by Stephen Lacey
August 03, 2017

By now, you've probably heard a lot about the debate over whether America can get all of its energy from renewables. If you've followed it closely, you might be sick of the heated back and forth. Who should you trust?

We wanted to cut through the noise and provide as much context as possible to our audience. In recent weeks, we produced two episodes of the Interchange podcast featuring Mark Jacobson and Christopher Clack, the two researchers at the center of the dispute.

In this extended transcript, we provide the text of both interviews. We hope it serves as a useful resource.

Part 1: Prof. Mark Jacobson & The 100% Renewables Scenarios

Stephen Lacey: This is The Interchange, weekly conversations on the global energy transformation from Greentech Media in Boston. I'm GTM Editor-in-Chief Stephen Lacey, in San Francisco sits Shayle Kann, he's the Head of GTM Research and GTM Senior VP and my co-host. Hey, Shayle.

Shayle Kann: Hey, Stephen. Let me ask you a question.

Stephen Lacey: Uh-oh, usually I'm the one asking questions to start this off.

Shayle Kann: Yeah, I have a question for you this time.

Stephen Lacey: Okay.

Shayle Kann: Just imagine that I were to say the following about your writing, the question is how would you react? So if I told you that your analysis is "riddled with errors," it's an "appalling delusion," an "unscientific fantasy," and "virtually every sentence is inaccurate," and finally, "the scale of your error is staggering." What would you think about that?

Stephen Lacey: That's just the regular comment board on GTM whenever I read an article.

Shayle Kann: All right, fair enough.

Stephen Lacey: Just kidding. No, I'd be embarrassed, I'd be mortified, I don't know what I'd do. I mean, I'd revisit my entire assumption about what it is I was arguing.

Shayle Kann: Right. Those are all quotes from various portions of this debate that's been going on online, on Twitter, in academic publishing, in the news over the past couple of weeks about 100 percent renewables and specifically about this paper that was written by Christopher Clack and 21 co-authors in the Proceedings of National Academy of Science that's a response to a paper by professor Mark Jacobson from Stanford in 2015 sort of designing a scenario for 100 percent renewables. I was giving you ... One of those quotes was from the Clack response to the Jacobson response to the Clack response to the Jacobson paper, I'll say that again, the Clack response to the Jacobson response to the Clack response to the Jacobson paper. That was all just the actual back and forth between the principals here. Then I gave you a quote from the National Review article about the Jacobson paper, one from the Forbes article about the Jacobson paper, one from the Jacobson response to the Clack response to the Jacobson paper.

Stephen Lacey: It's a good thing that Twitter changed its algorithm and made conversations easier to follow, because there were a lot of conversations after this paper was released.

Shayle Kann: I mean, I got lost in a bunch of ... I was in London the week that this all came up, the week that that PNAS paper was published, and all the responses kept coming. So I had this benefit of being off timing-wise, just in [different] time zones from everybody else, so I would wake up in the morning and scroll through my Twitter and just find dozens of different threads from different energy thinkers on Twitter responding to all of this. It was really unexpected, how fast this blew up and how much it enveloped the world of energy wonks for a brief period of time.

Stephen Lacey: Yeah, we caught wind that the researchers were going to be releasing this response to Jacobson's 100 percent renewable energy scenario, so we knew that this was coming. We wrote a story, our reporter Julian Spector wrote a great piece on the debate, talked to the folks who wrote this response, talked to Jacobson, and I think provided a comprehensive accounting of the debate. We knew this was going to blow up, but I don't think I understood how dramatically it was going to blow up, and I've never seen a record number of Twitter threads in one day before, it was just incredible. In fact, if you're kind of looking for the context of how people were reacting to this, we did a great energy gang episode, Jigar, Katherine, and I talked about this the week that that debate exploded.

Then Shayle and I decided we wanted to go straight to the source, and we wanted to interview professor Mark Jacobson. Of course, Jacobson is a professor at Stanford University, he runs the atmospheric and energy program there and has been a big advocate of this 100 percent renewable energy path, and Christopher Clack, who is the lead author on that response paper with 21 other authors, he's an energy modeling expert formerly at the National Oceanic and Atmospheric Administration. These are two really important experts with very strong points of view and different ways of seeing the world. So Shayle and I said, “Let's go beyond the debate and go straight to the source and talk to both of these gentlemen.” So in this episode, we're going to talk to Professor Jacobson, and we just had a really long conversation with Mark, we talked about the criticisms regarding his paper, we talked about the academic discourse itself. What stood out to you as some of the most important stuff that listeners should keep in mind, Shayle?

Shayle Kann: I think there are a few threads in here. One of them is this question of whether certain technologies specifically, and we talked about these in some detail, adding more instantaneous peak capacity by adding more turbines to existing hydro generators and also widespread underground thermal energy storage. Those are two among a few that ultimately are in the debate, but those are the two that we talked the most about with Professor Jacobson, whether those are realistic scaled up to the levels that he assumed in the 2015 paper -- that is at issue here. So that's one set of questions.

We also dug in a little bit with him, because he's made a bunch of comments about the motivations and potential conflicts of interests about the authors of the rebuttal paper. I think you can probably catch when you get to that section, both you and I are pretty skeptical that the authors of the rebuttal paper were motivated by a conflict of interest or are advocates for the alternative pathways any more so than Professor Jacobson is an advocate for his pathway, but he has a response to that. He points to a paper that informs his thinking that he wrote in 2009 that I'm going to check out. So there's a mix of this sort of ... the content of this, how it's going to be used, and then also what is going on in this debate, and why did this academic debate become so vitriolic in some cases?

Stephen Lacey: Yeah. The modeling aside, right? There's so much to dig into. The modeling aside, I'll tell you what I was unconvinced by, and what I was sort of convinced by. I was unconvinced by the argument that these are people with explicit agendas and are just pro-nuclear advocates looking to tear down Jacobson's work. I think he alluded to that a number of times, and I am very unconvinced by that, because both of us know many of the people who signed their names onto this paper or who authored the paper, and it's just not the case.

What I was convinced by was Jacobson's argument that he's trying to develop a plan that doesn't just focus on carbon emissions, that focuses on public health, on grid resiliency, and sort of using a distributed framework to make the grid more secure and our energy system in general more secure. I think if you're looking at those broader goals as a set, then there's a more compelling case for what Jacobson is arguing. We're not going to make a judgment on whether that is the best pathway, that's not what we're trying to do here, but he does make a compelling case that he's not just looking at carbon emissions, he's looking at all these other societal factors that are important in his plan, and that, to me, gets missed in this debate.

Shayle Kann: Yeah, I agree I wasn't entirely clear ahead of time, and perhaps this is my failing for not reading closely enough, that he was taking a broader look at with additional public policy goals in mind, so I was glad that he clarified that. And before we go into the interview, let me also just pre-empt some of the angry emails and tweets that I expect we're going to get regardless. First of all, we had an hour or a little less to chat with Professor Jacobson, there's so much in here, even just in the back and forth. Like I said, there's a response, a response to the response in response to that response, there's arguments in the press, there're too many things in here to get to, so we didn't get through all of the individual critiques or responses about that paper. We also didn't get into all the bigger picture questions about what it means and the way it's playing out in public policy, so we hope to do more as time goes on.

We also are planning to have Christopher Clack, the lead author of the response paper on this podcast as well, both to get his perspective and to ask him some questions in response to some of the things that Professor Jacobson told us in this podcast. So we're going to keep this conversation going. We do welcome feedback and thoughts from any of you. I actually think it'd be interesting for at some point to start off another episode by reading some of the things that you all have said to us about this, because I know there are just so many strong opinions about this in this energy wonk world, but forgive us for not covering everything in this podcast.

Stephen Lacey: So without further preamble, here is our conversation with Stanford Professor Mark Jacobson, who has been a major advocate for this 100 percent renewable energy, wind, water and solar scenario. We started the conversation up at the most basic level by asking Jacobson about the history of his research, and then we'll get into how it's evolved and the criticisms and the broader academic discourse.

Prof. Mark Jacobson: Well, we should back up because, I mean, we've published multiple papers on 100 percent clean renewable energy starting in 2009, and we did a world plan in 2011, we did a more detailed world plan that was published in 2013, we did a New York state energy plan in 2014, a California energy plan in 2016, and Washington state plan in 2015. 

Stephen Lacey: And all of those were based on 100 percent renewables?

Prof. Mark Jacobson: Yeah, they're all based on 100 percent clean, renewable energy in all energy sectors. Then we did a grid integration study in 2015, which is the subject that you just mentioned, but I should point out that among all these papers, and by the way, we're publishing next month, in beginning of August, we are publishing a 139-country plan that has 27 co-authors, and among all our papers we have 85+ co-authors, and we've had over 35 peer reviewers. So we're going to be talking a lot about this one particular paper in PNAS in 2015 that had four of our co-authors, but this is just one of multiple papers that has been peer-reviewed and evaluated and researched by over 85 researchers over the last eight or nine years.

Stephen Lacey: Okay. So the PNAS paper, did that wrap together all these other scenarios that you had modeled? What was different about this, and why is everyone paying attention to this one in particular, when you had done this a few times with more localized markets?

Prof. Mark Jacobson: Well, the one difference in ... The other papers were, what I'd call, they're really roadmaps to how different states or countries, like in the case of the U.S. or the world could go to 100 percent clean renewable energy looking at the annual average power demand, so not looking at the details of grid integration, whether the grid can stay stable. Now, I want to point out here that all our plans are looking at all energy, so that's electricity, transportation, heating, cooling, industry, agriculture, forestry, fishing, and the idea of our plans is to electrify all energy sectors and then provide that electricity with clean renewable energy.

So we're not only dealing with the current electricity sector and trying to keep the grid stable, but we're trying to ... We're talking about electrifying all the other energy sectors and then keeping the grid stable once you have electricity for all energy sectors. Nobody had looked at this issue at all, including nobody from the IEA or EIA or IPCC or any researchers at NREL or NOAA or anywhere. The only studies that had been performed were studies that looked at electricity, only the current electricity, maybe grown to 2030 or even further, but not converting other sectors or having converted maybe one other sector but not looking at all energy being completely electrified and providing that electricity with 100 percent clean renewable wind, water, and solar. So that study in 2015 examined the ability of whether ... it answered the question of whether the US grid could stay stable if we converted all energy sectors to electricity and then provided that electricity with clean renewable energy. There had been no other study on that ever.

Shayle Kann: Then, just to clarify, because we use the term grid integration a fair bit on this podcast when we're talking about things in the distribution grid and the need to control voltage spikes and the need for black start and all those kinds of things, when you talk about grid integration, and whether the grid could remains stable, at least in the context of this study as I understand it, mostly what you mean is matching supply and demand at any given time?

Prof. Mark Jacobson: Yeah, there are two definitions of stability, I should clarify. One is really looking at the stability over as we say voltage spikes and trying to get the actual ... making sure you're getting the right amount of current and voltage on the grid at the right time. The other is trying to match supply and demand on aggregate. We're really looking at the latter, which is matching supply with demand and storage. Well, so, there's supply of energy, that there's generation of energy, there's the storage of energy, and then there's transmission, and then what we call demand response, which is really shifting the times of peak loads by fight with financial incentives. Though we're looking at that, the matching of the supply and the demand rather than looking at the actual regulation of the transmission lines and trying to make sure the voltage stays stable.

