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Not Cool Ep 3: Tim Lenton on climate tipping points

September 5, 2019

What is a climate tipping point, and how do we know when we’re getting close to one? On Episode 3 of Not Cool, Ariel talks to Dr. Tim Lenton, Professor and Chair in Earth System Science and Climate Change at the University of Exeter and Director of the Global Systems Institute. Tim explains the shifting system dynamics that underlie phenomena like glacial retreat and the disruption of monsoons, as well as their consequences. He also discusses how to deal with low certainty/high stakes risks, what types of policies we most need to be implementing, and how humanity’s unique self-awareness impacts our relationship with the Earth.

Topics discussed include:

  • Climate tipping points: impacts, warning signals
  • Evidence that climate is nearing tipping point?
  • IPCC warming targets
  • Risk management under uncertainty
  • Climate policies
  • Human tipping points: social, economic, technological
  • The Gaia Hypothesis

References discussed include:

To have any hope of keeping global warming below two degrees, let alone 1.5 degrees, we're now looking at having to undergo relatively rapid societal transformation. We need to find the good tipping points or the positive tipping points in social, technological, economic systems that are going to get us onto a sustainable, flourishing future.

~ Tim Lenton


Ariel Conn: Hi everyone, and welcome to the third episode of Not Cool: a climate podcast. I’m your host, Ariel Conn. 

Today we’re talking about tipping points. We tend to think of climate change as a slow, incremental process, where things get gradually and linearly worse. But when a system reaches a tipping point, it loses those characteristics — it changes more quickly, less predictably, and often irreversibly. We’ll talk about whether it’s possible to tell when a system is approaching a tipping point, which elements of our climate system might be getting close to tipping, and whether we may have already passed any major tipping points. 

We’re joined by Dr. Tim Lenton, who’s a leading researcher on the subject. Tim is Professor and Chair in Earth System Science and Climate Change at the University of Exeter and Director for the new Global Systems Institute. He researches the ‘Earth System’, which refers to the complex web of biological, geochemical and physical processes that have shaped the chemical composition of the atmosphere, oceans, and climate of Earth. 

Well Tim, thank you so much for joining us.

Tim Lenton: Thank you for having me.

Ariel Conn: So you did a lot of the really early work on climate tipping points, and I believe you've been working on that and related issues since. I want to dive right in and just start by asking you what a climate tipping point is.

Tim Lenton: Yes, good question. A climate tipping point is a point where a little bit of change in the climate, maybe a little bit of extra global warming, tips a part of the climate system into a different state. So it triggers a transition from current configuration or state into some different state — for example, triggering the collapse of the overturning circulation of the Atlantic Ocean, which transports heats northwards and into northwest Europe. Or it could be triggering a dial back of the Amazon rain forest it, or it could be the tipping of the disruption of a major monsoon system. All of these are parts of the climate system that we would say mathematically have non-linear dynamics. They contain feedback processes that self-amplify. So you start to push the system and then it gets propelled under its own dynamics sometimes to transition into this other state. It doesn't happen all the time, but can happen in a range of these bits of the climate.

Ariel Conn: And so what would we expect to happen if a tipping point is hit? How does that impact the climate then?

Tim Lenton: Well it depends on the particular tipping element, as we call the bits of the climate system that could have these tipping points, because they have their own time scales. So ice sheets are very sluggish; The ocean circulation is fairly sluggish. But the dynamics of the atmosphere and of monsoons are incredibly fast. And the time scales of forests or coral reefs are somewhere in between. So if we tip an ice sheet — for example, we trigger the irreversible melt of the West Antarctic ice sheet, which we think might've already begun — we don't see the ice sheet melt instantaneously.

It has its own time scale of collapse governed internally and is in that hundreds of years; whereas if we tip the shift in the monsoon, let's say the Indian summer monsoon system, it could happen from one year to the next. So those kind of bound the opposite ends of the scale and time in terms of how quickly a bit of the climate system would respond. In many of these cases, though, the important thing is even if something's responding slowly, like an ice sheet is slowly melting, we might've triggered what is actually an irreversible process, or a very difficult to reverse process. That's one of the special qualities of tipping points.

Ariel Conn: So it sounds like you're saying we might have already done this in the Antarctic?

