Certainly, packets of sea ice, in say the Arctic, which have failed to fully reform in the last couple of years.

I think we need to think of lots of ways to communicate. And we tried some at 350. We organised what they called the largest art project in the planet's history. We do a lot with art and music and things.

I think the best way is to keep stressing, that, as we build out a new energy system, one of the best things about it, if we do it right, will be that it will be more local, more democratic, more distributed, and, in the long run, much more economically sensible.

I'm not sure I'm a very good source of advice since we're kind of making this up as we go along.

Scientists are telling us that 350 parts per million [of carbon] in the atmosphere is the upper limit. We're at 387 parts per million now, and we're up in that zone where the risk of going past irrevocable tipping points is elevated. It's no different than going to a doctor and learning your cholesterol is too high, and you're at risk for a heart attack. You have to work to lower your cholesterol and hope to get there before the heart attack comes.

We've been in lots of places that I suppose, by Oxford standards, would be considered illiterate, but everyone's completely conversant with the idea that here is a number, and that number is above it, and that's too high. It's not a very complicated idea.

If there's horrible flooding in Pakistan or a horrible heat wave in Texas, we're no longer able to call it an act of God, or a natural disaster, or something like that, the way we could have through all of human history until 35 or 40 years ago.