Summary

The world’s nations are moving toward agreements that will bind us together in an effort to limit future greenhouse gas emissions. With such agreements will come the need for all nations to make accurate estimates of greenhouse gas emissions and to monitor their changes over time. In this context, the National Research Council convened a committee of experts to assess current capabilities for estimating and verifying greenhouse gas emissions and to identify ways to improve these capabilities.

This report is focused on the greenhouse gases that result from human activities, have long lifetimes in the atmosphere and thus will change global climate for decades to millennia or more, and are currently included in international agreements. These include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorinated hydrocarbons (PFCs), and sulfur hexafluoride (SF6)—all of which are covered by the United Nations Framework Convention on Climate Change (UNFCCC)—and chlorofluorocarbons (CFCs), which are covered by the Montreal Protocol. The report devotes considerably more space to CO2 than to the other gases because CO2 is the largest single contributor to global climate change and is thus the focus of many mitigation efforts. Only data in the public domain (available to all without restriction or high cost) were considered because public access and transparency are necessary to build trust in a climate treaty.

The report concludes that each country could estimate fossil-fuel CO2 emissions accurately enough to support monitoring of a climate treaty (see Table S.1). However, current methods are not sufficiently accurate to check these self-reported estimates against independent data (e.g., remote sensing, atmospheric measurements) or to estimate other greenhouse gas emissions. Strategic investments would, within 5 years, improve reporting of emissions by countries and yield a useful capability for independent verification of greenhouse gas emissions reported by countries. Table S.1 shows that by using improved methods, fossil-fuel CO2 emissions could be estimated by each country and checked using independent information with less than 10 percent uncertainty. The same is true for satellite-based estimates of deforestation, which is the largest source of CO2 emissions next to fossil-fuel use, and for afforestation, which is an important sink for CO2. However, self-reported estimates of N2O, CH4, CFC, HFC, PFC, and SF6 emissions will continue to be relatively uncertain and we will have only a limited ability to check them with independent information.

METHODS FOR ESTIMATING GREENHOUSE GAS EMISSIONS

The report examines three categories of methods for estimating greenhouse gas emissions: national inventories, atmospheric and oceanic measurements and models, and land-use measurements and models. Under the UNFCCC, countries are required to inventory the human activities that cause greenhouse gas emissions, such as fossil-fuel consumption or forestry, and then multiply each activity level by its rate of emissions (emission factor). Uncertainties in the self-



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Summary T he world’s nations are moving toward agree- However, current methods are not sufficiently accu- ments that will bind us together in an effort to rate to check these self-reported estimates against limit future greenhouse gas emissions. With independent data (e.g., remote sensing, atmospheric such agreements will come the need for all nations to measurements) or to estimate other greenhouse gas make accurate estimates of greenhouse gas emissions e missions. Strategic investments would, within 5 and to monitor their changes over time. In this context, years, improve reporting of emissions by countries and the National Research Council convened a committee yield a useful capability for independent verification of of experts to assess current capabilities for estimating greenhouse gas emissions reported by countries. Table and verifying greenhouse gas emissions and to identify S.1 shows that by using improved methods, fossil-fuel ways to improve these capabilities. CO2 emissions could be estimated by each country and This report is focused on the greenhouse gases that checked using independent information with less than result from human activities, have long lifetimes in the 10 percent uncertainty. The same is true for satellite- atmosphere and thus will change global climate for based estimates of deforestation, which is the largest decades to millennia or more, and are currently included source of CO2 emissions next to fossil-fuel use, and in international agreements. These include carbon for afforestation, which is an important sink for CO2. dioxide (CO2), methane (CH4), nitrous oxide (N2O), However, self-reported estimates of N2O, CH4, CFC, hydrofluorocarbons (HFCs), perfluorinated hydro- HFC, PFC, and SF6 emissions will continue to be rela- carbons (PFCs), and sulfur hexafluoride (SF6)—all of tively uncertain and we will have only a limited ability which are covered by the United Nations Framework to check them with independent information. Convention on Climate Change (UNFCCC)—and chlorofluorocarbons (CFCs), which are covered by the METHODS FOR ESTIMATING Montreal Protocol. The report devotes considerably GREENHOUSE GAS EMISSIONS more space to CO2 than to the other gases because CO2 is the largest single contributor to global climate The report examines three categories of methods change and is thus the focus of many mitigation efforts. for estimating greenhouse gas emissions: national Only data in the public domain (available to all without inventories, atmospheric and oceanic measurements restriction or high cost) were considered because public and models, and land-use measurements and models. access and transparency are necessary to build trust in Under the UNFCCC, countries are required to inven- a climate treaty. tory the human activities that cause greenhouse gas The report concludes that each country could esti- emissions, such as fossil-fuel consumption or forestry, mate fossil-fuel CO2 emissions accurately enough to and then multiply each activity level by its rate of support monitoring of a climate treaty (see Table S.1). emissions (emission factor). Uncertainties in the self- 

