Ep36: Prof. Jim Skea 'It's climate, Jim, but not as we know it.'

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Michael Liebreich:  

Before we get started, please remember to like or subscribe to this video/podcast. It really helps others to find Cleaning Up. Cleaning Up is brought to you by the Liebreich Foundation and the Gilardini Foundation. Hello, my name is Michael Liebreich, and this is Cleaning Up. My guest today is Jim Skea. He is the Co-Chair of Working Group III of the IPCC. That's the Working Group that calculates emissions from the energy system, transportation, other parts of the economy and the planetary system. He is also co-author of the 2018 Special Report on 1.5 degrees centigrade, which did so much to change the public debate about climate change. Jim is also Professor of Sustainable Energy at Imperial College London. Please welcome Jim Skea to Cleaning Up. So, Jim, welcome to Cleaning Up. 

Jim Skea: 

I’m pleased to be here. I've watched a couple of episodes, so I'm ready for you. I just wanted to know whether you were Jeremy Paxman or Michael Parkinson. 

ML: 

So well, I was going to ask you the same exact question 12 times over. Probably it's going to be about RCP8.5. No, I won’t. What I'd like to do, actually… So just to give you a bit of background, our audience tends to be, well, it ranges from the real experts who will know their RCPs from their SSPs and godness knows what. But there's also a lot of people who are, you know, listening and watching for the general arc of history. Where are we? Where are we going? So maybe we could start by you introducing kind of what is the IPCC? How does it work? What have you been doing, and just give a little bit of an overview of how it's structured.  

JS: 

Ok. The Intergovernmental Panel on Climate Change is absolutely unique. It’s very important to remember that the I in IPCC stands for intergovernmental, not international. So, the governments are really an important part of that. And everything that IPCC produces is signed off by governments, produced by scientists, but signed off by governments. So, it's a very kind of collaborative activity, you know, if you're being very, very optimistic about it. So, what happens, it works in cycles of maybe five to seven years. It can take that length of time to get a new set of reports out. Over that time, hundreds and hundreds of authors will work together, you know, trying to produce the latest reports on the up to date science of climate change. And that science includes the impacts of climate change, and it includes all the means for getting emissions down as well. So, it really covers the range. And it's everything from physics, through to sociology, quite frankly, in terms of the disciplinary range. But at the end of it, we all have to develop our so-called summaries for policymakers, these documents that are 20-25 pages long and painfully, over a week, we sit down and negotiate word for word and sentence for sentence, every part of the summaries for policymakers with governments. But at the end of it, they've all signed up to it, and they can't back away from it, which is what makes IPCC so powerful. It's glacially slow. It's frustrating. It's all of these things, but it's the outcome that matters. And you can see, we've made a big difference over the last 3-4 years. 

ML: 

So let me give the kind of naive, you know, I have a science background, but I'm going to give it the sort of naive view of how this works, which isn't quite how the IPCC works, which is, first of all, you kind of work out how much we're emitting. Right? And that's, presumably quite controversial. And there's all sorts of different bits in the energy industry, in agriculture, land use, and whatever. And then with that, you would go into what is that going to do in terms of the temperatures? And then with that, you're going to go into what does it mean for the penguins, the harvests, the malarial mosquitoes and so on? So is it that linear process? 

JS: 

It’s a circular process, of course, because everybody claims they're the starting point and somebody else's the end point of it. So our physics and chemistry colleagues thinks it starts with looking at the atmosphere, and what might happen to it, and then they pass it on to the people who think about the penguins and the crops, and all that. And then finally they pass us off into Working Group Three. We have plumbers and the electricians who are given the job of figuring out how we reach these objectives that our scientists have set for us, but of course, we think about it the other way around - a bit like you started. Think about what people are actually emitting, think what it does, think about how you can get the emissions down, then maybe think about, well, if you fail to get the emissions down, these are the kind of things you will need to do to adapt to climate change. So, you can think of it as a circle around the three working groups, and you can start wherever you want. But you'll end up where you started, that's for sure. 

ML:  

Okay, so I would count myself definitely as amongst the sort of plumbers and electricians side <inaudible> the energy space, although not the sort of energy modelling that goes on within the, you know, in the community around the IPCC. And I would definitely say, I would claim, as you said, I would claim supremacy in the sense that this problem starts with what we're emitting, and then maybe some circularity right, it goes really badly wrong, then the power stations might be underwater, so you wouldn't be able to emit what you thought you were. But fundamentally, isn't the starting point what happens with the economy and the energy systems?  

JS: 

Yeah, well, just remember… There is, yeah, there's one bit of IPCC that everybody forgets about called the Task Force on Inventories, which are the people that produce the methods for calculating how much countries emit. And they are actually the… all the governments use that IPCC method for calculating their emissions. That's actually the starting point and it's been around for 30 years, you're developing the ideas on how to do that. And they're probably the most technician-rich part of IPCC, I should say, these are real anoraks, who know how to do these calculations, how to calculate the carbon loss from a forest, et cetera. And it is almost the starting point. But yeah, I mean… I'm Working Group III, I absolutely think it's the most important part of it, because that's where the answers are. 

