Welcome to the last of our series on Why Net Zero. I'm Myles Allen, professor of geo, professor of Geo System Science at the University of Oxford, and the Gresham professor for the environment. So those of you who've been attending all of these lectures, well done. Thank you very much. And, uh, just, I'll just start by reminding you how, uh, in the first of these Gresham lectures, I introduced you to some little lumps of coal. Just to remind you, each of which represents half a trillion tons of fossil carbon and which if burnt and released into the atmosphere would cause one degree of global warming. Together, they represent more or less the reserves of fossil fuels. We've got available underground, so one degree, two degrees, three degrees, four degrees, and so on. Now, in the six months that I've been giving these lectures, we, we, when I give you that first, when back when we originally discovered the need for net zero, we'd already burnt the first half trillion tons. We're working our way through the second one. We've got about a third of the way through already, and in the six months that I've been giving these lectures, we've burned about 1% of this half trillion tons of carbon. So 20 billion tons of carbon dioxide into the atmosphere in six months, enough to cause a hundredth of a degree of global warming. Now, a hundredth of degree doesn't sound very much, but that's in six months. So in five years, that's a 10th of a degree in a decade. If you add on the impact of other pollutants who are putting into the atmosphere like methane, getting on for a quarter of a degree, a quarter of a degree per decade, that's how fast the world is warming at the moment. Thanks largely to continued burning of fossil fuels. But the good news is we have resolved to stop this, the world has agreed on net zero and that will, so this later is about that good news, but qualified good news, because I started with the title, how the World Agreed on Net Zero. And what I'm gonna try to explain to you is the way we managed to agree on net zero was by not actually agree on what it meant. Before we start, I'd like to remind you where this carbon dioxide has been coming from. Look at this video of carbon dioxide emissions over the past 250 years, early 19th century Notice, one small island off the coast of northwest Europe was responsible for the vast bulk of human carbonide emissions. The idea caught on Germany, caught on. It's moved on to the eastern seaboard of the US by the end of the 19th century. It had spread out across the US and Japan was taking off early in the 20th century. You can actually see the impact of the world wars. India and South Africa are starting to show up. And after the second World War, we see the explosion of emissions as China took off, Indian industry took off, and we saw the developing modern pattern of emissions emerging. But I think it's worth remembering that video because, you know, looking around ourselves at all, the extraordinary wealth of the city of London over the years, that's where it came from. Britannia ruled disguise a long term before we ruled the waves. We were the origin of this problem, which is why th whenever they keep telling you how much of a climate leader the United Kingdom is, yeah, we are a climate leader, but not in the way you want to be. 2009, we just burned through the first half trillion tons of fossil carbon, and that was the year we published all the papers in which we showed what it would take to stop global warming, reducing emissions to net zero would be enough to stop global warming and the reducing carbon, the oxide emissions to net zero and the warming we end up at is determined by the total amount of carbon dioxide we dump in the atmosphere. So the number of little lumps of coal we work through, it doesn't particularly matter how fast we dump it. What matters is the total, and this was revolutionary at the time because the goal of climate policy was very different from that. It was stabilizing concentrations in the atmosphere and we were struggling to work out what concentration we should aim for. But this realization that it was the total amount of carbon you burned, that made us realize that actually a much better thing to focus on was just limiting this overall carbon budget. So far, that was the science. Only six years later we saw in the Paris Agreement, the world acknowledging, first of all the need to limit warming in particular to well below two degrees and pursuing efforts to 1.5 degrees. And that was an extraordinary achievement for the world's governments to accept, given what they also knew what it was going to take. Because not only had it become clear how important it was to limit warming below two degrees, but it had also become clear how hard it was going to be. And yet they still stepped up and said, yep, we're gonna go for this. So that was the extraordinary achievement of the Paris Agreement, which was well worth celebrating. And we'll come back to sort of how the Paris Agreement acknowledged this and the implications of all this as well. But just I'd, I'd like to sort of dwell a little bit on that. Those six years between those papers being published in 2009 and the Paris Agreement in 2015, we had a process in place, the intergovernmental panel on Climate change, which allowed the science behind those papers in 2009 to be assessed and digested by not only the scientific community, but also the world's governments and considered, you know, that made sure they understood it, had appreciated the consequences so that it could be adopted so quickly by governments. So they didn't end up just bickering endlessly about the science behind this commitment and got straight on to what they were actually going to do about it. So I think for an international environmental issue, this has gotta be one of the fastest adoptions of action or plan of action to deal with the issue imaginable. And people sort of worry about how slowly we're making progress on climate change. You know, that was a good six years and it's even more striking by the fact that those six years, particularly the year 2009, 2010, was actually characterized if you, if you're a climate scientist, we can all remember back then we were traumatized by a whole bunch of emails being leaked from u e a and, and lots of inquiries and lot, you know, it was in interminable headlines about climate science being corrupt and all the rest of it. So there was, there was a, there was a lot going on during those six years. There was a lot of pressure, I guess, from those who really didn't want this to happen, to make sure it didn't, and it nevertheless did. So despite the noise, despite all the shouting, the world's government's knuckled down and acknowledged what needed to be done. And since then we've had this commitment reiterated, um, and in particular pursuing efforts to limit warming to 1.5 degrees has been reiterated in the Glasgow Climate Accords signed in 20, uh, 20, uh, 2021. That was in, in Glasgow obviously enough, um, which you probably all remember cause that was the, the most, uh, the, the big climate conference that happened in the uk, um, just sort of just towards the end of the Covid pandemic. Um, of course, 1.5 degrees is particularly challenging, cuz remember I said, each of these lumps of coal takes us another degree of warming. So at the time we published the papers, we knew we just burnt the first half trillion tons, and we figured we had another half trillion to go before we got to two degrees. Well, of course, if you've, if you're aiming for 1.5 degrees, then you've only got half of that. So you, we, you know, aiming for 1.5 degrees cuts the remaining budget that was around back then. And of course, we've also eaten into it and still are. So, you know, we're eat we're eating into it from one side and we've just, we've, we've moved the goalposts forward on the other side. So there isn't very much left, which is why I reiterate again and again whenever I get a chance, we, we will Generate more carbon dioxide by burning fossil fuels than we can afford to dump in the atmosphere if we're gonna meet the Paris Agreement goals. That's a really simple fact that I don't hear climate activists and the sort of climate illuminati the people who, the, the sort of important people who, who talk about climate on, on the radio and television a lot, most of them are not actually climate scientists, but they have a background of central bankers or politicians or whatever. And they don't, they don't say this. And it's really important that everybody understands it. We will generate more fossil fuel, more carbon dioxide from burning fossil fuels than we can afford to dump in the atmosphere and still meet our cl our climate goals. And that simple fact has very profound implications,

