Climate change will affect security of individuals and populations as well as the security of states. The article reviews evidence on the scope and nature of the climate change challenge; reviews how these impacts manifest themselves in insecurity at diverse scales; and examines evidence on the political economy of adaptation responses to these impacts. I argue that climate security has been framed in public and policy debate over climate change such that climate change impacts are a threat to nation states in terms of their interests, their economies and their borders. This framing crowds out, subverts and constrains framing in terms of human-well being. I suggest that human security provides a broader and more encompassing notion of climate security than that focussed on security of states. Here, climate security focuses on the idea of freedom from harm and fear of individuals and communities and the capability to adapt to any imposed harm. From that human security perspective, the central analytical issues become those of vulnerability, adaptation and justice.