There is a point of no return after which warming becomes unstoppable - and we are probably going to sail right through it. It is the point at which anthropogenic (human-caused) warming triggers huge releases of carbon dioxide from warming oceans, or similar releases of both carbon dioxide and methane from melting permafrost, or both. Most climate scientists think that point lies not far beyond 2 degrees C hotter (3.6 degrees F).

While the high-level climate talks pursue their stately progress towards some ill-defined destination, down in the trenches there is an undercurrent of suppressed panic in the conversations. The tipping points seem to be racing towards us a lot faster than people thought.

The scientists are really scared. Their [global warming] observations over the past two or three years suggest that everything is happening a lot faster than their climate models predicted.

The first and most important impact of climate change on human civilisation will be an acute and permanent crisis of food supply. Eating regularly is a non-negotiable activity and countries that cannot feed their people are unlikely to be reasonable about it.

Fiat justitia, ruat coelum. (Do the right thing even if the heavens fall.) It's not nearly as naïve a maxim as it seems, because in the real world it often turns out that doing what is morally the right thing is also, in practical terms, the right thing to do.

There is a point of no return after which warming becomes unstoppable - and we are probably going to sail right through it. It is the point at which anthropogenic (human-caused) warming triggers huge releases of carbon dioxide from warming oceans, or similar releases of both carbon dioxide and methane from melting permafrost, or both. Most climate scientists think that point lies not far beyond 2 degrees C hotter (3.6 degrees F).

The real requirement, if we are to avoid runaway global warming, is probably 80% by 2030, and almost no burning whatever of fossil fuels (coal, gas and oil) by 2050.