Which Climate Path Are We On?, with Zeke Hausfather

Notable Quotes

• Shifting carbon emissions sources: “What’s interesting, particularly in the last few years, is that global coal use is no longer the biggest driver of increasing emissions. These days, it’s actually natural gas that’s adding more CO2 emissions than anything else.” (4:38)
• Problems with conventional “business-as-usual” metrics: “In a world where global coal use peaked in 2013, where clean energy prices are falling, where 2019 saw a record decline in coal use, the idea that we’re going to turn around, re-embrace coal in a huge way, and have it drive pretty much all the growth and global energy use of the next century is very unlikely … But a lot of climate science papers in the intervening years have referred to [this scenario] as 'business-as-usual.' We’re making the argument that we really need to stop doing that.” (12:18)
• Next steps to hit climate targets: “[Our current climate trajectory] is a reason for hope: we are making progress, we have falling clean energy prices, we have clean renewables … The trends are moving in the right direction, but not nearly fast enough to get to where we need to in terms of these climate targets.” (18:15)

Top of the Stack

• The End of Nature by Bill McKibben
• "Explainer: Nine ‘tipping points’ that could be triggered by climate change" by Robert McSweeney
• The Broken Earth trilogy by N.K. Jemisin
• "Endless Night at -50 Degrees: A Look at Life on an Icebreaker" by Henry Fountain
• "Wild storms and shifting ice: Two explorers talk about Arctic life" by Henry Fountain and Esther Horvath

The Full Transcript

Daniel Raimi: Hello and welcome to Resources Radio, a weekly podcast from Resources for the Future. I'm your host Daniel Raimi. This week we talked with Dr. Zeke Hausfather, director of climate and energy at the Breakthrough Institute. I'll ask Zeke about the past, present, and future of global greenhouse gas emissions. We'll talk in detail about the emissions trajectory that the world is currently on, and how that pathway looks different from some of the worst case scenarios that researchers have used in the past. We'll also talk about the crucial uncertainties that still remain when it comes to estimating future global warming under any given emissions pathway. Stay with us. Okay, Zeke Hausfather from the Breakthrough Institute, thank you so much for joining us today on Resources Radio.

Zeke Hausfather: It is great to be here.

Daniel Raimi: So Zeke, we're going to talk today about recent trends in greenhouse gas emissions, as well as looking towards the future about greenhouse gas emissions, and trying to get a sense of what pathway we might be on, and what pathways we might not be on. But before we do that, we always like to ask our guests how they got interested in working on environmental topics. So what brought you into this field?

Zeke Hausfather: So it's a long and twisting path on how I ended up doing climate science and energy system modeling. I think the most formative thing for me was probably as a freshman in college, back in 2001, I read Bill McKibben's The End of Nature, which was the first time I had really become aware of the climate issue and what it meant, and so that book was really formative to me. I spent a while as a college student being a climate activist, ended up later on going to work in the clean tech world as a data scientist, co-founded a company called Efficiency 2.0 that competed with Opower in the pay-for-based efficiency space. For many years, I did climate science as a hobby that grew out of my data science work, particularly around observational temperature records, reconstructing global temperatures, worked with the Berkeley Earth Group, for example, and then eventually, got a little bored of energy efficiency, and decided that my hobby was a lot more interesting than my career, went back, got a PhD, and now I do climate science and energy modeling as a full time gig.

Daniel Raimi: That's awesome. And of course, no offense to our energy efficiency enthusiasts out there, we love you too.

Zeke Hausfather: No, energy efficiency is hugely important, but 10 years was a good amount of time to spend on it.

Daniel Raimi: Great. Okay, so as I mentioned, we're going to talk about future greenhouse gas emissions today, and try to understand what trajectory the world might be on, and what that means for global temperatures. But first, I think it'll be useful to start just with a little bit of history. So, can you give us a short overview of recent trends in global greenhouse gas emissions? And this'll probably be broadly familiar to many of our listeners, but can you just give us a sense of how fast greenhouse gas emissions have risen in recent years and how that might compare to previous decades that we've seen?

