Gradually as the concentration of greenhouse gases goes down, Earth starts to cool again, and eventually you slip back into an Ice Age.

Perhaps the strange human desire to fly away from the planet, to "slip the surly bonds of earth," is a necessary impulse for discovering who we are.

Gaffes are rare in Mr Morgan's sober and balanced account, although a few slip through, such as the claim that myths (flat earth included, presumably) always have some basis in reality.