 So what I'm saying is that we only flourish on this planet because of the circular metabolism, because of life cycling, everything it needs. So we've got to be concerned with that process. If we've got any sense of self-preservation and survival, we are looking at the world through the wrong eyes or with the wrong worldview anyway, because we've grown up in a culture that has been telling itself that the world and the universe is a big clockwork machine where the response you get is kind of proportional to the input you give it. That I believe is basically a delusion. Hello everyone and welcome to the Circular Metabolism Podcast, the bi-weekly meeting where we have in-depth discussions with researchers, policymakers and practitioners, to better understand the metabolism of our societies, or in other words their resource use and pollution emissions, and how to reduce them in a systemic, socially just and context-specific way. Today we will talk about an essential concept to understand our ecological crisis, tipping points. In fact, several climate tipping points including ice loss both in Greenland and Antarctica, the slowdown of the Atlantic circulation and more on dangerously close and risk triggering a tipping cascade. To understand these risks and how to keep us in a safe space through positive tipping points, I have the great pleasure to welcome Professor Tim Lenton. Tim is chair in climate change and earth system science at the University of Exeter. In this discussion we'll cover how to understand earth as a system, the different types of feedback loops and cycles, the different types of tipping points from ecological ones to social ecological ones, as well as early warning signals for climate and social ecological tipping points. So with all that being said, Tim, thanks so much for being here and welcome to the podcast. Thanks for bringing me on to the podcast, Osteed. That's great. Yes, there is this topic of tipping points which I am so excited to discuss. Of course, you have just written or edited a major report on this and you have published many articles on this. Before we get to tipping points, I think we just need a short introduction perhaps of how did you get into biogeochemistry, modeling, understanding that the earth as a system, I mean, what was a bit your passion with this because this has turned into your career, right? I was an 18-year-old kid who got up to Cambridge University to study the natural sciences because I was passionate about science, read avidly as a teenager. It was a bit disillusioned with my degree, if I'm honest. But after a term at university, my dad gave me Jim Lovelock's books on Gaia, A New Look at Life on Earth, and I was captivated by that. It was just like my calling. I thought, yeah, that's what I want to research. I wrote to Jim and said, look, I'd love to research this and study this and help you out when I graduate. He wrote back saying, great, come visit and have a chat. It started from there, really. I was very lucky. I was 19 when I met my scientific mentor, if you like, Jim Lovelock. When I graduated my degree, I went straight into my PhD studies trying to work on Gaia as he called it, understand how life is involved in regulating the cycling and the concentrations of nitrogen and phosphorus in the ocean and oxygen in the atmosphere. It's just gone on from there, really. I've always been passionate about trying to understand the Earth as a living system and then explain that new scientific worldview to my students or to anybody else who's interested because it's like a worldview. We desperately need that shifted worldview now. Yeah, I mean, it's a long journey always, but if you study how life has transformed the planet in the past and how the Earth has gone through the occasional tumultuous change that actually got us to where we are now, interspersing long periods of relative stability and calmness, then you appreciate that when we evolve and the way we have and we start hitting the Earth system hard with our greenhouse gas emissions and all the rest of it, then you have a keen sense already. Well, I know the Earth is a bit to the Earth and the climate have tipped in the past. It seems intuitive that we could tip them again now, so I better start studying that. So that's what I was doing by the late 1990s onwards really, I suddenly thought, but I really must have a careful look at that. Yeah. I think it's fascinating. You already used some terms. I think that we might need to define a bit better. So you talked about circulation of flows, you talked about nitrogen, you talked about the Earth as a system. I think when we talk about tipping points, there is a certain grammar or vocabulary or jargon that we need to define for the listeners or the viewers. So for instance, when we talk about the system, we have to define this system that we're studying. We define it both in spatial scope, temporal scope, we define what are the feedback loops, what are the flows that we're studying within this massive system, especially when it's Earth, right? So perhaps can you help us buy a small example, explain us what is this Earth system, right? What do we study when we look at Earth as a system? Well, we study the thin film of life and the gas envelope of the atmosphere and the liquid envelope of the ocean and the organic matter of the soils and maybe the very top of the crust of the Earth. But the realm that some would call the biosphere as well, which is the realm that supports life. And in, to my definition, that that is the Earth system of Earth system science. There's another Earth underneath that that's powered by