This article relies on data from the 2005–09 World Values Survey to examine individual and cross-national variation in perception of the seriousness of global warming. The data show that a large majority of the public in all countries are concerned about the problem of global warming and that this assessment is part of a broader concern for global environmental issues. The widespread concern implies that global warming has the potential to generate mass political participation and demand for political action. Motivated by a value-based approach to the study of public opinion, the article shows that perception of the seriousness of the problem is positively correlated with high education, post-materialism, and a leftist position on the left–right scale. In addition, religious beliefs are important, suggesting that there is some diversity in the value basis for the issue and that it is not only linked to the ‘new-politics’ perspective. Variation across nations in wealth and CO2 emissions is not significantly related to the publics’ assessments of the problem, and, somewhat counterintuitively, people from countries relatively more exposed to climate-related natural disasters are less concerned about global warming. We suggest possible explanations for the latter finding and discuss our results in relation to the broader literature on environmental change, insecurity, and the potential for conflict.