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 VERIFYING GREENHOUSE GAS EMISSIONS TABLE S.1 Current and Near-Term Capabilities for Estimating National Anthropogenic Greenhouse Gas Emissions Current Major Sectors or Uncertainty for Uncertainty of Gas Activities Method Annual Emissionsa Possible Improvements in 3-5 Years Improved Methods CO2 Total anthropogenic UNFCCC 1 (developed Adopt most accurate methods in all countries 1 inventory countries)b CO2 Fossil-fuel combustion UNFCCC 1-2 (developed Adopt most accurate methods in all countries 1 inventory countries) CO2 Fossil-fuel combustion Atmospheric 4-5 Develop improved tracer-transport inversion 1-3 (annual) through new observations (14CO2, additional measurements 1-2 (decadal and models ground stations, Orbiting Carbon Observatory change) [OCO] replacement) and data assimilation CO2 Large local sources (e.g., Atmospheric 5 Develop and deploy a CO2 satellite program, 2 (annual) cities, power plants) measurements including an OCO replacement, new in situ 1 (decadal change) and models measurements in cities, and a research program to guide network design and satellite validation CO2 Agriculture, forestry, UNFCCC 1-4 (developed Adopt most accurate methods and activity data; 1-3 and other land-use inventory countries) improved emission factors through research and (AFOLU) net emissions comprehensive ecosystem inventories CO2 AFOLU Atmospheric 5 Develop improved tracer-transport inversion 4-5 measurements through new satellite and in situ observations and models CO2 AFOLU Land-use 2-4 Develop improved observations, data 2-3 measurements assimilation, and models with ecosystem and models research CO2 Deforestation and Land-use 2-4 (forest area Develop improved observations, Landsat 1-2 (forest area degradation source, measurements change) continuity, data assimilation, and models with change) afforestation sink and models 3-4 (emissions) ecosystem research 2 (emissions) CH4 Total anthropogenic UNFCCC 2-3 (developed Adopt most accurate methods and activity data 1-3 inventory countries) and improved emission factors through research CH4 Total anthropogenic Atmospheric 3-5 Develop improved tracer-transport models, new 2-3 measurements satellite and in situ observations, and improved and models emission models through research CH4 Energy, industrial UNFCCC 1-5 (developed Adopt most accurate methods and activity data 1-2 processes, and waste inventory countries) and improved emission factors through research CH4 AFOLU UNFCCC 2-4 (developed Adopt most accurate methods and activity data 2-3 inventory countries) and improved emission factors through research N 2O Total anthropogenic UNFCCC 2-5 (developed Adopt most accurate methods and activity data 2-4 inventory countries) and improved emission factors through research N 2O Total anthropogenic Atmospheric 4-5 Develop improved tracer-transport and 3-5 measurements emission models, additional observations and models N 2O Energy and industrial UNFCCC 3-5 (developed Adopt most accurate methods and activity data 3-4 processes inventory countries) and improved emission factors through research N 2O AFOLU UNFCCC 2-5 (developed Adopt most accurate methods and activity data 2-4 inventory countries) and improved emission factors through research CFCs, PFCs, Industrial processes UNFCCC 1-4 (developed Adopt most accurate methods in all countries 1-3 HFCs, and SF6 inventory countries)

