Many were rightly sceptical of the Paris Agreement’s choreographed performance of success, given its reliance on theoretical carbon trading, fantastical Negative Emission Technologies (NETs), and voluntary national ‘contributions’. But was COP21 the high-water mark of climate co-operation? Can COP26 rekindle the internationalist spirit required to keep even the idea of a globally co-ordinated effort alive, in the face of resurgent nationalism and the proliferation of apparently more immediate crises? This article explores the chances of COP26 reinvigorating international co-operation, and with it the flagging credibility of the whole Paris process. It focuses in particular on the Paris Agreement’s controversial Article 6 rules on voluntary carbon trading, and the urgent need to prevent emissions traded across international borders from counting towards Nationally Determined Contributions (NDCs)