How bad could climate change get?

Haydn - Yes. This will be something that people are really familiar with I am sure, for over the last few months, of the Extinction Rebellion protests and people like Greta Thunberg really raising alarm about this issue.

The simplest answer is we don't really know, but that's something to be worried about. We know that the definite effects of climate change are going to be really catastrophic for people around the world. And there’s a moral element to it in that the people who have contributed the least, who have burnt the least amount of stuff, are going to suffer the worst consequences. So we should do something even on the most likely outcome.

But what climate scientists do, what they look at is they model different scenarios. And the IPCC - the Intergovernmental Panel on Climate Change that people will be familiar with - gathers all these together and looks at what are the most likely outcomes of different scenarios? So if we pump this amount of carbon dioxide into the atmosphere will we get this amount of heating, what might the effects of that be?

But the problem is that they mostly look at sort of the most realistic outcomes. They don't pay as much attention to the very unlikely outcomes of five degrees or over. And if we were very unlucky, we hit a few bad feedback loops. So that's things like permafrost up in the Arctic melts and releases a whole load of methane, a much more powerful greenhouse gas. You might get sort of much more warming than you might expect. So the worry is for something greater than 5 degrees that it might be very bad indeed. It might affect the ecosystems that we rely on. So that's the sort of natural world that produce clean water and pollination and things like that for us. It might affect our ability to grow food or to have clean water and it might spark conflicts.

So the Syrian war and Sudanese war, it’s often said they were the world's first climate conflicts. So the worry is that if we are very unlucky and we have sort of very runaway climate change of over five degrees of warming, that you get huge amounts of people having to move because they literally can't live where they used to live.