the heat of internal radioactive decay and also the heat that's still left over from when the Earth was formed when it smashed together bits of rock colliding under gravity. And that heat is what drives the mental circulation and so on and so forth. But that's like those are like in my eyes, two systems. And it's the surface Earth system, if you want to call it that, bounded at the top by outer space and with a slightly fuzzy inner boundary somewhere, depending on the time scale, somewhere between the Earth's crust and the top of the bottom of the Earth's crust. That's the system that we need to be concerned with if we're concerned with our own life support system and what makes this such a remarkable planet for life for a real anomaly. We don't know how much for an anomaly, but clearly a very, very special place and a place where life is profoundly reshape the conditions for its own flourishing, meaning life is principally responsible for cycling all the elements it needs to flourish to build its bodies, if you like. And I did mention a couple of those as well. That's the relevant Earth system. And within that, we if we would probably define something we called the climate system, which would just be a way of referring to the bits that also the long term mean temperature and conditions of the climate at the surface of the Earth. So that shifts the emphasis a little bit more maybe to the atmosphere of the ocean to particular elements like and particular gases like carbon dioxide and methane as gases and their cycling. And maybe it places less emphasis on the cycling of another element like nitrogen or phosphorus. For example, we don't think of phosphorus as being particularly heavily connected into the climate part of the system, although, as usual, there's always some connection. So yeah, the climate system is essentially a subsystem of the living Earth system. And within the climate system, we could then define some other subsystems of that by which I mean an ice sheet like the one on Greenland or West Antarctica is a system in itself. And it's also a subsystem within the larger climate system, because it's kind of affected by the climate and has some effect on the climate. So it's kind of Russian dolls of systems and subsystems. Yeah. And then you look at the circulation of these dolls and sub dolls of how all of them interconnect and make one each other function. That's right. And it's like one of philosophers have fancy words for ontology. But like when you're looking at the world, you could take an object or a thing view of the world, and then you would label things like ice sheets, or trees, or an Amazon rainforest, or you could take a process based philosophy. And you could say, well, actually, maybe the processes are the primary thing. And maybe it's actually the cycles and the flavors of nitrogen or water that are more the primary thing we should focus on. Of course, there are both. And mostly in Western philosophy, we've opted for the thing approach, the object approach over the process philosophy. But the kind of science that I do speaks to certainly putting a bit more emphasis on a process based view of the world, because it's the processes that keep the world stable or propelling stability. And we are, of course, in the time of change, I think we can all agree on that and change is, you know, a process. So for those reasons, I have to weave both threads, the object and the process view. And it's just like you and I asking, you know, what does it mean to be alive? Well, that's really a process thing, isn't it? Because tragically, sometimes things die, but nothing has apparently changed from one moment to the next, but everything has changed. So in an object sense, nothing has changed in a process change. So something just changed profoundly. This is extremely interesting because, of course, you mentioned, if it's a process, there are dynamics within the process. So you talk about stability, change, and of course, we're going to come later to tipping points. There is this notion of what is too much, what is too little in terms of speed, in terms of magnitude, in terms of many different things. And of course, these are also the different vital signs. What is a vital sign in these circulations? What is the pulse that you're measuring? First things first, why do we care about cycles or what we might call the circular metabolism of the planet? Well, this is essential to our life support. So it's probably not widely known that if you take an essential element for life, like phosphorus, though, this is an element that is essential to the molecules in us that carry energy. It's also essential to the nucleic acids that carry information. Take an element like phosphorus and you look at the amount of phosphorus that comes into the earth as a system and the amount that might go out into rocks, if you like. So it might come in from volcanic processes and might go out in new rocks. It's tiny compared to the amount of phosphorus that's cycling round and round in ecosystems and in the whole biosphere, by which I mean any asthma phosphorus will go round and round your typical, say, forest ecosystem maybe 40 or 50 times before it's lost. So what I'm saying is that we only flourish on this planet because of the circular metabolism, because of life cycling, everything it needs. So we've got to be concerned with that process. If we've got any sense of self-preservation and survival, we also realize, oh, we've got this thing to claim it and we appear to be knocking it out of whack, as my late friend Bruno in the talk put it, and that tells us that, hold on a minute, if