This paper analyzes the theoretical and pragmatic implications for international relations and world politics of the new holistic approach to climate change articulated by Pope Francis in the Encyclical Laudato Si', particularly through the notion of "integral ecology". It is not my intention to offer an exegesis of the Papal document. I will rather try to illustrate and discuss its planetary hermeneutics. I emphasize that the Encyclical's perspective is not exclusively normative, and that, within the dynamic interplay between social structure and human agency, it can also be considered as a call to action. In this context, I suggest that both International Relations Theory and global politics have much to learn from the fundamental claims of contemporary religions in relation to climate disruption. In particular, Pope Francis' document, far from being just a new chapter in the unfolding process of the "greening" of religions, raises the issue of the sustainability of the present world system. Therefore, I contend that the perspective of the Encyclical calls for a radical transformation of international relations, since it emphasizes the deep implications of environmental issues on the entire spectrum of security, development, economic and ethical challenges of contemporary world politics. Against this backdrop, my objective is to connect the main tenets of the Encyclical to the environmental turn in International Relations Theory and to the new epistemological challenges related to the paradigm shift induced by the new planetary condition of the Anthropocene and the relevant questions arising for a justice encompassing the humanity-earth system. The Encyclical seems to suggest that practicing sustainable international relations means exiting the logic of power or hegemony, while simultaneously operationalizing the concept of care.