He agrees the crux of his book comes down to a single alarming sentence on page 28: “People have simply no idea how serious this issue is.”

It’s so serious, he said, that unless we reach a point where we stop emitting greenhouse gases entirely, 80 per cent of the world’s species will become extinct, and human civilization as we know it will be destroyed, by the end of this century.

Premise One: Civilization is not and can never be sustainable. This is especially true for industrial civilization.

Premise Two: Traditional communities do not often voluntarily give up or sell the resources on which their communities are based until their communities have been destroyed. They also do not willingly allow their landbases to be damaged so that other resources—gold, oil, and so on—can be extracted. It follows that those who want the resources will do what they can to destroy traditional communities.

Premise Three: Our way of living—industrial civilization—is based on, requires, and would collapse very quickly without persistent and widespread violence.

That is most certainly correct!

For the Nth time, I think this is a minor practical problem with little ethical importance. Ultimately, the moral law of sustainable emissions must be obeyed. The precise practicalities of how that is achieved are subject to a bracketed sort of morality for incomplete actions.

If six surgeons are in an operating theatre with a patient who desperately needs a procedure, it would probably be madness for all six to dive right in and start doing it simultaneously. Sometimes ethics requires a basic acknowledgment that complicated things need to be done in a sensible sequence.

I’m worried that you’re account of Kant’s catagorical imperative might have come from a leaflet. If we take Kantian morality seriously - it is very difficult to see what the maxim is that we could obey without producing a contradiction. The moral law is just that - a law, if you want to be free you obey the law. The law is act such that the maxims of your actions could be universal rules of legislation. In other words, they could be the empirical laws that determined everyone’s action. This produces serious problems in climate change ethics:

For example, you could try to reduce your emissions according to some criterion, but if everyone did that the economy would collapse and you wouldn’t be able to afford to reduce your emissions any longer. Of course, a collapsed economy might help mitigate climate change, but it certainly wouldn’t bode well for any story about the future anyone actually wants to tell.

Strictly, this isn’t a contradiction (it isn’t a rational contradiction that the economy collapses). However, since it negates the position from which I make my educated decision, it is just as contradictory as “Don’t kill - because if everyone killed there wouldn’t be a you”, or “Don’t steal from banks - because if everyone did there wouldn’t be banks”.

Our best estimate of our probability of doom might be a good day to decide where we concentrate our efforts: trying to adapt, trying to mitigate, or learning to geo-engineer.

This sort of all or nothing approach to life can only foster despair. It seems that the best of humanity has died in heroic effort, not standing laureated on a pedestal.

In fact, I think there is nothing that is more noble in the human animal than our continual determination in the face of absolute destruction.

Just ask grand-pappy Pikaia gracilens.

Whether we’re on the course to certain doom now, or whether we make it until the sun dies, or until the next natural ice age, the best thing we can do is attempt to make life as good and as peaceful as possible within our means now, and for the young’ns.