ML: 

Talk us through the Working Groups and Working Groups III, which of course, should have been called Working Group I which is the plumbers and electricians. But actually, it's called Working Group III, yeah. People modelling the energy system. The other Working Groups… 

JS: 

Yeah, right. The mitigation… Let me say, it's not just the energy system, because it's the land system as well, it’s everything that gives rise to emissions. Working backwards, Working Group II is the one that looks at the impacts of climate change. It's the penguins, the polar bears, etc. And they also look at the vulnerability to climate change, and the measures you can take to adapt, you know, genetic breeding of new crops that might be more climate resilient, building sea walls to project against sea level rise, that's the kind of thing they do. And then the people in Working Group I are the people who think about really what happens in the climate system, which includes the air, but it also includes the oceans, as well, and aspects of the way that we exchange gases with vegetation, and land cover. So, they do the science of that. And it's that group is everything from sort of the Paleo side of it going back and looking back hundreds of thousands of years, right through to the big, big models, where you press the button, and it takes several months for the answer to come out, which simulate the effect of different levels of emissions on the climate. So that's what they do. And we all talk to each other and I have to say, over the last five years, we've done a better job of talking to each other than we've ever done in IPCC before. 

ML:  

Okay, so Working Group III: emissions. Working Group I: the planet. And Working Group II, the impacts on everything, and… 

JS:  

Humans and ecosystems, and there's a bit of a battle between the human people and the ecosystem people, but… 

ML: 

They're all working in parallel, right? They're all working at the same time. They don't sort of sit there go, well, I can't do anything, because I haven't got my results from Working Group III. 

JS: 

Yeah, well, they’re kind of staggered on the go in the order. So, Working Group I usually goes first, then Working Group II, then Working Group III. So, they'll all be several months apart. And there is information that's passed from one to the other, to make it work. And I'll give you an example of one way in which information is passed. Our people in Working Group III, when they run their big energy models or land models, they need to know what the impact on the climate is of that level of emissions. Now, they can't run a dirty, great big, huge climate model that takes several months to run in order to do that. So, they take kind of cut down models, simplified models of the climate system, and then stick it on the back end of their energy models and figure out what that means for the climate. But these sort of reduced climate models come from our colleagues in Working Group I, so there's a kind of handover between the Working Groups and these kinds of issues. 

ML: 

But why are they doing that? Because, I mean, wouldn't you want to just have the Working Group III, the ones that decide what the emissions are going to be just doing the best damn job they can at working out what the emissions are going to be, why do they need to know the impact on the climate? 

JS: 

Ah, because in Working Group III, we have to do calculation <inaudible>. But remember, we've got all these issues about, you know, when we get to net zero emissions when temperatures peak, etc, because our people can produce new scenarios at the rate of knots, they do it really quickly. They need simplified climate models to be able to do that, and connected to levels of warming, etc. If we waited for Working Group I to do it, we would be waiting a very long time, because every time they get a new emissions scenario, they need to press the button and wait several months for the results to come out. 

ML: 

I guess what I'm fishing for is why do we care about the results? We, Working Group III types? Because what is it? I mean, there might be some, you know, like I say sometimes there might be some feedback on what we do. But generally, it's the other way around, right? We were all told the energy system is driving the climate, not the climate that's driving it. And so why wait, what's going on here? 

JS: 

Yeah, absolutely, causal chain, the causal chain is Working Group III causes emissions, Working Group I figures out what happens to the atmosphere. And Working Group II looks at the consequences. But then you look at the Paris Agreement and Article 2, that says we want to limit warming to well below 2 degrees, pursuing efforts towards 1.5, et cetera. And what our people are doing is not following the causal chain. They're working backwards and saying, what do we need to do in the energy system? What if the targets or the aims of the Paris Agreement are going to be fulfilled? And that's the way the logic works and why they're on the models and that kind of way, because, you know, we're working backwards, it's normative, we're deciding what we need to do in order to achieve an outcome. And that's the reason for doing it that way. 

ML: 

But, you know, what I'm fishing for also is Working Group III than just trying to produce scenarios? So, it's told what scenarios to produce, and it goes off and produces them? So, it's not really predicting anything, it's actually working backwards?  

JS: 

No, no… Well, I mean, let me say, Working Group III, its output and the perception of it is very influenced by these global scenarios. On the one chapter that produces these scenarios, these are the statistics from AR5, it's 6% of the of the chapter text. It's about 25% of the summary for policymakers, and 90% of the publicity and media coverage. There is so much that goes on in Working Group III, that's much more specific about, you know, it's the plumbers and the electricians stuff. What happens in buildings, how you get electric vehicles, transportation, and we've got chapters on finance, etc, which would be much more in tune with the kind of things that you're interested in your career, Michael, as well. So it's not just these big scenarios, there are other things in there as well. 

ML: 

Okay, so now talk me through the timing. Okay, so we got kind of the plumbing of the plumbers and on the other Groups like I, II and III. And what is the time and you've said that the whole cycle takes seven years, five to seven years? Where are we in the cycle? 

JS: 

We are getting quite close to the end, though subject to COVID. COVID is having an impact on the timetable, we started in about 2015, we'd be finishing in 2022. And it's taking seven years this time, at least because of all the special reports like the Special Report on Warming of 1.5 degrees, which took a bit of time.  

ML: 

Which you led. You were Chair or Co-Chair… 

JS: 

We share that between the Working Group. So that's the reason we collaborate. It was a cross working group collaboration. 

ML: 

I want to get… 

JS: 

Yeah, yeah. Okay, so once we got that one out of the way, it probably takes about three years to produce a report. What happens is the governments decide, first of all, what reports they want to produce during a cycle, that <inaudible> decision, for example, about all these special reports, then we set up a scientific meeting where people scope out what the report might look like in terms of content. Then we need to take that draft scope of the report, put it in front of governments, who then will have a good go at it in their plenary session. They might change it. Generally, so far, they've accepted all the chapter structures, but they've changed the internal detail a little. So, once they've agreed what the scope is, we then have to choose authors. And that is a difficult process. We need nominations from governments, for people to be authors of the report. And then we as the scientific leadership have to choose the authors from that list, taking account of gender, ethnicity, as well as, of course, let's not forget scientific credibility as well, that's got to be in there somewhere. So, we choose them. And then we start up a cycle where we have four lead authors meetings during a cycle, when we bring all of the 250 people together in one place, and they produce a first draft, which goes to expert review, a second draft that goes to government review, and then we finally revise, once again, the summary for policymakers before taking it. So, this might be six to nine months between each of these lead authors meetings, and that’s explaining the time.  

