There is a surge in global knowledge-making efforts to inform environmental governance. This article synthesises the current state of the art of social science scholarship about the generation and use of global environmental knowledge. We focus specifically on the issues of scale. -. providing globalized representations of the environment. -. and relevance. -. providing knowledge in a form that is considered usable for decision-making. Using the examples of the Intergovernmental Panel on Climate Change, the Intergovernmental Platform on Biodiversity and Ecosystem Services and the Millennium Assessment, the article discusses what policy relevant global knowledge does: how it represents the environment, and how this specific form of knowledge connects with governance and policy.