There is a conversation I do not know how to have, a conversation about what happens if we are heading for disaster. It is not a theoretical question for me. I have two daughters. The older has just turned 13, the younger is nine. On current projections we will pass the point at which it is possible to hold warming to 1.5 degrees above pre-industrial levels before the younger has finished school. By the time she is at university the coral reefs will be gone. By the time they are in their early thirties we will be committed to two degrees. By their forties they will inhabit a world in which the ice shelves are melting, the Amazon is burning, and ecosystems around the world are collapsing. A world of massive refugee flows in which hundreds of millions will die of hunger, heat, disease and the accelerating effects of social and economic breakdown.

It is difficult to see how our society could survive in anything like its current form in such a world. Five million Syrian refugees deranged Europe, a fraction of that has dramatically affected the dynamic of Australian society. What happens when tens of millions head north and south from Indonesia and equatorial or sub-Saharan Africa? When Central America or parts of India become uninhabitable? When Bangladesh and Myanmar flood? What happens when that occurs at the same time food grows scarce, water resources dry up and economic activity contracts to less than nothing as global commerce collapses? Last year I interviewed one of the lead authors for the International Panel on Climate Change. When the formal part of our conversation was over, we talked a bit about emission pathways and the fact we remain on the outer limit of projections, suggesting we are heading for four degrees or more of warming. He laughed. ‘We’ll never get there,’ he said. ‘Look around yourself. Think about the level of disruption we’re experiencing at only one degree of warming. The reality is human society will collapse long before we get to four degrees.’ For weeks afterwards I couldn’t get his words out of my head. I still can’t.