Moran and Salt (1996) and van Amstel et al., 1997). 4.2.2. Potential of the approach To evaluate the potential of the approach, inventories from di€erent sources were compared for various gases (van Amstel et al., 1997; Marland et al., 1997). Data sources include the UNFCCC, US Countries Studies Program (USCSP), the Emissions Database for Global Atmospheric Research (EDGAR) and the database of the Global Emission Inventory Activity (GEIA). The results of these comparisons are described below. 4.2.2.1. Carbon dioxide. Comparisons showed that di€erences between the inventories are generally less than 10% for CO2 emissions from fossil fuels; di€erences are greater in land-use change and forestry, agriculture, and biofuel combustion (van Amstel et al., 1997). Participants discussed ways to improve the IPCC method. For energy and industrial processes, no immediate action was necessary. However, this was not the case for land-use change and forestry. Here, problems originate from both the methods and data. Participants were more con®dent with data for forestry than those for changes in land-use. They also noted

that for this sector, clari®cation of the term anthropogenic emissions was a high priority. Of the approaches evaluated, participants identi®ed inventory comparisons as the most useful for evaluating CO2 inventory quality. For CO2 emissions from energy, national estimates can be compared with those prepared from the IPCC Reference Approach (IEA, 1997) using the International Energy Agency (IEA) energy statistics. Typically, the di€erences between national and IEA emission estimates are within 5% and many of these variations can be explained. 4.2.2.2. Methane. Emissions from National Communications di€er from those in the EDGAR database for all sectors by more than 10%. Discrepancies are highest in the land-use change and forestry and agriculture sectors (van Amstel et al., 1997). For instance, CH4 emissions from biomass burning were found to di€er from national inventories by an order of magnitude in some cases. Better emission factors are needed, especially for developing countries. 4.2.2.3. Nitrous oxide. As noted earlier, the previous version of the Guidelines (1995) underestimated global emissions of N2O from agriculture by up a factor of three. The Guidelines have been revised and comparisons of inventories should now be based on the Revised Guidelines for National Greenhouse Gas Inventories. However, few countries have applied this method yet. 4.3. Approach 3: model comparisons 4.3.1. Background Comparisons of atmospheric modelling results with inventories are relatively novel. Such an approach might be used to validate GHG inventories. In this approach, inventories are compared with emission estimates (or budgets) derived by combining atmospheric concentrations and chemical transport models, using techniques such as inverse modelling. Similarly, estimated and observed atmospheric concentrations can also be compared. In this case, models are applied in the forward mode to obtain estimated concentrations which are then compared to observations. Gridded emission estimates are typically used as input data. A key feature of model comparisons is that the signi®cance of the results depends on both the di€erence and the uncertainty of the two estimates. 4.3.2. Potential of the approach Currently, model comparisons cannot be used to validate or verify CO2 inventories at the national level. One reason is that the uncertainty of models (25%) is much larger than the uncertainty of national inventories (about 10%) (van Amstel et al., 1997). To

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

obtain national detail, more atmospheric measurements and improvements in models would be needed. However, for CO2, the use of models is more promising at the global scale. For instance, models can be used to potentially constrain CO2 ¯uxes from the terrestrial biosphere; such ¯uxes are poorly known compared to ¯uxes from other reservoirs (e.g. fossil fuels, oceans). With the exception of isotopic studies, few other options to validate terrestrial carbon ¯uxes exist. Among the gases considered, model comparisons show the highest potential for validation of CH4 inventories. This is due to two factors. First, the atmospheric distribution of CH4 is relatively nonhomogeneous; this facilitates the use of atmospheric transport models to map emission estimates. Second, model uncertainties are comparable (20±40%) with uncertainties of national inventories (30%). Both factors greatly enhance the e€ectiveness of model comparisons. Moreover, model comparisons for CH4 are feasible at all spatial scales. However, widespread application of this approach is currently limited by the small number of monitoring sites and measurement data. Where the sampling network is well developed, e.g. Europe, models can derive CH4 budgets at the global and zonal scales reasonably well. Comparisons can also potentially yield the sectoral detail needed for the re®nement of the Revised Guidelines, particularly if supplementary isotopic information is available. The potential usefulness of model comparisons was higher than anticipated for N2O, particularly at global and zonal scales. Regional budgets of N2O have also been compiled for Europe by Derwent et al. (1998) using data from an atmospheric monitoring site at Mace Head (Ireland). The potential of model comparisons is facilitated by the similarity of the uncertainty ranges of models and inventories. These uncertainties are about 240%. Further modelling e€orts should focus on improving the understanding of the stratospheric sink. 4.3.3. Limitation of comparisons Model comparisons are limited by several factors. The most important of these is the comparability of datasets and uncertainties surrounding inventories and models. First, the structure of emissions estimates from atmospheric models and inventories varies. Inverse models generally provide estimates of net (anthropogenic and natural) concentrations, or budgets and source categories, of a gas at a particular location and time. By contrast, inventories prepared for the UNFCCC include only anthropogenic emissions/ removals, are averaged over one year, and are typically at the national scale and by sector. For comparisons to be meaningful, emissions estimates from both the