Zeke Hausfather: Sure. So the recent years, the last two decades are very distinct. Back in the year 2000, China had roughly half the emissions as the US, global emissions had been growing modestly since 1990, but suddenly, right around 2001-2002, there was a turning point where China started adding an immense amount of coal. Their economy is growing very rapidly, they're building a new coal plant almost every day, and their emissions over the course of just six years doubled. They went from about three and a half gigatonnes of CO2, to about seven gigatonnes of CO2. At the same time, there was also a rapid increase in the rest of the world's emissions, driven largely by coal. The period from 2000-2010 was all about a global build-out of coal, particularly in the developing world.

Since 2010 however, and particularly since about 2012-2013, the picture's changed a little bit. Global coal use peaked around 2012-2013, and is still lower than it was back then. Global emissions were pretty flat from 2013 through 2016 or so, before ticking up in 2017 and 2018. And the picture's really changed, in terms of what the drivers of increasing emissions are. 2019, the jury's still out on what the final number is going to be, but it looks like most estimates are either of a fairly flat or modest increase in emissions globally, and that's almost entirely driven by increases in Chinese emissions. The rest of the world didn't change much at all between 2018 and 2019.

And what's interesting, particularly in the last few years, is that global coal use is no longer the biggest driver of increasing emissions. These days, it's actually natural gas that's adding more CO2 emissions than anything else. That, in some ways, is a better thing than if the emissions were still coming from coal because a lot of the natural gas that's being added is either replacing coal, or meeting new demand, but that new demand would have likely been met by coal in a world where we didn't have as much natural gas. The renewables are also a big part of that picture, and they were the second biggest addition of energy last year, after natural gas globally. But gas is the biggest driver of emission increases in recent years.

Daniel Raimi: And oil too has been pretty substantial, right? We are seeing growth of oil demand in the neighborhood of one million barrels to two million barrels per day, over the last few years. So, that's still a pretty substantial chunk of growth.

Zeke Hausfather: Oil is definitely consistently increasing over time, though it's only been about half of the additional CO2 that the gas has added, for the last three years at least.

Daniel Raimi: Right, great. Okay, thank you, that's super useful context. So with that brief snapshot of where we are, and where we have been over the last couple of decades, we're going to turn to the future. So, before we talk about future pathways for emissions, let's define at least one term, which is Representative Concentration Pathway, or RCP. When we think about future emissions trajectories, people often refer to RCPs. So, can you give us a brief overview of what RCPs are, including when and why they were originally developed?

Zeke Hausfather: Sure. So RCP stands for Representative Concentration Pathway, and they were developed in the lead up to the IPCC Fifth Assessment Report, which came out in 2013. And the interesting story behind the RCP is that, there was a previous energy modeling effort called the SRES scenarios, which stands for the Special Report on Emission Scenarios, it's an odd name for a set of scenarios, but so it goes. And the SRES scenarios were interesting in that, they modeled four different socioeconomic futures, A1, A2, B1, B2, each of which had different GDP, a different set of global population growth, and they presented a whole bunch of different scenarios that were all baseline scenarios in our SRES. And by baseline I mean, essentially how the world could evolve if there were no additional climate policy beyond what was in place at the time the scenarios were created.

And so it looked at a whole bunch of different possible futures that ranged from as low as about three degrees warming, to as high as five degrees warming by 2100. And so, that set of scenarios was originally created around the year 2000, so it was getting pretty old by the time the 2013 IPCC report was coming out. And so, there's a big desire to create a new set of emission scenarios, and socioeconomic scenarios, to model what might happen in the future. The problem was that climate modelers needed these scenarios, at least two or three years ahead of time, in order to have time to run the supercomputer models to produce the climate simulations needed for the IPCC Fifth Assessment Report. And the energy system modelers just didn't have enough time to do a full set of new socioeconomic futures.

