In Germany €200 billion has been invested in renewables, yet wind and solar energy each produce about 8 per cent of electricity per annum. For large parts of winter they produce little or nothing, and so there is no relief for the fossil fuel and nuclear plants (if the latter are given a reprieve) to produce the peak annual demand. The combined cycle gas turbines, with shafts designed to turn on and stay on, providing base-load electricity, are uneconomic when run in load-balancing mode: not only do they produce less and so have to charge higher prices, but more worryingly, the constant acceleration and deceleration shortens the lifetime of the shafts. Some turbines are being turned off until they are needed for baseload applications sometime in the future.

The starkest fact, hidden in Stern’s chapter on ethics, is the plight of the world’s poor. One of the most positive aspects of the last 20 years has been the doubling from 1.5 billion to 3 billion of the number of people in the world living in what the World Bank calls “the middle class”: those who have electricity and running water in the dwelling they call home. BP data shows that this has coincided with a 40 per cent increase in global energy demand, 88 per cent of which has been provided by fossil fuels, and less than 1 per cent by renewables. The World Bank predicts that by 2035 the middle class will grow from 3 billion to 5 billion out of a total population of 8 billion. BP estimates that the world demand for energy will increase by another 40 per cent in total; more than 80 per cent of that will again be provided by fossil fuels.

It would be immoral to stop that process. Even if the developed world was to halve its CO2 emissions over the next 20 years, the overall global emissions will grow as China, India and Africa continue their rise out of grinding poverty into a middle class existence. By 2050 more than half the world’s population will live in megacities, where local renewable energy will only serve people living on the top floor of high-rise buildings, and where nearby land is already dedicated to food production. Only fossil fuels and nuclear energy will power megacities in 2050, and it is too late now to expect anything substantially different. Over the last decade, as 600 million people left the Chinese countryside for high-rise cities, the growth in primary energy sources was more than 140 million tonnes of oil equivalent (toe) per annum while the best of the renewables was in the last year which saw a growth of only 10 million toe. This will continue for at least another decade in China, while India and Africa will start a phase of urbanisation that will last at least 20 years.

On the upside of CO2 emissions, ministers should bear in mind just one fact and one prospect for the future. The world’s biosphere has greened considerably — by more than 10 per cent over the last 30 years — because of the extra CO2. This figure takes into account the contrary impact of deforestation and land-use change and much of it has taken place where it is needed, such as in the Sahel. While the climate science community has been focusing on one source of global warming, it has been largely silent on the behaviour of the sun, and dismissive of those who point out that the pattern of sunspots is now mirroring that last observed at the outset of the Little Ice Age from about 1300 to 1850. The most recent work of the solar physics community has been reinforcing this message. As I pointed out in The Times in 2010: “One possible scenario for 2050, no less possible than any projected on the basis of climate models, is that we are in the middle of a deep solar minimum, and it is only the CO2 pumped into the atmosphere over the previous 100 years that is staving off cold climates that would lead to crop failure and mass starvation. The uncertainty is not only in the science and in the scenarios, but in what is a reasonable response today.” Remember there will be about nine times as many people on the planet in 2050 as there were during the Little Ice Age.