we're knocking it out of whack, something was keeping it stable before. How does that happen? And that then speaks to a number of things. It speaks to what you mentioned, this word feedback, that sometimes in a complex system like the earth or the climate, a change happens. But then within the system comes back a response that can sometimes damp the initial change and thus maintain stability. Occasionally, things go the other way. You get it, you cause a change in the system, you get a response from within the system that amplifies the initial change. And then, well, that's the other sign or type of feedback that then can be, well, a problem if it's changed that is being propelled away from what we like. So we'd certainly need to be concerned with that kind of cycle in the sense of a feedback loop, it's a cycle of causality, it's not necessarily a cycle of material stuff. Although often material stuff is involved. So yeah, we have the literal cycles of material elements like phosphorus, carbon, these things that we depend on. And then we have the causal cycles or the causal loops that can either stabilize or destabilize things that we've got to care about. And in that sense, when we're talking about the concept we introduced of planetary boundaries, we're trying to put a label on some of the big ticket things we've got to care about as our life support, like temperature or the climate, ozone layer, water cycle, nutrient cycles, biodiversity or nature or whatever you want to call it. And planetary boundaries is just very crudely trying to summarize, well, if we push some of these aspects of our life support system too far or too hard, it's going to be bad for us. And there's some kind of point beyond which it's really not sustainable to go. And that's what we were trying to get at and defining a planetary boundary. And that would then loop us back around to thinking about these other cycle things that, yeah, let's talk more about that as we go through, I think. Yeah. I think what's fascinating is what you just mentioned, this point, this point that, you know, if we push harder, then something either accelerates, decelerates, breaks or something like that. What is a good threshold? How do we identify it? How do we work with it? Exactly. And a tipping point, my favorite sort of subject is a particular kind of threshold, which is made very clear, because it's the kind of threshold where you go past it and then you trigger such strong amplification within a system that change becomes self propelling and you don't have to keep pushing it. The change just continues. So I often like to encourage people to think about leaning back on their chair because everybody knows you lean back to a certain point on your chair and you get to a point where a little nudge one way or the other is going to either take you off into a very different state, sprawled on the floor or tip you back upright. And yeah, that's one of those points where the tiny nudge one way or the other then suddenly gets amplified into two different very, very different outcomes. Now, for some, although not all of the planetary boundaries we identified, I could use this understanding we have of tipping points to be able to ground that notion of a boundary, because it begins to become clear, for example, with the ozone holes that opened up what was first discovered when I was like a not quite a teenager in the 1980s. There was a classic case where there was some of this amplifying stuff going on in the chemistry of how particular compounds that got into the stratosphere and then work their chemical, magic or whatever you want to think of it, on the surface of frozen ice particles of what are called polar stratospheric clouds high in the atmosphere would then we say catalyze the destruction of the ozone layer, which and that word catarysis is that is talking about an amplified process of the ozone destruction. So that was like a tipping point I'd grown up with in a broader sense of the world and also one that defined a kind of clear boundary like we didn't we don't want to know his own hole when we're starting to see the nasty consequences that could have that one's pretty clear. But as you said, we're not talking about a simple system like a chair. We're talking about this beautiful complex living Earth. And we don't pretend we understand it perfectly. So we're always talking probabilities because we never know, perhaps have a perfect foresight of where the tipping points are, but we don't have no we have some information, which is good as well. There's best. So we're navigating without a perfect map, but we don't have no map, we have we have a sort of map with some blurry bits. You have some points in the map, but you can see clearly in between, perhaps. Yeah, exactly. And that that's okay, because some information is way better than none. In this tipping point element, you say that, you know, you wobble a bit and you can either come back to a sitting position or fall on your back, right? So here we have two stable states, let's say, which are well defined. Yeah. How does it work with the Earth system? What is the stable state or is it a past state? And when was it this past stable state? And where are we going in this hot house? Earth state? You know, have we been in a tipping point for a long time? Or how does these dynamics work? And easier, I'm not sure it's a better entry point to take a step down from the global scale and look at what I call the tipping elements. I like I gave a label to the subsystems as the climate system or the Earth system that could clearly demonstrate these different stable