<affirmative>,

To come back to the Paris agreement. It's not clear, I, I essentially the Paris Agreement committed the world. And I was gonna say, it wasn't clear whether everybody in the room necessarily knew that was what it meant, but I I, I think they probably did. Um, so committed the world to hawk global warming within a generation. They didn't put it this way. And it's important not to read more into these agreements than it's actually written into them. My colleagues in international war are very particular on this sort of thing. Um, but because of course people tend to, people tend to sort of love to spin these agreements to say what, what the Paris Agreement means is this. And no, the Paris Agreement means what it said, but we are now at one and a quarter degrees of warming, by the way, on the radio you'll hear quite often, we're now at 1.1 degrees of warming, slightly frustratingly. This is because the most recent intergovernmental panel on climate change assessment decided in its wisdom to define the current level of warming as the level of warming over the most recent decade. And if you think about it, the average temperature over the most recent decade, if you're at a time where it's warming at a quarter of degree per decade, is going to be cooler than where we are today. So the correct statement of where we're at is not 1.1 degrees, it's one in the course degrees, And we're warming at a quarter, quarter of a degree per decade. So again, you don't need a complicated climate model to know it's not gonna be long before we reach 1.5 degrees at the current rate of warming, or to put it differently, it's not gonna, we don't have long left before we have to stop the warming. If we hit the brakes, now we've got about 20 years to stop the warming if we're going to limit it to around 1.5 degrees. And we got only about 50 years even if we want to limit warming to less than two degrees. And again, in that opening lecture, I emphasized this is not a complicated scenario or modeling result, it's just simple geometry. It's what it takes to bend the curve. So that's the time, that's the speed of transition that the Paris Agreement has committed us to, which is why, as I say, I'm convinced we need to stop global warming before we stop burning this stuff. The other thing the Paris agreement did was it asked the intergovernmental panel on climate change, this body that had sort of successfully processed the net zero science and, and got it into a form that governments could digest it and accept it to work out, whether it could be done in particular, this 1.5 degree goal, this because that was new and that was actually, that came outta nowhere completely blindsided us. I, we, we should have anticipated it, um, because it was being talked about by a lot of developing countries in the buildup to Paris. But to be honest with you, you know, when I saw the Paris outcome, um, I was completely staggered. And my initial reaction was really, um, I mean the idea that we would try and limit warming to 1.5 degrees. Up until then, all of our scenarios, the most optimistic scenarios we had available were looking at limiting warming to below two degrees. So, um, the, um, Paris Agreement actually as part of the agreement, they actually agreed to invite the scientific community, the intergovernmental panel on climate change to assess whether it was even possible. And that was actually a condition. Some countries who were sort of a bit nervous about this 1.5 degree goal made it a condition of signing on that they would re you know, they, they would, uh, that the United Nations body, the, the governments would request the scientists to do this assessment. And we did. Um, in 2018, it was the, um, it was a pretty breathless process because normally, um, in intergovernmental panel on climate change reports take, you know, six, seven years in their preparation, this one had to be compressed into about 18 months. But they didn't give us any breaks on the review cycle and the amount of government checking and so on. So we just had to work harder. Um, and, uh, you know, we basically came out with the conclusion of what it would take. And this is the central line of, uh, of, and again, this is, you know, negotiated language, so I apologize if it's not particularly, um, you know, media friendly, but this is what we could get everybody in the room to agree on reaching and sustaining net zero global anthropogenic CO2 emissions. Well, in this lectures you'll all understand what that means. Okay, now that's reasonably clear. Um, and declining net non CO2 rated forcing. Okay, well if you've been attending these lectures, you'll know what that means. It's a little bit more jargony. But basically what that means is we're reducing the energy imbalance due to other stuff in the atmosphere. Things like methane and aerosols and so on would halt anthropogenic global warming on multidecadal tone scales. And the word halt is there, again, this was a hotly contested word I think we started off with stop. Um, but certain countries, like small island states and so on, were concerned that we didn't wanna send a message that this would stop it forever, cuz we couldn't guarantee that. Um, because we don't really know what would happen. After many centuries of net zero greenhouse gas emissions and declining net zero CO2 emissions in declining rates divorcing, we couldn't really predict what would happen. So we came up with the word halt implying that, you know, it would, it would hold temperatures stable for at least a few decades. And that was how we summarized the, the what it would take to stop global warming. In the update from, uh, the sixth assessment report published a couple of years ago, um, we have what this means. So halting warming requires approximately zero global carbon dioxide emissions. You know, there's a, there's a range of uncertainty there, but, but you know, for for, for for working purposes, it's, it's around zero and declining methane emissions. So that's this, that's the biggest driver of this non CO2 forcing. Um, I've really focused on CO2 in these lectures because that's the big player in all this. Yes, methane matters. Um, and rumor has it, there's gonna be a lot of talk about methane in the COP 28 coming up in Dubai. Um, partly because the oil and gas industry feels it has a positive story to tell about methane and all the success they've had in controlling their methane emissions. Um, I think it's important for all of us to be clear, reducing methane emissions is a nice to have. But that reduction in methane emissions, even if achieved means a couple of tenths of a degree on peak temperatures whenever they occur, if we don't get carbon dioxide emissions to net zero, there will be no peak temperature. We won't stop the warming. So methane reductions are a nice to have and people who want to stress success love to say things like, we need to reduce methane emissions to keep 1.5 alive. And forget to mention, we need to keep reduced methane emissions and get carbon dioxide emissions to net zero by mid-century to keep 1.5 alive. Okay? And the second half is a lot harder than the first. So don't let them svengali you into thinking we've all done very well if we manage to reduce methane emissions and let's not worry about co2, we'll deal with that later. No, CO2 is the big one. If we don't get CO2 emissions to net zero warming will continue because every lump of coal we dump into the atmosphere drives up global temperatures by another degree. Doesn't matter what we do to everything else. So is it all sorted? Is the Paris Agreement settled the issue? The crucial article there is Article four. So Article two set the temperature goal well below two degrees, pursuing efforts to 1.5 and article four have just highlighted the most important parts in order to achieve the long-term temperature goal set out in article two, limiting warming parties, aim parties are the countries of the world to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century.

