This chapter highlights the key differences between the domains of “climate” and “security”. It then describes how notions of security have broadened in the last decades to encompasses environmental considerations, followed by a synthesis of how researchers have tried to understand climate-security links. The chapter highlights the elusiveness of consensus in research and considers how nevertheless the efforts to securitize climate change have accelerated, climate-security links have gained political prominence, and national and international institutions have established workstreams to address them. The chapter concludes by highlighting the contradictory co-existence of expectations of science-drivenness of climate change, disputed evidence and accelerating securitization – in other words, why are efforts to securitize climate change – a science-based issue – intensifying regardless of evidence disputes? This contradictory co-existence indicates that there is a disconnect between expectations of science-drivenness and political practice. Empirical studies of the role of knowledge in the context of specific conflicts can help understand this contradiction in the climate-security debates.