states, like you mentioned in the introduction of the great overturning of circulation at the Atlantic Ocean or the Greenland Ice Sheet or the Western Antarctica Sheet or the Amazon rainforest. In each of those places, we've got, well, various lines of evidence from Earth's past from models and from kind of theory to to believe that they have different stable states that they can be tipped into and out of. So for each of those, we can then, well, we can look around the Earth as a system and try to identify all those systems that might be tipping elements. And then we can ask ourselves, what information do we have about how close they might be to a tipping point? And could we force those systems past the tipping point? And if we could, what would the consequences be? And how big a issue is that? And should we do something about it? And that's sort of the exercise I've been doing on and off for 20 years and trying to because and trying to alert people to the basic answers because even nearly 20 years ago, when we were first looking at this, it was obvious that there were there were several tipping elements, several bits to climate system that could could be tipped into another state and that we would really care about the consequences. And in each case, we know it's at the core of this, it's that you can get to a point where within a system, you go from a situation where there were these damping feedbacks that maintain the status quo like preserving the ice sheet on Greenland. But if you were forcing it to melt, you shifted the balance of feedback and you could trigger a self propelling amplifying feedback. In that case, you get to a point where as the ice sheet surface drops in altitude that moves into warmer air, which melts things further. And at some point, you get a tipping point where that becomes what we call runaway feedback. Well, we would, I've been busy cataloging all the bits of the planet for which, yeah, there was credible reason to think you had the alternative stable state that existed and you could reach this tipping point of self propelling change. And the hard bit then is to try to work out how near that tipping point is. But we have ways of doing that imperfectly or getting a clue that maybe we can talk about more. But in essence, if you think about the example of leaning back on the chair near the balance point, you know that when you're near the balance point, things are actually a bit more sluggish. There's sort of, there's things that move the chairs and move around so fast near the balance point. And there's a more general thing there that as a system approaches a tipping point, the things that gave it resilience, that's a popular word, the things that were the damping feedbacks that tried to maintain the original state or status quo, they're getting weaker. And so the nearer you get to a tipping point, the more sluggish the system becomes because you hit it, but it can't recover. It wants to recover, but it can't recover as effectively. And we look for that signal of slowing down and also increasing variability will go along with that in a system as a kind of clue, a tipping point maybe approaching. And we can, we try to do that as best we can across all these tipping elements. But you rightly asked, well, well, how does that all add up? Because at some point, even if we try to be, I might say, reductionist and identify these separate systems that could tip, we then quickly realize, well, they're coupled together. And actually, if you tip one thing, it can sometimes make tipping another more likely. So if things are wired up like that, you realize, oh, well, eventually, they might be consequences of one tipping event, tipping another tipping another. They become very global and they have many ramifications. And that's where we can start to talk about, well, you mentioned a hot house. I actually think a wet house, if you can call it that is, is the, is the more worrying or the more likely kind of global tipping point because of rising waters and also rising sea level precisely that we could tip a kind of coupled loss of the ice sheets on both poles and it might unfold by human terms relatively slowly, but quite irreversibly and lead into the wet house. Equally, we could fundamentally reorganize the circulation of the ocean and thus the circulation of the atmosphere and the whole climate. Now that does not have to necessarily translate into amplifying the global warming or the global temperature change. It would still be an absolute catastrophe because if, as has happened in the past, if you reorganize the circulation of the ocean and you thus break the monsoon in West Africa and India and disrupt it in South America and all the other monsoons, well, given where people live and how many depend on the monsoons, we're all going to feel that is a catastrophe. Yeah, so I'm not sure which, but that's not wet house. If I have to give that a good, a snappy name, I have to think of one, but it's kind of, it's certainly catastrophe house, earth, even if it isn't a hot house. Yeah, so perhaps we can share, I think it's in your paper called Climate Tipping Points. You have listed nine of them. You have the Amazon rainforest, the Arctic sea ice, the Atlantic circulation, boreal forest, coral reefs, green light ice sheets, permafrost, West Arctic ice sheet and walkie's basin. So I think over there what's important, you mentioned some impacts, what happens when we tip. You mentioned their link, so there is the domino effect or the cascade effect that one can tip to another. And you also mentioned the irreversibility. Some of these we might have already