Abstract
While speaking truth to power has long been a major theme in political science and policy studies, commentators are increasingly skeptical about whether modelers and scientists are capable of developing truth, and whether power ever listens to them anyhow. This paper asks when does power listen to truth, and what lessons may be drawn from the last thirty years of multilateral environmental governance for improving the prospects for scientific advice for sustainable development? It focuses on the limited notion of truth called 'usable knowledge' and elaborates the political and institutional channels by which usable knowledge may be developed and better circulated and applied by policy-makers.