We perform content analysis on Carbon Disclosure Project (CDP) responses from 2003 to 2010, focusing on the extent to which firms account for indirect emissions and have exhibited convergence in carbon reporting. We also examine standardization in reporting and the variation of reporting behavior across industry and country. We find that the CDP has produced a mixed record of improved transparency. In some areas, such as Scope 2 emissions, the CDP has demonstrated an increase in transparency in later years. However, the transparency and quality of direct emissions and Scope 3 emissions have not improved over time. Japanese and European Union firms have increased transparency, while American firms have decreased transparency. Energy‐intensive industries have either increased transparency or remained the same, while less energy‐intensive industries have become less transparent. We demonstrate some evidence of a learning effect among firms after participating in the CDP survey. Copyright © 2012 John Wiley & Sons, Ltd and ERP Environment.