Earth system scientists put the kind of society complex enough for hospitals and higher education require an energy returned on energy invested in the teens. ‘Renewables’ (let’s call them low carbon, there isn’t anything very renewable about the blade of a wind turbine) barely touch that and often don’t get near.

• The picture is so varied that one can find statistics to counter this ‘barely touches the teens’ claim. Look at the totality of the picture and draw your own conclusions. I am just presenting some reasoning to justify a claim that we are heading towards a much lower energy future, maybe next century or something (which doesn’t have to be bad, provided everybody isn’t slaving for a class of energy-obese billionaires protected by a fascist police state).

• I looked into this a lot about 15 years ago, when it seemed that we were still in the last chance saloon on avoiding catastrophic climate change. The science might have moved on. I don’t have current sources anybody interested in the concept of eroei and the complexity it creates will have to look themselves.