Stephen Lacey: Just so that everyone knows, describe the sets of technologies that you're using to model this 100 percent renewable system. The primary energy is wind, water, and solar, but you're also talking about hydrogen production and underground thermal storage. Just outline the sets of technologies that you're modeling.

Prof. Mark Jacobson: Yes. In terms of electric power generation we'd be using onshore and offshore wind photovoltaics on rooftops in commercial government buildings, on residential buildings, on carports, parking garages, photovoltaics in power plants, as well as centralized power plants, concentrated solar power with storage, geothermal power for electricity, and also geothermal for heat, although in that 2015 study we didn't use geothermal for heat. Also small amounts of tidal and wave power, and then hydroelectric power, existing hydroelectric power in terms of the total annual energy used by hydroelectric. So we did not increase any hydroelectric power and we haven't in any of our studies for the continental US, and also for our 139 country studies that are coming out soon, we have not increased any annual average hydroelectric power.

Then in terms of storage we have three areas of storage. There's electricity storage, heat storage, and cold storage. For electricity storage, we'll use concentrated solar power with storage, pumped hydroelectric power, existing hydroelectric power dams, but in the 2015 study we wanted to increase the discharge rate from the hydro without changing the annual energy output, and also batteries. Then for heat storage we would use water, like hot water tanks and underground rocks to store heat seasonally, like it's done in Okotoks, Canada. And for cold storage we'd use ice and water, chilled water in tanks. Then also hydrogen is a form of storage that we're using. Then we also have short and long distance transmission and distribution that we calculate for costs, you have to estimate the cost of ... and we have demand response.

Stephen Lacey: We're going to spend the first part of this interview talking about the specific debate around this technology set and your 100 percent renewables scenario. Many of our listeners, I think, are very invested in this debate on either side, and so just a warning to them that we're not going to litigate this, we're not going to go through every point, we don't want to dwell on this too much, because I think it's easy to get mired in every single point, because if you paid attention to this debate, you know that there's a lot of back and forth here. Shayle and I are really interested in the meaning of this, the intentions of this study, what it says about academic discourse, what influence does this have on the way people talk about these issues and the way that public policy is formed. But first, I think, there are probably a few main criticisms of your paper that we should address head-on, and then we can move into some of those bigger issues.

The first deals with hydropower, which you model as sort of a backup generator and a way to balance the grid. The researchers of this recent study led by Christopher Clack contend that you say we need about 15 times more hydro capacity than currently exists to support the renewable grid you've modeled, and it relies on instantaneous supply of hydro in order to supply those services. So what do you say to those who believe that you've grossly overstated the abilities of hydro power on this system?

Prof. Mark Jacobson: Well, I would say that what your statement is not accurate, and how we do not rely on 15 times, we find that that's one option, that if we have a higher discharge rate ... Now, I want to be very clear about this that all we're talking about is increasing the discharge rate without increasing the annual average hydro output, so no dam size increases. In other words, instead of being able to discharge, let's say, 100 megawatts in ten hours, 100 megawatts of hydro in ten hours, we could discharge 1,000 megawatts in one hour, so that's an exact equivalent total amount of water that goes through the reservoir, but we're just using ... Because we want to meet these peaks and demand, we're saving the water, instead of spreading the usage out over time, we're using it more in spikes.

But I want to point out that this is just one option. In fact, we've just completed a set for 139 countries of the world we've done grid integration studies where we have zero increase in the hydro power discharge rate. So the first distinction is, that's one option that can work if it's a policy issue of whether we want to increase the discharge rate of hydro, because it's legitimate. The real question is not whether it could be done, it's a question of what is the upper limit to which you can practically do averaged over all the dams in the US, how many turbines can you add to the outside of a dam. And you need pipes that can go over the dam or through the dam or around the dam to go through the turbines, so it's technically possible to add turbines to a dam to increase the discharge rate. In fact, it's done all the time to lots of non-power dams in the US that don't have any power, and they add turbine to it or some turbines to it.

Now, the question is what's the upper limit? And that was not the question that we were criticized about. We were attacked by us making an assumption that we can do this, without realizing, yes, it is technically possible to do to add turbines to a dam, the real question is, what is the upper limit? That's a legitimate question to answer, but I want to be clear that we do not rely on that assumption, because we've done simulations now ane some of them are posted online, you can see where there's zero additional turbines. It's just one option.

Shayle Kann: I want to dig into this a little bit more if we can and spend some time on what this actually means. There's also been some debate in this back and forth about terminology and what are we talking about in terms of average annual output as you're describing, versus instantaneous output with the maximum peak capacity of all the hydropower would be. Basically what you're saying is we wouldn't add any new dams, we wouldn't increase their size, what we would do is add really a lot, at least in the the PNAS study, of new turbines, which would increase their peak generating capacity by an order of magnitude or more.

Now, I don't know about the rhetoric of the discourse and the debate back and forth, but the the question of what is the upper limit here? How much of this could we realistically add? What are the knock-on effects of doing so? What does it mean in terms of the environmental impacts and the area's local impacts? Those are questions one thinks you would need to grapple with in order to figure out whether the number in there, which results in a peak capacity, peak instantaneous capacity for hydro power of like 1,300 gigawatts, which is a lot, it's more than the total peak capacity of the entire system today. I do think that's a reasonable question to have to ask prior to saying this is a plausible scenario, right?

Prof. Mark Jacobson: Well, any type of research where you're making a proposal, then obviously there's more ... Anything that we're proposing that's happening in the future, we have to evaluate every aspect of it, and it's going to ... What actually happens in the end will likely be different than what is proposed. We were saying that this was a technically possible and economic ... Although, I should acknowledge that we did omit the cost of additional turbines, but we did calculate that or estimate that after the fact, that about 3 percent of the total energy cost, which did not change our conclusions. But, yeah, we had everything ... We proposed also a lot of wind power, and a lot of solar, concentrated solar power, and a lot of utility scale solar power, and each of those questions also have to be evaluated over time. Can we put in that much wind? Can you put in that much utility, solar, PV? We find that from a technical and economic point of view, because that's the lens we're looking at, that we looked at our study.

From a technical or economic view there's no limitation, it's a social and political question whether or not for example ... I mean, there's no ... I think you'll acknowledge that you can add 10 times as many turbines to a dam. There's no technical reason you can't do that. I mean, if we can put the dam there in the first place, why can't you just add more turbines? Then it comes to the question of the cost, whether you can actually ... Whether it's a good idea or not becomes a political issue. You have to actually go to every single dam. We can't evaluate every single dam in the United States that has power right now, and look downstream and say ... and then evaluate whether or not the community will accept a certain faster discharge rate for a shorter period of time, and to actually evaluate what's the impact of that on the downstream flow and whether that's acceptable or not. Whether it's acceptable is a political decision. As you know, in China, for example, they just put transmission lines between Three Gorges Dam and Beijing, just pile them up and just send them right through and without any obstacle, because that's a centralized economy. So you can do things if you really need to.

The real question is, and I think that's the where the framing is wrong here, is that a better solution than the alternative, which is ... The alternative is ... Well, actually, we have alternatives too, which I think are probably easier to implement, so I don't want to criticize that too much. But the alternatives that are being proposed by these naysayers are, let's put in more nuclear power, let's put in more coal with carbon capture, let's put in other things that maybe have other issues. If we wanted to power the world with nuclear, we would need 16,000 nuclear reactors, we have 400 in the world today. Is it more difficult to put in hydropower turbines that don't take up any new land, than putting in a bunch of nuclear reactors, that have all sorts of weapons proliferation risk, meltdown risk, mining issues, waste issues, high costs on their own?

So I think the question is framed wrong. The question is really how difficult is that compared to the alternatives? But it is a legitimate question to ask, is it possible, socially and politically possible to implement all those hydropower turbines? But I think what some of it ... There's been a lot of rhetoric about, oh, this will cause all sorts of flooding. Well it's not going to ... It may or may not, depending on what the actual situation is downwind, and how long you actually have to run the turbines for, because if you just have to run ... In some cases some would only have to run for like one hour at high discharge rate, but then they have much less flow for shorter periods of time.

Shayle Kann: So maybe this is right, and it is technically possible, and given the economics that you're modeling, economically possible to do this, and it sounds even you're not saying this is 100 percent certainty that this is the right solution or most plausible solution to get to 100 percent renewables.

Prof. Mark Jacobson: Exactly, it's not. I'm not even saying it's the best solution, I'm just saying it's one solution, and that's our purpose to show that, yeah, there is a solution out there. Okay, if that's not good, we can try to get a even better one.

Shayle Kann: Well, right. But then I'm curious ... I think the reason that this has turned into ... or at least one of the reasons this has turned into such a big public debate with so much ... because it's so charged, is that the way that your research in the study in particular has been utilized is then in policymaking, right? It's sort of used as well ... It was found in this research that it is possible and thus that is the direction we should take, this is what we should be going after. And I wonder whether you agree with that framing?

Prof. Mark Jacobson: Well, that's an incorrect statement. Yeah, that statement is absolutely incorrect. We've published multiple, seven or eight, 100 percent renewable energy papers prior to this, and policies were made based on those papers, not this paper.

Shayle Kann: But even in those states, I still --

Prof. Mark Jacobson: California adopted a 50 percent renewable energy plan, and part of that's based on our California energy plan study, which doesn't discuss adding hydropower turbines to dams.

Shayle Kann: Right, but I guess my point is, it seems like you have this ... I think it makes perfect sense to say, "All right, is there a plausible scenario in which you could do X? Could we get to 100 percent renewables using only wind, water and solar? What would it take to get there?" So you've modeled out a way to get there, and you can debate about whether the modeling was perfect or not, but that's what you've done. Then you model out some other ways to get there. Why restrict yourself though, to wind, water, solar? Why not say, "All right, and then there's some additional other scenarios that include a wider array of technologies."

Prof. Mark Jacobson: Well, now you're getting into the reason why we were attacked, because we were being attacked by people who have vested interest, largely by people who have vested interest in ... Or not actually invested necessarily, I don't want to say they're all ... There are some of them that have invested interest in terms of financials, others have just advocacy interest or research interests in other energy technologies, and they just don't like the fact, that we exclude nuclear power, that we exclude coal with carbon capture or fossil fuels with carbon capture and sequestration, and we exclude biofuels. These are the people who are attacking us, the people who are the strong advocates in these other energy sources.

We exclude these because of ... We've done it based on scientific results, and starting in 2009, well, actually, starting ... my whole career I've been evaluating energy technologies. I've been working in this 27 years, developing models to examine the impacts of different energy technologies on air pollution, climate, and human health, and evaluated biofuels in detail, have evaluated the impacts of different energy technologies. And in 2009 we looked at different energy technologies, including nuclear power, coal with carbon capture, biofuels, wind, water, and solar, and did an evaluation. The result of the evaluation is that while, for example, nuclear power was better than fossil fuels, it had many issues that put it at a lower ranking than wind and water and solar power technology. I can go into those details, that was the conclusion of a scientific result. So that's why for our energy plans we then determined, okay, let's take the best technologies, we have a limited amount of resources to fund a complete conversion of the energy infrastructure. Why focus on the Betamax, when you have the VHS?

