Mark Lynas’ 2008 book Six Degrees soon became a must-read for anyone concerned about the speed and severity of global heating. In its 2020 incarnation, updated to reflect the most recent scientific research and projections, Lynas’ analysis of how the world will change with each degree of warming pulls no punches about what’s at stake. But in leaving space for optimism and hope, the evidence he sets out becomes a powerful call to action as well as a timely and terrifying warning.