This paper highlights the basic economic principles behind the policy recommendations in the Stern Review and takes forward the analysis and proposals of the Review. It is written in the light of developments since the Review was published, reflecting on interaction with policy makers and analysts around the world and other commentators on the Review. Its authors argue that across the world, progress of understanding and developing the necessary policy response to climate change has been especially rapid in the last few months. Building on these developments and the Review team’s initial analysis, they outline a policy programme going forward for international collective action to tackle climate change.