The aim of this paper is to analyze the international polarization of per capita CO2 emissions with exogenous groups based on the Z-K measure (Zhang and Kanbur, 2001), whose main differential advantage lies on its factor-decomposability. In particular, we propose to use the factor decomposition based on Kaya (1989) by applying the methodology suggested by Duro and Padilla (2006). The main empirical results derived can be summarized as follows. First, the international polarization of emissions has significantly decreased over time during the period 1971-2006, when regional sets of nations based on the IEA structure are used; secondly, this decrease can be almost exclusively based on the reduction of the average dissimilarities among sets of countries and not due to a within-group cohesion process. Lastly, this reduction can be mainly attributed to the role of the affluence factor, and to a lesser extent, to the energy intensities. Thus, and given the values achieved for the different components, it seems that further reductions in the international polarization will continue be based on the economic convergence among groups. (C) 2010 Elsevier Ltd. All rights reserved.