This article examines the imperative for human rights under international law as a foundation for the public health response to climate change. Part I outlines the threats of climate change to human health and life, and describes the origins and early evolution of climate change as a human rights issue under international law. Part II summarises the current international legal framework for climate action, including recent landmark judicial decisions that have solidified government obligations to respond. Part III explores why the international response to climate change has nonetheless been inadequate. With a rising imperative for action, Part IV analyses emerging opportunities for public health advocates and other actors to drive urgent climate action. It concludes that the public health community, working with civil society organisations and communities affected by climate change, legal advocates, governments and other actors, should respond with political and legal action grounded in human rights under international law – bringing together scientific knowledge, ethics, practical expertise, wisdom and compassion