Stephen Lacey: I guess, couldn't the same thing be said about you though? Someone could say, "Well, now, you just have vested interests in wind, water, and solar, so you're going to ignore all these other technologies." I do take issue with the characterization of some of these other researchers, who I have known and interacted with and have listened to them talk about your work, and they don't feel like they're attacking you, they're critiquing it, they're going through a normal academic process. I just wonder if the same thing could be said about your interests in just promoting these technologies, if we're going to say that about those researchers who are critiquing your scenario.

Prof. Mark Jacobson: If you want to talk about specific people, we can do that, but I would ... just like go to the ... I look at this ... First of all, I have zero financial interests in any energy technologies. I do not make any personal investments in any of the energy technologies, and I don't take any research grants from companies that ... companies of any type. You want to look at the people who are criticizing me, they are primarily in the nuclear ... nuclear supporters, and many of them are advocates. There are also some who are carbon-capture advocates. In fact, the people in this paper, you can trace back ... A lot of the authors on this paper that were criticizing me have substantial interests of different types in either fossil fuels or nuclear power.

Shayle Kann: I'll just say --

Prof. Mark Jacobson: It's a fact. We can go through them one by one, if you want. I'll give you some ideas about that.

Shayle Kann: Yeah, I mean, listen. I'm not in agreement with you on the authors of the paper. I don't know all of them, I do know some of them, I don't think that their vested interests in nuclear, carbon capture, fossil fuels are driving their debate here. I also don't think that this is the venue to have that conversation, but I really don't think that that's ... That's certainly not the source of the criticism. I do think, to me, I guess, the big thing here is --

Prof. Mark Jacobson: Well, I'm going to dispute that. Okay, there are three authors of this 21 author paper that actually did any research on the paper. Ken Caldeira, Chris Clack, and this guy named Qvist, I'm not familiar with him. Ken Caldeira ... So they're three out of 21, the rest did no research on the paper. You can look on the paper itself, the paper lists what the contribution of each author is, 18 authors did zero research for the paper. They were just piled on to the paper, they may have read it and edited it, but they didn't do any research, they admitted that. Of the three, Ken Caldeira gave a talk in Paris, he criticized our paper and was promoting nuclear power along with three other people. Their whole point of their ... They gave or had a press conference, and their whole point of the press conference was to talk about why we should use huge amounts of nuclear power. Then I was in a debate with him, where he was on the side of using nuclear power. He admitted in that debate, he says, "I am not an energy expert."

Stephen Lacey: Right, Ken Caldeira is an atmospheric scientist.

Prof. Mark Jacobson: He is, but that's not an energy expert, let's be very clear. I'm an atmospheric scientist too, I had my Ph.D. in atmospheric science, but I've been working on energy for the last 15 years, as well. He admitted in this, he is not an energy expert, yet he put himself as a research author on a paper to criticize me, where he has previously criticized our work, because we don't include nuclear power. He's been a strong advocate for nuclear power, it's clear on the record that he is an advocate, and he's not an energy expert, he's admitted this himself.

Stephen Lacey: But what you seem to be conflating that these are people who are somehow paid by the nuclear industry to attack you --

Prof. Mark Jacobson: No, I'm not. I do not say that one bit. Okay, there's a difference between being paid, which is a shill, and I've never called them shills of the industry, they're not shills. They have a conflict of interest in what they were saying, there's a difference between a conflict of interest and being a shill. Conflict of interest is when you work on a given topic, like, for example, Jim Sweeney was a co-author on that paper and he receives funding for consulting from ExxonMobil, from the American Petroleum Institute, it's right on his website, I mean, because he acknowledges it. He stated in a talk, "We need fossil fuels to keep the economy rolling." So, yeah, and then you have Jane Long, who is a nuclear ... she's sitting on the board ... She was another co-author who piled herself on, she's sitting on the board of the Breakthrough Institute, which is a nuclear advocacy organization. Then you have somebody else whose research is in carbon capture. And then you have somebody else who's in the Earth Sciences Department, Earth Sciences School of Stanford, and he receives funding, and the school of Earth Sciences receives funding for ... Everybody gets two Ph.D. students in that department funded by the natural gas industry.

So you have people with financial conflicts of interest of what they're saying, and they don't disclose fully their their conflicts of interest. That is different from being a shill. I do not think any of them were actually being paid, but I think that they're biased by kind of what they strongly believe in or their research that is necessary to continue.

Stephen Lacey: I think what bothers ... I think we could probably get beyond this, but there's one thing that bothers me about this argument, this line of thinking, and that is that you could make that same argument for everyone who supports all these different kinds of plans.

Prof. Mark Jacobson: Well, that's not true, I do not ... As I've said, I do not --

Stephen Lacey: Hold on, organizations that have supported 100 percent renewable energy are organizations like Greenpeace, environmental groups that have been specifically anti-nuclear or anti-gas. So one on the other side of the debate could say that these are organizations with a very specific set of interests in a set of choice technologies that they think are the best and are therefore supporting work that supports their own thesis. So just because someone believes that and has modeled nuclear in their own scenario and believes that perhaps it could be a part of the mix, that doesn't negate their entire argument and critique, right?

Prof. Mark Jacobson: Well, first of all, I agree that, yeah, groups like Greenpeace and other advocacy organizations, sure. They admit that this is what they're supporting, they're advocates for it, and I don't have a problem with that, but they're not the ones right paper criticizing me. This is the problem, when you have scientists under the guise of being just researchers who are just not interested in actually ... or who don't have a conflict of interest, they're pretending as if they don't have a conflict of interest, when they do. I'm not saying all of them do, okay, so not all of the 21 authors, but there are a lot of them who do, and that's why they're on the paper, because they strongly want to criticize this, because they want to get their technology promoted more. This is just a fact, and I think it should be acknowledged, it's not ... Again, I'm not saying everybody on that paper has that, and everybody has it, there's a different reason each person was on that paper, but it's very clear from the record that several of them do have conflicts of interest of different types.

Shayle Kann: I think, let's see if we can move on. I think we're just not going to get aligned on this point, but it shouldn't impact the overall conversation, because even in your responses, though you've made this point a bunch of times about who the authors of the paper are, you've also engaged with their responses, so to your credit --

Prof. Mark Jacobson: No, no, I'd just as soon talk about the actual effects on this.

Shayle Kann: So let's do that.

Stephen Lacey: Yeah, do you want to go to the underground storage piece? I think that's another issue that has been talked about back and forth. Your paper puts a lot of stock in underground thermal storage for heating, chilled water and ice for cooling as you said. The detractors said that this is unrealistic and really the technology that you're outlining in thermal storage has been developed in a select few pilot projects. What's your response to the criticism about that storage technology, that it's relying on a mostly unproven complicated set of technologies?

Prof. Mark Jacobson: First of all, the underground part of it is rocks underground, basically. You can take a field, and it could be a park, the one ... I was an Okotoks, Canada which is one hour south of Calgary, where they have 52 homes that have been there since ... that were built in 2005, and each of the 52 homes, on the garage there is a solar collector that instead of water there's a glycol solution inside the solar collector that, during the summer, when the days are long, the sunlight heats up the glycol solution, the heat then gets transferred ... Well, the solution gets transferred, and the heat is transferred through pipes to a centralized building, small building. In the building the heat from the glycol solution gets transferred to water in pipes, the water in the pipes, the heated water then gets piped underground, there was a field which is now a park, Central park in this little community that's surrounded by homes and kids play on this field. I stood on it, I couldn't even tell there was a storage facility underneath me, but it was excavated down to 30 meters and filled with rocks and then the pipes for the water.

The water then goes down into the rocks, heats the rocks up to 80 degrees Celsius, the rocks were insulated around them, and then the rocks were covered up with dirt, and then grass has grown on it, so it's a play field. That heat is stored until wintertime, when snow is on the ground, and then the whole system is run in reverse, and that heat from the seasonal heat storage provides 100 percent of the winter time heating for these 52 homes. The cost of the actual storage portion of that is less than $1 a kilowatt-hour, which compares with around $300 a kilowatt-hour of storage. The efficiency is from summer to winter, I mean, from the collected heat, back to the heat that's transferred back to the homes is around ... I think it was 58 percent which is not high, but it's so cheap, and you're storing it seasonally, so it's over a long period of time, that you can provide plenty of the heat that you need.

So this is an existing technology, it's proven, and there are many systems around the world like this. They're not, like ... I shouldn't say there are like hundreds, but there up to a dozen or so, and it's cheap. So it's definitely a mature technology, it can be done, it's not under buildings, it's like a centralized district heating system, 60 percent of Denmark is under district heating, except they use water tanks instead of rocks underground. So, technically, why not? You can do it. But, again, you don't need to do all. This is, again, one option. We're not saying, this is the only way to do it, you can also use more heat pumps and electricity.

Shayle Kann: I just wonder ... It strikes me ... It's a similar kind of ... This debate about the underground thermal energy storage is a similar one to the hydropower one, which is, you're making the case like, look, this is plausible. This is possible, it's technically possible, and based on your calculations, economically possible. I think if you kind of read between the lines on the response it's like, well, maybe it's technically possible, but it's sort of unproven at this ... it's wildly unproven at this scale that you're talking about building in here. Both of those things seem to me like they can be true simultaneously, but it's just sort of how the framing of ... How the the research has been utilized and thought about, that maybe this starts to raise all these questions and issues.

If it's true that the underground thermal energy storage could work, and we could do it at the scale that you're talking about and the hydropower and all the other components of this, you'd have to admit, it's a narrow window you're looking at. It's like hitting a hole-in-one. All these things have to work at this scale at these prices. So is this the only scenario? No, obviously not, and you would say the same, but it does require a lot of things to go right for this to be the way that we should restrict ourselves.

Prof. Mark Jacobson: Well, look, when you're writing a paper ... Yeah, when you're writing a paper, you can pick multiple scenarios, or you can pick one scenario, but every ... I mean, the amount of work that goes into even one scenario is humongous, and so it's not like ... If we were so nimble that we could just do like 100 different scenarios, that would be great, but we have to pick one. We're trying to make a point that, okay, there is one scenario that's possible, there are others too, because we did a lot of sensitivity tests with these scenarios as well. You're saying that you have to thread a needle to actually make this work, but actually ... I'm not trying to be facetious or anything, but you're just kind of guessing now. You don't really know that. None of us know what's possible in the future, and it really depends on what we decide to do collectively. Sure, if nobody agrees to do it, nothing's going to happen, but let's say 60, 70, 80 percent of the people decide, "Yeah, we want to do this," then it suddenly becomes possible. Things become possible when people want to do it.

So our job is to say, "Well, if we could replicate this system, is this a solution?" So we think, "Yeah, if you could replicate the system, if you could replicate the hydro system, yes, that would solve the problem." Now, is that the best way to do it? We do not say that it is, we don't say it's the lowest cost, in fact, we acknowledge this is not necessarily the lowest cost solution. We don't say this is the best solution, this is just one of several possible solutions, and our point is to say whether this is possible or not. And we're being criticized by people saying, Well, you can't prove that that'll work on that large scale." Well, to be fair, you can't prove that it won't work. We were suggesting that ... these never suggest that it could work, if you could implement these technologies. Maybe we're talking about ... We're kind of talking across each other, because some people are looking at it based on the past, what could be done based on past history, versus what can be done if people decide they want to do it.