Now

Sounds reasonably unambiguous, but if you've been following these lecturers, you'll probably immediately spot there is a crucial ambiguity in that sentence. Anthropogenic emissions by sources and removals by sinks of greenhouse gases. What exactly do we mean by removals, by sinks here? Well, in the French and Spanish versions, interestingly of the Paris Agreement, it says anthropogenic emissions by sources and anthropogenic removals by sinks. So that's a little bit more specific, But the English version was the one that was negotiated and apparently so I understand from my international lawyer colleagues, that's the one you kind of have to go back to, um, for arguments over the interpretation. And actually that doesn't really make that much difference to what, to the issue we're coming to, which I've built up to during these lectures as to what exactly removals by sinks means. Anyway, they did make this agreement. We got to this net and the uk um, and I think we should all be quite proud of this fact was the first country to go beyond the Paris agreement and actually enact net zero into legislation. I think we beat the French by a couple couple of days. And in this letter from Teresa May, which was sort of sent around everybody, um, sort of noting this fact and, and celebrating this fact. Um, she, she and she pointed out, ending our contribution to global warming by 2050 can be the defining decision of this generat generation in fulfilling our responsibility to the next. So certainly Therea may felt that achieving net zero was ending our contribution to global warming. I mean, I think that's what most people think it means. So you may be disappointed to hear that the way it's actually formally defined in most accounting systems that are used by the companies and many countries around the world,

