This paper starts from the premise that international practices are neither stable nor universal but are in fact the product of time and space. It analyzes the processes of formalization and change in international practices using the case of the Intergovernmental Panel on Climate Change (IPCC), an intergovernmental institution producing regular assessment of the state of the knowledge on climate change. The IPCC is particularly interesting because of the numerous external and internal controversies that it has faced since its establishment in 1988 and the institutional and organizational changes that they triggered. The paper highlights the potential of controversies as methodological occasions to observe the situatedness of international practices and trace change over time. Controversies represent moments of contention in which the normalizing and universalistic effect of routines and procedures is momentarily suspended, thus facilitating the investigation of the particular space and time in which practices evolve.