Advocates for action on climate change face two main challenges. The first is to make everyone aware of the enormity of the problem. The second is to persuade anyone that anything can be done about it. Ignorance is bad enough, but inertia—induced by despair, denial, or the hope of a miraculous technical fix—is even more dangerous.

Climate change, as Robin Stott argues in this week's BMJ,1 poses grave risks to health.2 It threatens the essentials of life. It brings drought, floods, storms, and extremes of heat and cold that can lead to famine, homelessness, dislocation, destruction of communities, the spread of disease, and even mass migrations and armed conflict as people vie with each other for land, water, food, and energy. And let's not forget the effects on mental health of anxiety, insecurity, and a sense of powerlessness as we watch the grass wither and the ice-caps melt.

If medicine is about saving lives, not just by last ditch interventions but by trying to avert illness, then working to alter patterns of behaviour …