crossed and it's just these feedback loops that will make, for instance, the Arctic sea ice disappear, right? So some of them we have already crossed or what is the state here? This is both the beauty of science and the thing that frustrates not scientists. I think that it's quite hard to be absolutely definitive. We're in one of those times of profound sort of uncertainty. We've got quite a lot of evidence that part of the West Antarctic ice sheet could now be an irreversible retreat. It's a couple of major glaciers draining into the Amazon sea that drain a large chunk of the ice sheet, large meaning enough to raise the world sea levels by over a metre. We can't rule out that one's crossed. And we also stink from modelling that when you lose that part of the ice sheet, unfortunately that destabilises other parts of the ice sheet. So you might end up losing most of the West Antarctic ice sheet, which would be about three and a half metres of sea level rise in the long run. And then if we go round to Greenland, we know that Greenland is losing ice at an accelerating rate. We're just not sure if it could lose again about a metre or so of sea level rise equivalent. And at that point, a lot of the bits of Greenland that are stuck in the ocean would have gone and you'll be latched with the bits of Greenland that are on the land. And then we're not sure whether it'll restabilise or whether it'll reach a further tipping point where basically the amount of snowfall is not enough feature to balance the amount of melt. And then it is definitely committed the whole thing to go. And if the whole thing is on the way out, it's another seven metres of sea level rise. So it's hard to rule out that we can't be sure either way, but it's hard. But it's only hard to rule out that we might have committed to like 10 metres of sea level in the long run. The long run means it could mean thousands of years or it could go quicker if we keep warming things up. But 10 metres of sea level means if it's already baked in, which we're not sure, it means at some point, London, Shanghai, Amsterdam, New York, Boston, San Francisco, a bunch of cities are going to have to, well, they won't be where they are now in the long run. And you think, well, our thousand years doesn't matter or whatever your ethical position is. But I live in Exeter, it's a Roman city, it's been here, the best part of 2000 years, London's the same. So actually, even when I started writing about this 15 years ago, I tried to say that I'll be clear about my ethical time rise. And I am going to care about things that could unfold even on a thousand year time scale. Because many of us would identify something about our society that goes back, you know, thousands of years. So why not think about commitments we're making a thousand years hence? I think over here we have a very interesting point, because the irreversibility, I think many of us do not fully understand what does that mean. We often are very good with linear systems and linear responses, but very bad with exponentials, nonlinear responses, and all of that. And that also means that once we go, once we have tipped, we will not see again this, you know, these beautiful landscapes, but also these elements that keep us alive in a certain sense. So the 1.5 degrees, not just, oh, well, we missed it, we're going to do better next year. Yes, the worst kind of irreversibility is death, or even maybe worse than that, is the extinction of a species. For example, you're never going to get it back. But we're talking about, yes, as you put it, like mentally keying into that concept that we can collectively make commitments to lose things. Even if they haven't gone yet, we're not going to be able to stop them going. So I suppose you could think of it as having this macabre pair of being able to collectively create a kind of death for some things that we think are quite normal and might, when we thought about it, cherish or might want to preserve. Like, the death won't come immediately, certainly not from the sea level rise. But it's still, I find it like a moral proposition to consider us collectively committing, well, even the death of London now I think of it, but certainly the death of a major ice sheet. I'm not saying that ice sheet has always been there for all time. Of course it hasn't. But it's been there for all the time humans have been here, that's for sure, certainly in the case of the ones we've talked about. And when we go to talk to about other species or things like the Amazon rainforest, they've been here a lot longer than we have. And so it is something we really haven't got our brains around in a kind of collective cultural sense. But this is arguably because we are looking at the world through the wrong eyes or with the wrong worldview anyway, because we've grown up, or not as the case may be, in a culture that for 400 years or so has been telling itself that the world and the universe is a big clockwork machine where, like, the response you get is kind of proportional to the input you give it. And I believe it's basically a delusion. But if we continue to teach our kids that, and we continue to adopt an economic framework that is sort of strongly believes in or is connected to that, then, well, then it's going to take a bit of slapping out of that delusion. But unfortunately, we're all slap out of the delusion if we start to see more of the kind of off the scale extremes of the climate that we witnessed in 2023, everybody starts waking up and realizing that, hold on, the output doesn't seem to be proportional to the input here. What's going on? Yeah. And I think