Five years ago, there was widespread celebration after world leaders signed up to the Paris Agreement. However, despite pledging to pursue efforts to limit global warming to just 1.5 °C above pre-industrial levels, emissions have continued to rise. Many are saying the COP26 conference in late 2021, where world leaders will meet again, is a make-or-break moment to turn words into action. What needs to be achieved? What is the cost of failure? And where are the signs of hope for success? Justin Rowlatt and Navin Singh Khadka talk to Laurence Tubiana, CEO of the European Climate Foundation (ECF), who was previously France’s climate change ambassador and special representative for COP21, and a key architect of the landmark Paris Agreement. They are also joined by Christiana Figuerres, who was Executive Secretary of the United Nations Framework Convention on Climate Change (UNFCCC) between 2010 and 2016, and Dr Emily Shuckburgh, director of Cambridge Zero at the University of Cambridge, and reader in environmental data science at the Department of Computer Science and Technology. Producer: Zak Brophy Researcher: Soila Apparicio Editor: Ravin Sampat Sound Design: David Crackles