Let’s take a practical example. There is no prospect in the foreseeable future of airliners being able to run directly on electric batteries charged by renewable sources – to cross the Atlantic, say, the batteries would simply be too heavy. In this respect, kerosene is a remarkable chemical, storing so much energy per gram of fuel. We cannot simply stop aircraft flying – the world’s economy depends on aviation.

Kerosene, as burnt by today’s aircraft, derives from fossil carbon, and it is our emissions of fossil carbon that are causing the climate to change and the Australian bush to burn. However, it doesn’t have to be made from fossil carbon. It can be made by sucking carbon dioxide out of the air and combining it with hydrogen, which has been made by separating it out from oxygen in common-or-garden water (a process known as hydrolysis).

Of course this requires energy and it would make no sense to create such synthetic kerosene using energy from fossil carbon. However, if kerosene is made using renewable energy then it does make sense.

Producing synthetic kerosene in this way has been shown to be possible. However, the problem of producing it at scale is one of cost. It has been estimated that oil would have to exceed $US100 a barrel for synthetic kerosene to become viable.

With recent instability in the Middle East, this may happen in any case. However, this is the time for countries, especially those who have signed up to the Paris accord, to assert the following.