The fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC), published earlier this month, leaves no room for complacency.1 It makes clear that warming of the climate system is unequivocal and that the increase in globally averaged temperatures since the mid-20th century is most likely due to increased human induced greenhouse gas emissions. It also states that warming and resultant sea level rises will continue for centuries even if emissions are stabilised. When scientific consensus reads like this, we are in trouble. The time to act is now.

The threat to human health from climate change—through malnutrition, disease, and flooding—is substantial, and in some parts of the world, immediate.2 Most of the health burden of climate change is borne by children in developing countries.2 It is ironic that doctors, for whom protecting health is a primary responsibility, contribute to global warming through unnecessary attendances at international conferences.

Lord Kelvin, physicist and past president of the Royal Society, said, “if you cannot measure it, you cannot improve it,” and it is encouraging that doctors are measuring the carbon footprint of their conference activities. Kelvin also said, “heavier-than-air flying machines are impossible,” but he was wrong. Last year, many doctors used such a machine to attend the European Respiratory …