339

inventories and models must relate to the same group of GHG source/sink sectors, and cover the same time period. Second, both inventories and model comparisons are subject to sampling errors, systematic bias, and uncertainties. In national inventories, uncertainties are present in ®eld measurements, upscaling of measurements, and the statistics of national (economic) activities. Uncertainties in global budgets come about from the changes in reservoirs, the magnitude of the reservoirs themselves, calibration of the models, interpolation of the ®eld measurements, the inherent limitations of the models and uncertainty in processes. If a modelling technique has a wider range of error than an inventory method, it may not improve the accuracy or precision of an inventory. Any di€erence between the inventory and modelling estimates must also be tested for signi®cance. Therefore, more extensive quanti®cation of uncertainties in inventories and atmospheric models is required. 4.4. Approach 4: direct emission measurements 4.4.1. Background With current observing techniques, it is possible to measure the ¯ux of a gas upwind and downwind of major cities, and even nations. These techniques provide direct emission and uptake measurements on scales approaching national inventories and have been applied on the east coast of the US, in the UK (Fowler et al., 1996; Derwent et al., 1998) and in Europe (Martin, 1998). They may o€er an alternative method of validating national GHG emissions and removals. 4.4.2. Potential of the approach When evaluating the feasibility of using direct measurements to validate emission inventories, one must consider both technical and economic factors. For CO2, forest tower ¯ux measurements might help to estimate the net exchange of carbon between forests and the atmosphere. However, such measurements may not be cost-e€ective, particularly for the energy and industrial processes sectors. For CH4, large-scale measurement experiments are appropriate for surveys of oil and gas leaks, land®lls, enteric fermentation, biomass burning and agricultural CH4. These atmospheric measurements would need to be interpreted in conjunction with remote sensing and isotopic analysis. For N2O, direct ¯ux measurements at representative sites can be used to improve and validate emissions estimates from agricultural sources. Typically, biogenic emissions of N2O, as with other gases, show high spatial and temporal variability. Measurements should therefore be integrated over suciently long sampling

340

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

periods to smooth out signals and seasonal variations. Presently, emission estimates are based on a limited number of measurements and these do not always cover the ``full cycle'' of crop production, and agricultural, animal and waste management practices. The use of standard measurement techniques, developed in Western Europe and North America, for obtaining estimates is recommended for areas where emission factors are lacking.

5. Evaluating the uncertainties in national greenhouse gas inventories 5.1. Sources of uncertainty Sources of uncertainty in inventories vary depending on the activity. Developing quantitative knowledge about each source of uncertainty is essential for improving the quality of inventories. The meeting identi®ed ®ve independent sources of uncertainty in emission inventories: . . . . .

the measurements of ¯uxes; the development of emission factors; the activity data; the calculation method, including the assumptions; the errors in upscaling from the process to the country level.

