A group of us published a paper last year in nature which looked at nine or ten of these tipping points and looked at the possible connections amongst them. So we think there is a possibility of a global cascade which links eight or nine of them. And the problem here is once you start activating that entire cascade there is no turning back. It's the so-called point of no return. It's the dominoes start tipping you can't recover them. So that's the issue we face with Earth is that we may see a global tipping point made up of a bunch of individual ones that in sequence take the Earth to a much harder state even if we get our own greenhouse gas emissions down. So the ultimate threat that climate change presents is not a nice linear even temperature increase. The prospect of a possible global tipping point is the one we really need to worry about. And where might that lie? We don't know. We have to do more research but we have at least a good general understanding. We think that it doesn't lie as low as 1.5 or below. So we think we're probably okay up to the lower Paris target of 1.5 degrees Celsius. Mind you that's getting very close and we may hit it in only one decade. As you go above 1.5 we think the risk increases and by the time we hit three then we're fairly certain that you're going to get into bad territory as far as the tipping points are concerned. How does that relate to where we're going now with our climate policies? Well if you look at the Paris commitments that every country virtually every country is made the US, China, Australia, European Union and so on. If everyone met their Paris commitments we would still go to somewhere between 2.8 and 3.2 degrees temperature rise. That is very dangerous country in terms of the global tipping cascade. But the real problem is very few countries are on track to meet even their weak commitments and that includes Australia. If you actually extrapolate where we're going now if we just keep up with the type of policies we have today we would go above 3 degrees and approach 4 degrees by the end of the century. That would almost guarantee an uninhabitable planet for many regions of earth. So the tipping cascade is a central issue we need to keep in mind. I think it's the ultimate risk if we don't get greenhouse gas emissions under control.