Copyright: © 2025 Cámara-Aceituno J et al.Background: The analysis of the evolution of CO 2 emissions of a given region is of key interest to understand the effect of past policies and to better design the future ones. The 27 European Union countries (EU) constitute a unique region for such a study because it has a strong common policy for reducing CO 2 emissions and, therefore, it is of great interest to measure its influence. Methods: This study employed the logarithmic-mean Divisia index (LMDI) technique, an expanded version of the Kaya identity, the Tapio decoupling method, and convergence and cluster analysis. This study examined the driving forces behind CO 2 emissions, including population, economic activity, energy intensity, and energy sources. The period under study is 1990–2021. Results: The results obtained for the 27 member states were diverse. However, some common patterns have emerged: economic activity is the primary driver of CO 2 emissions, while energy intensity plays a crucial role in reducing emissions, even more than the contribution from renewable energies. The analysis reveals a consistent decline in recent years attributed to rigorous EU policies to meet the CO 2 emissions target outlined in its Nationally Determined Contribution (NDC). Notably, countries with longer-standing EU memberships tend to exhibit more positive outcomes. Additionally, a study on the convergence of the 27 countries reveals the existence of several clusters and clubs of convergence. Conclusions: This study offers valuable insights for evaluating the energy and environmental policies of EU countries, serving as a valuable resource for energy policymakers worldwide.