The ecological threat of planetary warming drives the international movement and campaigns attempting to turn back the rapid pace of climate change. As in other types of threat-induced collective action, scientists, activists, and ordinary people perceive that environmental systems and human civilization will be made worse off without mass mobilization in the present. Indeed, climate change may be the principal existential threat faced by humanity. The widespread nature of the threat, which encompasses inhabitants of the entire planet, creates the potential for assembling broad coalitions seeking a more sustainable future. The most successful organizing drives against the ongoing threat of global warming have appropriated resource infrastructures from preexisting environmental NGOs and transnational global economic justice networks along with everyday organizations, such as public schools (e.g., in the youth-based Fridays for Future and Sunrise movements), and social media.