The four materials that hold the world up

Vaclav Smil is the scientist Bill Gates says he reads to stay honest. His argument is deflating and clarifying at once: modern life rests on four “pillars” — ammonia, steel, cement and plastics — and on the fossil energy used to make them. Ammonia alone, as synthetic fertiliser, feeds roughly half the people now alive.

The numbers resist wishful thinking. Fossil fuels still supply around four-fifths of the world's energy; the four pillars are produced at billions of tonnes a year with no green substitute yet ready at that scale. Smil's point for the coming decade is not that decarbonisation is hopeless — it is that it will be slower, more physical and more costly than the slogans imply, because you cannot software your way out of needing steel.

Read cynically, this is a counsel of despair; read carefully, a corrective. Smil refuses to name target dates on principle — its own kind of honesty in a field full of them — and leaves the reader able to sort credible energy talk from marketing, a useful filter for the next five years of announcements.