Even

If we did it, it wouldn't stop global warming at all. And there will be great disappointment. We're doing well on paper. That's the coverage. If you go to the net, net zero, uh, track our website, um, you can see that 92% of the world economy is covered by some form of net zero commitment. 85% of the population, 88% of the emissions. They have a map which shows you which countries actually have these, um, in law, the dark green here or in some kind of, um, sort of sub legal commitment in in light green or in in discussion in brown and so on. So there's various, um, so the UK for example, if you click on it, you find that we've got a detail plan, we've got a reporting mechanism. Um, we're being a little bit ambivalent about whether we'll use international offsets. So, um, that gets red. Um, but we've covered all greenhouse gases, so, so lots of green lights for the uk. Um, you'll notice there are some countries on this map, which are blue, not very many. They're all countries in the tropics with large forests. And these are countries like Gabon that have already achieved net zero. Um, there's sort of, they've, well the, the net zero tracker is grumbling that they haven't got a detailed plan, but hey, they've already achieved it, so why would they need one? Um, and it covers all greenhouse gases and so on, which is interesting because um, that's a scene off the coast of Gabon. But of course that gas is for export, Gabon has a lot of rainforest, um, and um, they've actually done a pretty good job of protecting their rainforests and they've received a lot of money from the global north to protect their rainforest, um, which is all a good thing and undoubtedly, but, but you know, if we all defined net zero the way it's being defined by many of the world's governments, and I've just, it's not really fair to sing like Gaon. It's just an interesting example because there happened to be one of the few countries that's already, that claims to have achieved net zero already, what would actually happen. So in order to understand, let's quick recap. Remember our elaborate, um, hydraulic climate model that we had in the last lecture. I, I didn't, didn't bring it back cuz it's such a pain in the neck <laugh>. But, um, but, but this is just to remind you what it takes to, um, but I mean, you know, go back on, look, look on the, look on the video. Cause we worked hard on that model. If you didn't, if you didn't catch that lecture, um, and, and annoyingly that the, the, the technicians could have cut out the bit where I set it going and then go, oh, anyway. Um, but uh, but they didn't. So you can see the jokes as well. Um, if we want to stabilize atmospheric concentrations of greenhouse gases, okay, this is seconds in the model, but it could be years in the real planet. So com atmospheric concentrations in the middle, in blue, stabilizing atmospheric concentrations allows emissions to continue for many, many well seconds in the model or years in reality. Um, which is, um, makes life easier for people, but of course doesn't actually stop global warming. Temperatures keep rising in response to stable concentrations of greenhouse gases. If we actually want to stop the warming stabilizing temperatures, then we need declining concentrations of carbon dioxide in the atmosphere, which requires net zero CO2 emissions. So again, to remind you, this is what's going on in the carbon cycle today. We're pumping CO2 into the atmosphere at 35 billion tons of carbon dioxide per year. That's sort of average over the past decade or so. Agriculture and land use change. Deforestation adds another five to that. So 40 billion in total, hence 20 billion tons of CO2 in the course of these Gresham lecturers. Meanwhile, the biosphere is taking back 11 billion tons of carbon dioxide back out of the atmosphere and the oceans are absorbing 10. So the accumulation of anthropogenic carbon dioxide in the atmosphere adds up to about 20 billion tons per year. So 40 miners, so 19 or so 19 billion tons of carbon dioxide accumulating in the atmosphere every year. It, and it's the what we, how we deal with these absorptions of carbon dioxide in our definition of net zero that turns out to be the giant loophole that allowed the world to agree on net zero by leaving it a little bit vague and which may result in great disappointment if we actually achieve it and then discover it doesn't actually stop global warming. I'd just like to stress, there's nothing wrong with the science. If we got to net zero emissions from em, from emissions that are directly due to ongoing human activities, then we would stop global warming. So I'm not sort of backtracking on any of the science we did in 2009. The problem is the definition of carbon dioxide removal has been left a little bit vague. And this is, this vagueness is propagating out through the entire economy, um, including, you know, companies making net zero commitments and using offsetting and so on to achieve them, um, in a way that, you know, means it, it could be built in, locked in to, um, our, our decisions going forward and, um, making it very difficult to, to unpack. So I think, I think we've got a, a real challenge on our hands to get people back focused on what we originally meant by net zero, because that is, as Theresa May put it, what it will take to stop global warming. This is where we are. This is just taking those carbon, the, the the global carbon project numbers and you know, showing you how they add up. So 35 from fossil fuels in industry five from direct land use that's driving up and that, you know, we've got this passive uptake by the biosphere, meaning that's what the biosphere does without us having to do anything to it. It just is responding to the fact that we're adding more carbon dioxide to the atmosphere. Trees are growing faster cause there's more CO2 there and that sort of thing. The ocean's absorbing carbon dioxide. And now I've added an extra term here. Remember the, the hatching. Now remember that in that, uh, carbon cycle model, there were three tubes and as I added carbon dioxide to the atmosphere, it flowed quickly into a rapidly responding tube corresponding to the near surface biosphere and near surface ocean, and then trickled off slowly into the deep ocean if I, so, so the, the, the trickle out of the atmosphere was going to these two other tubes, some of it was going to the big fat one, some of it was going to the, the thin one, which was responding quite quickly. So it's, it's really important how much is going to each And the rate of flow into the big fat tube depends on the level of carbon dioxide in the atmosphere. Because remember the big fat tube, it was, it was a fat tube. So the, the the, the amount of carbon, the amount of fluid in it didn't change very much in the course of our experiments. I can go back and remind you of that with this graph. Here we are. So as we're driving co2, and you know, this, this black line is the amount of carbon dioxide in the, the, the deep ocean tube and it barely budges. Okay? So there is carbon dioxide flowing into it, but it, and, and it flows into it ever faster as the level of carbon dioxide in the atmosphere, um, uh, uh, rises. The green corresponds to that middle tube, the, the rapidly responding one. And you'll see there, although there's a bit of a delay, it basically goes up along with the level of carbon dioxide in the atmosphere. So it sort of keeps up with the atmosphere. And so when we st so, so the atmosphere is rising like this. The second tube is rising just a little bit behind it and the big fat tube wasn't really responding at all. So when we stop emissions the two thin tubes sort of, you know, equilibrate quite quickly and then they just slowly go down. Okay? So the important message in this is that carbon is going into is, is leaving the atmosphere due to two things. One, the rate at which we're putting it in. So that's driving some carbon oxide outta the atmosphere. And