Climate change poses a series of challenges to existing perceptions of what constitutes justice in global politics. In response to increasing environmental destruction in poor countries, climate justice-based arguments on how to responsibilize the largest carbon emitters have developed parallelly in academia and in activist circles. This chapter documents key differences between the demands of climate justice as they have developed in ethics, political theory and in international climate movements respectively. Despite these differences, both the theoretical and the activist conception of climate justice are challenged by the renewed sense of urgency as GHG emissions have not begun to drop significantly. New groups of activists translate the concept of climate emergency from the biophysical indicators to a political demand with a short deadline. We argue that both the ethical research agenda and the activists' demands for climate justice have gone through a period of renegotiation as a consequence of the confrontation with developments in global policymaking. This has both resulted in pressure to water down basic principles of climate justice and to alter the focus from transnational networks of solidarity to rapid state-driven decarbonization.