In contrast to many discussions based on annual emissions, this article presents calculations and projections of cumulative contributions to the stock of atmospheric CO2 by the major players, China, Europe, India, Japan and the USA, for the period 1900-2080. Although relative contributions to the climate problem are changing dramatically, notably due to the rapid industrialization of China, long-term responsibilities for enhanced global warming have not been transparently quantified in the literature. The analysis shows that if current trends continue, by the middle of this century China will overtake the USA as the major cumulative contributor to atmospheric concentrations of CO2. This has enormous implications for the debate on the ethical responsibilities of the major greenhouse gas emitters. Effective climate policy will require both the recognition of shared responsibility and an unprecedented degree of cooperation. © 2008 Earthscan.