Greenhouse gases can affect the climate by trapping energy from the sun that would otherwise escape the earth’s atmosphere. Various human and natural activities emit greenhouse gases, with the production and burning of fossil fuels for energy contributing around two-thirds of man-made global emissions in 2005 (see fig. 1). The remaining third includes emissions from industrial processes, such as steel production and semiconductor manufacturing; agriculture, including emissions from the application of fertilizers and from ruminant farm animals; land use, such as deforestation and afforestation; and waste, such as methane emitted from landfills. Carbon dioxide is the most important of the greenhouse gases affected by human activity, accounting for about three-quarters of global emissions in 2005, the most recent year for which data were available. Carbon dioxide (other) The 14 nations in our study differ greatly in the quantity of their greenhouse gas emissions, the sources of those emissions, and their per- capita incomes. Emissions in 2005 ranged from about 7 billion metric tons of carbon dioxide equivalent in China and 6 billion metric tons in the United States, to about 300 million metric tons in Malaysia. The contribution of various sectors to national emissions also differed across nations, with emissions from energy and industrial processes accounting for more than 70 percent of emissions in most industrialized nations and 20 percent or less of emissions in Indonesia and Brazil (see fig. 2). The Convention established a Secretariat that, among other things, supports negotiations, coordinates technical reviews of reports and inventories, and compiles greenhouse gas inventory data submitted by nations. The Secretariat has about 400 staff, located in Bonn, Germany, and its efforts related to national inventories are funded by contributions from the Parties. For the Secretariat’s core budget, Parties provided $52 million for the 2008-2009 budget cycle, of which the United States contributed $9.5 million ($3.76 million in 2008 and $5.75 million in 2009), excluding fees. The Convention requires Parties to periodically report to the Secretariat on their emissions of greenhouse gases resulting from human activities. Parties do not generally measure their emissions, because doing so is not generally feasible or cost effective, and instead estimate their emissions. To help Parties develop estimates, the IPCC developed detailed guidelines—which have evolved over time—describing how to estimate emissions. The general approach is to use statistics on activities, known as activity data, and estimates of the rate of emissions per unit of activity, called emissions factors. For example, to estimate emissions from passenger cars, the inventory preparers could multiply the number of gallons of gasoline consumed by all cars by the estimated quantity of emissions per gallon. The IPCC guidelines allow nations to use various methods depending on their data and expertise. In some cases, with adequate data, estimates of emissions can be as accurate as direct measurements, for example for carbon dioxide emissions from the combustion of fossil fuels which contribute the largest portion of emissions for many nations. The Parties agreed to the following five principles for inventories from Annex I nations: Transparent. Assumptions and methodologies should be clearly explained to facilitate replication and assessment of the inventory. Consistent. All elements should be internally consistent with inventories of other years. Inventories are considered consistent if a Party uses the same methodologies and data sets across all years. Comparable. Estimates should be comparable among Parties and use accepted methodologies and formats, including allocating emissions to the six economic sectors defined by IPCC—energy, industrial processes, solvent and other product use, agriculture, land-use change and forestry, and waste. Complete. Inventories should cover all sources and sinks and all gases included in the guidelines. Accurate. Estimates should not systematically over- or underestimate true emissions as far as can be judged and should reduce uncertainties as far as practical. Annex I nations are to submit inventories annually consisting of two components—inventory data in a common reporting format and a national inventory report—both of which are publicly available on a Web site maintained by the Secretariat. The common reporting format calls for emissions estimates and the underlying activity data and emissions factors for each of six sectors—energy, industrial processes, solvent and other product use, agriculture, land-use change and forestry, and waste. It also calls for data on the major sources that contribute to emissions in each sector. The inventory data are to reflect a nation’s most recent reporting year as well as all previous years back to the base year, generally 1990. The 2010 reporting format called for nearly 150,000 items of inventory data and other information from 1990 through 2008. The common format and underlying detail facilitate comparisons across nations and make it easier to review the data by, for example, enabling automated checks to ensure emissions were properly calculated and to flag inconsistencies in data reported over time. The national inventory report should explain the development of the estimates and data in the common reporting format and should enable reviewers to understand and evaluate the inventory. The report should include, among other things, descriptions of the methods used to calculate