The implications for Green political theory of the international community’s failure to avert dangerous warming are evaluated. An emerging conflict is identified between the Green-romantic value of restraint and the Green-rationalist value of protection, between a desire to preserve biotic systems and a distrust of scientific solutions to problems that are intrinsically social. In response, approaches are outlined that can help to navigate the current period of overshoot beyond safe planetary boundaries by informing choices among bundles of environmental harms. An ethic of restraint, encompassing non-domination and post-materialist values, can validly be justified without reference to ecological catastrophe. Meanwhile, in respect of preservation from climate-linked harms, the need for cooperation in support of scalable abatement measures suggests the necessity of accelerated research into ‘breakthrough’, low-emissions energy technologies. However, since technophilic preservationism is incompatible with existing environmental ‘logics of practice’, this strategy must mobilise political support outside the traditional environmental movement.