Stephen Lacey: This is actually a really good point, because I think when you start to get into these really sort of high decarbonization or high renewable energy scenarios, there is a little bit of talking past each other, because you're potentially threading the needle for a bunch of different technologies. So I've channeled a lot of the arguments of the detractors in this interview, but I think largely, when you look what detractors of your scenario are saying, that many of them are saying, "Hey, CCS and nuclear in particular, when you start getting into the 80 percent decarbonization range, they are very economic. They model out." But when you look at how they're being implemented, right? Go tell that to ratepayers in Georgia, Southern Company ratepayers, who are paying for the Vogel nuclear power plant, or the Kemper CCS power plant.

So in theory when you look at this deep decarbonization model, those projects can pencil out, depending on how you're modeling them, but you also run into the same sort of siting challenges, cost overrun challenges, potential lack of appetite to pay for those things in the short term. So we are talking about many of the same issues, no matter what technologies you're modeling when you get to these really incredible 100 percent scenarios.

Prof. Mark Jacobson: No, I disagree with what you just said, because, first of all, nobody has looked at a high penetration scenario with nuclear with 100 percent across all energy sectors. You're talking about studies that have looked only at the electricity sector, and that sector is only 20 percent of all energy. So 80 percent of 20 percent is 16 percent, so you're talking about studies that have examined 16 percent of all energy, not near 100 percent. There is no study that has ever been done that has shown that nuclear in high penetrations, close to a 100 percent decarbonization with a grid integration study has never been done. I challenge you to even name one study where they've looked at 100 percent decarbonization and did a grid integration study with that and included nuclear. I'm not saying it can't be done, but I'm just saying there has been no study. And people have mischaracterized previous studies, claiming that they've looked at that high penetration of decarbonization integration.

Shayle Kann: Can you just clarify for me, there's nothing buying this question, I have no idea. Why would it ... You're looking at the entire sort of energy sector largely by electrifying everything that isn't currently electrified, so it presumably results in a big increase in power demand, assuming that a study were run that that looked at nuclear as well doing the same thing, just electrifying everything, why would that make a difference relative to a scenario that just looks at the electricity sector on its own?

Prof. Mark Jacobson: Well, you need to ... Because there's certain portion that's heat ... There's a certain portion of heat that goes with it, and so you ... Well, first of all, when you electrify everything, you reduce your power demand on, we estimate, on the order of 40 percent, due to the efficiency of electricity over combustion and due to the fact they don't have to --

Shayle Kann: You reduce your energy demand.

Prof. Mark Jacobson: Both power demand. Well, we talk about power, power is just energy divided by time, so --

Shayle Kann: You mean ... right, so not like the colloquial power as electricity. I see.

Prof. Mark Jacobson: Yeah. So both power and energy demand go down by about 40 percent due to the fact that you'd no longer need to mine, transport, and refine fossil fuels, and that's around 13 percent of all energy worldwide, and the efficiency of electricity over combustion which is around 23 percent reduction of power demand, and then you can get additional power demand reduction due to an additional end use energy efficiency improvements. First of all, there haven't been studies that have accounted for that reduction of power demand when you electrify all energy sectors, these decarbonization studies. Then, second, then there have been no studies that have them taken that resulting electricity, looked at different mixes, and then tried to power, let's say, the whole US or a whole country. But there have been studies that have claimed that just by doing ... not with doing grid integration studies, that you can decarbonize and use nuclear power for the rest, but they didn't do a grid integration study. You're asking a question, well, whether or not if you just modeled the electricity sector, if you can just apply it to all energy?

Well, that depends. If you're actually only looking at, let's say, the electricity sector as it currently stands, which is 20 percent of all energy, then you have a lot for your wind turbines, and you have a lot fewer solar panels, so you haven't actually evaluated where you're going to place all these turbines and solar panels, if you need it to go up by a factor of three, let's say, and which we have done. We actually account for, when we model the winds, we account for the competition among wind turbines for available kinetic energy, which no other study has ever done, because you get a reduction of power supply by wind, for example, when you actually account for that competition of the different wind turbines.

So a lot of those studies, they overestimate their wind power as a result, but since they haven't simulated 100 percent renewable energy, they not only don't actually have the right number of turbines to actually simulate and to get the wind profiles from, they don't count for the reduction of the power demand, and there's a lot of details that aren't accounted for when you're only doing a smaller system, is my point. The fact is, they haven't done it, so how can they make this claim? How can they make the claim that you can get 80 percent easily, but you need nuclear for the remaining 20 percent? They can't prove that, they've never done a study on that. It's also contrary to common sense, because several studies have looked at when you do have high penetrations of nuclear.

In fact, the IPCC says, it says very clearly, the [Intergovernmental Panel on Climate Change] says that when you get my penetrations of renewable, nuclear and coal with carbon capture are not complimentary anymore. Low penetrations, they are complimentary to some degree, because you have baseload, but baseload becomes a liability when you have high penetrations of renewables. So it doesn't even make common sense why you would use more nuclear or coal or carbon capture at high penetrations.

Shayle Kann: Yeah. I think that the argument that folks are looking at nuclear might make for example is like, okay, next-generation nuclear reactor is being designed to be a lot more flexible, so that it can load follow, for example, and actually mitigate peaks and valleys and solar and wind generation. Now, I have no idea whether that's plausible or whether it's going to happen, whether it works at scale. I think it just all comes back to like, it seems like it's a tool in the toolbox, why restrict the toolbox?

Prof. Mark Jacobson: Well, okay. So I'm going to dispute that. We need to replace 80 percent of energy by 2030, and 100 percent by 2050 to avoid 1.5 degrees global warming. So 13 years, within 13 years, we need to eliminate 80 percent of all emissions, that's transition 80 percent of all the energy. It takes one nuclear reactor 10 to 19 years between planning and operation, and the construction times on the order of four to six years of that, the rest is planning time and financing time, site permitting time, and et cetera. Just to get one conventional nuclear reactor up, it takes 10 to 19 years. So take an average, let's say, of 13 years. That's 2030, even if you planned. It's impossible. It is absolutely impossible to decarbonize 80 percent, if we decide we want to go nuclear right now and by 2030. Where is this possible, doesn't mean it will happen, at least with wind, water, and solar, two to five years is the average time for new solar, new wind plants. So it is possible with that.

Now, you're talking about a technology, these small-scale nuclear reactors that don't even exist right now at any commercial scale that we know of. We only deal with existing technologies to the extent ... Well, I shouldn't say only, but for the bulk of it, because the only ones that we ... the only technologies that we're not dealing with that are not existing are long distance aircraft, long distance ships, where the technologies do exist to change them, but they haven't been transformed, for example hydrogen fuel cell and plus battery hybrid ships and aircraft. There are hydrogen fuel cell aircraft now in the air, but not long distance. But aside from those, which only represent a few percent of the total energy, yeah, we rely on existing technologies that we can implement today. We specifically do not want to guess that some technology might be available and then do nothing until that technology comes around. I think you agree because people have talking about all sorts of technologies for decades, like ethanol. Cellulosic ethanol, they started talking about it in 1981 and doing research on, and even today there's virtually no cellulosic ethanol factories around.

Shayle Kann: Sure. Yeah. For a while, I was really into the idea of those solar updraft towers; I don't know if you ever heard about those.

Prof. Mark Jacobson: Yes.

Shayle Kann: Right, that was the Mission Solar One. It was supposed to build the tower that was the tallest constructed -- anything in the world.

Stephen Lacey: I think there are still some investors out there losing money.

Shayle Kann: Yeah, in Australia.

Stephen Lacey: The MENA region.

Shayle Kann: No, I mean, I totally take that point. I think to me the distinction between what is commercially available today and what is not, I don't know, it's a little bit murky, like an example is you have a lot of concentrating solar power with phase change materials in your modeling, and you've made the point that it wouldn't have to be phase change materials, you can do molten salt for storage too. I mean, I've spent the past decade analyzing the solar market, and I'll just tell you like from my perspective concentrating solar power is a ... It's commercially available, certainly, it's also such a steep climb to make that economic, to get it up to scale at this point, and even the projects that we've got, like Ivanpah, the big flagship projects have had really serious production issues and uptime issues. So I'm not saying it's impossible, but like ... Yeah, but it's commercialized technology that to me I wouldn't rely upon, if I'm trying to move as fast as you are...

Prof. Mark Jacobson: I agree they should be cautious, but I should point out with concentrated solar, that there's a lot better things out there right now than Ivanpah. For example, I mean, just yesterday or today there is a ... Dubai, I think, or somewhere in the Mideast where there's a new concentrated solar plants PPA for like nine or nine and a half cents a kilowatt-hour. There's a new one in Chile, and there's one in Nevada that's a concentrated solar power with storage. So it's come a long way since Ivanpah, and those are not using natural gas. Ivanpah is not a good example.

Shayle Kann: No, I'm just using Ivanpah as like, it was a flagship CSP project, still the economics of CSP to me seem challenged. But, again, it does seem possible to me, it seems like a tool you should have in the toolbox. I totally understand and agree with that, it just seems ambitious and risky to restrict yourself. And I also totally agree with you that the the aggressiveness with which this must be undertaken if we are serious about hitting a two-degree climate target or anything like that, means you can't wait around for technologies that aren't here. I guess, my question ... Maybe this will draw it all back to sort of the policy end of this is, so then, the way that this plays out in a policy venue is many different ways depending on what you're talking about, but one example, which has made the news, some in California and some other places is like, all right, let's set a target. What should be incorporated within that target? Should it be 100 percent renewables that includes nuclear, excludes nuclear, could CCS count, could it not count, etc., etc.

I guess my question is, what is your opposition to the idea that you set that target with as wide an array as possible of technologies that can compete, and then to the extent that there's a market let the market decide what wins?

Prof. Mark Jacobson: You're narrowing your criteria to just reducing carbon. Our criteria are much broader than that, that we want to eliminate air pollution, we want to provide energy security, we want to minimize land use, we want to minimize other environmental degradation.

First of all, it takes energy to form the carbon capture equipment, and that energy is about 25 percent of the energy to run for the electricity you're generating from the coal. So you actually need 25 percent more coal to run carbon capture equipment in the case of coal with carbon capture. Therefore, and you're not eliminating any of the energy in the mining or the transport of coal, in fact,

Then, you're not capturing all the carbon. So in fact, you still have, at the end of the day, even after you've captured all this carbon from the smokestack, and then there's potential leakage from what goes underground, and that leakage varies depending on their site, but even ignoring that, you still have 50 times more carbon per unit energy than wind power, accounting for the emissions from the mining, the transport, and the remaining stack emission. Plus you do not decrease any of the other pollutants aside from carbon dioxide, all those increase 25 percent, so you really have more air pollution mortality from coal, and you just have less carbon dioxide.

So that does not in any way address our issue of air pollution in particular, which goes up under coal with carbon capture, and its opportunity cost when you compare it with wind. So it just beguiles me why people are promoting carbon coal with carbon capture. It makes no sense whatsoever.

Shayle Kann: Sure. I'm by no means a big advocate for carbon capture. I actually think the point that you're making here is an important distinction that I wasn't entirely clear on. It's definitely a big distinction between a lot of the studies that I've read that are the high penetration renewables scenarios, even if those are just looking at the electricity sector, versus what you've been doing, which is that a lot of those are optimizing for ... either they're optimizing for greenhouse gas emission reduction, or they're just saying, what does it take to build a reliable system with X percent penetration?