ML: 

Okay, so it'll be 2022 or 2023… 

JS: 

2022 we should be done. 

ML: 

And then there'll be this great big dump, which is the latest scientific thinking on climate. And it'll be the emissions, it'll be the impacts, and it'll be the whole planetary systems. The whole lot. If…. 

JS: 

No, it takes place staggered. What happens is Working Group One comes out first, they approve it, they get their report approved. And then Working Group… then actually Working Group III is scheduled to go before Working Group II in the cycle, which would be nice. We're trying to get promoted. We'll be number one soon. So you know, then, so the Working Groups come out. And then there's something called a synthesis report produced at the end of it, which tries to join… you know, the one ring that binds them all kind of thing that fills it all together. 

ML: 

Yeah. Now, with that fabulous preamble, can you tell us what it's going to say yet? Because I mean, you're already in the drafting process. And, you know, is it going to say it's even worse than we thought? The last round was AR 5, right? The Assessment Report 5, which was 2015. And yeah, we're going to be saying that the climate is even worse, even scarier, or are we going to be saying, it looks less scary than…? 

JS:  

Right, right. Now, you've put your finger on the exact thing that I can't specifically talk to you about, except in riddles, because this is work in progress. And we’re not supposed to talk about the draft conclusions from it at the moment. Because once governments have gone over it, and once it's been through another set of reviews, it might say something slightly different, or even a big bit different from you know, what the draft says at the moment. So basically, at the moment, I mean, Michael, if you want, if you want to review our draft, you can sign up on the website, get access to it all, but you have to swear in sort of virtual blood that you will not leak it to anybody in any way. 

ML: 

It's interesting, because a lot of people, it won't surprise you… But a lot of people have said, well, you know, Michael, if you have strong feelings about this stuff, you should be a reviewer. And I don't want to do that. I see my role as standing on the sidelines with a peashooter. 

JS:  

Yeah, yeah, well, that's absolutely fine. Or else standing on the lines and asking me to divulge this confidential information on the way. 

ML: 

What I'm doing… I'm doing it… So hopefully, the audience can get to get a sense of some of the politics and some of the processes. But nevertheless, you know, there is a body of science that has been produced over the last, you know, 5-6-7 years. And that's really what is going to be summarizing. It's not going to be new science. 

JS: 

It’s science that has been produced since the last assessment report in 2015. I mean, you may want to pick up that Special Report on 1.5 degrees that was so influential. But we also wouldn't cover exactly the same ground as that again, because it's been done. And actually, if you look at it, that came out in 2018. That was relatively soon after the last Assessment Report. And basically, on the scenarios and modelling side, people sort of dusted off their scenarios, turned the volume up to 11, as it were, in terms of limiting warming, and ran the same models again. They think there have been methodological improvements since then that we'll be able to report because people have had a lot more time to sit back and think, “is my model doing the right kind of thing? Are the things that I can do to change it?” So, I think the art of modelling, and I use the word art deliberately rather than science, has moved on a bit since that time. 

ML: 

On Cleaning Up we had Christiana Figueres - I'm trying to remember which episode, I'm going to say Episode Seven, I'm probably wrong, but it was around one of the earlier episodes - and she talked about the role of that 1.5, she actually talked about where it came from, from the Paris Process of the preferably near 1.5 degrees… talked about how within the UNFCCC, everything depends on the science, which is you, and therefore the origins of that report. But it was a game changer, was it not? I mean, you know, I suppose I'm not sure if I can ask you that question. I'm going to tell you it was a game changer. But were you surprised at the impact it had? 

JS: 

Yeah, let me just say, because we would all elected, the common scientific leadership in October 2015, which was just before the Paris Agreement was signed. And I recall all of us sitting in Paris watching the draft of the text emerge saying, please don't ask us to produce this 1.5 report. 

ML: 

That's exactly what Christiana said. She said that it was sort of a bolt from the blue. I mean, how the hell would you do this?  

JS: 

Yeah, yeah, we thought two degrees was difficult, you know, how to do this. Yeah. But I mean, in a way, we knew that there were huge expectations about the report to <inaudible>, because we knew the media had really wound themselves up on it. We knew that, for example, in the UK, the government was waiting for the 1.5 report, in order to up its ambition to, you know, and enhance the ambition of its Climate Change Act. So, we knew that there was a huge <inaudible> happening. And I think sometime in 2015, that report coming out in terms of climate policy, the planets completely aligned. Because you had the IPCC giving the evidence, you had the strength of the Paris Agreement. And then you had Extinction Rebellion, Greta Thunberg, et cetera, on the more civil society side. And I just think everything lined up. And I think the world is now a completely different place from the one it was back five years ago before we started this. 

ML: 

Certainly, so yeah, that 1.5 degrees report, I mean, first of all, it really informed the discussion, it said, If I were to paraphrase it said, you really want to be at 1.5 not at 2. There's a real difference in terms of outcome… 

JS: 

Yeah, it said… Of course, we are very careful not to be policy prescriptive. This is the one thing we're forbidden from being. But we did point out that there were substantial differences in the impacts of 1.5 and 2 degree warming, and the world would be a worse place at 2 degrees than it would at 1.5, unambiguously the case. Yeah. 