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 SUMMARY TABLE S.1 Continued Current Major Sectors or Uncertainty for Uncertainty of Gas Activities Method Annual Emissionsa Possible Improvements in 3-5 Years Improved Methods CFCs, PFCs, Industrial processes Atmospheric 4-5 Develop gridded inventories, improved tracer- 2-5 HFCs, and SF6 measurements transport inversion, and measurement of and models correlated variations of gases NOTES: 1 = 100% (i.e., cannot be certain if it is a source or sink). Ranges represent emis - sion uncertainties in different countries (e.g., 1-3 means that uncertainties are <10% in some countries, 10-25% in some, and 25-50% in others). Uncertainty levels correspond to two standard deviations. Shaded rows are the self-reported values; unshaded rows are the independent checks on the self-reported values from independent methods. aUncertainties for the magnitudes of decadal changes in national emissions can be computed from the numbers in the table using standard statistical methods. Decadal changes (the cumulative change in emissions over 10 years) are reported in the rows requiring OCO measurements because early estimation biases will be reduced in calculation of a decadal change. The uncertainty of a trend is reported as a percentage of the emissions at the beginning of the decade. bBased on 2006 data reported by five developed countries (Denmark, Greece, Portugal, the United States, and Poland) with a range of institutional capabili - ties for compiling inventories. In countries where AFOLU sources dominate energy and industrial sources, the uncertainties for total anthropogenic emissions would be much higher. reported national inventories depend on the data and synthetic fluorinated gases are currently too uncertain methods used to create them, which in turn depend on to verify national emissions. each country’s institutional and technical capabilities. The third method estimates emissions of CO2, In many developed countries, uncertainties are reported CH4, and N2O using methods that are conceptually to be less than 5 percent for national CO2 emissions similar to those used for UNFCCC inventories, but can from fossil-fuel use (Table S.1), which is the dominant be made using independent information on land cover. source. With the exception of a few minor sources in It can be used to estimate emissions from both natural the industrial sector, uncertainties are much higher for sources and land-use activities, such as agriculture and other greenhouse gases and sources and vary greatly by forestry. Satellite imagery provides the remote informa- country. Uncertainties for the net CO2 emissions from tion on land surface characteristics and change. This agriculture, forestry, and other land uses and for emis- information is converted into estimates of emissions sions of CH4, N2O, PFCs, HFCs, CFCs, and SF6 from using biogeochemical models constrained by measure- all sectors can be less than 25 percent in some countries ments of greenhouse gas exchange between the land and greater than 100 percent in others. and the atmosphere. Satellite imagery is particularly The second method for estimating greenhouse gas useful for constraining forestry activities and can be emissions, called tracer-transport inversion, is based used to determine the area of deforestation and forest on atmospheric and/or oceanic measurements of the degradation. The total annual change in forest area has gases and mathematical models of air and water flow. an uncertainty of 10-25 percent in northern forests and Tracer-transport inversion estimates the net sum of up to 100 percent in tropical forests (Table S.1). Uncer- anthropogenic and natural sources and sinks. Uncer- tainties in emissions from deforestation, reforestation, tainties inferred from tracer-transport inversions are and forest degradation are high for both annual values less than 10 percent for the net global CO2 flux to the and trends, ranging from 25 to 100 percent, because of atmosphere but greater than 100 percent for anthropo- uncertainties in parameters used to translate deforested genic CO2 fluxes at national scales (Table S.1). These area into CO2 emissions. Land remote sensing can also large uncertainties arise because of the small size of the be used to estimate agricultural emissions by identify- anthropogenic signal relative to the large and uncertain ing the areas using certain agricultural practices, such natural cycles of emissions and uptake, errors in the as paddy rice. Annual uncertainties in CH4 emissions reconstruction of atmospheric transport, and the pau- from rice production are 25-50 percent, and uncertain- city and limited distribution of observations. Tracer- ties in N2O emissions from synthetic fertilizer use and transport estimates of emissions of N2O, CH4, and the manure production are 50-100 percent.

