If we are to save humanity and the planet from the worst mass extinction of all time, worse even than that at the end of the Permian, we must stop at two degrees.

I am also sorry that I helped to start the anti-GM movement back in the mid 1990s, and that I thereby assisted in demonizing an important technological option which can be used to benefit the environment.

Once the 'portals of the future close - in Amazonia, Siberia or the Arctic - we will find ourselves powerless to affect the outcome of this dreadful tale.

If substantial methyl hydrate melt begins to occur in the Arctic Ocean basin, then the (carbon) accelerator will be jammed, and there will be nothing we can do to cut the speed of climate change.

An outdated view still prevails that a low-carbon lifestyle requires immense personal suffering and sacrifice. In my view, nothing could be further from the truth. All the evidence shows that people who do not drive, do not fly on planes, do shop locally, do grow their own food, and do get to know other members of their community have a much higher quality of life than their compatriots who still persist in making the ultimate sacrifice of wasting their lives commuting to work in cars.

At 1.24 am on 26 April 1986 Chernobyl’s Unit 4 reactor exploded after staff disabled safety systems and performed an ill-advised experiment to check – ironically enough – the reactor’s safety.

Only by advocating 'politically unrealistic' CO2 concentrations can runaway global warming be avoided. But what is politically realistic for humans is whollymunrelated to what is physically realistic for the planet.