ML:  

And that did change the narrative. That enabled, whether it was governmental action, but also whether it was action on the streets - Greta Thunberg and Extinction Rebellion - so it changed the political weather or the civic weather. Yeah. But I remember a fantastic press conference, where you said, well, it's within the limits of physics, it's within the laws of physics, but we'd have to really, basically, you know, there's a step change required in actions. I'm paraphrasing, but you'll remember the event.  

JS: 

Yeah. Well, I can remember what I said. I think it was, you know, was possible within the laws of physics and chemistry, we've now done our job as scientists, over to you governments if you want to do it. That was kind of the way I think it was put… 

ML: 

That was… I've got that quotation actually, of you on a slide, which I use in my, you know, as I talk, if somebody wants to have my views on the climate sort of science bit then I say, right, well, you know, my mate, Jim says it's within the laws of physics and chemistry.  

JS: 

I've got a physics degree so I must be right.  

ML: 

If I had to ask you, are you allowed to say whether you think it is likely that we will stick to 1.5 degrees? 

JS: 

Well, let me tell you the story. I can't tell you the answer. But I can tell you the way the discussions go. Every time IPCC produces a report, we say limiting warming to some level is challenging, but still possible. And then we produce a newer report that says it's very challenging, but still possible. And then we up the qualification of challenging, we are giving quite a lot of thought at the moment as to how we actually communicate, you know, where we are at the moment, because blatantly, I mean, just to say, you know, it was claimed, after the 1.5 report came out that we had 12 years to save the world. Now, IPCC never said that, but it was quite a good headline. And obviously, three years have passed, nearly, and we have not made the kind of progress that was anticipated, you know, when the 1.5 report said, this is the way we've got to get emissions down. It's not been happening, basically. So obviously, that has consequences for the kind of messaging that will come out in the next report, but we're still playing with the numbers, you know, etc. You know, at the moment as we assess the literature and figure it out, but yeah, I mean, obviously, it is a shame, that governments, you know, all the indications are that on the current path, we're on, even with the current pledges 1.5 is beyond reach if only these pledges are fulfilled. 

ML: 

Let's talk probabilities, because you've touched on a very important topic, because you've said that you're playing around with the wording saying it's challenging, and then it becomes very challenging. And there's this other whole sort of technology of wording, which is embedded in the IPCC reports about sort of very likely, highly likely, etc. And yet, you don't put probabilities on your outcomes? 

JS:  

No, I mean, when we do things like warming, I mean, for example, if we take an emissions pathway, there's uncertainty about what that means for the climate. So we will say something like this emissions pathway is likely to limit warming below, we have this graduated language where ‘likely’ means 66% probability or 2:1 in terms of horseracing odds. Or ‘about as likely as not’ as 50/50, evens, that kind of thing. But we don't attach probability to things that are only determined by political decision making, because we have no means of doing that. 

ML:  

No, but even on the physics, when you say something is likely or very likely, and then you translate that into the numbers, those are applied by, in a sense, committees of smart people, aren't they? They're not actual probabilities that arise, you know, analytically, are they? 

JS: 

Yeah, they do. Absolutely. And the models, I mean, I mentioned that, you know, the kind of the reduced climate models that come out of Working Group I, that Working Group III on the emission <inaudible> and these models are actually probabilistic. They have formal probabilities built into them. And that's where the numbers are coming from, when we say a specific emissions pathway is likely to limit warming to a level, it is a formal probabilistic calculation from these sort of cut down climate models. 

ML: 

But is that based on sort of Monte Carlo simulations or… 

JS: 

Yeah, Monte Carlo simulations of the key uncertainties around things like the climate sensitivity of the system, which the scientists can put a number to, and look at the probability density functions. 

ML: 

Why don't you just make up probabilities that you put into those models? And then you look at how often it leads to? 

JS:  

But the probabilities are based on observation and tuning the models to observations. 

ML: 

And what about your great colleagues in the… You know, maybe not in your Working Group, but where they'll say things like, there might be two papers that say the number of penguins will decline and one that says it will increase, so it’s likely to decline. ? Is that just kind of probability… 

JS:  

But I wasn't talking about penguins. I was talking about global warming and temperature numbers, which you can put a probability to, I mean, sure, you get new layers of uncertainty, you know, when you walk through from the warming levels, the level of rainfall through to actual climate impacts, the probabilities are there. But if we mention a probability, it does have a basis in Monte Carlo modelling, for the most part. 

ML: 

I think, yeah, I want… Because I'm a mechanical engineer, I truly am. I'm not even a plumber or an electrical engineer. For me, you’ve got the uncertainty at one end, and then, you know, you kind of add them all up. And it leads to… And there's a whole, I mean, there’s 100 page documents about how you manage and how you communicate uncertainty in engineering and in science, and it does seem when I read some of the Working Group output, it all seems that you know… 

JS:  

Yeah, sometimes the <inaudible> expert judgement, which is another way of saying that it, you know, is exercise, you know, when you need to look at a piece of literature, especially when you're looking at the impact side… 

ML: 

Is that not dangerous when it's a small community of scientists that are peer reviewing their thing, and then allocating a likelihood to it being correct, but it's a mate of theirs that they probably, you know, studied under or you know, viva-ed with or whatever. 

JS: 

The IPCC has been struggling with this question of how to do expert judgement over the years. You will find in many of the statements that's qualified by a statement like high confidence or medium confidence, and that confidence level comes from combining the amount of evidence that's available with the level of agreement with the different kind of papers that are produced. So, you're never looking, if it was anything that was obtained by getting, you're just wanting your mates would unambiguously be a low confidence statement. Because there was not enough evidence there, there would have to be dozens or hundreds of papers in the literature. And if they're all going in the same direction, that will end up as high confidence. But if it's you and your mate, it’s low, and we have ways of checking that when we produce the reports as well. 

