In this paper we draw on Science and Technology (STS) approaches to develop a comparative analytical account of the Intergovernmental Panel on Climate Change (IPCC) and the Intergovernmental science-policy Platform on Biodiversity and Ecosystem Services (IPBES). The establishment of both of these organizations, in 1988 and 2012 respectively, represented important ‘constitutional moments’ in the global arrangement of scientific assessment and its relationship to environmental policymaking. Global environmental assessments all share some similarities, operating at the articulation between science and policy and pursuing explicit societal goals. Although the IPCC and IPBES have different objectives, they are both intergovernmental processes geared towards the provision of knowledge to inform political debates about, respectively, climate change and biodiversity loss. In spite of these similarities, we show that there are significant differences in their knowledge practices and these differences have implications for environmental governance. We do this by comparing the IPCC and IPBES across three dimensions: conceptual frameworks, scenarios and consensus .We argue that, broadly speaking, the IPCC has produced a ‘view from nowhere’, through a reliance on mathematical modelling to produce a consensual picture of global climate change, which is then ‘downscaled’ to considerations of local impacts and responses. By contrast IPBES, through its contrasting conceptual frameworks and practices of argumentation, appears to seek a ‘view from everywhere’, inclusive of epistemic plurality, and through which a global picture emerges through an aggregation of more placed-based knowledges. We conclude that, despite these aspirations, both organizations in fact offer ‘views from somewhere’: situated sets of knowledge marked by politico-epistemic struggles and shaped by the interests, priorities and voices of certain powerful actors. Characterizing this ‘somewhere’ might be aided by the concept of institutional epistemology, a term we propose to capture how particular knowledge practices become stabilized within international expert organizations. We suggest that such a concept, by drawing attention to the institutions’ knowledge practices, helps reveal their world-making effects and, by doing so, enables more reflexive governance of both expert organizations and of global environmental change in general.