This chapter provides a comprehensive narrative of the central role of Stockholm in the evolution of climate change science, one of the most significant scientific specializations relevant for global environmental governance.. With roots in Stockholm-based Svante Arrhenius’ still remarkably precise calculations in the 1890s of the magnitude of the greenhouse effect, the narrative shows how Carl-Gustaf Rossby, after an initial career in the United States, returned to Sweden from where he managed to build and maintain institutions and networks on both sides of the Atlantic in the postwar decades and secure a stable base for a new understanding of the geophysics and chemistry of climate. Swedish climate science, including expertise in glaciology, became recognized as world-leading, with an early and firm institutional foothold being established at Stockholm University. Of global environmental relevance, it produced entrepreneurial science diplomats like Bert Bolin, a climate scientist and founding chair of the Intergovernmental Panel on Climate Change (IPCC). This trust-building combination of institutions, networks, and policies enabled the continued evolution of Stockholm-based innovative platforms for global environmental governance leadership.