Climate change is unequivocal. The fourth assessment report of the Intergovermental Panel on Climate Change has recently projected that global average surface temperature will increase by 1.1 to 6.4°C by 2100. Anthropogenic warming during the twenty-first century would be much greater than that observed in the twentieth century. Most of the warming observed over the last six decades is attributable to human activities. Climate change is already affecting, and will increasingly have profound effects on human health and well-being. Therefore, there is an urgent need for societies to take both pre-emptive and adaptive actions to protect human populations from adverse health consequences of climate change. It is time to mainstream health risks and their prevention in relation to the effects of climate change on the medical research and policy agenda.