Imagine you wake from a deep sleep to discover that you are at the helm of a supertanker which is heading at high speed towards some cliffs. The instrument panel is unresponsive and you are unable to steer – crashing into the rocks seems inevitable – it is only a matter of time.

You close your eyes hoping that it is only a bad dream, but when you open them again you see that the nightmare is real and you are now closer to the cliffs. In fact, you perceive that the supertanker is actually accelerating towards its doom. Is there a way that you can cut the engines? You scrabble around trying everything to slow the ship – the minutes tick by and you think that all your frantic actions may have at least slowed the rate at which you are accelerating – but you are still going faster than when you first woke and you are now considerably closer to the cliffs.

Without instruments, it is not possible to accurately predict when you will hit the rocks, but you estimate that, if the ship keeps up its current speed, in about half an hour you will have passed the point of no return – even if you cut the engines completely at that point, the momentum that you have will mean that your ship will become a shipwreck.

Then you realise that, if you could only find some way of putting the engine into reverse, you could power your way out of the problem. With a huge sigh of relief you sit down – you’ve got a whole half hour to work out how to put the engines into reverse – panic over – you make yourself a nice cup of tea and peruse the crossword.

So what was all that about? The supertanker is the climate system, its speed is the rate of emissions, the frantic scrabbling to slow the ship down are the hard-fought emission reduction negotiations, the cliffs are dangerous climate change and each minute of time is a year. In thirty years, with the current lack of progress, we will have burnt the trillion tonnes of carbon that will make dangerous climate change inevitable.

And the reverse gear? That is proposed techniques to remove carbon dioxide from the atmosphere. Successful applications of such technologies could pull us away from the cliffs. But do such techniques actually exist and even if they did could we actually implement them in time and at sufficient scale? No-one knows and this isn’t the time to be wasting time on metaphorically drinking tea and doing the crossword.

The climate models that avoid a 2°C rise in global mean temperatures assume such ‘negative emissions’- even though we don’t know if they could work. Strip those ‘technological imaginaries’ out of the models and even the most optimistic emission reductions are insufficient to avoid climate chaos. To avoid emitting a trillion tonnes would require us to reduce emissions by 2.5 per cent per year every year from now on. To understand just how challenging that is consider that emissions have been growing by about 2 per cent per year for the past three decades. The only year in the past decade in which global emissions fell was in 2009, the year after the financial crash, and then by just 1.5 per cent. The following year it rebounded by 5.9 per cent.

A belief that mitigation alone can avoid dangerous climate change lies somewhere between the wildly optimistic and the delusional. It’s time to start looking at whether there is a reverse gear.

This opinion piece reflects the views of the author, and does not necessarily reflect the position of the Oxford Martin School or the University of Oxford. Any errors or omissions are those of the author.