Tim Lenton: Yeah, it's alarming isn't it? What we see is, so the West Antarctic ice sheet is unusual in the sense that it's a load of ice stuck onto bedrock well below sea level for the most part, with a few mountain ranges sticking up. And we know that that makes it prone to a particular kind of instability, that if you start to trigger the retreat of major glaciers, particularly if they have a particular topography of the bedrock underneath, then they can go into an irreversible retreat. What we've observed in the last decade or so, very convincingly, is that one of the major ice drainage basins, as they're called in West Antarctica, draining into the Pine Island Basin embayment, as it's called around West Antarctica — that one seems to be in this irreversible retreat. 

And that's not the only part of the West Antarctic ice sheet, but the problem is, when one bit goes, it then has knock-on effects to the other bits of the ice sheets. It kind of undermines them, if you like, and triggers them ultimately to retreat, at least in models. So we might've begun what you can think of as the tipping of the dominoes of West Antarctic ice sheet breaking up. I'm not saying that with 100% certainty, but if that is the case, that means we've made a commitment already to a bit over three meters of sea level rise from West Antarctica.

Ariel Conn: So that leads into this next question I have is, what is the impact then on the rest of the Earth and the climate system if that shelf melts?

Tim Lenton: If we've triggered the melt of the West Antarctic ice sheet and committed ourselves to three meters of sea level rise, in the long run, that's already a major issue for some mega cities near the coast. London, for example, has a barrage, has a defense against storm surges and sea level rise, but it's only designed to withstand up to about two meters of sea level rise. So we're already in this situation where, in the long run, we'd have to think hard about the ability to prevent major flooding in a major city of the UK there. 

We also at the moment can’t rule out that the Greenland ice sheet is also in some kind of irreversible melt. It's certainly shrinking at an accelerating rate and retreating up onto land, and we're not sure whether it's going to re-stabilize on land or continue melting. And that's worse because that's another — up to seven meters of sea level rise. So we could already be in a situation where we're committed to eventually causing on the order of 10 meters of sea level rise just with the one degree of global warming we've had so far. Now it actually fit with data from Earth history, which shows that the sea level, on the long term, is incredibly sensitive to small temperature changes, but yet would completely reshape coastal or near-coastal inhabitation by people. So that's just one kind of tipping point, and it's a difference of their impacts if we talk about much faster responses like disrupting the monsoons in the tropics.

Ariel Conn: What does that mean, "disrupting the monsoons in the tropics”? I feel like, especially in recent years and this year, we're seeing more news stories about extreme storms.

Tim Lenton: Exactly. So if we took the example of the Indian summer monsoon as an iconic monsoon system: All monsoon systems are driven by the seasonal summer heating of the land happening faster than the heating of the neighboring ocean. And that sets up rising air over land that draws in moist air from the ocean, that then rises, and then the water in it condenses, and that's the monsoonal rain. When that water condenses, that releases heat, latent heat and condensation, which then drives the monsoon circulation: a great big circulation of air where you have the dry air returning at altitude back over the ocean. And it spins around in a great cycle. Now, monsoons switch kind of on and off on a seasonal basis, and there's a kind of tug-of-war going on anyway where, as global warming or global heating happens, it warms the northern land mass of Eurasia faster than the ocean to the south.

And that ought to be strengthening the monsoon in India for example, but at the same time, there's a whole lot of air pollution going into the atmosphere over India, and has been for decades. And that suppresses the heating in summer of the surface of the continent because the load of sunlight's getting scattered or absorbed in the atmosphere instead by this great cloud of pollution above India. Up to now, that pollution cloud has won the battle and has actually been overall weakening the monsoonal rains in India and impacting the rice harvest. But as this tug-of-war with the global warming signal is underway, it does sometimes seem to be manifesting in more extreme precipitation.

So this is clearly a complicated picture where we're really not sure which way things are going to go in some ways, but we know we're dealing with a very volatile system anyway that has these strong feedbacks within it. So, is it responding eventually with more extreme rains or are we even running the risk of collapsing the monsoon in some sense? The jury's partly out on this. I suppose the thing to know is that we're already interfering with something that's vital for food production and livelihoods for upwards of a billion people.

Ariel Conn: I’m also sort of intrigued by what you're saying about the pollution almost mitigating some of the effects.

