The Ice Age Risk Hidden Inside Global Warming — 30 with Guyon Espiner S5 Ep2 — RNZ

[00:00:00] Speaker 1: Nau mai, haere mai, piki mai, kaki mai, kio rei tiwi and welcome to 30 with me Guy and Espina. We do 30 minutes with one guest and no cuts, so what we record is what you get. Well back in 2009, Johan Rockström led a team which introduced the world to the idea of the nine planetary boundaries that we must stay within, breach the boundaries for things like climate change, biodiversity, pollution and fresh water and we risk irreversible damage to our life support system. Johan Rockström co-starred with David Attenborough in the Netflix documentary Breaking Boundaries, now that was a few years back, so how many of the planetary boundaries have we breached now? And why is Johan Rockström increasingly concerned about the collapse of the Atlantic Ocean circulation system known as AMOC, once considered a far-fetched plot device in disaster movies like The Day After Tomorrow? Johan Rockström is a Swedish climate scientist, he's published more than 150 research articles, he's written five books and his TED talks have been watched by millions, so let's start the clock, 30 minutes, with Johan Rockström. Johan Rockström, welcome to 30. [00:01:23] Johan Rockström: Johan Rockström. Thank you, thank you, great to be with you Johan. [00:01:27] Speaker 1: Johan Rockström. So let's start with the planetary boundaries and outline how this works, these are what scientifically designed guidelines really are they to ensure we maintain the health of the earth? [00:01:40] Johan Rockström: Johan Rockström. Yes, I mean the planetary boundary science is actually a result of quite extraordinary advancements in earth systems science over the past 30 years, where we today understand that our planet is a biophysically self-regulating system with a number of environmental processes that regulates the stability of the system. We today understand that the last 12,000 years since we left the last ice age is an extraordinarily stable equilibrium state of the planet and is held in this basin of attraction called the Holocene thanks to the feedbacks, the sustainable feedbacks that that cools and dampens stress to the system. And we also now understand scientifically that there are tipping points, a number of biophysical processes and systems that are at risk of shifting dramatically from helping us and keeping the planet stable to self-amplifying and pushing the system away from stability. You put all that together and what the planetary boundary science did was to ask two questions. One is what are the environmental processes that regulates the ability of the planet to remain in a stable, resilient, for us life-supporting state? And the second question, which is the breakthrough, is can we for each of these processes, and we identified quite quickly nine environmental processes that scientifically are evidenced to regulate the health of the planet, can we for each of these nine find control variables, quantifiable, scientifically evidenced indicators that we can put scientific evidence behind and set safe boundary levels where we have support, scientific support that go beyond them, and we put ourselves in danger, but keep ourselves within them, and we have a high chance of staying within what we call a safe operating space for human prosperity and equity, basically keeping the planet as close as possible to a Holocene-like state, the warm stable interglacial that we have been benefiting from since we left the last ice age and started the civilizational journey that has taken us to the modern world of [00:03:50] Speaker 1: today. Okay, so you've identified climate, biosphere, land use, fresh water nutrients, ocean acidification, aerosols, ozone depletion, and novel entities, things like plastics and other man-made materials. How many of those nine planetary boundaries have we breached now? [00:04:12] Johan Rockström: Yeah, so our latest assessment, which was published in October 2025, concludes that we've reached seven of the nine planetary boundaries. This is very dramatic. It means that we truly have a planetary crisis on our watch. So it's not only climate, it's also what I call the biosphere boundaries, that we are losing too much of biodiversity, which regulates the health of ecosystems, both in the ocean and on land. We're over consuming fresh water, we're changing land systems, which is key for carbon stocks and carbon uptake. We're overloading with nitrogen and phosphorus and we're overloading with chemicals and we're even, and that's the seventh boundary that was just breached, we're even putting the ocean biology at risk through ocean acidification. So what we are doing, which is very unfortunate, is that while we are in the midst of a climate crisis emitting so much greenhouse gases that we're causing and heat imbalance on planet earth, we're at the same time eroding the resilience of the capacity of the planet to buffer that climate crisis. So we're doing a double mistake, which is represented through the planetary boundary [00:05:25] Speaker 1: science. So how damaging could this be? I think you're on record as saying that we are pretty close to or have now reached a global catastrophic level, which is defined by some as an event that could kill or seriously harm more than 10% of the human population. I mean, is it that bad? [00:05:48] Johan Rockström: Well, we are following a trajectory right now that if we continue on the journey we're on, which is continue to burn fossil fuels and increase greenhouse gas emissions, continue to losing biodiversity, continue deforestation, continue overuse fresh water, continue overloading nitrogen phosphorus, continue overloading with chemicals. I