The Revised Guidelines (Table A1-1, Reporting Instructions ) provide a table of uncertainty estimates for emission factors and activity data by sector. This table was highly contentious. Participants recommended that it be improved. Firstly, the table should be developed with a greater sectoral breakdown, making it consistent with the IPCC Reporting Tables. A rating system was proposed as a semi-quantitative approach to estimating uncertainties. This approach would standardise the estimation of uncertainty and would be an immediate improvement over the current IPCC method which asks countries to give a high, medium or low con®dence ranking to an emission estimate. Rather, countries could assign an uncertainty rating to an emission factor, activity data or emission estimate. To capture the uncertainty due to the algorithm used, an additional column should be added to the table. Secondly, countries could be encouraged to report their inventory data as a range in addition to an absolute number. This would illustrate the variability of the estimate. The Revised Guidelines should also help di€erentiate between random error and systematic bias, and to identify the main sources of error. Finally, some participants suggested developing a

hierarchy of uncertainties, as this might establish priorities to reduce them. 5.2. Estimating, reporting and reducing uncertainty Participants considered several aspects of estimating, reporting and reducing uncertainties. They also examined the potential approaches for reducing uncertainties. A summary of their discussions is given in Tables 4±6. 5.2.1. Estimating and reporting uncertainty A priority is to develop a framework for estimating and reporting uncertainties. The IPCC/OECD/IEA Inventories Programme should study how countries estimate their uncertainties for national inventories and use these ideas to scope future work. Semi-quantitative techniques for estimation of uncertainties should be evaluated according to the method and the quality of the data. These techniques could be based on the following schemes: . using a percentage range of uncertainty, based on a nominal scale of ``very high, high, medium, low and very low''; . expressing uncertainties as a percentage of the contribution of a source/sink to total national emissions; . expressing uncertainties as upper and lower ranges of emission estimates; . using quality assurance ranking systems to report uncertainties.

5.2.2. Reducing uncertainties For CO2, participants felt reasonably con®dent with the quality of energy data; energy emissions were estimated with the lowest uncertainty (<10%). Uncertainties of emissions and removals from land-use change were highest (>50%), while forestry was lower (>25%) (Table 4). Uncertainties for emissions from industrial processes were estimated at 15%. To reduce these uncertainties, participants felt that improved activity data are required for energy data in some countries (e.g. former Soviet Union), land-use data for all countries should be improved, with emphasis on forest inventories, deforestation and reforestation rates. They also felt that clearer de®nitions of anthropogenic and natural emissions in the land-use change and forestry sector were required. For estimates of CH4 emissions in the energy, agriculture and waste sectors, participants felt that uncertainties of 230% should be possible for most national, annual inventories. The sectors with the highest uncertainties are biofuel combustion and biomass burning;

Comparisons should be made based on the IPCC Reference Approach ±

The quality is good for fuel combustion where activity data exist Better focus is needed particularly to distinguish between combustion emissions and process Better data are needed for: tropical deforestation, reforestation, soil carbon processes and land-use statistics Better forest inventories; anthropogenic de®nition The problem is not the method; better activity data are needed; need to develop a ``docket'' approach for ®eld testing and quality assurance trail <10% 215%

>50%

>25% ±

Energy Industrial processes

Land-use change

Forestry Overarching

The IPCC should collaborate with and support land-use change and forestry global databases ± Comparisons should be made between national communications and international databases