ML: 

If we could, at this point, go back to those famous scenarios, because you do coalesce a lot of the, you know, you say it's 5% of the work, but it is kind of, you know, 90% of the press coverage that comes from, looking at your output on these famous scenarios. These are the RCPs. and then the SSPs. Do you want to first just talk about what's an RCP? And what's an SSP for the benefit of our audience? 

JS: 

Not sure. <laugh> 

ML: 

Is that not sure you want to or you can't remember what they are?  

JS: 

Unfortunately, I can. Do you have a spare hour or so for me to explain this, Michael?. <laugh> Right. Right. Okay, the big quest for it. Once upon a time, we followed the logical cause-based thing that you that you mentioned at the beginning, we started with emissions, looked at the impacts on the climate and went to impacts. And that didn't work very well, because of the time it takes to run climate models. So the idea came up that you could start this process in the middle of the causal chain and work backwards and work forwards. So, the RCP stands for a Representative Concentration Pathway. And that refers to the concentrations of carbon dioxide in the atmosphere. So, we developed a set of scenarios that said the concentrations of the carbon dioxide in the atmosphere will follow this pathway into the future and a set of ranges was done, and that enabled Working Group III to work backwards and say these are the levels of emissions that would be associated with these concentrations. And then allowed the people in Working Group I in the physical sciences to run these concentrations through their big models, and figure out what it meant for temperature, precipitation, you know, rainfall, sea level rise, etc. And then that could be passed on to Working Group II. And it was, in a way, because of the great clunkiness and slowness of the climate models that caused us to do that, so that we could start in the middle of that causal chain and work in both directions. Now, if we had brilliant quantum computing, and could do everything instantly, you could revert to the original causal way of doing it. If you could press the button on these climate models and run them quickly. 

ML: 

Those scenarios, those RCPs, Representative Concentration Pathways, they spanned all of the sort of known and vaguely reasonable outputs of the energy and the various emitting sectors. Right? They went from no outputs through to high outputs.. 

JS: 

Yeah, yeah. I mean, it meant that the high outputs - and no doubt you're going to take me to a place, Michael, where you were going to argue that some of the higher ones were unreasonable, but I'm happy to kind of debate that - but yeah, they were anything, if you were wanting to turn it into warming, they were anything probably between about 2 degrees, and I don't know, even 6 or 7, by the end of the 21st century, the kind of range they had. 

ML: 

So, I wouldn't argue that they were necessarily implausible back in the mists of time. Before I had even heard of climate change when I was worrying about the dotcom crash, and god knows what. But I just wanted to kind of establish they were. But it was an output that at some point was considered plausible. And in fact, it was a requirement that it was plausible when they were defined the word plausible pops up in the literature here, there and everywhere. And there was a low plausible if we did lots of stuff, and there was a high plausible if we didn't do anything. And then that define these figures of 2.5, 4.5, 6.0, 8.5 that was the range, right? 

JS: 

Yeah, that's exactly right. But just to say they were not premised on anything about emissions. I mean, obviously, there was a little bit of kind of intuition about it. But there was no assumption about the socioeconomic changes required to get to these concentration pathways. That was the purpose. It was to take it in the middle. You had to work backwards to say, well, what would this Concentration Pathway mean for emissions? And that was the job of Working Group III where I am to do that. 

ML: 

Okay, so it was a concentration of greenhouse gases in the atmosphere. But it was a pathway, so it was related to a particular year. 

JS:  

Yeah, it was a pathway: by 2030 it reaches this level, 2050, then 2100. It was absolutely a pathway. 

ML: 

Yeah. Okay. And then your Working Group had to sort of figure out how to hit those numbers… 

JS:  

Exactly. Yeah. Which is why we work backwards. 

ML: 

You work backwards. So, working Group III, its job is no longer forecasting, but now working backwards to hit those four outcomes.  

JS: 

Exactly. It's more… I mean it does do kind of unconstrained projections as well, but basically, yeah, it's a back-casting job, not forecasting. 

ML: 

Right. Okay. And you're absolutely right, you know exactly where I'm going with this… 

JS: 

I do. I know. I can see it coming. Yeah, I'm waiting for you to hit me with it. 

ML: 

You've now got SSPs, just give us SSPs, which is an attempt to sort of fill in some of the color around those routes. 

JS:  

Yeah, right. So, the RCPs had no socioeconomic assumptions behind them at all, they were just pathway numbers. And so when our people turn these into scenarios, they used to take very much a kind of a business as usual look at socioeconomic development and say, against that background, you know, global growth is whatever percent a year, baseline emissions of CO2 increase at 1% a year or whatever, they will take that as their… What the purpose of the SSPs, which stand for the Shared Socioeconomic Pathways, was to provide more color, and more alternatives around human development against which these different concentration pathways could be set. So, they ended up with five different Shared Socioeconomic Pathways that have different assumptions about global population growth, about economic growth, and some other aspects as well. And the way they did it was they did a classic two by two, you know, kind of business school diagram. And one of the axes was how difficult it is to mitigate. On the other axis was how difficult it is to adapt. And the purpose of constructing the scenarios in that way, were so that they could be used by each of the Working Groups. So it would  have meaning for Working Group II, that does the impacts and adaptation. For Working Group III that does the mitigation. And then the Working Group I input is kind of the concentration pathways and the ambition, and you can treat the RCPs, which are physically defined against the SSPs, which are defined by socioeconomic pathways and put them in a kind of a matrix. And in some of the socioeconomic pathways, it's much easier to hit a given warming level than it is for others. So, there's one that usually has the word sustainability attached to it, and they are the costs of limiting warming to a given level are much, much lower than in ones that are called fossil fuel development or whatever, where it becomes much more challenging. 