Tim Lenton: There's more than one monsoon system in the tropics. We could also talk about West Africa and the Sahel regions, south of the Sahara in West Africa, where you have a monsoon that seasonally, the rains jump northwards into the Sahel in May/June time and cause — famously the Sahel had a severe drought through the 1980s, and that's now at least partly attributed to aerosol pollution that was biased to the northern hemisphere of the planet, because that's where most of the industrial activity has been going on.

Ariel Conn: Oh wow.

Tim Lenton: So in that case, we have a human signal contribution to a very famous drought that led to famines in sub-Saharan Africa. And since the '80s, we've sort of cleaned up some of the air pollution in the industrial north, and that's one of the things that you could say has contributed to the rains to some degree returning in the Sahel. But we have a separate problem that in some climate change scenarios, we see an abrupt warming of the Gulf of Guinea Ocean, which is kind of in the nook of south of West Africa if you like. And if that happens, it can trigger  — it's not exactly a collapse of the monsoon in West Africa, but it locks the monsoon, the intense rains, to just stay nearer the coast, along the coast of West Africa — and they don't, in the models at least, jump north into that part of the Sahel. So if that were to happen, that would be pretty catastrophic for the band of sub-Saharan West Africa there.

Ariel Conn: How comfortable do you feel in saying that we would be able to recognize that we're getting close to a tipping point, if in fact we are, versus figuring out too late that, oops, we've already passed it?

Tim Lenton: That's a great question. I've spent quite a lot of the last decade testing out some mathematical theory which says that whenever a complex system's approaching a tipping point, there are some characteristic early warning signals beforehand. And they’re quite counterintuitive, because before one of these abrupt and perhaps irreversible shifts in the system, the system will actually become more sluggish in its ability to recover from provocations or perturbations it's getting from the world, if you like, or from the variability it experiences. That's actually a signal of that system's resilience, as we call it: its ability to bounce back from perturbation is getting weaker. But it seems kind of sluggish, and I guess more and more sluggish. That's actually the warning signal that it could lose all resilience. At that point, it can just roll off into some other state.

So what we've been able to do is show that before known past abrupt climate changes, this early warning signal was present quite clearly in fact. And also in model worlds, climate models were able to force tipping points to happen, and we can show that before they happen, these early warning signals are there. So of course we started to turn our attention to real climate data, and we do begin to see some of these characteristic signals that we call slowing down in the climate system. So of course we carry on working on that in trying to deduce whether we're getting an early warning of an impending tipping point. In all of this, there's nuance, so the method works best and is most reliable when we have a clear separation of time scales. We want to look at a situation where part of the climate system's actually been forced fairly slowly compared to its own internal dynamics, and that we're also monitoring it much more frequently than its internal dynamics.

And the truth is, humans are forcing the climate system, or bits of it, quite quickly. So the best early warning signals would probably exist for the faster bits of the climate system — the monsoons, maybe some fast responding vegetations and biomes, like the vegetation in the Sahel. And for ice sheets, or the ocean circulation, it's a difficult exercise to get the early warning signal, and we need to be able to reconstruct natural variability over centuries, if not millennia. But that said, some of my colleagues do work on that and we might still have the potential to get some warning that bits of the climate are going in the wrong direction. My hunch though is that we're not going to be smart enough to act on that information. It might just be a useful forewarning for adaptation, to try and lessen the impact.

Ariel Conn: When you talk about these systems becoming sluggish, can you give an example of what sluggishness looks like?

Tim Lenton: Let's take the Amazon rainforest as a possible candidate here. It experiences droughts and has been doing more frequently actually recently, part of the overall climate change that's happening. And it's also experiencing more fires associated with those droughts. Sluggishness in this context would be how quickly — or rather how slowly — does the forest bounce back from a drought or a fire. Sluggishness would mean a slower recovery of the tree cover, and the greenness, and the vegetation; compared to a more resident state where it would bounce back quicker, if that makes sense. That biological example is perhaps a bit more intuitive, literally things growing or not, compared to the same thing for ocean circulation.

If I tried to visualize that for you, it'd be like saying there's variability in the climate naturally and when the ocean circulation is resilient, it might get stronger or weaker, but it recovers quickly to its preferred strength. When it's less resilient and the tipping point is nearer, when it gets a nudge it goes on a longer excursion. It might vary in strengths for longer and more before it finally recovers. And eventually it reaches a point where it doesn't recover: You weaken it and instead of bouncing back, it switches off. 