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 VERIFYING GREENHOUSE GAS EMISSIONS 2. Independent review by an international body to determine whether appropriate procedures and meth- ods are being used to prepare national inventories, to identify inconsistencies within and between reports, and to take action if problems are uncovered, and 3. An established mechanism through the Inter- governmental Panel on Climate Change (IPCC) to incorporate new information and strengthen inventory methods. Because fossil-fuel CO2 emissions can be estimated with reasonable accuracy using UNFCCC inventory methods (Table S.1) and because of the broad interna- tional support for the reporting framework, UNFCCC procedures have been, and will likely continue to be, the primary means for monitoring and verifying greenhouse gas emissions and reductions under a new international climate treaty. However, the current sys- FIGURE S.1  Global anthropogenic greenhouse gas emissions  and activities covered by the UNFCCC for 2004. These gases  tem has shortcomings for this purpose: include CO2, CH4, and N2O, as well as HFCs, PFCs, and SF6  (the  F-gases).  The  emissions  of  each  gas  are  weighted  by  its  • Developing countries do not provide regular, 100-year global warming potential. Note that including short- detailed emissions reports. lived greenhouse agents (e.g., ozone precursors) or decreasing  the  time  horizon  over  which  the  global  warming  potential  is  • The availability of independent data against calculated will decrease the fractional importance of fossil-fuel  which to check self-reported emissions is limited. CO2.  SOURCE:  Figure  1.1b  from  IPCC  (2007b),  Cambridge  • Estimates of CO2 emissions from land use, University Press. as well as emissions of other greenhouse gases, have uncertainties that are greater than the expected emis- sions reductions over a treaty’s lifetime. Although uncertainties in emissions estimates are high overall, it may not be necessary to obtain accu- The committee’s recommendations are aimed at rate measurements of all greenhouse gases to support overcoming these weaknesses and improving the capa- treaty monitoring and verification. The majority of bility to estimate and verify greenhouse gas emissions anthropogenic greenhouse gas emissions covered by in support of a climate treaty. Although some will take the UNFCCC are in the form of CO2, primarily from many years to implement, most will yield results within fossil-fuel use (~74 percent in 2004; Figure S.1) and a few years. secondarily from deforestation (estimates range from 12 to 22 percent), making these two activities an obvi- ous focus for monitoring. RECOMMENDATIONS The committee’s recommendations fall into three FRAMEWORK FOR ESTIMATING AND broad categories: (1) strengthening national green- VERIFYING GREENHOUSE GAS EMISSIONS house gas inventories, which will likely remain the core of a global monitoring and verification system; (2) The UNFCCC framework for reporting national improving the ability to independently and remotely emissions comprises three main elements: estimate national, annual fossil-fuel CO2 emissions and to monitor emission trends; and (3) developing the 1. An internationally negotiated and accepted capability to make accurate estimates of national CO2, capability to monitor national, anthropogenic emis- N2O, and CH4 emissions and CO2 removals from sinks sions of the most important greenhouse gases,

