This year marks another milestone in the accumulation of carbon dioxide in the atmosphere. It has now reached 400 parts per million, and the rate of accumulation continues to rise. The experience of the past few years suggests that normal politics and diplomacy are unlikely to solve the problem of climate change. Only one thing is guaranteed to solve it: technological advance.

We can do this. To defeat the axis powers, the allies developed the atom bomb. When threatened in the cold war, the US sent a man to the moon. When threatened by global warming, we surely need a similar effort to save the planet. The Manhattan and Apollo projects engaged the best minds of their ages from a few nations. But today the effort needs to be international.

The project would need a clear aim – like the atomic bomb or a man on the moon. We suggest the following: to enable bulk electricity to be produced more cheaply by solar energy than by any fossil fuel. The scientific challenges involved in achieving this goal are great. They involve the collection of the energy, its storage and its distribution – often at considerable distances.