So I like to use the physical analogy of a chair — not a fancy office chair, just a good old fashioned chair. Upright is one stable state for a chair. On its back on the floor is another stable state for a chair, and the person sitting on it who is foolish enough to do this experiment. But if you play with a chair, you can find a balance point where it could go one way or the other. It could return to upright or it could fall over backwards. And if you mess around with a chair and you feel the dynamics of the chair near that balance point, you'll find that they're very sluggish near the balance point — but once you start tipping it, it accelerates and it rapidly goes into one state or the other. That's just a little bit of a physical example to try at home to get a slight sense of what we're talking about.

Ariel Conn: Okay, I really like the chair example. I think that's really helpful. So there's sort of two directions that I want to take my questions next, and I think I'm going to start by switching to the 2 degrees Celsius that the IPCC has been advocating we try not to hit, and especially the 1.5 degrees Celsius that's still this potentially unrealistic ideal, but we'll see. How did they choose those numbers?

Tim Lenton: Well, the 2 degrees C target has a long history, actually. Really it began life in the 1980s before the Intergovernmental Panel on Climate Change had even officially been instituted, but in the opening discussions for why we needed it and why we needed a scientific assessment on global warming and climate change. Even then, good researchers knew some of the risks that were being run with the changing climate and the possibility of triggering major ice sheet loss, for example. And with relatively less information then, it was clear that warming the planet too quickly or too much would pose a threat to UK systems to adapt, as well as to certain ice sheets and so on. And crude estimates, even back then, started to fumble around towards a couple of degrees warming as being potentially dangerous. It represented a rough estimate of how much warmer recent so-called interglacials — warm spells between ice ages — had got.

And we know, for example, in the last interglacial — maybe it was actually less than 2 degrees warmer, we think now — but the sea level was up to 10 meters higher. For example, major ice sheets were lost. So all of this information fed in right from the start as good reasons to think why we might want to limit the temperature increase pretty hard. I personally think 2 degrees was a round number that had some scientific evidence behind it, but might also be seen to be politically achievable. Recently we've seen, understandably, a shift towards, "Oh, if only we could limit the temperature rise to 1.5 degrees. And what on Earth are we going to have to do to make that goal?"

That's because lots of science has happened in the intervening decades that’s shown us that we're already running the risk of climate tipping points, if we haven't crossed some already, and that unfolding and possibly irreversible damages are highly undesirable. So we've upped our ambition nominally in terms of these goals for, I think, pretty good scientific reasons, but sadly we've done it against the backdrop of still rapidly increasing greenhouse gas emissions. So as the target comes down, the hopes of meeting it drift off the table, to be honest, tragically.

Ariel Conn: I've read stuff of yours in the past where you suggest that a global temperature is probably not the only thing we should be looking at, anyway.

Tim Lenton: That's right, yeah. I think I might be foolish to even have ventured into that territory because I think it's hard enough for politicians and policy makers to wrestle down even the beginnings of the complexity of the climate system. So trying to suggest to them that they don't just worry about temperature change might be a bridge too far, unless they're a very rare one with a very good science education. But basically the reason why one would think about more, what sounds like very abstract concepts like how much extra heat energy is being trapped in the surface and the system and the climate, is because it's actually that extra heat energy — which is like a flux of energy that we sometimes call radiative forcing — that's the thing that actually melts ice sheets or drives the climate change in the first place. So I experimented with whether we could actually more tightly define some of these tipping points in terms of that extra radiative forcing. The trick is then how on Earth to operationalize that or make that understandable to this complicated policy decision process. But it's going back to the physics; That's the reason to think about it that way and maybe it’s at least useful for scientists to be absolutely clear what the driving physics is.

Ariel Conn: I think you actually bring up a really interesting problem that we have here, and that is we have this problem that's incredibly complex, and yet we need to try to simplify it so that people don't need to have PhD's in climate science to be able to follow and address the problem. How do we do that?

