In 1992, the United States and other parties, including both developed and developing nations, agreed to try to limit dangerous human interference with the climate by participating in the United Nations Framework Convention on Climate Change. The parties agreed, among other things, to report on their emissions of carbon dioxide and five other gases whose buildup in the atmosphere is believed to affect the climate. The parties developed standards for these reports and processes for periodically evaluating the reports. Expert teams selected by the parties review the developed nations' reports; staff of the Framework Convention's administrative arm (the Secretariat) assess developing nations' reports. GAO agreed to describe the results of the most recent reviews and assessments of reports from selected economically developed and developing nations, as well as the parties' plans to improve the reports. For the developed nations, GAO agreed to study four geographically dispersed nations with high levels of emissions--Germany, Japan, the United Kingdom, and the United States. For the developing nations, GAO studied China, India, and Mexico, which also have high emissions levels and are geographically dispersed. These nations are not representative of others; therefore, GAO's findings cannot be generalized.

In their most recent reviews, expert teams found that the United Kingdom's 2000 and 2002 reports on greenhouse gas emissions and the United States's 2000 report were largely complete, although the teams noted minor findings, such as the lack of information on quality assurance methods, which the nations were encouraged, but not required, to include in their submissions. In contrast, they found that Germany's 2001 and Japan's 2000 reports lacked critical elements, such as the required documentation that was essential to understanding them. Preliminary checks found that all four nations' 2003 reports were largely complete. Secretariat staff have not assessed inventories from China and India because these nations have not submitted them. According to Secretariat records, China and India plan to submit inventories in February 2004 and November 2003, respectively. Secretariat staff assessed Mexico's most recent inventory, but they reported few details about it because their policy is to consolidate the findings of all the developing nations' inventories submitted during a year. To improve the inventories, the parties are changing the reporting standards and review process. For example, starting in 2004, developed nations must present their inventory reports in a standardized format to facilitate review, and developing nations must report data for more years and gases than before. Also, in 2003, the parties began conducting more rigorous reviews of developed nations' inventories, but no such changes for developing nations are planned.