Nor should the ambitions for research be limited to renewables. There are other forms of fossil-fuel-free energy, such as nuclear. Innovation in nuclear energy is not easy: such power plants are dangerous and need vigilant, independent regulation; they are unpopular and currently vastly expensive. But a civilisation that looks decades or more ahead cannot exclude new forms of nuclear from the research agenda.

Living with it
Radical innovation is the key to reducing emissions over the medium and long term, but it will not stop climate change from getting worse in the meantime. This is where the realism comes in: many people will have to adapt to a hotter Earth, and some of them will need help.

Wealthier countries (including China) have promised $100 billion a year to help poorer ones. The trouble is that it is not clear what counts towards this total or what the money is for. If the Paris climate conference dissolves in rancour, this will probably be the cause. The priority should be research into crops that can survive extreme weather; better sanitation and health care to make the poor more resilient to climate shocks; and cheap energy, whether green or not. The poor need all these things more than they need gifts of green-power technologies that even the West finds too expensive.

The final strand of new thinking ought to be research into cooling the Earth artificially. Climate models suggest that global warming could be slowed by spraying particles into the stratosphere or by using salt crystals to make clouds whiter, and hence better at reflecting sunlight. No one knows whether such “geoengineering” projects can be designed in a way that does not replace existing climate risks with worse new ones. But that is a reason for research and debate, not for looking the other way. Geoengineering is not a substitute for cutting greenhouse-gas emissions (for one thing, it does not stop carbon dioxide from changing the chemistry of the oceans). But putting it off-limits, as many greens desire, is foolish.

In short: thinking caps should replace hair shirts, and pragmatism should replace green theology. The climate is changing because of extraordinary inventions like the steam turbine and the internal combustion engine. The best way to cope is to keep inventing.