Decarbonisation is harder for transport, heating, industry and agriculture. That is, a doubling of the decarbonisation rate requires much more than a doubling of the policy effort. The low-hanging fruit has been picked.

There are many indicators of energy security. Few measure what really matters-an affordable and reliable energy supply-and the trade-offs between the affordability and reliability. Reliability is physical, affordability is economic. The latest Russian invasion of Ukraine highlights some of the...