Swedish climate scientist Johan Rockström led a team which introduced the world to the idea of the nine planetary boundaries that we must stay within. Breach the boundaries, including climate change, biodiversity, pollution and fresh water, and we risk irreversible damage to our life support system. Rockstrom is increasingly concerned about the collapse of the Atlantic Ocean circulation system known as AMOC, once considered a far-fetched plot device in disaster movies. Rockström spoke to Guyon Espiner.