it's very interesting because over here, you very much have this ontological versus processed approach, right? That the tipping points are an ontology or are an object by themselves, but also are part of this circulation humans as well. So yeah, it's very interesting that you introduced that before. Yeah, I like the way you asked the question originally. And I sometimes think, yeah, there must have been something you might call a tipping point, perhaps an evolutionary tipping point in the human couple to the earth sort of story. It's hard to pick a finger on it, but at which, oh, gosh, we entered the what's called the Anthropocene and we all we entered the Great Acceleration and we went into this mode of what really appears to be driving it possibly its own destruction. I think the most compelling case is to be made for the switch into the kind of persistent economic growth, which some people obviously would celebrate. Some of us would have reservations about and that only really comes with the Industrial Revolution. Prior to that, there really was a strong damping feedback that you might get a little bit richer, but then you tended to have or have a bit more food production, but then you tended to have more kids and you just dilute the gains among more people and that damp damp the thing down again. The crux of what the most fundamental change that probably ties back to the origins of capitalism and extractivism and all of its sins is the point at which you switch into a long-run growth regime because as people get richer, instead of thinking I'll have more kids, they think, no, I have fewer and I'll educate them more. And then you get into this, essentially you get the beginnings of what has been, for what is it now, essentially in a half or so, some called long-run economic growth, but at great continuing to accelerate escalating cost on our life support system and everybody knows when they scratch their head hard enough that that just can't continue. As people have said for decades, sensible people have said for decades, you cannot continue to grow indefinitely on a finite planet. Yeah, as Kenneth Boulding was saying, you need to be either a madman or an economist to believe that. Exactly. And he said that in what was it, 1970? So before we switch gear to even more complex elements, which would be like socio-ecological systems, there is this one last piece that I would like to introduce, which are early warning signals. Where do these fit in in this whole tipping point? When a system reaches a tipping point, as it approaches, what you're seeing is the damping feedbacks that maintain the old status quo are getting weaker, and then some amplifying feedbacks that are about to really take over and propel change are getting stronger. So it's like a tug of war or something. Now, that's going to give telltale signs because in the complex world systems are getting kind of nudged all the time by little changes. And then you can watch how a system responds. And as you approach the tipping point, the system gets less and less good at recovering from the little shocks it might get from the world because the damping feedbacks that want to maintain the status quo are losing their power. And so that manifests as, oh, I nudged the system and now it moves further than it did and it struggles to come back. So it slows down in a literal sense of recovery, but the variability or variance in the system goes up. So we expect to see this coupled change, the statistical terms increase in the variance, but coupled with something we technically talk about as correlation in time or autocorrelation. But it's really just saying if a system is slowing down, then at one point in time, like today is more like yesterday and tomorrow will be more like today as the system slows down and we can statistically measure that. So we look for those coupled signals as a clue that our damping feedback or resilience in our system is getting weaker. That's not a cast-iron guarantee that we're about to hit a tipping point. What we should do as scientists is have other additional reasons to be thinking the system we're looking at could tip and that evidence can be because it has in the past, for example. Now, once we've got those ingredients we think, okay, yep, this is a system could tip, we can look in the data essentially for that. It's technically called critical slowing down behavior. We look for those statistical signals and of late other groups have been getting stuck into this as well. We've begun to get confident enough in the method and have enough data to be able to see that we can look at, say, the hours of rainforest from space, from satellites, from actually including from the International Space Station and we're looking at things like the fluctuation of the moisture content of the forest, which kind of, if the biomass of the forest fluctuates, the moisture content fluctuates as well, we can look at something like that and we can see, oh no, those fluctuations are slowing down over the last 20 years doesn't mean we're right at a tipping point, but it means the system is losing resilience. That's a worry and that's just one of many examples where we start to see this as possible and it gives us extra information about what's going on and where we're supposed to raise the alarm bells. Yeah, so more points in your map, I guess, to read your direction. So I'd like to picture bring about socio-ecological systems and how can we apply tipping points within these because as if ecological systems were easy enough and not complex enough, if you add a strata, a layer of humans that are completely