When we feel hot indoors, the first thing most of us do is open a window or turn down the thermostat. We do not look for new technologies to regulate indoor climate, or seek to change our countries’ policies.

Yet the mind-numbing complexity of climate change has caused many philanthropists to overlook one compelling fact: burning coal contributes about 40 per cent of the total CO2 released into the earth’s atmosphere every year, or 8 of every 20 pounds of carbon released. And if we want to turn down the earth’s thermostat most immediately, the first step is to stop construction of new coal-fired power plants and ultimately phase out the most polluting old ones as well.