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 SUMMARY from agriculture, forestry, and other land uses, and to The lowest-tier methods (Tier 1) are simple and use independently check self-reported estimates of CO2 default values for emission factors. Tier 2 methods are emissions from deforestation, reforestation, and forest similar but use country-specific emission factors and degradation. other data, and Tier 3 methods incorporate complex approaches and models of emission sources. Universal application of top-tier methods would significantly Strengthened National Greenhouse Gas reduce uncertainties in reported emissions but would Inventories also significantly increase costs. Thus, at a minimum, The two recommendations below are intended to top-tier methods should be used for the most important improve the accuracy of national inventories and facili- greenhouse gas sources in each country. tate comparison with independent methods. The first Recommendation. Annex I countries should develop recommendation would extend reporting of UNFCCC and implement standardized methods for preparing inventories to every country, and the second would and publishing inventories that are gridded at spatial increase the spatial and temporal resolution of emission and temporal resolutions appropriate for the particu- estimates. lar greenhouse gas and source. Recommendation. UNFCCC par ties should strengthen self-reported national emissions inven- Because the atmosphere is not well mixed at coun- tories by working toward try scales, spatially and temporally heterogeneous emis- sions imply complex variations in the greenhouse gas • Extending regular, rigorous reporting and abundances both at the surface and in the atmospheric review to developing countries, and column. Independent estimates of national emissions • Extending top-tier (most stringent) IPCC based on tracer-transport models require some prior m ethods to the most important greenhouse gas knowledge of the pattern of emissions. Many Annex sources in each country. I countries are compiling spatially and temporally resolved greenhouse gas emissions, but a standard UNFCCC reporting guidelines differ for devel- method for producing gridded measurements does not oped (Annex I) and developing (non-Annex I) coun- yet exist. Gridded inventories would provide informa- tries. Annex I countries report annual estimates for tion at spatial and temporal scales better matched to all anthropogenic sources and sinks of six greenhouse the dynamics of the atmosphere and thus facilitate gases (CO2, CH4, N2O, SF6, PFCs, and HFCs) and a comparisons of reported emissions with atmospheric time series of annual estimates going back to 1990. In methods. They would be particularly useful for check- contrast, non-Annex I countries are required to produce ing reported HFC, PFC, CFC, SF6, and fossil-fuel only a periodic inventory of CO2, CH4, and N2O at the CO2 emissions. The optimal sampling scheme will vary sector (i.e., energy; industrial processes and product use; among emissions sources and greenhouse gases and agriculture, forestry, and other land use; waste) level, must balance cost and complexity against value. without a detailed source breakdown. Most developing countries have produced only one national inventory to Independent Estimation of Fossil-Fuel CO2 date. Financial and technical assistance will be required Emissions for developing countries to build an ongoing capacity to collect, analyze, and report emissions information regu- Independent verification of the self-reported fossil- larly. Significant improvements in national inventories fuel CO2 emissions of individual countries will require from 10 of the largest emitting developing countries additional atmospheric measurements and improved (e.g., China, India) could be achieved at relatively mod- tracer-transport estimates of emissions. The density est cost (about $11 million over 5 years). and coverage of measurements would be improved (1) Countries choose among three tiers of methods for by establishing new stations near cities and other large calculating emissions and removals of greenhouse gases. local sources and in sparsely sampled regions and (2)