mean, but that's the problem, Gary, that all these curves continue rising. When you project that forward, then we see that by 2050, I mean, within just 25 years, we will be crashing through a two degrees Celsius level of global mean surface temperature rise, and that we at that point are at risk of crossing multiple tipping points, which can lead to a situation where the planet no longer on aggregate is helping us, meaning dampening the stress we're causing cooling the planet, while it instead can self-amplify and push us on a drift away from stability, which means that even if we would turn off our greenhouse gas forcing, the planet will continue getting stuck. Not necessarily a collapse of the planet and not a runaway, but that we get stuck in a situation where it gets worse and worse and worse, less and less livable conditions. I define that as an unacceptable catastrophic event. So it's not that we are facing that tomorrow morning, but within a very short timeline, if we don't turn things around very fast now, and that is something we have to recognize that the full catastrophic impact may be in 25 years, which I consider being a blink of time. But the determination of whether or not we face that catastrophic risk is now. It's the commitment moment is what we're doing within the next 5 to 10 years will determine what happens over the next 25, 50 hundred years. [00:07:41] Speaker 1: Okay. Well, for climate scientists and climate agreements, the magic number has been staying within 1.5 degrees warming above pre-industrial levels, right? 1.5 to stay alive. We breached that, as I understand it, in 2024, didn't we? So is the 1.5 target now gone? [00:08:05] Johan Rockström: Well, to begin with, I mean, that's quite reassuring from a scientific perspective, that the 1.5 degrees Celsius number signed on in the legally binding Paris Agreement in 2015 is a planetary boundary. That is a limit. It's wrongly defined often as a goal or a target. It's not a goal or a target. It's a limit. Go beyond it, and we enter danger, just like the planetary boundary science has defined it. Now, yes, you're right. In 2024, we, for the first time, experienced exceeding beyond 1.5. We saw how that hurts. It hit, you know, the insurance companies assess over 200 billion US dollars of assets were impacted. Millions of people were impacted by floods, droughts, heat waves, human-reinforced storms. We saw the pain of experiencing that. But that doesn't mean that we permanently breached 1.5, because scientifically, we define the global mean surface temperature limit as the moving 10-year average. So we're not yet beyond, permanently beyond the 1.5 boundary. However, our scientific conclusion over the last, just last year, is that we will inevitably breach 1.5 more permanently within the next decade. So we are very rapidly moving in that direction, unfortunately. And particularly because we're seeing that global warming is accelerating right now. And this is exactly what the planetary boundary science has been predicting, that when we lose the resilience in the system, in the Earth system, the buffering capacity goes down, which can lead to accelerated warming, even if we don't necessarily accelerate our burning of fossil fuels. So yes, we are heading towards what we call overshoot, meaning transgressing the boundary of 1.5. It will very likely happen very soon in the next few years. And our challenge, therefore, is to try to do everything we can to come back after overshoot, which we scientifically conclude is still possible. But it will require two things. One is rapidly phasing out oil, coal and gas. But secondly, also coming back to the safe operating space of the biosphere boundaries, because we need a resilient planet, a healthy ocean, healthy natural ecosystems on land to be able to absorb carbon and to help us back within that 1.5 degrees Celsius boundary. [00:10:33] Speaker 1: If we breach that boundary, what does the world look like? [00:10:40] Johan Rockström: Well, you have the immediate impact of breaching 1.5 more permanently, which is more suffering. I mean, we've been suffering at the level of billions of co-citizens in the world. More fire, more heat waves, life threatening heat waves impacting on labor productivity, impacting on agriculture and food security because of changes in hydrology, floods, droughts, more disease patterns spreading across the world, higher risks of pandemics, very, very high increase in frequency of human reinforced hurricanes, typhoons, higher frequency of El Nino events. So basically, a more turbulent planet and much tougher life conditions. That's one, very high certainty on that occurrence. The second risk, which is more uncertain scientifically, is that we then enter a domain where we're likely to cross tipping points. We are at risk of pushing the on button of irreversible melting of the Greenland ice sheet, of the West Antarctic ice sheet, even crossing the tipping point for the Amazon rainforest. We're very likely to lose large parts of the tropical coral reef system that are already at that tipping point level, abrupt thawing of permafrost. All these systems are scientifically shown that somewhere between one and two degrees Celsius of warming, with a median level of assessment of 1.5 degrees Celsius, is where they are likely to cross the thresholds. If they do that, what happens then is that we commit to a less and less resilient planet that will start hitting back, start really sending invoices back to the world through accelerated warming. Because all these tipping point systems in their healthy state, they help to cool the planet. And we know this, you know, a stable ice sheet is a big, big slab of ice, which is white, and it reflects 