the other is the total amount we've already emitted. That's what's driving it into the deep ocean. And so in this figure, I've hatched the part of the flow into the biosphere and the oceans. I've just distributed it uniformly between the biosphere and the oceans. You can quibble about exactly how it would be distributed, but the total is correct. That's due to the cumulative, the accumulation of carbon dioxide or accumulation of emissions since pre-industrial times. And you'll see in a minute why it's so important to separate out that contribution. Suppose we were to decide we were gonna achieve net zero tomorrow, okay? And take full advantage of the accounting systems that the United Nations Framework Convention allow. And by the way, people argue about whether this is true. So I should probably add using U N F C C accounting rules and a good lawyer, okay? But if you have a good enough lawyer, you could probably get away with this as a definition of net zero under U NF triple C accounting rules. And look what's happened. We've reduced our fossil fuel emissions by quite a lot. Um, we've introduced so-called nature-based solutions to balance remaining land use emissions. So we've, we've, uh, we've, uh, replanting forests, uh, to compensate for any further emissions from land use. Um, we, we've done this overnight, so the absorption both carbon dioxide by the oceans and the land hasn't changed. It's, it's just continuing as it did last as it did yesterday. And these bars all balance as I hope you can see that the green and blue bars are the same thing as the red one. So we have momentarily achieved net zero, okay? But to remind you, article four, the Paris agreement is about in order to achieve article two. So that's not net zero because it wouldn't deliver article two. Article two is stopping global warming. And if you wanna stop global warming, you need to sustain net zero over many decades. It's not good enough just to get there for a year. So that's really important. We need to not only reach net zero, we need to sustain net zero over many decades. And of course, as soon as we stop putting, as soon as we reduce the rates at which we put carbon dioxide into the atmosphere, the rate at which it is taken up by the oceans will drop because there's two components to what's going into the oceans and the land. There's a component which is driven by the fast response to what we're pumping in all the time. And this hatched component which is driven by the accumulation of carbon dioxide in the system as a result of past emissions, by the way, you'll notice the hatched bars were a little bit bigger here than they are here. That's because I'm assuming that we don't get there for a few decades. And so there'll be more carbon dioxide in the system. So that might be the sort of one and a half degree situation around mid-century. The more carbon dioxide we put into the system, the more we depend on the natural biosphere and oceans taking it out again to stop global warming. And we can put a number on that. You may remember, I've, I've kept on talking about 0.3% per year at various cast on in, in these lectures that tells us how much, how fast we need the natural system to take carbon dioxide out of the, out of the atmosphere in order to hold temperatures stable as a fraction of the total amount of carbon dioxide we've put into the atmosphere. So if by the time we get to one and a half degrees, we've released, uh, some, so one and a half of these lumps of coal or um, doing the maths, uh, rapidly in my head about three, around 3 trillion tons of co2, um, don't hold me to that. Um, then we would um, we would need about 10 that we would need nature to be taking carbon dioxide out of the atmosphere at a rate of 10 billion tons per year. That's a quarter of our current emissions just to keep temperatures stable. Now if we leave her alone, nature will do that if, and that's a really important point and actually one of the really profound things that's occurred to me in the course of preparing these lectures, and I think there's gonna be a paper written about this shortly, is that the responsibility to protect those natural sinks because we need them to keep temperatures stable, actually depends on how much carbon milk had we've put into the atmosphere. So thinking about that movie of all the countries in the world that have a unique responsibility to protect the natural world, to allow it to take carbon dioxide back outta the atmosphere when we've achieved net zero is the one you live in. And interestingly, of course the UK doesn't have much nature. We're quite small. So the amount that the UK is responsible for because of our cumulative historical emissions, about 250 million tons of carbon dioxide per year. So not far off our current emissions of the uk, we're gonna be counting on that being absorbed somewhere and it'll be mostly absorbed somewhere else in the world. So maybe we should be thinking in our international negotiations rather than priding ourselves on how fast we're reducing emissions. How should we be supporting countries like Gabon who we are absolutely counting on absorbing carbon dioxide to keep temperatures stable after we've achieved net zero That is enough to stabilize concentrations. But as we've stressed, that's not enough to stop the warming if you actually want to stop the warming. Cuz here you can see there's a balance between flows of carbon dioxide into and out of the atmosphere. But that would, that just holds the atmospheric concentration stable. In order to get temperatures to stop rising, we need the atmospheric increase to go negative. We need nature and humanity between them to be taking some 10 billion tons of carbonide back out of the atmosphere every year and to keep doing that for decades. So nature will do that for us if we leave it alone and protect it and stop deforesting it and stop turning it into range land to grow stakes and so on. But it's gonna, that, that comes at a cost, a cost to those mostly developing tropical countries where we're counting on these forests doing this work for us. And I think this is something we should be talking about. How are we going to compensate these countries for doing this favor we need them to do to the rest of us in order to keep temperatures in order for net zero to mean what we think it means, which is enough to stop global warming. The other new element that's shown up here is that we've balanced all our remaining fossil fuel emissions with what I'm calling engineered removal. So deliberate removal of carbon dioxide from the atmosphere and disposal probably back underground cuz that's the cheapest place to, to get rid of it. The crucial point here is that in a durable net zero regime, all of the bars, these, all of the bars that are directly affected by human activity balance. So if we're still using fossil fuels and it's an if, I don't know if we'll still be using fossil fuels, we probably will be, we need to get rid of all the carbonide they generate permanently by sticking it back underground. That's geological net zero that I emphasized we needed in that first, that's a necessary component, not enough for a durable net zero, but it's necessary. It's not sufficient, but it's necessary for a durable net zero that would meet the goals of the Paris Climate Agreement. As well as that we also need to stabilize the biosphere. So we need any remaining emissions. And it's important that this brown bar probably doesn't just include any remaining emissions from food production, but also any remaining emissions from what we call earth system feedbacks, things like forest fires and so on, which may have got worse over the past, over the next may get even. They've already got worse. They're probably gonna get worse still over the next few decades releasing carbon from our natural world back into the atmosphere. So we need to balance the biosphere and we need to let nature do her work and take this carbon