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 VERIFYING GREENHOUSE GAS EMISSIONS by deploying a CO2-sensing satellite. Measurements of intensity of CO2 “domes” over a country’s cities and radiocarbon (14C) would enable fossil-fuel CO2 emis- power plants are consistent with reported fossil-fuel sions to be separated from non-fossil-fuel sources and emissions. A replacement mission is expected to cost sinks. Together, the new measurements and the grid- about the same as the original, $278 million. ded inventory estimates in Annex I countries would Recommendation. Extend the international atmo- provide the information necessary to reduce errors in spheric sampling network: the transport models and to overcome the noise from the natural variability of the biosphere. Information • To research the atmospheric domes of green- derived from all sources could be synthesized in a data house gases over a representative sample of large local assimilation system to produce accurate estimates of emitters, such as cities and power plants, and anthropogenic CO2 emissions and trends at national • To fill in underrepresented regions globally, scales. The three recommendations that follow repre- thereby improving national sampling of regional sent critical components of this larger effort that could greenhouse gas emissions. be deployed within 3 years. Recommendation. The National Aeronautics and The atmospheric sampling network, coordinated S pace Administration (NASA) should build and by the World Meteorological Organization’s Global launch a replacement for the Orbiting Carbon Obser- Atmospheric Watch (GAW) and operated by the vatory (OCO). National Oceanic and Atmospheric Administration (NOAA) and agencies in other countries, comprises Most fossil-fuel emissions emanate from large approximately 150 stations around the world that local sources such as cities and power plants. These measure a host of greenhouse gases from the ground, large sources increase the local CO2 abundance in the ocean surface, and air. The stations in the network atmosphere by 1-10 parts per million (ppm), a signal were purposely located away from large local emitters that is significantly larger than the signal from natural to minimize contaminating the signal from natural sources and sinks. NASA’s Orbiting Carbon Observa- sources and sinks with the signal from fossil-fuel com- tory, which failed on launch in February 2009, would bustion. However, adding ground stations or aircraft have had the high precision (1-2 ppm) and small sam- to measure emissions from power plants and cities pling area (1.29 × 2.25 km) needed to monitor these would enable the network to monitor both types of large local sources and to attribute their CO2 emissions signals. New measurements of relevant trace gases (e.g., to individual countries. No other satellite has its critical greenhouse gases, isotopes of carbon), their biological combination of high precision, small footprint, readi- fluxes, and meteorological variables would be made at ness, density of cloud-free measurements, and ability locations radiating from the center of each large emit- to sense CO2 near the Earth’s surface. ter. This research initiative would yield data needed to The OCO was designed to study natural CO2 calibrate satellite measurements of large local emit- sources and sinks. It would have demonstrated the ters (see previous recommendation), demonstrate an technology for estimating CO2 emissions from space independent capability to monitor large local emitters but would have had two limitations for a climate treaty. from ground stations and aircraft, and document long- First, with a revisit period of 16 days, it would have term shifts in fossil- versus non-fossil-fuel sources in sampled only 7-12 percent of the land surface, enabling urban and industrial regions. An initial goal could be only a small percentage of large local emissions sources to deploy instruments at a statistical sample of large to be monitored. Second, it would have had a 2-year emitters (e.g., 5-10 within a research budget of $15 mil- lifetime, providing only baseline data against which lion to $20 million per year) in the United States, but to measure future trends. A replacement for OCO international partners would ideally extend the effort launched in the first few years of the coming decade in other countries. and a subsequent mission at the decade’s end should be The GAW network is capable of achieving the able to determine if trends in the number and average sub-ppm precision in CO2 measurements necessary

