Issues as large and widespread as climate change suffer from the paradox of rational choice: while it is collectively rational to take action in the face of climate change, it may seem individually irrational to make fundamental lifestyle changes due to the high personal cost and immeasurably small effect a single set of actions will have on the environment as a whole. The importance of change at the individual level, however, is far greater than most people recognise, and such change when taken up by billions will make a decisive difference.