All this is based on a clear view of the science that is consistent with advice from the Intergovernmental Panel on Climate Change (IPCC). It has identified man-made emissions of CO₂ as the principal driver of the rise in temperature over the past century (about 0.7C). In one scenario, where we carry on as usual, the central projection for the rise is 1-1.5C by mid-century and 3C by end-century. However, if temperature rises more than 2C, serious impacts such as rising sea levels, drought, storms and damage to food supply will occur. The 80 per cent figure, therefore, is set at the level considered necessary to prevent this threshold being crossed.