Inventory comparisons Inventory quality assurance Uncertainty Sector

Table 4 Uncertainty and proposed improvements for CO2 emission estimates

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

341

both sources are important in developing countries. For most sectors, the most e€ective way of reducing uncertainties is to improve the activity data, not the method (Table 5). For N2O, participants estimated uncertainties for energy, industrial processes and agriculture. Compared to CO2 and CH4, these ranges of uncertainty of 30% to 70% seem high. In fact, they are expressed as percentage ranges and are therefore not directly comparable with the uncertainty estimates for CO2 and CH4. The highest uncertainties originate from agriculture (70±80%), and the lowest from industrial processes (30%). One of the main sources of uncertainty of N2O is the emission factor. This arises when an emission factor is measured in one world region, and then applied to another. The ranges in Table 6 take this bias into account. The other source of uncertainty arises through error propagation of the calculations. To reduce the uncertainty in N2O estimates, participants recommended development of standard IPCC methods for measurements. Globally, there are only a few major sources of industrial N2O, which makes it easier to obtain site-speci®c emissions and to reduce uncertainty in this sector. 6. Summary and conclusions The meeting examined four approaches to assess the quality of GHG inventories. These were inventory quality assurance, inventory comparisons, model comparisons and direct emission measurements. Ranking the usefulness of the various approaches was dicult. The suitability of each approach depends on the gas, the sector, and the purpose of the inventory. Participants, nevertheless, endorsed all approaches as appropriate for improving inventory quality, and recommended further work in these areas. For instance, inventory quality assurance and inventory comparisons are e€ective tools at the national level. However, more research is needed to develop quality assurance as a technique. Over the longer term, model comparisons are useful for testing the accuracy of GHG inventories. Models might be used to estimate carbon ¯uxes from land-use change and forestry at the continental level. Model comparisons are valuable here since this sector has a relatively high uncertainty in the global estimates. At the national level, model comparisons show more potential for assessing CH4 inventories than for other GHGs. Participants recommended continued co-operation between the inventories community and modellers. Direct emission measurements lend themselves to the evaluation of national inventories of CH4 and N2O.

Waste

250%

Large scale biomass burning

230%

230%

Rice

Land®lls

240%

Manure

235%

Biofuel combustion

220%

±

Oil re®ning

Enteric fermentation

±

Oil and gas production/ distribution/ transmission

Agriculture and land-use change

230%

Coal mining

Energy

Uncertainty

Category

Sector Disaggregation from the country scale to coal mining region, to individual mine, coal handling practices, above and below ground operations, open-cast vs. deep mining Quantify and re®ne country to country variations at production sites, transmission and distribution pipeline losses, leakage losses at consumer premises Quantify and improve databases on re®nery losses Improve statistics and emission factors for small sources, domestic stoves and industrial biomass usage Disaggregation into animal types, feed, management, age and population statistics on country-speci®c basis Need to separate intensive management lagoons, and disposal on arable and nonarable land Scaling with respect to cultivar type, rice management, water regimes, use of organic waste and fertiliser Attention should be given to area burnt, biomass density, previous extent of burning, ecosystem burnt, statistics of fuel burning, emission factors and measurements for di€erent crop residues More attention to be given to historical waste disposal rates, reporting land®ll operations by extent and volume, land®ll gas extraction, measurement of land®ll gas decay functions

Inventory quality assurance

Table 5 Uncertainty and proposed improvements for CH4 emission estimates

±

Remote sensing of ®res; land-use data from satellites; large scale experimental campaigns

±

±

Imagery for area under rice cultivation, isotopic analysis with measurements

±

±

Remote sensing and direct measurements o€er signi®cant potential

±

Aircraft surveys of pipeline leakage

±

Direct emission measurements

Comparisons are dicult because most countries use the same method

±

±

Comparison between countries and within countries

±

±

±

Inventory comparisons

342 B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

Promote research to quantify/verify: the unknown soil sink, industrial sources, atmospheric source of N2O through oxidation of NH3

80±100% ?

70±80% 70±80%

- direct - animal waste management - indirect new sources/sinks

Biomass burning

Agriculture and land-use change

Agricultural soils

70±80%

± Industry

30%

IPCC should provide a recommended method

Clari®cation of the term anthropogenic; IPCC should provide a recommended method; research on process modelling

Compare countries and regions with similar conditions

IPCC should provide a recommended method

Promote research to quantify emissions from: mobile sources (emissions from 3-way catalysts), ¯uidised bed reactors Direct measurement of major sources by recommended methods Remote sensing of the extent of forest ®res Fossil fuel Energy