emissions estimates, the rationale for selecting the methods used, and information about the complexity of methods and the resulting precision of the estimates; information on quality assurance procedures used; discussion of any recalculations affecting previously submitted inventory data; and information on improvements planned for future inventories. The Secretariat coordinates an inventory review process that, among other things, assesses the consistency of inventories from Annex I nations with reporting guidelines. The purposes of this process are to ensure that Parties are provided with (1) objective, consistent, transparent, thorough, and comprehensive assessments of the inventories; (2) adequate and reliable information on inventories from Annex I Parties; (3) assurance that inventories are consistent with IPCC reporting guidelines; and (4) assistance to improve the quality of inventories. In supporting the inventory review process, the Secretariat provides scientific and technical guidance on inventory issues and coordinates implementation of Convention guidelines. Inventory reviews are supervised by the head of the reporting, data, and analysis program within the Secretariat. By June each year, the Secretariat checks each inventory for completeness and format, called an initial check, and conducts a preliminary assessment before submitting it to an inventory review team for examination. The Secretariat assembles inventory review teams composed of scientists and other experts from around the world to review inventories from all Annex I Parties according to the Convention’s review guidelines. The inventory review teams assess inventories in September by reviewing activity data, emissions factors, methodologies, and other elements of an inventory to determine if a nation has employed appropriate standards, methodologies, and assumptions to compute its emission estimates. From February through March, the inventory review teams develop inventory review reports outlining their findings. In accordance with the Convention’s principle of common, but differentiated responsibilities, non-Annex I nations’ inventories’ format and frequency differ from those for Annex I nations. The reporting guidelines, which have evolved over time, encourage non-Annex I nations to use the IPCC methodological guidelines in developing their inventories, but do not specify that they must be used. While they submit inventories to the Secretariat, non-Annex I nations’ inventories are not stand-alone documents. Rather, a non-Annex I nation’s inventory is a component of its national communication, a report that discusses steps the nation is taking or plans to take to implement the Convention. Non-Annex I nations do not have to use the common reporting format or submit a national inventory report. Moreover, they do not submit an inventory each year, but instead the Parties to the Convention determine the frequency of their submissions. Parties have not agreed on a regular frequency for non- Annex I nations to submit their inventories. According to expert inventory review teams, the 2009 greenhouse gas inventories of seven Annex I nations were generally comparable and of high quality, although some of their emissions estimates have substantial uncertainty. In contrast, we found that the most recent inventories from seven non-Annex I nations, although they met reporting guidelines, were of lower quality and generally not comparable. Finally, experts identified several barriers to improving inventory comparability and quality. All of the inventories submitted in 2009 by the seven selected Annex I nations were generally comparable and of high quality, according to the most recent inventory reviews conducted by expert review teams under the Convention. The reviews found that six of the seven nations— Australia, Canada, Japan, Russia, the United Kingdom, and the United States—used appropriate methodologies and data, employed reasonable assumptions, and did not systematically either over- or underestimate emissions in their 2009 inventories (covering data from 1990 through 2007). The one exception to this was Germany’s 2009 inventory, which the review team said did not follow guidelines for its agricultural emissions, in part because of its attempt to use newer methods. The change significantly reduced estimated emissions from agriculture, though the sector is a relatively small contributor to Germany’s total emissions. One inventory reviewer familiar with Germany’s 2009 inventory said its overall quality was fairly good. In addition, Germany appears to have addressed the issue of its agricultural emissions in its 2010 inventory submission by returning to its previous methods, which had the effect of increasing its estimates of emissions from agriculture. Experts said that the seven selected inventories were generally comparable, which means they generally used agreed-upon formats and methods. In addition, nine experts we interviewed said they were of high quality and did not have major flaws. These findings show significant improvement in the seven nations’ inventories since our 2003 report. For example, we reported in 2003 that both Germany’s 2001 submission (covering data through 1999) and Japan’s 2000 submission (covering data through 1998) lacked a national inventory report, a critical element that explains the data and methods used to estimate emissions. Nearly all Annex I nations—including Germany and Japan—now routinely submit this report. In addition, the review team found Russia’s 2009 inventory showed major improvements.