back out of the atmosphere in order to keep temperatures stable. So that's what net zero needs to mean if it's to deliver what we think it needs to mean to stop global warming. So we're in this tricky situation that, you know, we've all agreed what the answer is net zero, but what was the question? And I'm reminded of that scene and the hitchhiker's guide to the Galaxy where these two scientists have been, you know, doing this calculation for 10 million years or something and then the commuter spits out, um, 42 and then the two scientists say to each other, I think we're gonna get lynched and I am worried, you know, um, is that gonna be the fate of the, the, the, the, the scientists who came up with net zero when people realize that they've all achieved net zero by implementing all the account complicated accounting rules that be done and it's not done. The trick of stopping global warming. So I can't overemphasize the fact that net zero can mean many things, but it has to include one thing we need to stop fossil fuels from causing global warming. And, and this is where it gets a little bit more controversial and where I really struggle, as I say, to get the climate establishment to, to say this, even though they all acknowledge it's true before the world stops using fossil fuels, we don't have time to stop global to, to wait until we stop burning fossil fuels entirely to stop global warming. So that simple statement, we need to stop fossil fuels from causing global warming before the world stops. Fossil stops using fossil fuels is a very profound and very important observation and you won't hear any of the climate establishment saying it. And I've banged on it all. I'm not gonna list names cuz it look like I'm name dropping. On the one hand it's not very fair, but I banged on a lot of them to say this and they all acknowledge it's true. And they say they give various excuses for not saying it, it doesn't suit our narrative, okay? It'll make people feel The the worry people have is if you say that it implies that we can, because if you say we have to do this, we can do this, which means we can stop fossil fuels from causing global warming, which means we, there is such a thing as responsible use of fossil fuels and that really worries people. They don't want to send out the message that actually there's a way of stopping fossil fuels from causing global warming. But there is, and we have to do it and we're not gonna do it if we don't admit it and start talking about how, because in these scenarios that meet the girls of the Paris Climate Agreement, there's two of them that are basically fossil elimination scenarios. The dark green here is fossil without capture of co2. The dark blue is with capture of co2. And you can see in these two scenarios, P one and P four, we pretty much eliminate our use of fossil fuels by mid-century. Okay, e with or without carbon capture, P one requires to meet the goals of Paris climate agreements, an immediate 30% reduction in primary energy demand, not fossil fuel demand, but energy demand. That's never happened. And no government in the world has any interest in reducing primary energy demand at that sort of rate. P four implies quite extraordinary levels of bioenergy production. We'd have to turn all of the tropics over to producing bioenergy pretty much by mid-century, leaving food production where, I don't know, um, in order to deliver energy requirements without fossil fuels. The other two scenarios, the ones which I would regard as the only ones in this collection that are remotely plausible, involve still using fossil fuels after the date of net zero. Some important people do get this, this gentleman presidents, um, Sultan Al Jabba, Dr. Sultan Al Jabba is the president of COP 28 happening in Dubai in uh, November. And a lot of people are very sort of anxious about the fact that the new, the next climate conference is gonna be happening in Abu Dhabi, um, in a country whose wealth is entirely built on fossil fuels. But I'd like to say, I'd like to see this as an opportunity if we can get them off talking about methane, which they're so proud of. Yes, we get it. You've done very well on methane, but let's talk about co2. We, the presidency acknowledges we need to be laser focused on phasing out fossil fuel emissions. Notice he's saying phasing out fossil fuel emissions. They're not going to say we need to fa phase out fossil fuels. They're enough. That's what they sell. But they have acknowledged we need to phase out fossil fuel emissions. And there's only one way to do that. That's to capture all the carbonide that's generated when you use fossil fuels and get rid of it permanently back underground. Well, it's not clear that they've accepted that second part, but that is what it takes. So we need to stop fossil fuels from causing global warming before the world stops using fossil fuels. Watch this space to see if I can get any of the climate establishment to say this before December. I'm not backing myself, but maybe Sultan Hal Chaba might be the first to quote another Arab gentleman a long time ago, Sheik Giani, the uh, OPEC oil minister back in the 1970s pointed out that the stone age didn't end because we ran outta stones. And the oil age won't end because we run out of oil. Global warming must end before we stop using fossil fuels. And that has profound implications for everyone's position going into Cop 28. We have to make sure that those who produce use and benefit from using fossil fuels and we will continue. The reason I put this nice picture of an airplane flying off into the sunset here is because I guarantee you there will be, there will be airplanes flying around the world in 30 years time when we need to get to net zero in if we're going to meet the goals of the Paris Climate Agreement and they will be burning kerosene. The reason I'm sure of that is because they've already been built. So just to sum up how the world agreed on net zero, First of all, largely by being a little bit vague on what it actually means, and this is dangerous, people need to be clear what the implications of their commitments are. It's very dangerous to have a global commitment to something while actually allowing different countries to have different definitions of what it actually means. And if you just add it up, unfortunately everybody tends to adopt the definition that works best for them. So cumulative historical emitters like the UK don't like to talk about the implications of our historical emissions for the need for the biosphere to clean up after us. Um, countries with large biosphere resources and small historical emissions like Gabon love to talk about that. So if everybody adopts the definition of net zero that works best for them, we certainly won't stop global warming. Even if we all succeed in reaching net zero according to whatever definition we decide allowed current definitions, if, you know, even if they're all implemented perfectly and nobody cheats, won't actually stop global warming. There are definitions out there that would stop global warming, but unfortunately because of this vagueness, if everybody, if everybody adopts the easiest one and that after all is the rational thing to do, if you ask a lawyer, you know which definition to choose, while they're gonna choose the one that's best for the client, they're doing their job. And if everybody adopts the definition that's best for the client, we won't stop global warming To stop global warming to actually meet the goals of the Paris Climate Agreement. All of our definitions, our understanding of net zero has to include geological net zero. That's a balance between all carbon dioxides still generated by burning fossil fuels and carbon dioxide permanently injected back into the Earth's crust. It'll need much more than that as well, but it has to have that and that's what I hope the conversation will focus on as we all gather in Dubai in December. Thank you.