ML: 

Right. So, in sort of that SSP, the Shared Socioeconomic Pathway 2, you've got lots of rich people who work together, and it's quite cheap to mitigate emissions and so therefore, you end up with a better outcome. 

JS: 

Yeah, that's SSP 1, let's not get technical about it is one of them. SSP 2 is the middle. 

ML: 

We will, I can assure you put a link into the show notes that will correct all the mistakes that I make in trying to interpret. 

JS: 

Well, absolutely. I hope you do the same for me as well. 

ML: 

There is, you know, as you've described, and as we've seen, there is this thing called RCP8.5, which, 20 years ago, defined the upper end of the emissions pathways, and which I have looked into and lots of others have looked into. And we're just baffled by why it's still regarded as in any way serious because it's so far from any plausible pathway. But instead of saying, well, it's not plausible, so we'll get rid of it. What the system seems to have done is to say, we’ll remove the requirement for plausibility. 

JS: 

Right, let me just say on this right, because, you know, I may or may not be in agreement with you offline with my official hat on Michael, let me neutrally say what you need to assume, to think that an RCP8.5 pathway is plausible. You need to think all of the policies that have been put in place over the last three years are reversed. You need to think that all of the wind turbines that have been installed are dismantled and we don't replace our photovoltaic cells. This is a world in which climate policy goes backwards, not one in which climate policy continues 

ML: 

Not just policy… 

JS:  

And also technological change because we've seen the reduction in the solar PV. Absolutely, yeah… 

ML: 

Solar PV has to suddenly cost five times as much. We have to forget about electric cars. Daimler has to start designing vehicles for the fuels that come out of coal to liquids. I mean, you know, of course, you could create some, as you say, the laws of physics and chemistry would certainly enable us if we were to really step on, pull every lever possible to produce emissions, the laws of physics and chemistry would allow us to get to 8.5. But we're not headed there, are we? 

JS: 

No. So Working Group… Well, I mean, some of the people argue that if you look at the projections for 8.5, as they were made several years ago, we have followed closer to the 8.5 path, then we have that. Yeah. So that's the kind of argument you hear now, I would argue against that as well.  

ML: 

Hang on a second. That argument is made, but that's because we've got two errors that cancel out. RCP8.5, those emissions are made of that…what the actual emissions are made up of much lower ones from energy and higher ones from land use, but that doesn't mean just because you know that those two errors will continue to compound over the next 80 years. That's simply wrong.  

JS: 

Michael, one thing I'm perfectly sure about is that the next Working Group III, when the reports comes out, we'll have something to say about that.  

ML: 

Well, I'm delighted because meanwhile, I'm sitting here and I'm looking at the US National Climate Assessment, which uses RCP 8.5 as business as usual. I'm looking at McKinsey reports, all of McKinsey's climate work uses RCP8.5 as business as usual. I'm looking at literally thousands of reports from the Working Group II community, the impacts. What is it, impacts and… 

JS: 

Adaptation and vulnerability.. 

ML: 

Yeah, literally thousands of papers, and I've just looked today, as you'd expect, and they're still producing papers using RCP8.5 they're even calling it business as usual. And my worry is at all, and by the way, all of the press as you say, all of the press immediately just use business as usual RCP 8.5, the papers are full of beautiful report produced by the National Trust on damage to their properties from climate change, all of it dependent on RCP 8.5. And this is an absolute mess, is it not?  

JS: 

Yeah, yeah. And, you know, just to say that there's a lot of lock-in in the scientific community, you know, which you when you've got these kind of slow timetables for things like IPCC, you could end up citing papers that were done several years ago, when the state of knowledge was different. So what I would say about it, there has always been a temptation, if you're in the Working Group II, impacts world, to say, look at a best case and a worst case, you know, because that's kind of what you do. So, they have tended to take the most extreme RCPs. When they're doing the analysis, they'll take a relatively optimistic the 2.6 one, which is lower, but they also take the 8.5 as the kind of high one, just to say in Working Group III. My fellow co-chair and I are trying to ban the use of the expression business as usual, because it's not particularly helpful, you know, at the moment for that very reason. But yeah, I mean, you're absolutely right. Now, one of the counter arguments you will get from colleagues in the physical science community, is that we run a risk of creating sort of runaway positive feedbacks from release and natural releases of methane or carbon dioxide at higher levels of warming, that mean that the RCP 8.6 scenario is not impossible. But again, it's one of these two contradictory things because the emissions, the human emissions are not are not really believable anymore. But on the other hand, the natural indirect effects might take you back up there again. 

ML: 

But are you going to get to the bottom of that in AR6?  

JS: 

Absolutely. Yeah.  

ML: 

I've looked into it. I'm not a scientist, I'm scientific, but I'm not from that… But what I'm looking at is that the energy related emissions, there's a 600 gigaton gap between a plausible path and the RCP 8.5. And when I look at the feedbacks literature, the worst I can find is a potential, by 2100. I can find 114 gigaton potential positive feedback. And I just find it, you know, so the positive feedback, I'm very worried about them, right? Most of their impacts, as far as I can see, happen in the next century and further out, which doesn't mean they're not important. But pretending that they can happen by 2100 feels to me really, really… How can I put this, I'm trying to do this without using the word fake science. But it feels really un-robust and very easy to attack. The reason I care is because I want to be able to defend this stuff. And then I'm worried that I won't be able to because it's just transparently a castle built on sand. 

