Scientists in the IPCC and other bodies suggest that to avoid severe environmental and human impacts (see figure 1), the rise in mean surface temperature by the end of this century should be kept to less than 2°C (3.6°F) above pre-industrial levels. This will require a switch to a low-emitting global economy and is a challenging, though achievable, goal. To reach it the world must define global emission reduction targets (see figure 2) – and associated national commitments – for 2030 and 2050 and gradually reduce emissions to meet those targets.