Um, thank you so much Professor Allen. I've got a question from one line and then perhaps we can turn to the audience in just a second. So the question I've got from one line is, uh, what should we expect from the upcoming uh, COP 28?

Well, there's the hope is an acknowledgement of, of this reality. Um, I mean they're in a, if they don't acknowledge that, you know, given this is the fossil fuel cop let's it let it be the cop where we work out how to stop fossil fuels from causing global warming, that would be a fantastic outcome. It could be the most important cops in Paris by a long shot if, but if in, you know, if it's only about sort of a, you know, pledge on methane and you know, maybe a little bit of, you know, we're gonna work, we're gonna work on our own emissions a bit, um, then I'm afraid it won't be so, and right now it's sort of, you know, the jury's out what's gonna happen, but there's definitely an opportunity then and there's definitely an enthusiasm from the presidency to make them up. They want this to be remembered positively. So who knows? Keep hoping.

Um, hi. Thank you very much. So I think when it comes to the kind of idea of mandatory take back as you are advocating it, the difficulty is always, I suppose how is that implemented? And you know, you can either, there's a lot of scenarios of implementing that that add a lot of costs to the taxpayer, but then there's also obviously all these scenarios that put the burden on fossil fuel companies to do it. But I think your characterization of Sultan's position is definitely on the more generous end of what, you know, some people argue at the moment. So the question is, you know, if you take Saudi Arabia as an example, is there any specter of the Saudi Arabian government forcing Saudi Aramco to, to price the cost of geological storage into the cost of, of the oil and gas products?

They have made very clear to me. I mean I, I've been there, talked about it. Um, they've made very clear to me they'll only do that if people are prepared to pay it. But, and I then asked them, well, would you be prepared to at least say that? So would you be prepared to tell the world that if the world was willing to pay for carbon neutral oil, if you like, you know, oil for which you've already got rid of the CO2 before you even sell it, um, that they would be willing to deliver it. Cuz they'll say privately to me, yes, of course we can do that, it's not a problem. You know, they, they've got all the resources to do it, um, but they grumble, nobody will pay for it. So, okay, as I say, come out in public and say that and then it's gonna be up to government of Germany and Britain and so on to say why we're not buying that kind of oil. Why are we still buying the old stuff? So I think we could make a lot of progress with just putting some simple facts out there and, you know, the industry, and maybe these aren't facts, maybe this is just what they say to me to shut me up, um, because, you know, but they claim to be able to do this, so let them say so and then it's gonna be on their customers as to why we're not buying it.

This may be a naive question, but I mean, where are all these carbon sinks going to be exactly geographically in the world? <laugh>?

Well, crucially, it's in, in a nutshell it's bank where it came from. Basically, ironically, all of the countries in the world that have been blessed with fossil fuel reserves, um, are also blessed with carbon storage reserves because the sort of rock formations that you need, um, to trap hydrocarbons are exactly the rock formations you need to trap carbonide. So fortunately though, it's better. The, the better news is the, the storage resource is actually much better distributed around the world than the hydrocarbons because you to have hydrocarbons, you need the right rock formation and you need the hydrocarbons to have formed there at some point in the past. Whereas to trap co2, you just need the right rock formation. So, um, there's actually plenty of places where we could put co2, um, which, uh, you know, where, where the in in countries which don't have hydrocarbons in the first place, so for example, and also countries that have depleted all their hydrocarbon reserves like the uk um, you know, if it was established that you need to get rid of CO2 as a condition of using fossil fuels, um, the UK would sell the North Sea a second time over because the North Sea is a perfect place to put it. Um, and again, I don't understand why this isn't front and central part of our government's negotiating position because we clean up literally.

Yeah. Thank you. Um, so when you say carbon sinks, is, is that an active, uh, is that a, is that an act that some it, does it happen automatically or do we have to do something? I mean, extracting hydrocarbons has some implications to development or so they say, uh, but putting it back in does not seem to have any incentives, uh, that the taxpayers will be happy about. Sure.