90% of incoming solar radiation back to space. It's a cooling system. When that system irreversibly melts, the surface gets darker and it starts absorbing more heat. That's what we call the feedback, the self-amplifying feedback. That's what we really do not want to happen. I mean, I would even say we cannot allow it to happen. That's why we're trying to argue that we need to turn this around very, very rapidly. [00:12:57] Speaker 1: Okay, so from what you're saying, in your framework of the nine planetary boundaries, climate change isn't just one problem among nine. It's the one that can trigger all the others, right? I mean, that's the sort of cascading logic you seem to be outlining. [00:13:16] Johan Rockström: That's right. We have nine planetary boundaries. They're all interconnected. The biosphere boundaries, the nature boundaries, regulates the strength and health and the capacity of the planet to absorb the stress caused by our heat imbalance, which the climate change boundary represents. Through our fossil fuel burning, we add greenhouse gases that absorb heat. But the other way around is actually, exactly as you say, also correct, that if the heat continues, it weakens the biosphere boundaries, the rainforest systems, the hydrological cycle, the soils, the wetlands, they all weaken and are more likely to go from stable and dampening and cooling to unstable, amplifying and warming. So this is a completely interconnected system, which actually means the following: that even if you focus only on solving the climate crisis, if that's the only thing you politically or even business-wise are able to focus on, you have no choice today. You have to consider the whole planet. You have to consider all the planetary boundaries, even if you only want to come under 1.5 degrees Celsius, because even if you stop emitting, stop burning oil, coal and gas, you'll still fail unless you solve the fresh water, the biodiversity, the nitrogen, phosphorus and land boundaries simultaneously. [00:14:41] Speaker 1: Okay, let's talk about the AMOC, the Atlantic Meridional Overturning Circulation, or AMOC as it's called. What is it and why is the collapse of it or the prospect of that so alarming and worrying? [00:14:57] Johan Rockström: The AMOC, which is one of the three thermal haline pumps that regulates the whole ocean conveyor belt, so basically the currents across all the ocean systems on planet Earth, is a phenomenally important system that regulates the currents across the Southern Ocean to the Northern Ocean in the Atlantic. It is a thermal haline pump, which we understand quite well. It is saline warm surface water flowing from the Southern Ocean up across the Gulf Stream in the US and reaches the tip of Greenland. At that point, it releases heat to the atmosphere, which makes it, by the way, more pleasant to live in my part of the planet, which is in the Nordic region. This high density, heavy water having released its heat, so cold saline water, is so heavy that it sinks and thereby drives the engine that makes the water then flow back on the ocean floor back to the Southern Ocean. And this drives the whole ocean conveyor system, which then regulates heat exchange in the ocean. And remember that 90, 90% of the heat caused by our fossil fuel burning and our greenhouse gas emissions is not in the atmosphere causing the 1.5 degrees Celsius we just talked about. It's stored in the ocean. So the ocean is this massive thermostat storing the bulk of the heat imbalance we're causing. That's really the big, big resilience engine on the planet. And the AMOC is one of the systems that keeps the system stable. Now, so that's number one. Number two is it has a switch. And we know this. It's well scientifically established that over the past hundred thousand years, the AMOC has been shutting on and off several times. And we also understand why. Because what happens is that when you get a very, very high flux of fresh water, for example, through melting of ice sheets, it dilutes this very saline, high density surface water. And the more it's diluted, the less heavy it is, and the less fast, the slower it sinks. And that slows down the engine. So it has happened before. We understand the physics. And also we have observations now that it has slowed down already now by 15%, very likely because of the dilution, because of rapidly melting ice sheets in the Arctic. So that is the basic science. Then we also have evidence today, which is quite unequivocal actually, that if it would shut down, it would be a global, it would have global catastrophic impacts. It would accelerate warming. Net warming would increase even faster globally. It would change the monsoon system. So it would impact even on causing more droughts and fires over the Amazon. And it would have an abrupt catastrophic change of weather conditions in Northern Europe and North America and Russia. [00:18:04] Speaker 1: In terms of that, sorry to interrupt you there, but in terms of those changes to climate in Europe, I mean, so you would, the tropics would heat, but Europe would go what, into some sort of ice age conditions under that scenario, would it? [00:18:21] Johan Rockström: That's correct. That's our understanding that the AMOC and how it operates is what gives this very conducive weather condition in the Northern Hemisphere by adding heat to the atmosphere. And if that shuts down, it would be an abrupt sudden cooling that can be a cooling, you know, exceeding an abrupt cooling of more than 10 degrees Celsius of reduction, which would be like entering an ice age condition for the Nordics, Russia, parts of Canada, but particularly the parts over North, North Europe. And so that would be a very, very catastrophic