30±70%

Inventory quality assurance Uncertainty Category Sector

Table 6 Uncertainty and proposed improvements for N2O emission estimates

Inventory comparisons

Direct emission measurements

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

343

This approach is applicable to both di€use sources and localised ``hotspots'' of trace gases. Further progress is needed to ensure that national GHG inventories can be monitored and veri®ed for compliance under the Kyoto Protocol. Several steps were recommended to advance current understanding of sources and removals of GHGs. These recommendations are summarised below and listed in Appendix A. Over the long term, the implementation of these recommendations may lead to further revision of the Revised Guidelines ± the basis for legally binding commitments. Firstly, participants suggested there is a need to develop a common terminology for inventory quality. Relevant criteria include: completeness; consistency; transparency; comparability; accuracy; precision; error; and uncertainty. Although their meanings are distinct, these terms are often not used rigorously. Validation and veri®cation were also considered as useful concepts for assessing inventory quality. Secondly, participants identi®ed sources of uncertainty in national emission estimates, and recommended ways to minimise them. For biogenic and natural sources and sinks, however, there are limitations imposed by the natural variability of the system. More data and improved methods will help reduce uncertainties, but not eliminate them. For many gases and sectors, the barrier to better inventory quality is often the underlying data, not the IPCC method, which is scienti®cally robust. But some methodologies are still evolving, such as land-use change and forestry, soil carbon, and the ``new gases'' (e.g. HFCs, PFCs, and SF6). For the ``new gases'', the main issue is emission rates that change with new technology, making it necessary to update the IPCC method. Thirdly, participants developed likely ranges of uncertainty for GHG inventories by sector. They identi®ed the development of a framework for estimating and reporting uncertainty for national estimates as a high priority. Such a framework would improve the current IPCC scheme of high, medium and low. Both qualitative and quantitative approaches were suggested, all requiring further development. Future meetings on uncertainties were recommended. Participants recommended that the IPCC develop codes of good practice to improve the availability of underlying data for inventories. These codes will help countries prepare national inventories, develop emission factors and conduct emissions measurements. They would be based on internationally accepted procedures. Moreover, they could be applied to obtain data in regions where none exist and to extend global databases on activity data and emission factors. These data could eventually be incorporated into the Revised Guidelines. An example is conducting forest surveys in order to establish growth rates, carbon densities, etc.

344

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

Participants felt that clearer de®nitions of the terms anthropogenic and natural were important for reducing the uncertainty of biogenic sources and removals of GHG. This clari®cation would help di€erentiate between anthropogenic and natural emissions in national GHG inventories ± a principal objective of the Revised Guidelines. Finally, participants recommended the use of the IPCC Reference Approach from the Energy Sector of the Revised Guidelines for veri®cation of CO2 emissions from energy. They also suggested that the IPCC develop reference approaches in other sectors, again for veri®cation. Acknowledgements We would like to the thank the participants and organisers from the Dutch National Institute for Public Health and the Environment (RIVM) and the CKO/ CCB Centre on Climate Research Utrecht, and Wageningen Climate Change and Biosphere Programme. In particular, Margot Van Blomestein and Audrey Glynn, without whom the organisation of the meeting would have been very dicult. Ann Johnston and Amy Emmert provided editing and word processing assistance. We would also like to thank the speakers, co-chairs and rapporteurs at the meeting: Leonor Tarrason, Dick Derwent, Youba Sokona, Gregg Marland, Ron Sass, D.C. Parashar, Arvin Mosier, G.X. Xing, Diogenes Alves, Xu Deying, Roberto Acosta, David Fowler, Tinus Pulles, Pojanie Khummunghol, Frank Neitzert, Thomas Martinsen, David Griggs, Wiley Barbour, Ian Galbally, Bojan Rode, Tim Simmons, Susan Subak, and Dudley Sama Achu. The views expressed in this article are strictly those of the authors and do not represent those of the United Nations Development ProgrammeÐGlobal Environment Faculty or Intergovernmental Panel on Climate Change Appendix A. Recommendations of the meeting The meeting made the following recommendations. Inventory quality assurance. In the immediate term, further research on inventory quality assurance is a high priority for verifying and for assessing the quality of national GHG inventories for all gases. Inventory comparisons. Existing inventories (national and scienti®c) and independently derived emission estimates, should be compared with default and independently derived emission factors and international statistics, at a range of scales to ®nd the largest di€erences. These di€erences should be explained using the details of activity data and emission factors.