Prof. Mark Jacobson: No, it's exactly what they're doing. They're either minimizing carbon or minimizing cost, but they're not looking at the cost of air pollution at all.

Shayle Kann: Right, but if you were ... I mean, it's an interesting question then, if you were just saying, forget all the other side effects, you could imagine a target that set a goal of 100 percent clean energy and included CCS, not that I want to be the guy who's defending CCS a whole lot, but you could have that, and then you could set restrictions on life cycle emissions, or you could require offsets or something like that. That could be a thing that's incorporated into policy one way or another, but I think back to our point at hand about what's plausible and what should be designed into policy? It is an interesting question of, as we're designing this, are we saying what we're going after is we are mitigating climate change? Or, is it we're mitigating climate change while trying to co-optimize for local air pollution, environmental effects, local economic effects, you could name any number of additional factors?

Prof. Mark Jacobson: Yeah, well, for each researcher they have to decide that. We've been clear from the beginning, we are trying to address air pollution, which four to seven million people die every year from air pollution worldwide, including 65,000 in the US, global warming, and energy security, it's trying to minimize land use and other environmental impacts. In that 2009 paper we were looking at trying to minimize 12 or 13 different impacts simultaneously to get what we think is the best solution in terms of health, the environment, and the world around us. This is really the difference between our studies and a lot of these other studies, which are looking primarily at just carbon.

Stephen Lacey: Well, that brings me, I think, to the policy implications, and I've got to ask you this question, because I think a lot of the debate emanates from intention, or the debate revolves around your intention. Is this meant to be a blueprint for policy makers, or is this an aspirational document? What exactly are we talking about here.

Prof. Mark Jacobson: Well, we realize that the end result will not look like what we propose. It's both an aspirational document in a blueprint, in the sense that the blueprint part is, we would like countries and states and cities to adopt a goal of 100 percent clean renewable energy by no later than 2050, with 80 percent by 2030, based on what we think is the science behind this, that is not only necessary, but it's possible. So the the blueprint part is just really the end goals, but the actual details of how the system will work out is going to ... it's not going to work out exactly like we're proposing at all, or might not even be remotely the same, but I think all these terms of the amount of proportion of wind and solar, it'd probably be reasonably close. Yeah. Because we realize, it's going to change. We're just saying, it's possible, here's one way to do it, we think there are multiple ways to do it, so we don't want people to just rely on this way, but this is at least one way, and so that gives people confidence that they can go forward.

As you get closer to 100 percent, you'll sort out the remaining details. I saw a talk yesterday by somebody who works in Germany, and they looked at the number of outages, because Germany has now 35 percent renewables on the grid. Utilities, like two decades ago, a decade ago even, they were saying it's impossible to get more than 20 percent of renewables on the grid without instability. Now, we think that we have shifted this discussion, so it's no longer whether we can get 20 percent of renewables on the grid, it's whether we can get 80 to 100 percent of renewables on the grid, and that's a big shift. But in Germany, the utilities were saying the same thing, all these renewables are going to cause all these blackouts, but in fact he showed data that the blackouts, even though the renewables has gone up steadily, announced at around 35 percent, the blackouts have been ... the number of hours of blackouts have been cut in half in the meantime in Germany.

Stephen Lacey: Right. And there's a lot that we could say about that because there are major factors that contribute to the lower outage record in Europe compared to the US, mostly because they're not as vulnerable to extreme weather and they bury their lines, but we can say that the presence of a lot of renewable energy doesn't cause more blackouts.

Prof. Mark Jacobson: Well, what he said, just if I can finish this, is that it was because, even though there were challenges putting all this renewables, is that the grid operators adapted to the situation, and they just developed the necessary technologies to get the voltage regulation right. So it's really a question of, as you actually force the system to higher percentages the grid operators figure out how to solve the problem.

Stephen Lacey: Right. Grid operators in the US have said the same thing. Down in the southeast, where they're starting to get 20 percent and over 20 percent wind during the nighttime hours, grid operators there have said, this is just the floor, we can get a lot more. And of course, in California and in PJM and other places they've said the same thing. I'm a little bit confused as to what you're saying, I just want to clarify here. So what I'm hearing in this interview is that this is one pathway, you believe it works, but it's not necessarily a set target for policy makers, they can work within this framework and sort of decide what mix of technologies and how exactly you get to this. I have seen you tweet out in different forms that 100 percent wind, water, solar is the only moral choice, and so that implies that other choices are perhaps immoral. I'm wondering if you can reconcile those two things for me.

Prof. Mark Jacobson: Well, I should point out that that particular tweet is not my tweet, I retweeted that, just to be clear. Well, first of all I should point out that our goal of 100 percent by 2050 ... I mean, I think you can get 100 percent by 2040 or 2045 in some places, but at least 80 percent by 2030 is a goal that I think definitely needs to be adopted in policy, and I strongly ... and that's based on the science of what we've done. As you pointed out, I don't prescribe that we need to do exactly ... or proposed every single technology that we proposed. For example UT underground thermal energy storage, we don't need it as much as we proposed, I just couldn't run every scenario with different amounts, because you could use heat pumps. In my own home, I have heat pumps, I have no gas in my home, it's all running electricity. Right now, I'm exporting 80 percent of my electricity back to the grid, even though I have electric cars, everything. Then I have heat pumps, so I don't need the underground thermal energy storage, just runs on electricity.

So you could, instead of having UT underground thermal energy storage, you could have more electricity running heat pumps. Instead of having hydroelectric power dams, you could have more batteries or CSP. Though, yeah, the point I want to make, there's a variety of ways to get there, there's not only one way. The point of our 2015 paper was, here is one pathway, it's not necessarily the best pathway, it's not the only pathway, it's just one pathway. That's why I'm a little shocked at how much criticism this one group had over one pathway. They tried to pretend as if we're saying that's the only way to do it, and then went out of their way to really just try to criticize it to death with a clear intention to kill the idea, when there are multiple pathways.

This should be a collaborative effort, we should all be working together to solve this problem. If they have competing ideas, if they have ideas that they want to use more nuclear, or coal with carbon capture, biofuels, fine, let them put those out. My feeling is, they just weren't getting enough attention for their ideas, so they decided they had to try to crush our idea, and I don't think that's the way to do it.

Stephen Lacey: Isn't this how academic and and peer-reviewed research is supposed to work, though, where people come on and critique? It seems to me a very normal part of the process. I will say that, having talked to a number of the folks, and knowing some of the folks who have been critical of your paper, and hearing them talk about the criticism, they don't come across to me as personally attacking you, they are generally thoughtful people. They believe there are multiple pathways. Certainly they're concerned about locking in certain technology pathways, I think that's probably where a lot of that emanates from. But, to me, from an outsider looking in, who's just generally curious about how the heck we achieve the climate targets that we actually need to achieve with no technologies skin in the game, it seems like a pretty healthy debate that is now gotten personal.

Prof. Mark Jacobson: Okay. The paper that was written on our paper is not normal in any way, shape, or form.

Stephen Lacey: Why not?

Prof. Mark Jacobson: It is completely abnormal way to criticize a paper, because --

Stephen Lacey: What is the normal way and why is this different?

Prof. Mark Jacobson: The procedures, normally, if somebody who wants to criticize another paper, they would write what's ... like in the case of the Proceedings of the National Academy of Science, they would write what's called a letter to the editor, that we would then respond to. The letter ... In fact, in the PNAS description, they describe a letter as, if you have criticisms of a paper, you're supposed to write a letter to the editor, and that could get published after some review, and then the authors can respond. They did not write a letter, they wrote what's called an article or a research article or a research report, and that article then is not normal. You can look through PNAS or any other journal, and you will not find a research article written on other papers, just their whole purpose is to criticize that other paper. They're all in the letter section. They somehow were able to get a research article.

The Proceedings of the National Academy of Sciences also has a requirement that all authors must materially contribute significant research to be concluded on as an author on the paper. This group admittedly only had three out of 21 authors who actually did research on the paper, it says right in their paper. So they've managed to push by 18 authors, to pile on authors to increase the credibility of the paper, which is not normal and it's not even allowed in the PNAS policy. They not only got an article published out of it, but they had 21 authors. This allowed them to then submit a news release. In fact, both Ken Caldeira's organization, the Carnegie Institute, and one of the other authors' organizations submitted news releases, that then allowed them to garner ... because there was a research article not a letter, to garner significantly more attention in the press.

So there are two major irregularities in the paper. You can look through the literature, the scientific literature, and you will not find full paper research papers, that are supposed to be for scientific research, there's zero new scientific research in this paper, it's just a criticism of our paper, and that goes in the letter section.

Stephen Lacey: Is that why you feel attacked?

Prof. Mark Jacobson: Yeah. Well, the fact that this was a ... Yeah. Well, it was even more significant than that. The main criticism that anybody's talking about in their paper is that we made two model errors, and one of them ... These claims were absolutely wrong, we did not make any model errors. In one of the cases, they claim that our hydro assumption, where we increase the discharge rate of the hydro without changing annual energy output was a modeling error. The main author in particular kept vehemently saying even after the fact, this was a modeling error, this just proves that his whole model is wrong and that there's an error in it.

Now, he was informed in February 2016 in writing, and he responded to it, so he got this, that our increase of the discharge rate was an assumption we made, it was not a modeling error. It was an assumption we made, there's a very explicit ... that we didn't include ... we did not state clearly in the article itself what that assumption was, but I clarified to him after the article was published in writing what this assumption was. Despite this, he refused to include that information in the paper, and in fact, he went so far as to state in the paper, "I hope there's some other explanation for this," even though he had an explanation. So the first author intentionally omitted information that we provided him about an assumption, then claiming there was an error. He then claimed another error, he just made something up out of thin air that there was another error, because he's like saying that some number was a maximum number, when it was an average number.

He got his paper published based on the claim that ... it was then spread out throughout the media in the New York Times and all the media outlets that we made modeling errors, when there is not a single modeling error in this paper. This is what annoys me, because that is my profession, I'm a modeler; that's what I do. And I know when I make an error or not. He was falsely claiming that we made an error, and he refused to retract that claim, and he still published in that paper. So on top of the problems with the actual submission of the paper violating PNAS policies, then he's also claiming we made errors, and then he's refusing to acknowledge our explanation that was clearly made to him, even going so far as to claim, "I hope there's another explanation," when he had another explanation in his hand, but refused to publish it.

Stephen Lacey: So where do you go from this debate in terms of your modeling, your reaction to this debate and the sort of the influence on the the broader discourse?

Prof. Mark Jacobson: Well, fortunately very few people are affected by this paper that came out. Our goal is just to continue doing what we're doing, and to that end we have 139 country paper roadmaps coming out very soon, and we also are finalizing grid integration studies for 20 world regions encompassing all 131 countries. And we're working on city plans, developing plans for individual cities. There are in the United States about 35 cities that have committed to 100 percent clean renewable energy, there are now 100 companies that have committed to 100 percent clean renewable energy around the world, in fact, in that case. Our goal is to develop the science behind ... We want to try to solve these problems, my whole career ... that's my goal is to try to solve air pollution and climate problems and use scientific and engineering tools to do this. So that's what I'll continue to do to try to address the problems of air pollution, climate change, and energy security.