And so as a stop-gap measure, they created these four representative concentration pathways that were broadly four levels, roughly consistent with some of the levels in the previous SRES scenarios, as well as some more aggressive mitigation scenarios. And the idea was, these four representative concentration pathways ended up far enough apart in 2100, that you get climate model outputs. They're very distinct, that was one of the main impetuses behind it. And so, what's interesting though is unlike the SRES scenarios where they were all potential no policy baselines, the RCPs only had one scenario that was created by an integrated assessment model that didn't have a carbon price in it. And that's RCP 8.5. Both RCP 6 and RCP 4.5 work consistent with the range of no policy based on some literature, but the actual model used to generate them did have a carbon price.

It's possible both to have a modest mitigation scenario, and an optimistic baseline scenario that overlap each other. Right? And so what we ended up with the RCPs was, this case where only one of the scenarios was generated as truly a baseline scenario, but that scenario, RCP 8.5, was not particularly representative of the full range of baselines in literature. It was roughly the 90th percentile of baselines when it was created. So if all of the integrated assessment modeling runs that people had done looking at potential outcomes in the absence of climate policy, RCP 8.5 was around the 90th percentile of those, in terms of emissions. And it's, as we can talk about in a bit, it's become substantially less likely since then. What's happened in recent years is the replacement for the old SRES scenarios has finally been completed.

It's called the SSPs, or the Shared Socioeconomic Pathways. They had originally planned for it to be completed before the 2013 IPCC report, to merge the RCPs back into this more consistent socioeconomic modeling framework, that ended up not happening. It took another four years longer than they thought, or five years. But we finally have a new set of scenarios called the SSPs that has consistent socioeconomics across all the models that looks at a whole wide range of baseline no-policy outcomes, and gives us a much better infrastructure of scenarios to work with going forward.

Daniel Raimi: Right. Great. Got it. So the RCPs that are most commonly used today, there are four of them, there's RCP 2.6, 4.0, 6.0, and then 8.5. Is it 6.0 or 6.5? I can never remember.

Zeke Hausfather: It's 4.5 and 6.0 but...

Daniel Raimi: Okay, great. And just in case you've heard sirens in the background there while Zeke was speaking, the RCP police are after you, so watch out.

Zeke Hausfather: It's an occupational hazard of being in downtown Oakland.

Daniel Raimi: Yeah, right. So let's talk now about one particular RCP that has received a lot of attention, which you mentioned just a moment ago, and which you write about with Glen Peters in a recent article in the journal, Nature, where you essentially make the case that RCP 8.5 appears extremely unlikely, far more unlikely than it was, as you suggested, when it was initially developed. Can you explain briefly why? What about RCP 8.5 makes it so unlikely?

Zeke Hausfather: Sure. And to give an important caveat, what we're really arguing in this Nature piece is that the emission scenario underlying RCP 8.5 is unlikely. There are multiple different ways to get to that radiative forcing, and I'll get into that in a little bit, but to back up and discuss our Nature piece, essentially as I mentioned, RCP 8.5 was originally generated using roughly the 90th percentile of no-policy emission scenarios in the literature. And in practice, what that means is, it was generated using a scenario where global coal use expands dramatically by the end of the century. So in RCP 8.5 emissions scenario, the world is using roughly five times more coal by 2100 than it's using today. Now, when this scenario was originally created in the mid 2000s or late 2000s, that didn't seem like that crazy of an assumption, right? The world had been adding coal at an accelerating rate, Chinese emissions had doubled in the course of five years.

And so, projecting that increase out to the future with coal meeting the majority of energy demands, was not necessarily the most realistic assumption, but it was a reasonable assumption to make. Today, in a world where global coal use peaked in 2013, where clean energy prices are falling, where 2019 saw a record declining global coal use, the idea that we're going to turn around, re-embrace coal in a huge way, and have it drive pretty much all the growth and global energy use of the next century is very unlikely. And so, what we're pointing out in this Nature piece is that, that scenario, we need to stop referring to it as business-as-usual, or as the most likely outcome of current policies. We can't necessarily preclude the possibility that the world will decide to burn all the remaining coal we have, but it's much more of a worst case scenario now than a likely outcome.