Model comparisons. In the longer term, model comparisons show potential for validation and veri®cation of global, regional, and national GHG inventories. The use of model comparisons is recommended, using both forward and inverse models. To improve the reliability and accuracy of GHG emission inventories, model comparisons should be carried out at various levels. Direct emission measurements. In the medium term, direct emissions measurements are a priority for improving estimates of CH4 from several emissions sources. These include: oil and gas leaks; land®lls; biomass burning; and rice paddies. Uncertainty. A high priority is a framework to de®ne, estimate, and report degrees of uncertainty in GHG inventories. First, the IPCC should study how countries estimate uncertainties for their national inventories. Second, a framework on uncertainties should be developed through the IPCC process. This framework should allow degrees of uncertainties to be reported at a higher level of sectoral detail than in the current Guidelines. The reporting of the sources of uncertainty could be made explicit for emission factors, activity data and the algorithms used in calculating estimates. Codes of good practice. To help reduce uncertainties in national GHG inventories, codes of good practice for the preparation of national inventories, the measurement of emission factors, and direct emissions of CO2, CH4 and N2O should be developed through the IPCC process. These codes of good practice should be based on accepted procedures currently employed in countries with mature research programmes. They should be applied to obtain more comprehensive emissions data in regions where good quality data are lacking. Data generation. To reduce uncertainties in national inventories, a higher priority should be placed on data generation. . For CO2, improved activity data need to be collected in all countries for land-use change, rates of reforestation, deforestation and a€orestation, and forest inventories. Priority should be given to ¯ux measurements from forests and soil carbon exchange processes. In the energy sector, e€ort should focus on reducing systematic rather than random error. For veri®cation, participants strongly recommended comparing emissions estimated using both national methods and the IPCC Reference Approach. . For CH4, every e€ort should be made to improve the systematic collection of basic data and to disaggregate this data. Priority should be given to documenting and reporting of historical waste disposal rates, land area and volume extents, land®ll gas extraction, and land®ll organic matter decay functions. Other priorities are to carry out large-scale

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

measurements for determining emission rates from coal, oil and natural gas production and distribution. . For N2O, participants agreed that existing N2O inventories should be compared at a range of spatial scales. Anthropogenic. Consensus should be developed on the meaning of this term to di€erentiate anthropogenic from natural sources and removals of GHG. This will help reduce uncertainty in land-use change and forestry inventories and agricultural sources. Emission factors. Default country-speci®c emission factors should be compared with data from the literature. Glossary of terms. A glossary of common terminology relating to the quality of national GHG inventories should be developed through the IPCC process. Co-operation. There is a need for increased co-operation between the inventories and modelling communities. This will result in a better assessment of anthropogenic in¯uence and its overall e€ect on the climate system through the use of models. Halocarbons and sulphur hexa¯uoride. A high priority should be placed on improving the IPCC estimation methodologies for HFCs, PFCs, and SF6. The IPCC Reporting Tables should be disaggregated so that emission estimates for the individual gases can be monitored against atmospheric measurements. References Bosseboeuf, D., Chateau, B., Lapillonne, B., 1997. Cross-country comparison on energy eciency indicators: the on-going European e€ort towards a common methodology. Energy Policy 25 (7±9), 000±000. Jallow, B.P., Molnar, S., Murdiyarso, D., Perdomo, M., Fitzgerald, J.F., 1996. In: Braatz, B.V. (Ed.), Greenhouse Gas Inventories, Interim Results from the US Country Studies Program. Kluwer, Dordrecht. Derwent, R.G., Simmonds, P.G., O'Doherty, S., Ciais, P., Ryall, D.B., 1998. European source strengths and northern hemisphere baseline concentrations of radiatively active trace gases at Mace Head, Ireland. Atmospheric Environment 32 (21), 3703±3715. EEA, 1997. AIR, Atmospheric Emission Inventory Guidebook CDROM. The European Environment Agency, Copenhagen, Denmark. Fowler, D., Hargreaves, K.J., Choularton, T.W., Gallaher, M.W., Simpson, T., Kaye, A., 1996. Measurements of regional CH4 emissions in the UK using boundary layer budget methods. Energy Conversion Management 37 (6±8), 769±775. Graedel, T.E., Bates, T.S., Bouwman, A.F., Cunnold, D., Dignon, J., Fung, I., Jacob, D.J., Lamb, B.K., Logan, J.A., Marland, G., Middleton, P., Pacyna, J.M., Placet, M., Veldt, C., 1993. A Compilation of inventories of emissions to the atmosphere. In: Global Biogeochemical Cycles, vol. 7. Murray Hill, USA, pp. 1± 26. IEA, 1997. CO2 Emissions from Fuel Combustion: a New Basis for