Tim Lenton: I think most listeners would've at some point got on a jet airplane and flown somewhere and been comfortable doing that. But there's a lot of relatively complex physics going on around building that aircraft and flying the thing, and we all did our own internal risk calculation about taking that flight and getting on a plane, and it scares some people more than it scares others. When we flip around to the climate problem, it's considerably more complex than an aircraft, but we're quite well equipped as humans to deal with risk management under uncertainty — in this case, perhaps profound uncertainty, because we acknowledge that the system we're interfering with is so complex, and we all have to acknowledge that we don't fully understand it. But that shouldn't paralyze action.

In the case of the climate system, if we used a sort of finely honed risk management sensitivity and we understood and internalized the risks we're running, driving the temperature of the planet up, we ought to be working much harder to limit the temperature rise and get lots of other co-benefits from switching our energy sources and readily sort of reinventing our future. Maybe that wasn't the clearest of answers, but we don't have to wrestle down the complexity and uncertainty in order to act, and we shouldn't have to.

Consider the financial crash in 2008 and 9. Nobody would've said at the time, "I understand why that happened. I could wrestle down the complexity of the financial system," but it didn't stop our government spending trillions of dollars, or pounds, or Euros bailing out the banks, because it was a situation of profound uncertainty, but the stakes were incredibly high. And we were able to react decisively in that situation. The tragedy is that we aren't doing the same thing with a much bigger risk: the climate system. But in principle, it can happen. We have the capacity to act under uncertainty, and in this case, it's an existential threat. So we ought to be able to switch those capabilities on.

Ariel Conn: What type of policies would you like to see enacted?

Tim Lenton: Well, I personally would put a pretty hefty price on carbon dioxide emissions or the extraction of fossil fuels that are going to lead to those emissions, and I'd put a sensibly set price on other greenhouse gas emissions. I'm a bit agnostic about how you apply that pricing mechanism. I'm not an economist by training, but I've got no personal problem with whacking a hefty price on that very damaging pollution. And then if that means having to redistribute the burden of taxation from other things in our economies and our societies, then that's fine and we should do that, because at the moment we're catastrophically undervaluing the damage that is being done by greenhouse gas emissions.

So we’ve got to fix that right off the bat, and that will immediately help promote changes that are underway anyway, which is, let's electrify energy, let's take fossil fuels out of the equation of power generation, and switch to, I think, a healthier energy-replete future powered quite a lot by renewable energy to be honest. Lots of that available. Let's electrify transport, wherever possible, underground. If we need hydrogen fuel cells or whatever to get what remaining aircraft we want to use off the ground, then we’ve got to work some technology magic there. 

We also need to stop the land surface and its ecosystems from still being a net source of greenhouse gases because of bad land use practices, deforestation, et cetera, and really look after the land, the ecosystems, change our agricultural systems so they're locking up greenhouse gases, carbon in particular — not releasing them.

We need to regenerate some natural ecosystems — integrated forest help in this. As you can tell, the laundry list is a long one, but we know lots of things we can do, and the bigger the penalty on the pollutant, the greenhouse gasses, and the bigger the incentive to act to get them out of the atmosphere rather than adding them, then the more our economy, as it were, would work to help solve the problem rather than, at the moment, it's just working to help create it.

Ariel Conn: I'm curious what your response is to people who say they don't want to look at these extreme situations because they think they're less likely to happen, and instead focus on the problems that we know are most likely to happen.

Tim Lenton: Well, I think they might be wrong about the likelihood. There's been a widespread presumption that these are high impact but very low probability events, but the evidence from the real climate, so far, is rather arguing they are higher probability than might've been assumed. But if we set that to one side, whether you believe me or not on that, does it really matter whether it's death by 1,000 knives or by the guillotine? At the end of the day, hopefully a lot of us can agree on the severity of the issue we're faced with.

And even if you took my climate tipping point out of the equation, I think a lot of us would agree that to have any hope of keeping global warming below two degrees, let alone 1.5 degrees, we're now looking at having to undergo relatively rapid societal transformation. In simple terms I would say we need to find the good tipping points or the positive tipping points in social, technological, economic systems that are going to get us onto a sustainable, flourishing future and get us off the kind of train wreck of ongoing fossil fuel burning and simplistic GDP growth paradigm that's currently still ruining the planet. So in simple terms, whenever you think about the climate tipping points, perhaps we can all appreciate that tipping points could also happen in society for the good or for the bad, but we need some for the good if we're going to have a long and happy future on the planet. Let's go out and find those, and try and trigger those to happen.

