The Cost of Ambiguity and Robustness in International Pollution Control Anastasios Xepapadeas 1 Athens University of Economics and Business and Beijer Fellow xepapad@aueb.gr January 8, 2011 1 I would like to thank an anonymous reviewer, Stergios Athanassoglou and the participants of the Climate Change and Common Sense workshop in Honour of Tom Schelling, Manchester 20-22 October 2010, for valuable comments and suggestions on earlier drafts of this paper.