During its 20 years of publication, the journal Global Environmental Change has given visibility and coherence to the eponymous research paradigm. Global environmental research has brought forth new kinds of knowledge about the multi-scale interactions between physical and social dimensions of the environment. This essay reflects on some of the problems with making and governing these global kinds of knowledge, as suggested through the perspectives of a nascent geography of science. I use climate change - an emblematic theme of global environmental change research over the last 20 years - to examine three facets of the global environmental change paradigm: making global kinds of knowledge, globalising environmental values and the governance of knowledge-making. New global kinds of knowledge have gained power and visibility in contemporary scientific, public and political fora and yet such knowledge can be 'brittle', easily cracked and broken. A geography of global environmental change knowledge therefore demands we turn our attention away from the globalising instincts that so easily erase difference and collapse meaning, and instead concern ourselves with understanding the relationships between knowledge-making and human culture in evolving places. Only then will we recognise the ambiguities, voids and blind spots in our understanding of the world's complexity.