345

Comparing Emissions of a Major Greenhouse Gas, 1972±1995. Paris. IPCC, 1992a. National greenhouse gas inventories: transparency in estimation and reporting, Parts 1 and 2. Final report from the Workshop held 1 October 1992, Bracknell, UK. IPCC, 1992b. Preliminary IPCC national GHG inventories. In-depth review, Part 3, Bracknell, UK. IPCC, 1994. Overview of preliminary national GHG inventories. Interim report, Bracknell, UK. IPCC, 1995. IPCC Guidelines for National Greenhouse Gas Inventories, vols. 1±3. Paris. IPCC, 1996. Meira Filho, L.G., Callander, B.A., Harris, N., Kattenburg, A., Maskell, K. In: Houghton, J.T. (Ed.), Climate Change 1995, The Science of Climate Change, Contribution of WG 1 to the Second Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. IPCC, 1997. Houghton, J.T., Meira Filho, L.G., Lim, B., Treanton, K., Mamaty, I., Bonduki, Y., Griggs, D.J., Callander, B.A. (Eds.), Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories, vols. 1±3. Paris. Marland, G., Rotty, R.M., 1984. Carbon dioxide emissions from fossil fuels: a procedure for estimation and results for 1950±1982. Tellus 36 (B), 232±261. Marland, G., Boden, T., 1993. The magnitude and distribution of fossil-fuel-related carbon releases. In: Heimann, M. (Ed.), The Global Carbon Cycle. Springer, Berlin, pp. 117±138. Marland, G., Brenkert, A., Olivier, J., 1997. CO2 from fossil fuel burning: a comparison of ORNL and EDGAR estimates of national emissions Discussion paper submitted for an Expert Group Meeting on Methods for the Assessment of Inventory Quality, 1997, Bilthoven, The Netherlands. Martin, P., 1998. Estimating the CO2 uptake in Europe. Science 281, 1806. Moran, A., Salt, J.E., 1996. International greenhouse gas inventory compilation systems CORINAIR and IPCC. Report prepared for EU Directorate General XII Environment Programme, CEC contract no. EV5V-CT94-0387, May. Mosier, A., Kroeze, C., Nevison, C., Oenema, O., Seitzinger, S., van Cleemput, O., 1998. Closing the global atmospheric N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle. In: Nutrient Cycling in Agroecosystems, in press. Olivier, J.G.J., Bouwman, A.F., van der Maas, C.W.M., Berdowski, J.J.M., Veldt, C., Bloos, J.P.J., Visschedijk, A.J.H., Zandveld, P.Y.J., Haverlag, J.L., 1996. Description of EDGAR version 2.0: a set of global emission inventories of greenhouse gases and ozone-depleting substances for all anthropogenic and most natural sources on a per country basis and on a 1818 grid RIVM/ TNO report 771060-002. Schipper, L., Haas, R., 1997. The political relevance of energy and CO2 indicators: an introduction. Energy Policy 25 (7±9), 000±000. UNFCCC, 1997. Emissions estimates submitted by Parties to the Convention through national communications. UNFCCC website, http://www.unfccc.de. van Amstel, A.R., Kroeze, C., Janssen, L.H.J.M., Olivier, J.G.J., van der Wal, J.T., 1997. Greenhouse Gas Emission Accounting. Preliminary Study as Input to a Joint International IPCC Expert Meeting/CKO-CCB Workshop on Comparison of Top-down versus Bottom-up Emission Estimates WIMEK/RIVM report 728001 002. Bilthoven, the Netherlands. Bo Lim is an atmospheric chemist from the University of East Anglia, United Kingdom. From 1987 to 1995, she carried out research on the long-range transport of atmospheric pollutants at institutions in the United Kingdom and in France. Since then, she has managed the Greenhouse Gas Inventory Programme for the Intergovernmental Panel on Climate Change. This programme developed methods for estimating national greenhouse inventories under