And part of the problem, as we point out in this Nature comment, is that the fact that RCP 8.5 was never intended to be business-as-usual, was not communicated very well to the larger climate science community—if you read the original energy modeling papers that created these scenarios, it's pretty clear, that was the 90th percentile. But a lot of climate science papers in the intervening years have referred to it as business-as-usual. And so, we're making the argument that we really need to stop doing that. Now, the emission scenario underlying RCP 8.5 is not quite the same as the concentration scenario RCP 8.5. So when RCPs are called Representative Concentration Pathways, and they're called representative because the model that generated it is one of a number of possible ways to get to that level of radiative forcing.

So for example, if we had a world where we only increased coal 300 percent instead of 500 percent, but carbon cycle feedbacks—so carbon from melting permafrost, from the Amazon turning into a more of a savanna-like ecosystem, from changing ocean chemistry—if those carbon cycle feedbacks end up being higher than our models currently think they are, which is a real uncertainty we have, you could potentially get to that level of concentrations with a somewhat lower emissions pathway, certainly not on a current policies trajectory. It would be really hard to get to 8.5 watts per meter squared.

But if we had three times the current coal use by the end of the century, we can't rule that outcome out. And so, there's different ways to get to that level of forcing. Similarly, all of these RCPs are based around the end of the century, the year 2100, and it's important to emphasize that the world does not end in 2100, our models just end in 2100. And so, as long as we keep emitting CO2 and other greenhouse gases, the world will continue warming. And so even if we don't get to this RCP 8.5, five degree warming outcome by 2100, if we keep emitting at current levels, we'll probably get there before 2200, right?

Daniel Raimi: Right.

Zeke Hausfather: And if we keep increasing emissions, we'll probably get there by 2150 and so, we're not out of the woods on that front. And then finally, there are big uncertainties in climate sensitivity. So, if you look at how climate modelers turn future emissions into warming, there are three different sources of uncertainty. One is what are future emissions, right? Are they going to be low? Are they going to be high? That's something that really comes down to socioeconomics, to political decisions, that you can't really use physics-based models to predict. You can just look at a different range of possible emissions. But beyond that, there's also the carbon cycle feedbacks I mentioned earlier.

So how much additional carbon is released from things like permafrost, there's the earthworms, and then there is climate sensitivity uncertainty. So how does warming affect the behavior of clouds? How does it affect the reflectivity of the earth's surface? How does it affect the amount of water vapor in the atmosphere? And all of these things act as feedbacks that reinforce the warming you'd otherwise have, and potentially make it stronger. And so, if you look at the climate models for a given emission scenario, say a scenario where global CO2 emissions double by the end of the century, you could have anywhere between about 1.5 and 4.5 degrees warming per doubling CO2 at equilibrium. And that itself is a wide range of uncertainty.

And so that means that even though there are more modest emission scenarios, we can't rule out potential high warming outcomes. So we point out in our comment in Nature that current policies, the policies the countries have in place today, if you extend them through the end of the century, we'd be on track for probably somewhere around three degrees warming. But that's a best estimate, assuming that we know what carbon cycle feedbacks and climate sensitivity is, if you take the uncertainties from those into account, we could probably have anywhere between, 2.3 and 4.4 degrees warming under current policies by the end of the century. And so we can't necessarily rule out these very high end warming outcomes of four degrees plus even in a current policy world.

Daniel Raimi: Right. So, one way that I internalized this when I was reading your piece is that, even though we think that an emissions trajectory like RCP 8.5 is very, very unlikely, some of the warming effects that we could experience might be more in the range of what people think of as an RCP 8.5 outcome, even under a lower emissions trajectory.