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 SUMMARY to detect the atmospheric signal from widespread but which maintains the CO2 sampling network and has unconcentrated sources, such as land-use fluxes. It also the facilities and expertise to collect and process the provides an opportunity to make concurrent measure- samples; by the Department of Energy, which oper- ments of other gases that are needed to derive total ates a suitable accelerator mass spectrometer at Law- carbon emissions from a region. However, huge areas rence Livermore National Laboratory; or by another of the planet are not adequately sampled by this net- national laboratory or a university capable of making work. For example, there are only a few sites in Africa the measurements at the required precision. Interna- and South America. Expanding the GAW network to tional partners could help extend this capability to observe the variations in greenhouse gas abundances other countries, providing a more global capability for in countries with the highest emissions would greatly verifying fossil-fuel emissions. improve the independent verification of emissions Implementation of the recommendations to through tracer-transport modeling. Expanding the net- enhance atmospheric sampling and UNFCCC inven- work to obtain frequent vertical profiles from aircraft tories should lead to rapid improvements in monitoring and balloons would constrain atmospheric transport and verification. Rigorous inventories in all countries, and allow more meaningful comparisons with satellite added in situ stations, a replacement for OCO, and the 14CO2 measurements would increase the number retrievals of column-averaged CO2 than ground-based measurements alone. Negotiators should work toward of high-resolution greenhouse gas measurements by participation in the cooperative network by all major orders of magnitude, improve transport models, and e mitting countries and by groups of neighboring significantly reduce errors associated with natural smaller countries. Implementing this recommendation emissions. The loss of any one of these measurement will require financial assistance and capacity building systems would increase the uncertainty for tracer- to aid the poorest countries that dominate the most transport inversion, making the uncertainty in the undersampled regions. emissions estimates greater than the 10-year reductions likely required under an international treaty. Recommendation. Extend the capability of the CO2 sampling network to measure atmospheric 14C. Independent Estimation of Fluxes from Land-Use Sources and Sinks Estimating fossil-fuel CO2 emissions from tracer- transport inversion is complicated by poorly under- Emissions and removals from land use are highly stood natural emissions of CO2 that fluctuate and uncertain both because of uncertainty in the levels can be as large as or larger than those from fossil-fuel of activities such as deforestation or forest planting sources. Adding 14C measurements to the atmospheric and because of uncertainty in the emissions per unit sampling stations that measure CO2 (CO2 sampling of activity. Implementation of the first recommenda- network) would provide an unambiguous means to dif- tion below would provide useful estimates of land-use ferentiate between the CO2 from fossil-fuel and non- activity levels that could be used to check self-reported fossil-fuel sources because modern organic material values in UNFCCC inventories and also enable more contains radiocarbon from cosmic rays and bomb tests, accurate land-use emissions reporting from develop- but the 14C in fossil fuels has long since decayed away. ing countries. The second recommendation would It would also provide key measurement constraints to deliver improved estimates of the emissions per unit improve tracer-transport inversions. The 14CO2 mea- of activity. surements would enable fossil-fuel use to be estimated Recommendation. Establish a standing group to pro- at subcontinental scales with uncertainties low enough duce a global map of land-use and land cover change to be useful for verifying self-reported emissions. at least every 2 years. This will require a commitment The 14CO2 measurements could be made at a small to maintaining the continuous availability, in the incremental cost (~$5 million to $10 million per year public domain, of Landsat (or an equivalent satellite) for 10,000 measurements, including half in the United and high-resolution satellite imagery. States). This initiative could be undertaken by NOAA,

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 VERIFYING GREENHOUSE GAS EMISSIONS Landsat imagery provides an independent check land-use emissions of CO2, N2O, and CH4, which have on the activities that create the largest CO2 emissions the greatest uncertainties in the national inventories, from agriculture, forestry, and other land use. Estimates primarily because of high uncertainty in emission fac- of global land use and land cover must be made often tors. Continued research on the biogeochemical cycles enough to detect important changes, such as forest of these gases is needed, especially on the CO2 emis- clearing or planting (e.g., 1-2 years in most forests). sions caused by deforestation and forest degradation, A lthough individual Landsat scenes are publicly CH4 emissions from rice paddies and cattle, and N2O available, regular production of a gridded map of the emissions from fertilizer application. Research is also world would allow country-specific information to be needed on the natural cycles of CO2, N2O, and CH4 extracted on a routine basis. Such a map would enable because natural emissions interfere with the detection countries to validate land-use emissions and would of anthropogenic signals. This research has to be sup- provide a basis for improving land-use inventories in ported by ecosystem flux observations and ecosystem developing countries. inventories. For example, eddy covariance towers mea- The maps could be produced by the U.S. Geological sure the exchange of carbon between vegetation and the Survey—which has a long history of creating, distribut- atmosphere at more than 100 sites in the United States. ing, and archiving Landsat products—NASA, or a uni- The towers provide valuable information on trends in versity. For the satellite platforms, either NASA has to ecosystem responses to management and climate, and keep a successor to the Landsat Data Continuity Mis- a subset could be maintained to support verification sion in its mission queue or another agency will have research at relatively low cost (~$100,000 per station to maintain the capability. The moderate-resolution per year). (30 m) imagery should be supplemented with statistical As with fossil fuels, gridded inventories of emis- samples of high-resolution (1 m) imagery to monitor sions from agriculture, forestry, and other land use logging, forest degradation, and certain agricultural would facilitate cross-checks with other kinds of mea- practices (e.g., rice cultivation). Such high-resolution surements recommended above. Currently, the only data could be obtained either by adding the capability intensive U.S. ecosystem inventory focuses on forests to the Landsat platform or by acquiring unrestricted (the U.S. Department of Agriculture’s [USDA’s] For- targeted samples from government or commercial est Service Inventory and Analysis program). Making satellites. Without this medium- and high-resolution annual measurements of all the major carbon pools and imagery, we will lose our capability to check the domi- their trends in other ecosystems—including croplands, nant source of agriculture, forestry, and other land-use pastures, and nonforested natural ecosystems—would (AFOLU) CO2 emissions. greatly reduce their emissions uncertainties, which are commonly greater than 100 percent. The cost of Recommendation. An interagency group, with broad a comprehensive ecosystem inventory would likely be participation from the research community, should substantially less than the cost of USDA’s forest inven- undertake a comprehensive review of existing infor- tory ($65 million per year), which includes more field mation and design a research program to improve sites (more than 100,000 plots) than are necessary for a nd, where appropriate, implement methods for greenhouse gas monitoring. estimating agriculture, forestry, and other land-use emissions of CO2, N2O, and CH4. IMPLICATIONS FOR AN INTERNATIONAL CLIMATE AGREEMENT Methods for producing greenhouse gas invento- ries evolve as more is learned about how to measure International agreements to limit future green- and translate activities into emissions. Improvements house gas emissions will require that countries be able to U.S. inventory methods could eventually become to monitor and verify emissions as well as removals part of UNFCCC reporting through the established by sinks. Within a few years of their implementation, process managed by the IPCC. The most important the above recommendations would establish rigorous component to improve is agriculture, forestry, and other annual national inventories of greenhouse gas emissions

