Climate change is a global problem but why do only some international organizations in the field of international security address it as a security threat? This paper argues that we urgently need to make better sense of how states can live in the Anthropocene (i.e. the notion that our current times is an age of human-caused planetary transformation, including climate change, loss of biodiversity, and environmental degradation) but in practice mostly act as if they don’t. The main argument of the paper is that the fact that many militaries, diplomats, and state representatives are by now likely aware of the adverse effects of climate change, yet are still acting to preserve the status quo, invites us to explore the Anthropocene as politics. To do so, this paper draws on international practice theory and the concept of communities of practice to develop an analytical framework to study how climate risks become governable in practices of epistemic co-production that establish common understandings which makes it possible for practitioners to imagine a problem, analyze it, and propose solutions. The framework is appliedto study how EU climate security is being shaped, with a particular focus on recent policyactions within the Common Security and Defence Policy (CSDP) devised to address the security implications of climate change.