346

B. Lim et al. / Environmental Science & Policy 2 (1999) 335±346

the United Nations Framework Convention for Climate Change. More recently, she joined the climate team at the United Nations Development Programme. Here, she oversees a global programme on National Communications for non-Annex I Parties. This programme covers greenhouse gas inventories, mitigation analysis, and vulnerablility and adaptation.

Pierre Boileau is a graduate in chemistry from the University of Ottawa. He obtained his degree in 1987 and has worked in the environmental ®eld since. His most recent work has focused on ambient air quality issues such as urban air pollution and greenhouse gas emissions. He helped develop the Canadian national inventory of greenhouse gases for reporting under the United Nations Framework Convention on Climate Change. The last two years he has worked with the IPCC/OECD/ IEA Programme for National Greenhouse Gas Inventories in Paris, helping to ®nalise the Revised 1996 IPCC Guidelines and develop the companion software program. He has now returned to Canada to work on policy issues related to Canada's National Implementation Strategy for the Kyoto Protocol.

Yamil Bonduki has a forestry degree from Los Andes University, MeÂrida, Venezuela, and a Masters in Regional Planning from the University of California, Berkeley, USA. He worked as a technical advisor for the Venezuelan Forest Service, and since 1993 has been working on climate change issues, mainly on greenhouse gas inventories and mitigation. He was a visiting scientist to the Organisation for Economic Co-operation and Development in Paris, France, under the IPCC Greenhouse Gas Inventories Programme and is currently working as a climate change technical consultant at the United Nations.

Andre van Amstel is trained as a physical geographer at the University of Amsterdam. He worked at the National Institute of Public Health and the Environment from 1991±1996 where he was responsible for the national greenhouse gas emission inventories for the ®rst National Communication from the Netherlands. Since 1997 he is working at the Wageningen Agricultural University, at the

Environmental Systems Analysis Group. His main interest now is greenhouse gas emissions from agriculture.

Leon H.J.M. Janssen studied Physics and Mathematics at the University of Utrecht. At the Joint Laboratories of the Dutch Power Companies he did research into the dispersion of air pollutants and the measuring of concentrations of the main greenhouse gases carbon dioxide and methane. Next, as policy maker at the Ministry of Housing, Spatial Planning and the Environment he coordinated the First Netherlands Memorandum on Climate Change which laid out the Dutch climate policy. In 1993 he joined the National Institute of Public Health and the Environment where he worked on the use of Kalman®ltering as a data-assimilation method to evaluate the methane budget of Western Europe and the Netherlands using high resolution concentration measurements and dispersion models. He was co-organizer of the IPCC Expert Meeting on Methods for the Assessment of Greenhouse Gas Inventory Quality in November 1997.

Jos Olivier trained at the Free University in Amsterdam in physics. He works at the Netherlands National Institute of Public Health and the Environment (RIVM) since 1990 as senior scientist and co-ordinator of international emission inventories, with a special interest in energy-related topics. Currently, he is co-convenor of the Global Emission Inventory Activity (GEIA) of IGAC/IGBP and also participates in Expert Groups on Fuel Combustion and Industrial Processes of the National Greenhouse Gas Inventory Programme of the IPCC.

Carolien Kroeze is a biologist from the University at Groningen in the Netherlands. She completed her Ph.D. study at the Amsterdam University in 1993 with a thesis entitled ``Global warming by halocarbons and nitrous oxide''. Since 1994 she works at the Wageningen Institute for Environment Climate Research (WIMEK) of the Wageningen Agricultural University, the Netherlands. Her ®eld of study includes environmental systems analysis, in particular biogeochemical processes leading to greenhouse gas emissions.