event in that region. But I think that the key issue here is actually what happens at the global level, which is a net warming. So yes, you have these regional differences. But what is key today is the following. In the latest IPCC assessment, the Intergovernmental Panel on Climate Change, the sixth assessment, which was based on our understanding of the AMOC functioning up until science, up until 2019, 2020, was that we could not quantify the risk. And the assessment was that there's a low likelihood of a shutdown this century, so between now and 2100. But there's low to medium confidence, meaning that we have little, not limited evidence. Since then, just over the past five years, there have been multiple big studies that have run big climate models and really revisited this risk and concluded that we've underestimated the likelihood of a shutdown even within the coming 50 years. There are studies showing that there's even a 30% likelihood of a drastic slowdown over the coming 50 years if we continue burning fossil fuels as today. And if you ask the AMOC experts today, they will tell you that the likelihood of a really significant slowdown, not necessarily a full shutdown over the coming 50 years, is today a likelihood of somewhere between 1 and 10%. Now, for a likelihood of 1 to 10%, for a catastrophic impact, anyone who understands risk, risk being equal to likelihood times impact, knows that if an impact is unacceptable, then a likelihood of 1 to 10% is is unacceptably high. Nowhere in society we would ever accept that kind of likelihood. That's the [00:20:54] Speaker 1: point we've reached with the AMOC. Yeah. So just to drive this home, and correct me if I've got this wrong, but the relationship between climate change and the AMOC is that with global warming, we are melting ice and putting more fresh water in the ocean, and that is disrupting the AMOC, right? [00:21:12] Johan Rockström: It's that, and actually, which we had underestimated but is now being proven, we change hydrology as well. So by warming the planet, you get more evaporation. More evaporation meets more humidity in the atmosphere, which means actually more rainfall. So you get more fresh water. So the AMOC is impacted not only by melting ice, but also by inputs from more fresh water from the hydrological cycle. [00:21:38] Speaker 1: And is it a binary thing? I mean, can it be switched on and off? And I think you were saying that that has happened in the past, if we go back through records. Exactly. It has happened in the past, and it's [00:21:50] Johan Rockström: happened several times in the past, and it is binary. And I mean, the thing is that for us in our world, we have difficulties in handling things occurring over a hundred year period, which of course geologically is a very, very short, is an abrupt event. So it may take a hundred years before it's completely shut down, or it may even take longer than that. But yes, it is a switch on and off. [00:22:18] Speaker 1: Let's spend the last nine or so minutes on a possibly more optimistic note, or talking about what we can do. To stay within these planetary boundaries, does it mean us giving up this quest for endless economic growth? Or can we provide decent standards of living for, what, eight billion people and still significantly reduce global energy and resource use? [00:22:46] Johan Rockström: I would say, well, to start with, we've come to a point where we've reached what I call a saturation point on planet Earth. Whether you define that in planetary boundaries or not is secondary. The point is that there's no more free space, neither in the atmosphere, nor in forests, nor fish in the ocean. Nowhere is there any more opportunity to operate according to the old economic paradigm, which was invented at a time by Adam Smith and the big economist, when actually one could admit that we were still a small world on a very big planet. You could add pollution to the atmosphere, you could overfish, you could kill whales, you could cut down trees and it didn't have massive planetary scale impacts. That era is now over. We filled up the whole planet. It's all saturated. We now have to be smart and operate within finite budgets of a safe operating space. This, of course, means that there is just one carbon budget, one nitrogen budget, one biodiversity budget, one freshwater budget that we all need to share. So there is a very, very significant equity and justice dimension, which means that the GDP-based growth model we have been running over the past 200 years is obsolete and will not take us to the future we want. Does that mean that economic development and modern well-being is now over? The answer is no, definitely not. On the contrary, we have so much evidence that we can be both prosperous, innovative, and I would even argue that if you operate and be guided by planetary boundaries, you are more likely to innovate yourself and be more resource efficient and take yourself to the future that we are already seeing that we're heading towards, the electrified, digital, green, energy-powered global economy, which is more modern, more fair, more resilient and independent and more local. And this is a future that I think is a more positive future. So sustainability and the planet boundaries is today guiding us towards a better future, not backtracking ourselves. And we do have evidence that, you know, both with regards to returning to the safe operating space on energy and returning to the safe operating space on the food system, we have solutions, we can achieve that. [00:25:23] Speaker 1: If you look at ozone depletion, it's one of the boundaries where we are actually going in the right direction. And it's interesting, isn't it? Because that was