So, so when I was, the crucial thing is that carbon sinks this, the crucial ambiguity in the, in the Paris agreement is removals by sinks is a little bit ambiguous on whether that's removals that result from a immediate action or removals that result from actions that already happened. So by raising carbon dioxide concentrations in the atmosphere, that was an action that we've done over the past 200 years. We've made trees grow faster. So is that an anthropogenic sink? Well, it's a little bit unclear. Um, some of them are classified as anthropogenic sinks. And if you, if you remember the carbon cycle later, i, I rabbited on about the sanctioning managed land and unmanaged land. And it probably all got a little bit sounded like accounting, but it's a really important issue. If we declare the whole world is managed, which is sort of the direction we're on at the moment, then people are allowed under the rules to take credit for this passive uptake of carbon that results from just trees growing faster because of our past emissions. But crucially, if we want to actually, if we want net zero to mean what we, what Theresa May thought it meant to stop global warming, then we need to only include in the removals side of the ledger things that result from immediate actions, things we do to grab CO2 and get rid of it, rather than just sort of allowing nature to take its course. This isn't a course to belittle the importance of nature taking its course. Cuz and that's why I was emphasizing that countries like the UK have a particular responsibility to preserve the ability of nature to to, to absorb that co2. Um, but yes, those active removals of CO2 are expensive and unless we find a very, some very, very rich entities to pay for it, it's not gonna happen. But again, as I stressed in the opening lecture, those rich entities exist in 2022. The fossil fuel industry made. We, we paid them 13 trillion US dollars. That's what we spent on fossil en well energy, but mostly fossil energy. In 20 22, 2 years earlier, three years earlier in 2019 before Covid we spent about 6 trillion on energy. The cost of supplying it had certainly not gone up by 7 trillion. The cost of getting rid of all of that carbon dioxide, capturing it and sticking it back underground would be about $6 trillion. So somebody can afford this, it's just not us. That's the point.

Uh, thank you. Um, I think this follows on quite nicely from what you were just saying actually. So I do really appreciate where you are coming from with emission free fossil fuels and like obviously we're not gonna solve this without carbon capture and storage, but how do we get them to phase down fossil fuels, phase down energie and tax the rich if we are just telling them to focus on carbon capture and storage, does it not let them off the hook?

I don't, I think, I think just so I don't think it lets them off the hook at all. Cause carbon capture and storage is, is expensive. They, they need, you know, they should be building this stuff like there's no tomorrow they need to be spending the enormous profits they're making at the moment on building CO2 disposal capability. But instead we're allowing them to get away with saying, oh, we're investing in renewables so we're, you know, we're slightly green. Um, so don't worry about what we're doing on fossil fuels. That's like, you know, that's like a water company saying, well you know, we're, we're investing in mulland management to reduce runoff, so don't worry about the fact that we're dumping sewage on the beaches. No fix it. So we need to establish the principle that if they wanna sell stuff that causes global warming, they've gotta fix it. Take back that CO2 that their products generate and get rid of it permanently. Once we've established that principle, then, you know, we don't need them to do that tomorrow, but we need them to be doing that by mid-century, then the conversation can move on. I don't think that's letting them off the hook at all. In fact, if anything, I think the current situation of just sort of telling them we're gonna close them down at some point in the future, that's totally letting them off the hook cuz it's allowing them to sort of carry on making money willy-nilly. The classic case of letting fossil fuel interests off the hook is that Cumber and coal mine for which, which is entirely consistent with the UK's net zero plans apparently because planning has only been approved till 2049, it's beggar's belief, okay? I think that's what should have happened is that planning should have been conditional on getting rid of the CO2 and then the company, then we'd found out whether the company really wanted that call.

Thank you. Thank you very much. So leading on from that observation, what role, what level of dependency does the UK's net zero transition have on scalable and commercially viable carbon capture and storage?

Well, we could make a huge, we could make a massive difference here because we're, you know, we've got a responsibility to do it. We've got the resources to do it and we've got what we claim is a supportive policy environment. So, you know, for example, but the, the net zero transition authority, the, sorry if only it was the Net zero transition, the North Sea Transition Authority, their mandate is to get as much oil and gas out of the North Sea as possible. Why, why isn't their mandate to get as much north as much oil and gas out of the North Sea as possible Can consistent with net zero? Because the UK has a net zero commitment. Why isn't net zero in their mandate? And you know, we've raised this with politicians. They say, well don't worry, net zero applies to everything. So you don't, you don't need to mention it. It's like, well, okay, if it applies to everything, let's mention it. Make it part of that. So this could be, this could be in the energy bill, which is before Parliament at the moment. It's not, you know, Brian Worthington put up a, an amendment in the Lords to sort of raise the issue. The government sort of said don't worry about it, we've got this in hand, please withdraw your amendment. And that was the sort of convention. So she did. But you know, unless the heat's kept on it, you know, I'm not holding my breath. But the irony of all this is that it's such an opportunity for us cuz it would create an industry that if we committed to doing this, it'd be very hard for the rest of Europe not to do the same. And we'd be the ones who'd be, they'd have to pay to get rid of their co2. You

Know, the client Earth took the government to account for the sort of lack of robustness in their net zero strategy. Well

Ask your MP why geological net zero is not part of the energy bill. Why, why Net zero is not part of the North Sea transition Authorities mandate simple questions, they've got a vote on it. Let's see what happens.

Professor Allen, I'm afraid to say it is now seven o'clock, so we ought to wrap up, but obviously, um, you might want to take questions from the audience in person at the end afterwards. Um, very happy to, uh, may I may I just remind people that Professor Mars Island is back next year and so he has another series of lectures about net zero and they are when Net zero, the last, this one, this year is, you know, is why Net Zero next year is when net zero and it's starting on the 26th of September. Um, so we hope to see you all back here for that. It's gonna be brilliant. Um, so will you please all give a very large round of applauses for Professor Miles Allen.