Stephen Lacey: Professor Jacobson, thank you so much for your time, we really appreciate you coming on the show.

Prof. Mark Jacobson: Thank you for having me on the show, I appreciate it.

Stephen Lacey: Thanks everyone for listening. Thanks to Wunder Capital for sponsoring the show. If you want to help more listeners find this podcast, give us a rating and review in iTunes podcast store, you could find us on Stitcher, SoundCloud, iTunes, anywhere you get your podcasts. Send a link of this to your friends and colleagues as well. And we'll catch you next week. Shayle Kann, good conversation this week.

Shayle Kann: Yep, thanks, Stephen. Thank you, Professor Jacobson.

Stephen Lacey: I'm Stephen Lacey with Shayle Kann, and this is the Interchange, weekly conversations on the global energy transformation from Greentech Media.

Part 2: Dr. Christopher Clack & The 'Evolutionary Dead End'

Stephen Lacey: This is The Interchange, weekly conversations about the global energy transformation from Greentech Media. I'm GTM Editor-in-Chief, Stephen Lacey, joined by GTM Senior Vice President, Shayle Kann. Hey, Shayle.

Shayle Kann: Hey, Stephen.

Stephen Lacey: We're back in familiar territory this week. Once again, we are revisiting Mark Jacobson's famous, some might say infamous, 100 percent renewable energy scenario. Now I promise, we're not starting an entire series devoted to this topic; rather, we're rounding out our previous conversation with Jacobson by turning now to Dr. Christopher Clack, the lead author of the critique of Jacobson's modeling, which was published in the Proceedings of the National Academy of Sciences in June. If you haven't heard our earlier interview with Jacobson, you might want to go back and give it a listen. These conversations are meant to complement one another.

A quick primer on Dr. Clack. He's the CEO of Vibrant Clean Energy based in Colorado. It's a company that does weather forecasting for wind and solar, does grid modeling. He's done a lot of grid modeling over his career. He worked at the National Oceanic and Atmospheric Administration. He did work for the National Academy of Sciences. He was at the University of Colorado. So this is a guy who understands modeling and has been working in the renewables space for quite a long time. So we just wrapped up this long conversation on Jacobson's modeling, on Jacobson's rebuttal to Clack's rebuttal on the meaning of the debate over 100 percent renewables and what Dr. Clack's intentions were in targeting Jacobson's work.

So Shayle, flag some of the more important moments for us. What stood out to you?

Shayle Kann: So we spent a bunch of time with Clack going sort of point by point through a bunch of the responses that Jacobson had, when we spoke to him a couple of weeks ago, to Clack and his collaborators' paper. And those are all important, I think, one by one just so that you can hear both sides of the equation. But actually, the part of this conversation that I found to be the most valuable was the part that we didn't get to when we spoke to Jacobson a couple of weeks ago. And that was one of the other areas of criticism in Clack's paper about Jacobson's work, which was the need to integrate questions about transmission infrastructure and transmission requirements and the siting of resources when you're trying to do a comprehensive, quote unquote, grid integration study, which is what Jacobson was setting out to do and didn't incorporate into his modeling.

And so I think Clack had a good explanation of why that is really important and why that can set limitations on the technologies that you're modeling if you don't account for it otherwise. What about you?

Stephen Lacey: Yeah. Well, it turns out when you're calling your study a grid integration scenario, there are very specific things that you need in there, and I think that's the biggest beef that Clack had, and he walks through why the study itself wasn't a grid integration scenario. And I think that brought us to a couple of moments when we talked about semantics and the importance of language. And while Clack and his co-authors clearly had problems with the modeling itself, I think the reason why they decided to go public with this and to kind of go after the framing of Jacobson and his co-authors was because of the way they describe the study itself and the outcome of the study. So it really, to me, revolves around language and how Jacobson is selling this and how supporters of the scenario are then selling it in the policy arena.

Shayle Kann: Yeah, I think that's right, though we tried to dig into that a little bit with Clack as well and I think his response would be it's not just the framing of the issue, it's also ... He believes that a bunch of the assumptions that were baked into Jacobson's model in at least that one study in PNAS a couple years ago are just totally implausible or, as he stated, in error. So he thinks it's more than just framing, he thinks this is sort of not academically rigorous.

Stephen Lacey: So I think that's enough preamble. Let's actually hear from Christopher Clack. We begin the conversation by asking him what possessed him to jump into this debate in the first place.

Dr. Christopher Clack: Essentially, I was trying to work, as a lot of other people were trying to do, working on this energy transitions idea of how do we actually transition the United States and other places around the world to low carbon futures and how do we do it in a way that's cheap or as low cost as possible because we want to be able to continue this for as long as possible. And so I followed Mark's work just like a lot of other people did and I saw some of the work. And when this paper first came out, the PNAS paper they published first came out, I was surprised by the results, but I thought, "This is great. We can actually have something here that does change the way forward." But then as soon as I started reading through it, I found there was a bit of an issue with the paper, and the more I dug into it, the more issues I found.

And so first, I contacted Mark and pointed out the issues and sort of encouraged him to make a correction or change what's in the paper to make it clearer and also to correct mistakes. He didn't do that and continued not to do it in the public and elsewhere. And so it seemed like it was the only way to actually get a correction in the literature was to actually go ahead and write a peer review article on it. And we tried to do our best to do a peer review article so that we were actually trying to talk about the broader picture, not just about the paper, which probably didn't come across to a lot of people, but the idea was to say anyone who's doing this type of modeling has to do a bare minimum to be believable because it's such an important topic. And so we used that paper as a counterpoint to show where these things have gone wrong and why they're important.

Stephen Lacey: So to be clear here, you're not saying that it's a bad question to ask whether we can get all our energy from wind, water, and solar. As you said, you are thrilled that someone was trying to tackle that idea. You're just arguing that this 2015 grid study from Jacobson and his colleagues provided an unreliable guide to getting there. Is that fair?

Dr. Christopher Clack: Yeah. So that's a very good question to ask. Can we do 100 percent renewables, not just wind, water, and sun, but all renewables is a good question to ask. And the reason it's a good question to ask is every study that I've seen that is rigorous and the study I've done myself with colleagues and co-authors show that 100 percent isn't possible and if you do force it on the system within models, it becomes very, very expensive and very, very difficult to keep everything running. And so, of course, people having studies to look at this is really important and if someone comes up with a way to do it, the point is that there's so much evidence saying that you can't do it from rigorous analysis that if you do show it, you have to show it with so much evidence that people can actually read it and understand it and duplicate it. And unfortunately, the PNAS paper was way off the mark in that respect. Not only is it not repeatable, there were mistakes in it. It was kind of sloppy in a lot of its work.

And so we ended up having to get it changed because the lead author wasn't going to publicly change any of the statements that they were making. And unfortunately, in science, we have to self-correct, and the only way we could do it at that point was write a peer-reviewed paper.

Shayle Kann: So one of the things that Jacobson pointed out when we spoke to him a couple of weeks ago was that he's been publishing various iterations of 100 percent wind, water, and solar scenarios in lots of different venues for lots of different locations with some different technology combinations. He kept pointing out that the version that was in that specific PNAS paper isn't the only pathway to get there; you could have less hydro, you could have more CSP. You could do a bunch of different things. Why pick this paper to critique and was there something distinct about it because it was published in PNAS that you thought, "This was what we need to go after"?

Dr. Christopher Clack: Yeah, that's a good question. So if you actually go through and look at the papers he has published with his co-authors, the vast majority of them aren't actually looking at trying to supply power at some high resolutions. So they're almost all looking at can a state looking at its resources have enough power on an annual basis or something of that order to power itself from a certain set of technologies. And primarily, they are all wind, water, and sun, and we can talk about that a bit more later on.

But essentially, one of the reasons we had to do this one is because they were masquerading this paper as a grid integration study, which it is not, and that then garnered it with a lot of support from people that said, basically, "We've looked at this rigorously or a scientist has looked at this rigorously and has shown that you can do it," and, actually, you can't from that paper. And all the other papers that they've done are pretty much related to showing there's enough, so 100 percent for Washington state or 100 percent for New York state and things like that. They're not actually done from looking at can they supply the power at the time it's needed, where it's needed.

The few that they did do, Mark wasn't actually the lead author. There's some good ones by Bethany Frew, one of his students. Excellent research done by her. And that actually shows the same thing that we're showing, which actually shows that once you go above 80 percent, the costs actually go up very high. And even in those papers, it shows that actually the costs double from 80 percent to 100 percent and so that's in actual support of what we've been talking about in our paper. And so if you go in and dissect the papers that they've actually published on that, you start very quickly dwindling down the number that you could actually talk about looking at actually operating the grid. And this is the only one they've done where you actually operate the grid in any way with this high level, 100 percent, and it just, unfortunately, doesn't stand up to scrutiny.

Shayle Kann: It strikes me when you're describing, you said a minute ago that all the other studies that you've seen suggest that it is not possible. I think it makes sense to spend a minute parsing language here, 'cause it seems to me that you've got three questions. If you're trying to say, "Can we do 100 percent wind, water, and sun," you've got three questions within that. One is it technically possible, meaning could you, with any amount of sort of commercially available or nearly commercially available resources, power the grid nationally with just those three things and keep the lights on. So could you maintain reliability, so that's the technically possible. Then there's is it plausible from a political standpoint or an environmental standpoint or all the other things that'll come into play if you actually try to implement this solution. And then there's the is this economically preferable amongst all the possibilities for how to get to 100 percent.

And I want to have you be clear on what you're saying here, because when you're saying it's not possible, you're talking about cost doubling. That strikes me as the last question. Is it economically efficient to do that? Are you saying it's also technically impossible?

Dr. Christopher Clack: So that is a good point, and I want to be clear. So if you do the gross analysis, which a lot of us have done, which is look at the resources available, and I call that the unimpacted resource, so before you install any wind turbines or solar panels and things like that. Is there enough energy available to power the whole United States with wind, water, and sun? And the answer is a categorical yes. There is enough energy available to power the United States.

But then it gets to the second question, which becomes more important, which is, is the energy available when you need it? And so when you look at any 100 percent study that's been done thus far, there is a technology which essentially fills the gap of renewables, either diurnally, so in the days, or seasonally. And seasonally is the bigger issue than the diurnal one. I think the diurnal one could be easily solved. The seasonal one is a much bigger problem and then when you look at the inter-annual, so between years, that's an even bigger and much harder problem. And the question whether that's possible is open; we don't know the answer to that question, if that's possible.

It looks like if you blend technologies together, you can get up there to a high amount, but we just don't have the data available to know whether you can do that long-term. We just don't know. We don't know what the consequences of lots of wind turbines will be on the resource. We don't know whether we have these big lulls and peaks in wind. We don't know the effect of climate change on the irradiance for solar panels. So we just don't know the answer to that. So very quickly, the answer is we don't know.

And then the third part when we talk about cost, you have to think about moving the power around, so whether you can move it around and it be reliable. We've shown that 80 percent or so is reliable, so you can get much higher than we've got today. At 100 percent, again, we just don't know whether we could keep it reliable because of all these interactions. And the reason I say that is when we're at 100 percent, we've got no wiggle room. If we're at 85 percent or 75 percent, the inter-annual changes, we've got some buffer capacity built into the grid, for example, to absorb that. When we're relying solely on the vagaries of the weather for everything for 100 percent, we've got nothing else and that's the key. And so that, again, is the question of we don't know. You can run simulations where you can power everything with batteries, say, or some storage with wind and sun and solar.