Ariel Conn: I really like that sentiment. You've been doing this for over a decade now. In that time, what has surprised you most, both good and bad, with respect to how people are responding, and what the science has said?

Tim Lenton: For the climate system, the shock that we might already have gone past a tipping point or two at the poles, with the evidence that accumulated that we're losing the West Antarctic ice sheet, or we've begun to lose it; and the evidence that continues to accumulate that Greenland is shrinking at an accelerating rate. I feared 10 years ago when we drew up the map of climate tipping points that these were real facts, and they might be imminent, but I wasn't expecting them necessarily to be that imminent. So that's been a genuine unpleasant shock. 

As for human reactions, where do I see hope? Well, I see hope in the sudden mobilization of collective attention on this issue led by inspirational individuals like Greta Thunberg over here in Europe — a kid that just looks at the science and goes, "Oh my word, this is my future you're ruining. There's no point going to school. I'm going to protest outside my school every Friday." That's now a global movement. It's an entirely logical global movement I think.

We have something called the Extinction Rebellion here in the UK, which is a sort of all age groups incarnation of exactly the same recognition. Is it leading to much actual change? Well, I suppose time will tell, but before really widespread change can happen, you have to have this kind of political change, and peaceful protesting, and shifting of the issue up the agenda. So that's a source of comfort and hope. 

The other thing that excites me is, even absent any serious climate policy, we're seeing really incredible uptick of electric vehicles, at least in rich countries. And we're seeing the price of renewable electricity out-competing coal burning, certainly in several major nations, and that's really exciting. It means even without having properly priced climate pollution, greenhouse gases, just the intrinsic technological innovation and change is starting to give us the better option as the most economically viable one.

Ariel Conn: And then, we have a little bit of time left, so I want to ask you also about the Gaia hypothesis. First, what is the Gaia hypothesis?

Tim Lenton: Well, the Gaia hypothesis, as it was conceived in early 1970s by Jim Lovelock with the help of Lynn Margulis, is the proposition that all life on the planet is part of a self-regulating system that maintains atmospheric composition, and in a very unusual chemical state, and may also be involved in the long-term in regulating the climate. Now that was the Gaia hypothesis of around 1972, and since then of course Jim Lovelock and others, including myself, have learned more and realized more about how the tight coupling between living things and the atmosphere and the climate has evolved over time. And sometimes life is — we recognize — is a destabilizing force that triggers major change in the whole Earth system, or Gaia, as we might call it. And humans seem to be case in point of that. We're clearly disrupting a previously more stable configuration with our new metabolic waste products and fossil fuel burning. So it could be in the beginning of one very rare transformation or change times for the planet.

Ariel Conn: You made that sound like there are other instances in the past where life has also been destabilizing.

Tim Lenton: Yes, but we wouldn't be here to talk about it if they hadn't happened, which is the beauty of it. So one of them is when a little creature we now call a cyanobacteria managed to do something utterly incredible, which is what we think of as the normal form of photosynthesis, but it actually is the most difficult form of photosynthesis of many that are going on among microbes on the planet. The cyanobacteria pulled off the trick of splitting apart water molecules to get electrons so they could stick on carbon dioxide to reduce the carbon down into sugars. That was an invention that ultimately led to a profound rise in oxygen in the atmosphere, which we call the Great Oxidation event about half way through the planet's history, 2.5 billion years ago, that irreversibly created an oxidizing atmosphere. It didn't bring the oxygen up to modern levels, but it took a big step in that direction.

There's then another turbulent time with the rise of complex life, which ultimately ends with land plants appearing, colonizing the continents, from about 450 or so million years onwards. They finally bring the oxygen, fairly abruptly actually, up to modern levels, to a level that you and I can exist and talk about it. But those changes were not entirely smooth. We definitely think that at least one of them was a major tipping point change. So that's one of the, from a human perspective, one of the best tipping points in the history of the planet because we couldn't be here without them. So not all tipping points are bad of course, and maybe it lies in the eye of the beholder.

Ariel Conn: So if humanity accidentally wipes itself off the face of the Earth, future species will be grateful?