non-logical human beings and organize into societies and interact with these ecological systems, you know, there is this famous element that says that there are some social tipping points if more than 25% of population adopt a certain behavior, then we have this cultural tipping point. How do you approach, you know, territorial or socio-ecological systems with the glasses that you already have? I tend to, first of all, look at it through the feedback glasses because I know it's on deep level and you could say it's a mathematical level and in this case you're going to have to buy into the view that there are some sort of laws of nature essentially that all of us as scientists have kind of signed up to that. But I would go to the message of socio-ecological systems through the same lens as a feedback and say, can we have or do we have a situation where the balance of feedback in this now even more complex system with the people in it could shift and the amplifying feedback that can exist in these systems, can it get to a point where it's strong enough, where it becomes self-propelling, which is by my definition a tipping point. How do I go about that? Well, I would look, do the same I do for the planet or the climate, you look into history and you say, oh yeah, there are some apparent tipping points here. There are these political process that turn into a violent or a nonviolent revolution, which then fundamentally change the trajectory of a nation. Or, oh, we went from horse-drawn carriages to cars in a decade in US cities that start the 20th century or a bunch of other examples. And then you ask yourself, or I ask myself, okay, this is interesting, what are the reinforcing feedbacks that can behind these tipping point changes? Well, protests and political revolutions are a classic example. The first person to protest is very brave. They're putting their life on the line sometimes, aren't they? But they crucially, by changing what's called their publicly stated preference, they're making it incrementally easier for the next person to break from social norms as they're called and join them in the protest, who makes it incrementally easier for the next one and so on. And sometimes that reinforcing feedback can get strong enough to cause exponential growth, self-propelling change, as we all saw with the climate protests movement and as we've all seen in history with other examples. And then you discover, oh, well, that's just one case of social contagion dynamics that can apply to other things, like a bank run as they're famously called when, you know, as soon as some people start thinking, oh, I'm not sure the banks are safe place for my money, I better queue up and get my money out. Other people start going, oh, my God, they're worried about the bank being solvent. They're taking their money out, I'd better go and take my money out and then that and so on. Right, so it's obvious that those ones are tipping points and strong reinforcing feedback. Technology is really interesting in our relationship with it, but it's not hard to dig around and learn a bit about those fields and realize, oh, yeah, actually, the people who are specialists on what's called diffusion of innovation have been saying for over 60, 70 years that, hey, there's a common pattern here that new innovation suddenly take off exponentially in their uptake, and that there's a bunch of stuff usually going on there. It's partly because people sometimes are imitating what other people do in taping up, in this case, a technology or a behavior. So that's very pure social contagion that gets called. But also, the more we make something, if it's a technology, the better we get at making it, so the more attractive it becomes to us to adopt it. But also, the more we make something, usually the cheaper it gets to make economies of scale we call it. And that's a reinforcing feedback as well. Now, all these reinforcing feedback sometimes going the melting pot together to together become strong enough to give you a tipping point like horse-drawn carriages to cars or something like that. Or at the moment, it's like petrol diesel cars to electric cars. So these are some of the positive tipping points that you call them? Yeah. So then my basic argument is, well, look at the evidence that we're crossing, we're starting to cross the bad climate tipping points and risking domino effects and things for a real genuine existential risk. And we've left it too late to just incrementally try to tackle climate change and stop all fossil fuel burning and greenhouse gas emissions. That's not going to cut it. So we're not going fast enough. We're doing something to try to act on climate change. But we're going about, I reckon by my latest estimate, somewhere between seven and 10 times too slowly at decarbonizing the economy. So we've got to believe we can find some pretty strong amplifying feedback. So we're going to amplify the change we need to technology and behavior change to get to basically stop emitting greenhouse gases. And that means finding and triggering what I call positive tipping points positive. Because in the normative sense, it's a very positive thing to avoid what will otherwise be, by my own calculations, the harm to billions of people later this century. So positive in that sense, accepting that every tipping point of behavioral and technological change will always run possibilities of losers as well as winners, beneficiaries as well as those who will feel like they suffer from the change. And where disbenefit or suffering from change intersects with people who are already suffering or less well off, then there's