Zeke Hausfather: Yeah. But at the same time, if climate sensitivity is on the high end and we were on an RCP 8.5 emissions trajectory, we'd have like seven degrees warming, right?

Daniel Raimi: Right.

Zeke Hausfather: And so that truly nightmarish outcome is no longer on the table, it's very unlikely to be on the table, which is a good thing. And as we also point out in our comments, it's a lot harder to meet Paris Agreement targets of limiting warming below two degrees, if the world is on track for warming of five degrees. The socioeconomics needed, the population growth, the level of technological progress, et cetera, that can get the world to five degrees, makes it really hard to get down to two degrees.

And so the fact that we're in a more modest baseline scenario now, or a more modest current policy scenario means that, it is a lot more possible to bend that curve down. And so that is a reason for hope, we are making progress, we have falling clean energy prices, we have clean renewables where the single largest source of new electricity had added worldwide last in 2018, which is a big change from previous years. And so the trends are moving in the right direction but not nearly fast enough to get to where we need to in terms of these climate targets.

Daniel Raimi: Right. And before we move on, there are a couple of terms that you mentioned, that I just want to pause and define for listeners who might not be as familiar with this subject matter. One of them was radiative forcing, and the other one was, you used the phrase watts per meter squared, which is in reference to the RCPs. So, can you briefly define for us radiative forcing for people who don't have a geophysical background? And then tell us what watts per meter squared means, and how it refers to the numbers in the RCPs? Basically a preview of this is that, the RCPs... The numbers that are attached to them, 2.6, 8.5, and so on, in reference to watts per meters squared. So first can you give us radiative forcing definition, and then watts per meter squared.

Zeke Hausfather: Sure. So, the RCP numbers actually are the radiative forcing in that scenario in the year 2100, and watts per meter squared is the unit in which the radiative forcing is calculated.

Daniel Raimi: Got it.

Zeke Hausfather: So radiative forcing essentially, the simple version is it's the amount of additional heat that's being trapped by the atmosphere. So if we had left CO2 at preindustrial levels, the earth would roughly be an equilibrium, the amount of energy coming in from the sun would be balanced by the amount of energy radiating back to space, and the temperature of the planet doesn't really change. But as we add more greenhouse gases to the atmosphere, suddenly we have more heat coming into the system than is going out of the system. And that energy imbalance is calculated in units of watts per meter squared.

So essentially, how many watts of energy for every square meter of the planet is being added to the earth system compared to how much is radiating back to space. And so that's how we define radiative forcing. And it's a nice unit to take all of these different greenhouse gases, and aerosols, and various other factors that affect the climate and put them together into a single unit that reflects for any given period of time, how much additional heat is being trapped.

Daniel Raimi: Great. And so it does take into account all of the different greenhouse gases that could be playing a role, not just CO2?

Zeke Hausfather: Well not just greenhouse gases, it takes into account reflective aerosols, it takes into account changes in albedo, how reflective the surface of the earth is, if for example, you have less snow cover in a warming world, you have more bare ground that is absorbing more heat. So pretty much anything that affects the amount of heat that is retained in the earth system gets included in these radiative forcing estimates.

Daniel Raimi: Great. So yeah, my ignorance of climate science is being exposed once again. So, turning from the discussion of which pathway we're on, and what the equilibrium climate sensitivity might be and related issues, when you think about this from a policymaking perspective, I know your background is in climatology, but you think a lot about policy and policy decisions that have evolved over time. What are some of the major implications of both, the fact that it appears very unlikely that we're on a RCP 8.5 type emissions trajectory, and also what are the implications of the uncertainty that still remains around whatever trajectory we happen to be on?