Tim Lenton: Well who's to say, but we are humans, so it would be a profound act of collective self-disinterest and misanthropic not to want to create a long, happy future for our descendants, whatever they may be. At least that's my take on it. And the cyanobacteria, they caused this incredible, great oxidation, but they're still with us and they're inside animal cells and plant cells doing all the photosynthesis I can see around me as I look out of my window at the green trees and grass. So they caused ultimately an absolutely profound change, but they made their way through it and still triumphed. That's far from clear for humans, but that's the challenge we've given ourselves, really, is: are we going to make this a transformative change for the whole planet, including ourselves, and seeing the other side of it? Or are we just going to be a kind of futile blip in the future geological record that some unimagined lifeform or alien lifeform is going to eventually dig up from Earth's future? I know which one I'd vote for.

Ariel Conn: Hopefully the former.

Tim Lenton: Yeah, definitely the former, but I have friends who have argued that they're just going to drive around as fast and as hard as they can to bring down the end sooner because they think that we're a mess and we should extinguish ourselves. So there's all shades and colors in the rich tapestry of human life, isn't there?

Ariel Conn: There is. You recently published a paper on Gaia 2.0, which is an extension, I believe, of the Gaia hypothesis — sort of a more recent model. What is that about?

Tim Lenton: So the central point I'm trying to get across there is that what's unusual about us as a species, humans, is now in the 21st century we are, or we're becoming, collectively aware of the global consequences of our actions. We talked a minute ago about the cyanobacteria 2.5 billion years ago. Well, they transformed the planet, but I don't think anyone would say they had a collective awareness of what they were doing as they were doing it, because they're very simple creatures in comparison. So that awareness we have of the global consequences of our actions is something unusual and arguably new in Gaia or in the Earth system. I wouldn't say we're doing a great job yet of using that awareness of the consequences of our actions to change our actions, but some of us have started to change our behavior and our consumption habits because we think that they are unsustainable.

The exciting thing for me is, if we bring, as a species, a little bit of self-awareness into the existing self-regulation and workings of the Earth's system, what form could that take? Where could it take us? What lessons would we take from the biosphere, or Earth history, to try to make a happier, more flourishing, sustainable future for ourselves and all the other living things we need, because they're our life support system? It's a proposition that there is something new — and that's why I called it Gaia 2.0 — that little bit of human collective self-awareness in the Earth's system; and there are new feedbacks emerging, but it's still unclear which way it's going to go.

They range from global technocratic geoengineering schemes, which imagine that some privileged subset of humanity are going to geoengineer a preferred climate that they're presumably going to decide on for everybody else to take or not; through to much more, you might say organic responses, where we look to work with nature, or Gaia, to support its self-regulating mechanisms and its resilience, and help it flourish because we know that we flourish with it, if you know what I mean.

Ariel Conn: Maybe you even said this specifically, but this sounds very much like a human tipping point that we're sort of striving for.

Tim Lenton: I think so, and I think we're basically, whether we acknowledge it or not, we're in a time where either we live up to our name, which I think means — homo sapiens, I think it means wise people — either we find that wisdom or we don't. So I think we're in a time where it could tip one way or the other, but some of us would like to do everything in our power to try and tip that kind of shift in collective awareness, collective action, and relationship with the rest of the world around us, in simple terms. So that's going to be quite profound and quite exciting, I think, if it does happen. I'm not saying it will happen, and I see reasons for hope and reasons for despair at the moment. But at least there's a lot to play for; I mean, the chips are down.

Ariel Conn: Is there anything else that you think is important to mention that we didn't get into?

Tim Lenton: No, we covered some good stuff there.

Ariel Conn: Okay, excellent, well thank you so much.

Tim Lenton: No problem.

Ariel Conn: On the next episode of Not Cool, I’ll be speaking with Jessica Troni, who is the Senior Programme Officer responsible for the UN Environment’s Global Environment Facility’s Climate Change Adaptation portfolio.

Jessica Troni: Consideration of climate risks in government — national government — and business decisions isn't enough. We also need to partner with local communities so that we plan for adaptation in a way that makes sense to local communities, and that delivers benefits to poorer, unrepresented people. 

Ariel Conn: I hope you enjoyed this third episode of Not Cool. My next interview with Jessica Troni will go live on Tuesday, September 10th. In the meantime, please join the climate discussion on Twitter using #NotCool and #ChangeForClimate and let us know what you think of the show so far. 

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