a case where, I mean, I think CFCs, which were creating that hole in the ozone layer had been around since the 1950s. They were in refrigerators, they were in fire extinguishers, they were in everything. And then when scientists rang the alarm bells in the 1970s and the 1980s, the world reacted. I think it was the 1987 Montreal Accord or whatever it was called, the Montreal Protocol in 1987. And we phased them out and we've done the right thing in that response with remarkable speed. So why hasn't climate change produced its own Montreal Protocol moment? [00:26:11] Johan Rockström: I'm so glad that you take that up because you're right. The stratospheric ozone layer is one of the nine planetary boundaries, is the protective stratospheric layer that protects us against dangerous UV radiation. And yes, we were threatened by, you know, we had an existential risk, impacting potentially on life conditions on the southern hemisphere, so in New Zealand, not least. And policy listened to science, and industry innovated, and we came back into the safe space on the stratospheric ozone layer. So we have been planetary stewards before, we can manage the planet at the planetary level. And the question then was, what made the Montreal Protocol possible, and how does that compare today? Well, I would say that three things were in place to successfully deviate away from this existential risk of ozone depletion. One was the science was established. I mean, it gave a Nobel Prize to Paul Critson and colleagues. Number two, policy listened. Policy trusted science and listened to science, and there was trust between countries to act collectively, collectively as a world community. And number three, we had solutions. Industry was ready to innovate. Now, for climate, we have until very recently not been able to tick off these three. The climate science is established. Policy has actually listened. I mean, we have the Paris Agreement, we have the UNFCCC and the climate accord. I mean, we have a difficulty right now on distrust. But, but strictly speaking, policy has already locked us in on a trajectory to solve this problem. But we've lacked number three, we've lacked the scalable solutions. But since just five, six years, that's no longer the case. We know that electrifying is today, across all economies in the world, much cheaper, much smarter, much easier to do with wind and solar than with coal. We have no reason today to power even mobility with diesel and petrol, which is shocking cost at the pump because of the homeless sound, when it's much cheaper and smarter. It's actually more, more pleasant even, I mean, it's cooler to do it electric. So we are actually for the first time reaching what I call a Montreal moment for the climate crisis. Indeed, the energy transition is a bigger challenge than phasing out chlorofluorocarbons. But it's, it's finally coming to that point where there's no excuse to act. And I think this will actually, this is one reason why we're seeing some pushback today, that the climate transition has now matured so far, and is so likely to succeed, that is becoming a real threat to the oil, coal and gas incumbents that, that try to resist all change and stay on a business as usual path. [00:29:18] Speaker 1: So just finally, given that, are you optimistic that we can make this energy transition and possibly stay within at least if not quite 1.5, then pretty close to it? Are you an optimist in any sense on climate change? [00:29:39] Johan Rockström: Well, it's a really difficult question then because on the one hand, scientifically, I'm not optimistic. I'm really nervous. There's never been reason to be as nervous in my professional career as today because we are coming so close to tipping points and we're still not able to bend the curves. So that, that makes me pessimistic. It makes me also pessimistic when I look at the world today, our fragmented distrust and, and the populism and nationalism, and actually quite frankly, short-termism that we see across the world. And, and all focus is on, on military conflicts. And, and it's so sad to see what's happening in the US with regard to science and sustainability and climate. But what makes me still have some light in the tunnel is what we just touched on that we have now so much evidence that we reached this Montreal moment on the climate transition. We also know that the food system transition and the energy transition are the two big transformations that can bring us really back into the safe operating space. And both of them have solutions and have multiple benefits, both for health, security, prosperity, and equity. So it's a kind of a win-win-win outcome. And finally, I just came back from Colombia and the Santa Marta process. For the first time in human history, 57 countries gathered to accelerate the phase out of fossil fuels. And, and that was actually a very momentous event. It, it created, it was clear that this is a significant number of countries, 25%, 30% of global GDP really decided that now enough is enough. Now it's time to start bending the curve and move away from this dependence, not least on, on, on, on, on undemocratic supply of oil and gas, but also that it can give more resilient and secure and prosperous futures. So in that sense, we are in a, in a very, very challenging, yes, but also a space where we've reached a maturity point when we can move this forward. So I see that as, as an important positive sign. [00:31:54] Speaker 1: Well, thank you very much for sharing your expertise with us. We really appreciate that. Thanks for inviting me. That was 30 minutes with Johan Rockström. That was 30 with me, Gaia Nespina. We'll catch you next time. Ka kite. [00:32:30] Speaker ?: Thank you.