But you quickly run into a bigger issue in my opinion, which is, okay, let's say we have a 100 percent system, hypothetically. Now you've got to think about working out forecasting of load and of the weather, because that's your fuel source now, seasons or years ahead of time with really good accuracy so that you know how much energy to store, how much to shed, how much to transmit, how much to consume. And you need to do that all the time, predicting far enough ahead that you will never run out of power because you've got nothing there as backup. And so even though you can do it without, say, forecasting, you can say on paper, "If we knew what the weather was and we knew what the load was, we can match supply and demand." That's very different to the real world scenario of having to plan for six months in advance what winter's gonna be.

Prime example is if I could tell you today what the weather was gonna be everywhere in the United States on Christmas and what exactly the energy consumption was gonna be over the entire country and how people were gonna travel, I think I'd have built a very sophisticated model. And unfortunately, when I worked at NOAA and looked at how weather forecasting is done, and if you believe Lorenz, it's almost impossible to forecast the weather that far ahead. And so ...

Shayle Kann: I'm not sure I'm clear on why we are incapable of doing that. Obviously, we're not capable of knowing the exact weather on December 25th as of today, but, certainly, that's already true one can ... We have a general sense of what the diurnal and the seasonal fluctuations will be. We know that there's gonna be a lot less solar generation in winter than in summer and I think we can be reasonably accurate in terms of the overall differential, so we build, then, a bigger reserve margin of hydro, for example, in the winter. I mean, are we so incapable of figuring that out, or are you just saying we haven't yet proven that we can?

Stephen Lacey: And before you answer that, Chris, I do want to just give people a little bit more detail on your background. You're the CEO of Vibrant Clean Energy. You do wind and solar forecasting and grid modeling. You spent a large part of your career working on those issues, having done some important work at the National Oceanic and Atmospheric Administration, work for the National Academy of Sciences. You were at the University of Colorado and you were also a co-lead on a 2016 paper in the journal Nature Climate Change looking at how the US could slash carbon emissions 80 percent cost effectively. So you're not just some armchair academic, you've worked a lot on the modeling yourself and on weather forecasting.

So you can go on to answering Shayle's question, but I just wanted to set that out for our listeners.

Dr. Christopher Clack: Yeah, like you said, I've worked a lot and spent a lot of time working on this and thinking about it. And the problem is that if you look at the spread of, say, temperature on ... I'm picking Christmas Day 'cause it's an easy one to do, or New Year's Day, there's a very large variation in temperature year on year of the temperature, for example, on one specific day. And the point I was trying to illustrate is that we don't have enough capability and I don't think we ever will have the capability to be able to predict that far ahead with enough accuracy to be able to say we can hold this much reserve and we're going to be fine because of the way the weather works, just it isn't possible.

And I'm not saying that we can't get close to that and I'm not saying that we should use anything other than zero carbon generation. But what I'm trying to say is that when you run up to this 100 percent, it's a very different way of operating society and energy production, even to 99 percent or 90 percent because you don't have any room by definition for anything else to be able to help in the mix.

Shayle Kann: So back to this, the three parts here. So it sounds like what you're saying is on the question of technical feasibility, you're saying we don't know. You're saying that Jacobson's work does not prove that it is technically feasible, nor does any other work prove that it is technically impossible. On the question of plausibility, you're saying you are highly skeptical of plausibility that it would actually maintain reliability on the grid. But it sounds like you're not going so far as to say you think it's completely technically implausible, but, again, Jacobson's work doesn't prove it in your mind. And then on the cost question, you're just saying it would be, at least based on the research that you respect and have done, you think it will be prohibitively expensive. Is that all accurate?

Dr. Christopher Clack: Yeah. I mean, I would clarify that saying something like you haven't proved that it's not true is impossible to not prove in negative. But what I'm trying to say is that, yes, I think there's enough energy out there. The crux of the problem and, unfortunately, this is with all energy work and that's why it's sometimes more difficult to communicate, is it gets very quickly into the details and becomes very difficult. And so I would say I'm hoping that there will be some solutions that prove me wrong, essentially, and that show that you can do this long term. But at the moment, there isn't any evidence that you can do it 100 percent. There's lots of evidence that you can get to 80 percent. And the reason I bring cost into it is because this is not gonna be a blueprint for the rest of the world to do it if you double or triple the cost of energy. It just isn't, unfortunately, going to happen unless you can somehow convince people of the externalities, which we should do.

But yeah, so the long and the short for me is that when we analyzed Mark's paper with his colleagues, we just found that it didn't show any of the things that it said that it did on the title and the abstract, essentially, and it didn't show any of the things that people were using it for in support of. And that was the main crux of the whole thing is we want to see papers like that and we want people to continue to pursue it because it's important to try and get the answers either way so that we can move forward as a society. It's too big a problem to avoid asking the questions. But sadly, this paper that was written just didn't at all do any of those things.

Shayle Kann: So when we spoke to Professor Jacobson, he used the term grid integration study a lot and a minute ago, you just said this is not a grid integration study. What is a grid integration study and why is this not one?

Dr. Christopher Clack: So a grid integration study is something that looks at how you would incorporate renewables into the electricity grid or energy grid and how it would operate through time when you've incorporated those technologies into the grid. And when I say incorporate into the grid, immediately, you have to be thinking about transmission. You have to be thinking about siting. You have to be thinking about how they operate each technology and also the cost of integrating them and the interplay between different generators and how that interacts with both the demand side and also the transmission power flow as well.

Shayle Kann: Is that what you did in your 2016 study in the journal Nature Climate Change where you looked at how to slash carbon emissions 80 percent cost effectively? Is that the kind of modeling that you were doing?

Dr. Christopher Clack: So yeah, in that paper, in fact, we were very clear to state that this is not a full grid integration study. So we were clear and stated we didn't do a grid integration study, a full one. What we did was what we call a reduced form grid integration study and so what that meant was we didn't explicitly look at every single transmission line in the US. We looked at a reduced form subset of that and modeled the power flow and said that with those assumptions, we can get to 80 percent reduction by 2030 in the electric sector with quite strong growth in the electric sector. But we were very clear in that study that it wasn't a full grid integration study because we didn't take into account forecasting the load ahead of time, forecasting the weather ahead of time, and we didn't model every single transmission line in the US either.

Shayle Kann: So then why is that a knock on Jacobson's work? I think it's ... I don't know that I've seen many full grid integration studies of the sort that you're discussing because it's incredibly difficult to do. Why should that be a knock on his work when a bunch of the other studies also have not been full grid integration studies? Is it how what he believes the conclusions show?

Dr. Christopher Clack: Well, it's firstly that they say it is a grid integration study. Secondly, it's 'cause they do model none of the transmission at all and they site none of the generation assets. So they don't do anything of a grid integration study, all they do is balance supply and demand in a zero dimensional model. So that's why. So most of the other studies that I've seen, and maybe I'm incorrect here, but most of the studies I've seen, when they're not a grid integration study don't say they are a grid integration study. And what that does by saying that is it tries to buy credibility for the study more than it deserves. And you can say we did something close to a grid integration study or things like that if you did like we believe we did and NREL does very good grid integration studies. But this paper didn't do anything close to anything relating to a grid integration study. It's a simplistic supply and demand summation model rather than anything to do with the realities of actually integrating anything into a grid.

Stephen Lacey: And this is one of the critiques that we actually didn't get to in our long conversation with Professor Jacobson. We kind of veered off in a bunch of different directions. We didn't get to address this one, which I regret, but you do write in your critique that the analysis ignores transmission capacity expansion, power flow, and the logistics of transmission constraints. Similarly, those authors do not account for operating reserves, a fundamental constraint necessary for the electric grid. So again, they're really not modeling any real world conditions on the grid that would be necessary to integrate these resources.

Dr. Christopher Clack: Yeah, and I believe we also showed that they don't actually site of their new generators. So if you read their paper, they just assume that they put all the new wind and solar where it already exists today or whenever the model was initialized. And so they don't actually look at where we would place new wind and solar, for example, which is something we spent a lot of time having to work on for our Nature Climate Change paper because it really matters to know whether you can place generators where you want them. And that makes a big difference on how much power you produce, when you produce it, and how you build transmission to that area and get it to where it's needed.

Stephen Lacey: So, of course, language matters greatly, but is this an issue of semantics? I mean, if Jacobson had talked about his work differently or labeled this slightly differently, would we not be having this conversation about the real world grid modeling itself? I mean, is this about a fundamental flaw or is it just about how it's characterized?

Dr. Christopher Clack: Well, it's a fundamental flaw because it appears as a lack of understanding of what a grid integration study takes to do on their part in terms of what a grid integration study is and what you need to do to show it and that is one of the worrying parts. But also, it then misguides the public perception because they can then look at the PNAS paper and say, "Look, someone showed that 100 percent wind, water, and sun is perfectly feasible and technical because they've done a grid integration study on it and shown that it is." And to that point, that's one of the main issues with the paper is people are saying that it's done something that it hasn't and that's partly because of the way it was presented in the paper and also the way it was publicized afterwards.

And so, to me, if it had been caveated with, "This is a hypothetical and it isn't for policy, it's just looking at simple supply and demand," then that would've been fine. But in my opinion, that wouldn't have been published because we've had a lot of those in the past and also it doesn't show anything that we don't already know in the collective academic community. And so, yes, language matters, but that's what all papers are about. The language in the papers is how it's taken and then the publicity side is taken and then it ends up with a lot of people don't actually read the paper itself because they can't or don't have the time to. And so then you go off what the academics are saying and that makes it even harder for people to discern what the truth of the situation is.

Shayle Kann: So let's get into just a couple of the specific critiques beyond the transmission question and whether this is a grid integration study. The one that we spent probably the most time with Professor Jacobson talking about and the one that I think has gotten maybe the most attention in the press coverage of this back and forth has been around the use of hydro where in his study, in the PNAS study, Jacobson and his colleagues basically assume that we add a huge amount of additional turbines to existing hydro generators so that we have maximum instantaneous output of 1,300 gigawatts from hydro, which is, as you point out in your rebuttal, more than the entire capacity of the electricity system today. And you called that a modeling error in your response and then he responded to that saying, "No, this is not a modeling error. This is a deliberate assumption that we are making. We think that it is possible to add additional turbines to existing generators such that they could provide this much instantaneous output."

So can you help us parse this? I know I've gotten a bunch of responses from people where they're just confused as hell about what's going on with this hydro assumption, because it seems to be really central to this question of whether the study is feasible or not.

Dr. Christopher Clack: Yeah, sure. So yeah, I mean, this one is the one that got latched on the most because I think it's the easiest to conceptualize and to understand. And there's plenty more, but this one, to me, was one of the bigger ones partly because it's such a large error. And so first of all, if you make an assumption that's impossible, that's still an error in our opinion. But the main point is that if you read through the paper and look at the capacities installed for all the different generation types, it says the capacity quite clearly in their tables and the capacity for hydro was 87 gigawatts or so, which is roughly what there is today in the US. Then when you look at their plots in the paper, you see that the hydroelectric power is dispatched or sent to the grid for multiple hours, 12 hours at a time at 1,300 gigawatts, so that's 1,300 gigawatts.