Zeke Hausfather: So in terms of the need to mitigate climate change, this doesn't change much at all, right? The need to limit warming below two degree as codified in the Paris Agreement, never was based on having a five degree counterfactual, right? Whether the world is on track for five degrees, or four degrees, or three degrees, we still need to mitigate to try to get to as close to two degrees or below as possible. And so the steps that countries need to take in terms of mitigation don't really fundamentally change depending on the baseline, where it does affect some policy decisions is around adaptation. So, if a five degree world is much less likely, if the two meters of silverized high end estimate associated with RCP 8.5 is much less likely than it used to be, our planning for adaptation in the century changes a little bit as well.

We may want to make decisions for a worst case outcome of four degrees instead of five degrees, and all the various impacts that would entail across agriculture, and ocean rise, and heat stress, and other issues, or other impacts of climate change. So I think it's more on the adaptation side that this changes the policy calculus in the mitigation side. We're still very far from being on a pathway toward two degrees than we need to be. And so the types of actions countries need to take on mitigation don't really change.

Daniel Raimi: Yeah, that makes sense. And so you've answered all my questions that I had planned in advance when talking about these issues, but I wonder if there are any questions that I haven't asked, or any topics that you want to expand on, around this general topic area that we haven't talked about yet?

Zeke Hausfather: Sure. So I can mention briefly, one of the big uncertainties in future warming is climate sensitivity. And that's an area that we've been really hard pressed to reduce the uncertainty of. In fact, in some ways it's a little embarrassing for the climate science community because, back in 1979, Jules Charney published a big report, and in that report they estimated that if we double CO2 in the atmosphere, the world would likely warm somewhere between 1.5 and 4.5 degrees centigrade. And fast forward to 2013 and the last big IPCC report, and lo and behold, the range of expected warming for doubling CO2 is 1.5 to 4.5 degrees centigrade. Now Charney was probably a little over confident in his assessment back in 79, and we certainly have a lot more evidence now that sensitivity is probably not likely less than 1.5 degrees, and not likely that much over 4.5 degrees, but it's still a really tough thing to narrow the estimates of.

And there's been a lot of talk recently because, the latest generation of climate models, the ones that are currently in the works for the upcoming IPCC Sixth Assessment Report, which will be released in 2021. A number of those models show very high climate sensitivity values, essentially saying that if we double CO2, the earth might warm by 5 or 5.5 degrees. And if that's the case, that really is worrying, it means that it's almost impossible to limit warming to below two degrees, for example. It means that a scenario that you thought would give you three degrees warming, might give you four and a half degrees warming instead, if climate sensitivity is actually that high. But thankfully, we shouldn't over-interpret these results, only about 70 of the 30 models that have reported value so far, have very high sensitivity estimates, the rest don't. The rest are pretty much in line with the previous generation of models.

Daniel Raimi: Sorry Zeke, just one quick clarification. You said... I think you meant to say 7 of the 30, but it sounded like you said 70 of the 30, could you clarify?

Zeke Hausfather: I meant 7 of the 30, yes.

Daniel Raimi: Okay, good. Yeah, 70 of the 30 would be really... that'd be really something.

Zeke Hausfather: 7 of the 30 models that have reported so far have very high sensitivity values. We expect about a hundred models to ultimately participate in the current round of climate modeling. And so, it's a little premature to judge what's going to happen with the full 100 models based on just seven. And so, it certainly means that there are real risks of high sensitivity that we need to take into account. There are long tails in these estimates that are really hard to fully eliminate, but at the same time, we'd have other lines of evidence from the earth's distant past, from the observational temperature record, from these things called merchant constraints, where you look at how other climate variables we can observe are related to climate sensitivity and models, and all of these lines of evidence suggest that climate sensitivity is probably around three degrees per doubling, again with this range of 1.5 to 4.5 or so. And so, it's probably premature to conclude that climate sensitivity is higher than we previously thought, even though this is yet another bit of evidence that there are long tails of uncertainties that we need to take into account.

