This report is a synthesis of the debate carried out with Prof. John Roemer in the conference series “Facing climate change” organised by Catalunya Europa Foundation in the context of the Re-City project. This session, entitled "How nations can cooperate to meet the climate-change challenge" consisted of a public lecture, a seminar with participants from the academic sector of Catalonia and a lunch-debate that brought together personalities from the economic, social, political and business sector of Catalonia.