a political need to spot those cases. And, well, essentially provide what we call social safety nets of support for those who might be disbenefited for something that's for the debt we can all agree has to be for the collective good to avoid the extraordinary kind of harms that are going to escalating from a climate change. And so these positive tipping points, I think you have identified a couple of them. You mentioned the electrification of vehicles. I did. I mentioned electric vehicles, because you just look at the data from Norway in 10 years, the markets tipped from to 90% electric vehicle sales in 2023. And globally, I would argue my group's analysis would suggest we're very close to, if not past, a kind of global market tipping point. But we could probably think of it market by market. So a lot of Europe is already, I think, past the tipping point to electric vehicles. The Chinese market has the US markets a couple of years behind. But the point is, the more electric vehicles and the more, crucially, the more batteries for electric vehicles that get made, the cheaper the next battery has got gets to make, and also the better the next battery that EV gets. And we're near that cost parity tipping point. We're already at the tipping point, that the total cost of ownership of an electric vehicle is cheaper than or competitive with a petrol or diesel car in many markets. And we're even getting to the point where the purchase price is the same, knowing that their cheaper to run electricity is way cheaper than petrol or diesel. So that one's underway, and it's not a perfect technology, the new technology, but for sure it's way better than the one it's replacing. And then the other really big one is the power sector. It's electricity generation. It's the tipping point from fossil fuel power, electricity to renewable power. We're really, you know, I'm sat in the UK, where we in the last 10 years of or since 2012, we went from 40% of our power from coal burning to pretty much zero. There's one coal burning power station left in the UK and it's closing in September this year. So in less than nine months time. And all that 40% and a little bit more has been taken over by renewables. And as hopefully listeners will already know, there's exponential growth of solar power and wind power worldwide. And the solar power is they're both coming down in price all the time, the more they're deployed, but solar power is coming down in price the fastest. And for that reason, my colleague Femke and I say it's predicting robustly that, you know, maybe we're already past the tipping point in the solar power to have the potential to dominate even by 2050. There's a number of conditions that need to be met for that to happen and it could go faster. But we're already in a sense at the point where, yeah, those reinforcing feedbacks, the more panels I deploy the cheaper the next panel gets are so strong that they're beginning to rule the day or rule the dynamics. And even if you, for whatever political reasons, think you want to try and preserve the coal burning or the coal mining industry somewhere, you might find yourself faced with, in this case, you could call them economic forces that are so strong. Do I be able to? I'd like to summarize perhaps our discussion about these tipping points, right? I think for the listener or the viewer, they really need to take home perhaps a message about this dynamic component. Is it going from one state to another? What is something that after 20 years or so still surprises you or whenever you say to someone you feel like this is still blowing your mind about these tipping points are so essential in our everyday life or in our everyday understanding? Yeah, yeah. I mean, only kind of pinch myself sometimes when I wake up and realize, oh my word, we're right on potentially on the cusp of five big tipping points in the climate to commit ourselves to irreversible and damaging changes, like a loss of major ice sheets and loss of carbon frozen soils and so forth. Yet at the same time, I pinch myself because we have one get out of jail card left. And that is the evidence that we're also seeing this self propelling tipping point change happening in our social world and our technological world with a much faster than expected exponential growth of some things, things being crucial things like a renewable power supply electrification of the activities around us and arguably of some social and political changes, although it always seems frustrating, it always seems like why has that happened? Why hasn't that happened? But there's a lot of evidence that it is starting to happen. And that's what keeps me saying the knowledge that maybe the positive tipping points can win the race against the negative climate tipping points. What an existential and nail biting match over here. Perhaps, could you recommend this with a movie or a book that you would like to recommend for people to inspire themselves or continue the discussion? Of course, you had the discussion that inspired you to become a researcher. Yeah, I would have to say if you've never read it, you have to read James E. Lovelock Gaia, The New Look at Life on Earth, 1979, I think he first published it. That book changed my life. So did the next book he wrote, The Ages of Gaia, A Biography about Living Earth. In fact, the second one is, for me, better than the first. They changed my life, so they might change yours if you've not read them. Well, fantastic. There you go, everyone. You have more to read and to understand. After that, many thanks, team, for our discussion. It was lovely. Bye, Sarah, Steve.