JS: 

Yeah, well, I just wish you'd signed up to review our second order draft, Michael. I can't say what it says and how it's constructed for obvious reasons. But you might sleep more peacefully at night if you actually read it. 

ML: 

But Jim’s when it's.. particularly I think the worry is Working Group II, continuing to say, look there's this, you know, this scenario is still produced, right, there are people publishing, you know, RCP8.5 or SSP8.6, whatever, it's that one… they're still publishing it. And so why wouldn't somebody who's trying to, you know, to, as you say, there's a natural tendency to use the most extreme scenario, why wouldn't they still use it? Because… I mean, the words businesses as usual wont’ ban them from using it as a baseline, will it? 

JS: 

So, Michael, just wait for the Working Group III report to come out. If you want to challenge Working Group II, you need to get my colleague Hans-Otto Pörtner from Germany to challenge him on the 8.6 because you know, that, I mean, we have very different scientific communities working on IPCC, working at very different pieces. And this is the cycle where we actually have the best kind of linkage between the Working Groups we've ever had, I mean, often they were really quite siloed in previous cycles. This time, because of the special reports we've worked on, on 1.5 degrees and on land, people have really got together. The number of meetings I've been on, where scientists from different working groups gather and are battling these issues and addressing them is much higher this time around than it was before. And I hope when the reports come out, which is the time you need to make the judgement, I hope we've done it, you know, we've raised the bar. 

ML: 

I will definitely, you know, I will read them in great detail. And with great joy. 

JS: 

You read the SPM, quite wisely. 

ML: 

I read more than the summary for policymakers, I can assure you, I don't necessarily read all 3000-4000 pages of the whole thing. But my question would be, why produce a scenario that is not plausible. Knowing that whatever you say, people are going to abuse it and treat it as the baseline and business as usual. And then you can say, well, but we said and it says on page 72 of Working Group III, that you shouldn't do that. But you know, it says you can't compare RCP 4.5 with 8.5. And yet the National Climate Assessment of, the US National Climate Assessment 2017 does exactly that. 

JS:  

Yeah. Well, I wasn't responsible for the US National Climate Assessment, Michael. But you know what I want to say that there's something I should have said right at the beginning, which is the IPCC doesn't do its own research, it reviews work that's been done by other people. So sure, there's lots of papers that have gone on and done that. And one of the jobs we have been working with for years to assess all these papers on this piece of literature and it's not just the scenarios, that's not the only line of evidence we've got. We also have a big chapter in the report, but it's happening. It's showing what happened in the real world over the last five years, which will cover the dramatically falling cost of photovoltaics and batteries. And we'll figure out what the kind of differences that that makes to forward projections as well. So, you've got to see the whole picture. 

ML: 

Okay, but if I come to the Working… I know you're not, you know, your chair Working Group III, but you've talked about your colleague who chairs Working Group II, will they use, refer to in any way papers that use RCP8.5 as effectively business as usual baseline or will they strike those out of the record and pretend they don't exist? Because they are worthless. 

JS:  

Yeah, their job is to assess the literature and whatever went into it. So, you know, I think they have to refer to these papers. But in assessing them, they might want to reflect on the plausibility or otherwise or evidence that's coming in from other places. For example, the Working Group III model, because then, you know, the nature of the scenarios that are being written by the people that we assess in Working Group III are actually changing in character a bit. 

ML: 

But what do you say to them if they were to refer to a paper that uses something called SSP3 8.5. Because SSP3, the Shared Socioeconomic Pathway 3, cannot produce 8.5 watts per square meter by 2100. And yet there's all these papers that that take a population because they want to get the biggest possible impact for their impact. And they produce, they use a population from SSP3, with a warming from RCP8.5, which can't be produced by SSP3, and those papers are out there. Are they going to refer to them?  

JS: 

You’ve read that literature more closely than I have Michael, that’s all I can say. 

ML: 

Well, but I'm worried about it. Because literature is out there. Hundreds… well scores of papers about 15 to 20 every year still being published today using a scenario which your Working Group can't replicate. 

JS: 

Yeah, that's why we do a synthesis report at the end of each cycle. So, you can't believe how intense the scientific discussions will be as the different tribes gather together to put these different elements all in one place. 

ML: 

Jim, you've been very patient with me. I've given you...  

JS:  

No, I knew what was coming, Michael, that was fine. 

ML: 

Yeah. You know in a sense, the flip side of saying. oh, it's all terrible and whatever, is how can we work better together, because I come from a world of, you know, energy modelers, who are, you know, coming out of the latest data, which I helped to assemble into great datasets when I was, you know, building New Energy Finance, and oil companies that have got incredible knowledge of what it really costs to do, you know, extraction of the fossil fuel side of things. You know, the wind, the finance community that really knows how much it costs to build offshore wind farm or whatever. One of the problems that strikes me as these communities are almost completely separate. I have never met an integrated assessment modeler at one of the conferences I go to, to my knowledge.  

JS: 

Lucky you. Okay. Right. So just to say, I mean, that's why I mentioned, you know, 90% of the media and 6% of the content. If you actually went to our energy systems chapter, you would find far more people that are closer to the kind of issues. They're either doing things like modelling, how do you fit large volumes of variable renewables into an electricity system, they are actually getting into these kinds of issues that are much closer to the market in the short term. And when we started this whole cycle, we actually had a scoping meeting, you know, just to get us going. And we had a bunch of people, both from the policy world and the business world who came along. And the biggest advice was, it's not all the year 2100. Decision makers want, need to know what happens in the next 5-10 years, or even sooner and so when we scoped out the report, as well as that traditional integrated assessment modelling 2100 chapter, we have a much shorter term chapter that's on the timescale of the Nationally Determined Contributions and the Sustainable Development Goals for that kind of timescale. And then we have a pile of sectoral chapters where you have, frankly, you know, the plumbers, the electricians, and the car mechanics have come out to the woods, and they're working on these much shorter term issues. And we have people from the business sector who are actually acting as review editors or coming in as authors. We have a big automotive manufacturer in there, we've got an oil company, you know, there are people really engaged with us who come from what you might call the real world. 