Daniel Raimi: Right. That's super interesting. That'll be really fascinating to watch over the next few months, and maybe years or two as the full results start to come in. And I'd also suggest to listeners, if they want to get a sense of some of the policy implications of the long tails that Zeke is referring to, we did an episode, I want to say about six or seven months ago, with Gernot Wagner from Harvard, where we mostly talked about his mentor, the late Dr. Marty Weitzman, who did a lot of policy work around, or I should say more theoretical work around the implications of those long tails. And then we had Bob Litterman on the show a couple of months ago, where we talked about the same thing. So it certainly ... This question of equilibrium climate sensitivity and how long are the tails, is one that people are thinking pretty hard about in the policymaking community.

So with that, I think we're going to close it out. And now Zeke, I want to ask you the same question that we ask all of our guests, which is, what have you heard, or watched, or read recently, related to the environment, or climate change, or any relevant topic that you think is really interesting, and that you'd recommend to our listeners?

And I'll just briefly start us off with a really cool news story that I read in the New York Times from a couple of weeks back now. The article was called, “Wild Storms and Shifting Ice: Two Explorers Talk About Arctic Life”, and it was a really nice, visual heavy, interactive article, that I read online, that showed lots of pictures, and some videos, from these two scientists who were working up in the Arctic measuring, I think taking ice core samples to try to get a sense of paleo climate. I don't actually know what they were doing with the ice core samples, but they were definitely taking ice core samples, and then learning stuff from the ice core samples, and it was a really fun article, gave you a sense of what it might be like to actually be up at one of those stations. So how about you Zeke, what have you been listening to, and what's on the top of your reading stack?

Zeke Hausfather: Sure. So the most recent thing I read that was quite interesting was, some of my colleagues at Carbon Brief had been working for about a year on this big explainer on climate tipping points, which is an issue that's very much in the public eye at the moment. And so they just published it yesterday, and so it's a really long article on carbonbrief.org, that goes into all the different tipping points, interviews with a bunch of the top scientists in each of those fields, and tries to provide a good summary of what we know, what we don't know, where the real uncertainty is, and how sometimes the science is not quite as clear in terms of tipping points as it gets portrayed in the media. So, that was a really helpful article in looking into that.

On a slightly different note, something I read recently that touches a little on the environments, but in an indirect way is, I read a quite excellent series of books by N.K. Jemisin called, The Broken Earth Trilogy. I think all three of them won the Hugo Award, which is the first time ... That's just the biggest award in science fiction and fantasy, and which I think is the first time an author has ever had three Hugos in a row for a trilogy. And it's a really interesting look at a fictional world that's very much defined by tectonics, and geology, and exploring how that might shape societies, it was quite interesting. So if you need something that's a little bit of a break from the dry academic articles, I'd recommend The Broken Earth Series by N.K. Jemisin.

Daniel Raimi: Great. Yeah, we'll put up a link to both the Carbon Brief article, and that series that you mentioned on the show page. And I want to note that we're recording this on February 11th, it might air a couple of weeks from that time, so we'll make sure you can find the link to the Carbon Brief article because probably, it won't be a yesterday when you're listening to this episode that it would have been published. So let's close it out there and once again, I want to say thank you so much Zeke for joining us today on Resources Radio, and talking to us about RCPs, equilibrium climate sensitivity, and so many other fascinating topics. We really appreciate it.

Zeke Hausfather: No worries. It was great to be here.

Daniel Raimi: You've been listening to Resources Radio. If you have a minute, we'd really appreciate you leaving us a rating, or a comment on your podcast platform of choice. Also, feel free to send us your suggestions for future episodes. Resources Radio is a podcast from Resources for the Future. RFF is an independent nonprofit research institution in Washington, DC, our mission is to improve environmental energy and natural resource decisions, through impartial economic research and policy engagement. Learn more about us at rff.org. The views expressed on this podcast are solely those of the participants. They do not necessarily represent the views of Resources for the Future, which does not take institutional positions on public policies. Resources Radio is produced by Elizabeth Wason, with music by me, Daniel Raimi. Join us next week for another episode.