This article offers a concise account of the known science underpinning the greenhouse effect and global warming. The greenhouse effect is described at different levels of sophistication. It explains how greenhouse gases work and their relative contribution to warming. Climate models are introduced, as are climate sensitivity, feedback mechanisms and uncertainties. It explains how disruption of the thermohaline circulation could make Europe colder in a warmer world. Global warming sceptics are discussed. The role of political bodies like the IPCC is described, as are the main ways we can respond to warming: mitigation, accommodation and protection.