ML: 

I’m glad to hear it because I've been pushing people, although, I said I quite like to stand on the sidelines with my peashooter, I’ve been pushing people. And you know, when it comes to electricity modelling, the people that I tend to hang out with, they would say, well, if you're not modelling on a half hour basis, you know, right through the next, you know, however many years you want to do, which, you know, I don't know if you can even do that computer power wise out to 2100. But if you're not resolving at the half hour basis, then everything is just a kind of, you know, finger in the air and is not going to be correct. 

JS: 

Yeah, well, the colleague who specializes on that in our chapter on energy systems, actually models on a half hour basis, and has a model that covers every piece of kit in Europe. And he runs it on cloud computing, with all his PhD students connecting their computers together, that stuff is happening. And this guy is actually used by governments and other people to do their modelling for them, for policy design. 

ML: 

Now, I'm really excited to wait until the AR6 comes out. But one other issue is that certainly in AR 5 and historically, that a lot of the data used was just really, I mean, ancient in terms of renewable energy, clean energy, because by the time you used, you know, there was the AR5 came out in 2015 some of the literature that that it relied on came out in, you know, 2008, using data on renewable energy costs from, you know, literally the early years of this century. And it was just kind of, you know, people in my environment, we just look at it, and we just, we just, you know, roll our eyes or burst into laughter. But when we look at it… 

JS:  

Yeah, yeah, well, sure, there is that time delay. But I think because of the declines in… costs have just been so big of the last three to four years, there's been a lot of literature that's out there that is being covered, you know, in the work that’s being done. The question is whether it's found its way into these big integrated assessment models, it's found its way into the models, that, for example, do electricity systems and half hour slices. That's absolutely the case. But it takes time to work into the integrated assessment models. 

ML: 

But the reality is, sitting where I sit, I still worry that a lot of that data has not even made its way into IEA  and into the oil companies’ models. Right. And they are enormously further along than anything I've seen, you know, from the IAM community.  

JS: 

Well, just to say a couple of colleagues and I have just finished an article we sent off to Technology Forecasting and Social Change in which we systematically compared IEA, oil companies’ and IPCC scenarios and deduce the impact that changing expectations on renewables costs, had had on some of the output, that was part of the paper. So, I've got all these issues on everybody's been guilty of it. They haven't kept up with it. Absolutely. 

ML: 

Yeah, you name those names. The names, you've just used in, I would say, where is Fraunhofer? Where is DNV GL? Where is Bloomberg New Energy Finance? The people who've been, you know… and by the way, even those names have been too slow looking at the technology progression and the cost reductions. 

JS: 

Yeah. Well, you know, if you were producing scenarios, you had an invitation to put your scenarios into our database to be covered there. I don't think there's anything to stop you doing that. 

ML: 

We tried very hard, by the way, the problem that we had, because I talked to quite a few people about this. The problem was they don't go out to 2100. And they all go out some 2050, some to 2070, and so on. So, it wasn't I don't think it's been possible, unless maybe it's not too late. In which case, let's do it. Because I would love… 

JS: 

Yeah, yeah, please do it. Because we actually have two calls for this for scenarios, one for the scenarios that go to 2100 that are global, and other for scenarios that are sectoral and shorter term. 

ML: 

Jim, what's the deadline for those scenarios? 

JS:  

I honestly can't remember, but you will be getting an email tomorrow morning telling you how to do it, because we'd love to have your scenarios.  

ML: 

And there's a few people that I can try… And I actually had a few people who said, yeah, we, you know, we would provide us scenarios. Part of the problem is, do you have any resources to work, you know, to put them into a sort of standardised format? <inaudible> I think that Naki’s team in IIASA could do a great job on that. 

JS: 

They do. Well, they've got lots of scenarios. They're one of the main producers that, through the MESSAGE model that they run. Yeah, yeah. But just to say it's, you know, it is a bit time consuming to put them in. And we also think that some people may have worried about confidentiality, because some of the issues do involve making assumptions, exposing the assumptions you've made about things like prices, the costs of technologies, which some people might find quite sensitive. 

ML:  

Jim, you and I could keep doing this for the rest of the evening because we're both so fascinated by it. Very much looking forward to AR6. I am somewhat heartened, but I'm going to reserve my peashooter rights to snipe at it when I see it. But I will always do it in good faith. All I want is the most robust set of information on which, you know, I and my… the people I interact with can form their judgments and put assets to work and hopefully accelerate climate action through the small number of leaders that I help to influence with my information and my commentary. So, with that, I'd love to just thank you for the time and your good nature in participating in this Cleaning Up episode. 

JS: 

Yeah. Okay. That's great, Michael. It's a delight speaking to you, as ever. 

ML: 

Thanks very much, Jim. So that was Jim Skea, Co-Chair of Working Group III of the IPCC, talking about how emission scenarios are produced and what they’re used for. My guest next week on Cleaning Up is Teresa Ribera. She's a Deputy Prime Minister and the Spanish Government Minister for the Ecological Transition. Please join me this time next week for a conversation with Teresa Ribera.