Human civilisation today faces two unprecedented challenges: the threat of climate change and the peaking of global oil supply. Energy supply has been one of the strongest factors in determining human history, and there are strong signs that we are now in the early stages of an energy transition that will shake our economy to its core. At the same time, the accelerating evidence of climate change has made this environmental crisis a top international priority. Rarely are these two issues considered in combination, but each affects the way we can respond to the other. The possibilities for our future range from 'techno-explosion' to civilisation collapse - but another possibility is energy descent, where available energy and organisational complexity progressively decline. Many sustainabili