Climate change is a problem all businesses have to face. It also presents a test for how they will use the power to create a sustainable future.

The UN estimates that half of the world's population, 3.2 billion, now live in cities, compared with 13% (0.2 billion) in 1900, 29% (0.7 billion) in 1950, and 37% (1.5 billion) in 1975.