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 SUMMARY as the core of a monitoring and verification system. sions of CH4 and N2O from all important AFOLU Procedural verification by an independent interna- sources, even for estimates from improved inventory tional body would be supplemented by independent methods. a nd transparent checks on fossil-fuel combustion In addition to improving estimates of AFOLU and deforestation, which together are responsible for emissions, the satellite surveys and inventory improve- about three-fourths of all UNFCCC greenhouse gas ments recommended in this report would allow moni- emissions. Targeted research would ultimately lead to toring of individual projects aimed at creating carbon improved monitoring and verification of all greenhouse sinks to offset emissions. The ecosystem inventories gases. would provide the baselines against which an offset Realistic near-term goals are to reduce uncer- project could demonstrate its effect on carbon uptake, tainties of fossil-fuel CO2 emissions to less than 10 which is necessary because carbon fluxes to and from percent in annual, national inventories and to provide ecosystems fluctuate with the weather and other fac- checks on these emissions, especially from large, high- tors. They would also provide a means for monitoring emitting countries—such as the United States, China, natural sinks and sources on unmanaged land. or India—using independent methods that are equally An additional benefit of the proposed expansion accurate. Although national inventories of AFOLU of the system to monitor greenhouse gases is that it emissions are currently relatively inaccurate, a realistic would enhance our ability to monitor and study natural near-term goal is to reduce uncertainties of AFOLU carbon sinks on land and in the oceans. The natural CO2 emissions and to be able to estimate remotely the sinks are not counted in UNFCCC inventories, but most important activities that cause these emissions they currently absorb about half of greenhouse gas (deforestation, afforestation, and forest degradation) emissions (approximately evenly divided between land with <10 percent uncertainty. In contrast, fundamental and oceans). Because they are so large, changes in the research is needed before it will be possible to estimate natural sinks could weaken the impact of a treaty. The national emissions of N2O, CH4, and the synthetic proposed additions to atmospheric sampling, invento- fluorinated gases with reasonable accuracy using inde- ries, and tracer-transport inversion would significantly pendent methods. The need for fundamental research improve our ability to monitor and study the natural is especially evident in the high uncertainties for emis- sinks.

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