And so that backs up the renewables and that actually makes a big difference to the cost because there's no cost involved to that, one. And two, you're getting, essentially, free energy when you need it with this huge capacity of hydroelectric power. And it's one of the reasons why we felt we had to publish the paper because there was never a correction coming out from the team to correct and point out that there was this deliberate assumption that they claim they made, yet they didn't state it anywhere in the paper and never publicly stated it anywhere either. And so if it was an assumption that they deliberately made but withheld that from the public, then that could be something else. But we called it a mistake because we believe they were honestly just trying to do good work and trying to do good and we thought it was just a mistake. And when we looked at the paper, there was no clear indication that it was not a mistake.

Shayle Kann: So representing Jacobson here, so his response to that, I think, would be ... Or regardless of his response, this is a bit of a semantic debate at this point whether or not it was in the original paper. We now know, or at least based on what he's said, we know what he meant, which is 87 gigawatts represented average annual output, not peak capacity for that hydro and 1,300 gigawatts is peak capacity. And the way that you get to 87 gigawatts and some ridiculously low capacity factor as a result, the way you get to 87 gigawatts of average annual output and 1,300 gigawatts of peak capacity is just by adding all these additional turbines and then very, very rarely using them except for in the times when they are needed for those multi hour periods, like you mentioned.

So do you have a critique with that idea too? You consider that to be implausible or was it mostly just around the language they used where they said capacity and honestly didn't define that as peak instantaneous capacity and being distinct from average annual capacity?

Dr. Christopher Clack: Yeah, I do have a couple of issues with it. It sounds a lot like backtracking because if you look at the tables, all the other capacities they agree are installed capacities, but they've decided now that they've changed the definition for particularly hydro. All the others, they still claim are capacities. Are we to assume now that instead of them being capacities, they're some sort of bizarre average? So I'm kind of confused as to why this is the way it is, but it's good that now we're able to talk about it because if we hadn't have published our paper, no one would've known about this in the public and we wouldn't be able to have a discourse about it.

But they're moving on to saying, "Can you install these turbines?" The answer is clearly not. If you go to NREL and look at their reports, which are cited by Mark's papers, they show there's around 12 gigawatts of easily installable additional capacity at hydro power plants today. If you were to dam up every river that's actually technically possible, you would get 370 gigawatts and there's no room to fit loads of new turbines for these power plants. And I want to state that these things aren't zero space entities, they take up large amounts of room. For example, the Hoover Dam power plant stations take up roughly 10 acres of space. So they do take up space and to get the water to flow through them, you have to build penstocks, which can be up to 10 meters in diameter where you have to drill through the dam themselves. And then you layer on top of that, unfortunately, things like some of these are runoff dams. Not dams, sorry. Runoff river hydro, which means that you can't actually store the water up like they're suggesting.

And to give some scale of why we think it is an important one is they produce in one 12 hour period enough water to cover the whole continental US with roughly 2.8 inches of water and that's a lot of water going down a very small space. And so whether or not it's technically feasible to fit the turbines in, which we believe isn't. From all the evidence that we've seen and from all the studies that have been done, it just isn't even technically possible. Even if you imagine that and you suspend your disbelief for a minute, the amount of water that you're throwing downstream at those time periods is gonna cause immense flooding issues and then for the rest of the year, immense drought issues.

So we keep talking about the Hoover Dam because it's an iconic one, but if you can imagine releasing the entire capacity of Lake Mead or close to it, let's say half the capacity of Lake Mead in the 12 hour period, I think downstream, there would be some issues with that. And then for the rest of the six month period, you don't release anything. You're gonna cause droughts and flooding simultaneously.

Stephen Lacey: So you point out that there's this supply problem, particularly related to hydro. There's also a demand problem according to your critique and that is that the 2015 Jacobson study assumes that industrial loads are extremely flexible. Over 60 percent of energy intensive industrial demand is flexible and that flexibility, that demand response can be offered in eight hour blocks. And for massive aluminum smelters, for example, that would be nearly impossible or a bunch of other industrial sites to force them to shift their demand or to shut off their machinery for eight hours at a time would be nearly impossible. Walk me through that assumption and why you think it would be so difficult in the real world.

Dr. Christopher Clack: Yeah. So this is one that gets very complicated very quickly and you can do a lot of hand waving. But essentially, what the paper states is a very large portion, over half, of all demand is essentially flexible. In fact, it's a much larger portion than that, but let's just say it's half. And so what that means is that in eight hour blocks with no warning, you may not be able to use energy, essentially. So if you're an aluminum smelter, or you're a car manufacturing plant, or you're a cement manufacturing plant, or you're a server farm that needs to be running Google or Greentech Media's website, any of these things has, according to their paper, huge possibility to be, essentially, told, "You can't run now, you need to run later."

And to me, there's two big issues with that. One is some industries can't do it, like you pointed out, so they can't ramp down. And if they could, that will start costing money. Okay, there is gonna be some economic cost and or they will want to be paid to do that. That's not modeled in their paper at all and so the cost associated with ramping down these industries, even if they wanted to and could do, is not in there. So we don't know how much additional cost that would cause.

The second problem, which is less talked about, but equally important in my opinion, is at some other time, they then have to use that power that they've accumulated up, that eight hour period if you like. And what that means is that on the demand side, you suddenly now have to think about having all this extra capacity, just like you do on the supply side, to basically be able to ramp up your production or your use of electricity to maybe one and a half to three times what you were using before, the demand time use, to actually use that energy up when it's provided.

And so if you can imagine a car factory, for example, has to shut down for eight hours and then when it comes back online, it has to be at two and a half times the production that it was previously and then in six more hours, it has to then go back down to 40 percent. You suddenly start seeing that you have all these big extra costs on the consumer side to be able to match these big fluctuations in what the model is trying to say it should do in terms of supply and demand. And there is no cost associated with that and or feasibility of looking at what that would actually do to industry and whether they could actually build that capacity to actually take care of that energy supply.

Shayle Kann: In some ways, I feel like, look, if you're gonna try to draw out a 100 percent renewables or 100 percent clean energy scenario, there's no way to do it that doesn't involve assuming some things that right now seem sort of crazy. Even if you're gonna do it with nuclear and CCS, there are an abundance of questions about both of those technologies, both their cost profile, their political plausibility, and so on. And so sometimes, I have this hard time trying to figure out which things I'm supposed to say, "Well, certainly, that's difficult today, but we're talking about the 2050 scenario and we're trying to model out something very aggressive, so I'll give this one a pass." Versus when I'm supposed to say, "No, I draw the line here. Industrial loads are not that flexible." And sometimes, and this is a case for me where the potential for demand flexibility seems hard to me to put a number on.

Dr. Christopher Clack: Yeah. I think that's fair, but I think there are some things that I believe are almost impossible to change. Physics is one of them. And so the aluminum smelter, the one that you mentioned, they will solidify if you let them cool for long enough and so there is a hard limit on that. There is gonna be some areas where there's obviously low hanging fruit in terms of demand management. The problem is that what will end up happening with the system if you start modeling it is that you get this constantly dynamic system where you end up finding, or we found anyway, that above 10 to 20 percent levels becomes really hard to start seeing any economic benefit or benefit to the grid.

And so what we see with that is that, we tried to be clear in our paper that more technologies help, so we're not ruling out these new technologies. We're just saying that taking them to the nth degree to try and force 100 percent scenario when maybe a 95 percent or a 90 percent is much more feasible and faster to be able to get to, you can get more people behind it, seems like a better goal because the planning for that is so very different in all sectors of the economy than the 100 percent scenario, which like you say, there's always these things that we have to do. And I get a little bit concerned that 2050's only 33 years away. That's not very long in terms of energy, but the problem is we're going to have to reinvent, with the 100 percent scenario, every single fiber of our economy, not just the energy side, but the demand side if we follow that sort of direction.

And that, to me, seems like we're basically making it harder for ourselves, almost shooting ourselves in the foot, rather than trying to do something that's got more technologies involved in it that all can help and all do their wedge parts and actually help us drive down emissions faster because we can get more people behind it in terms of showing that this way. And then you can change, you can bend that trajectory as technologies improve or get better. But if you're aiming for something that's so hard right from the get go that's somewhat impossible and you have to hope that one or two technologies that are either not commercial or not even proven yet do all the work by 2050, then that's much harder to start building towards in my opinion.

Stephen Lacey: In talking to Mark, one of the things I came away from that conversation more sympathetic about was that this critique did seem to be outside the bounds of normal academic peer review or academic discussion. That by publishing this paper rather maybe a more detailed analysis of your own, it seemed to be hitting straight at Mark and his co-authors themselves and so that's why he felt under attack. Do you see your paper, your response as outside the bounds of normal academic protocol or a breach of protocol? If not, why? And if you do see it as something unique, why'd you do it the way you did?

Dr. Christopher Clack: So I don't think it's unique. I think there's other examples in history where this has happened. You can think of the vaccine papers. You can think of other papers that have also had similar impacts. I believe there was a massive debate in health between fats and sugars where a similar situation played out. But what I will say is that we wrote a peer review paper because there is new science in it, there is new analysis in terms of scalability rates, in terms of analyzing the results. I think that one of the tenets of science is reproducibility and critiquing other work. I don't believe that's any different. I think it's unusual in the sense of that we had to publish something for the authors to take notice of the criticism they were receiving in terms of the mistakes that have been notified to them.

But I'd say that we were doing it in the way that we did was we needed a peer review paper to self correct the literature 'cause the literature was showing something that was categorically mistaken and inappropriate for what it was saying it was doing. And we didn't want to be the type of people that just went behind people's back and tried to get a paper retracted because of its mistakes. We wanted to have a discourse and a talk larger about the issue in terms of how do we solve this problem. This problem is too big to worry about people's egos and to worry about whether people feel attacked or not.

It's a big issue that we're all going to be impacted by in the future and so we needed to have the scientific literature corrected. And we did a peer review and the peer review has agreed with us and the editorial board of PNAS agreed with us. And so it eventually got published even though it's a paper that most of us didn't want to have to do in terms of having to write a peer review paper of this nature. But we wanted to add to the literature and we wanted to add to the scientific discourse about it so there's some self correction within our field.

Stephen Lacey: I'm keen on hearing a little bit more about that because some say the Jacobson paper is aspirational. It's just one pathway and policy makers will figure it out and they'll take that among many other pieces of analysis and figure out the best way for their locality, their state, or the country. And what you're saying is that, no, this is extremely important. This potentially puts us on a pathway that is not realistic and I'm wondering why you see it as so important. I mean, what role does Mark's paper have in the discourse and why do you think it's a pathway that we want to avoid that would make you publish in the way that you did? Because you mentioned the occasional times that people might publish a peer review critique like this. You mentioned vaccines and when it comes to vaccines, there's a very clear health consequence to people not giving vaccines to children. And so what you're saying is that there's something much bigger here that we should be paying attention to which warranted your unique type of critique. Explain.

Dr. Christopher Clack: Yeah. So, essentially, climate change is going to have massive health implications for a lot of us and the poorest are gonna be hit the hardest as is always the case in these sort of things. And so when you look at the 100 percent scenarios, and this comes back to partly cost, but also other things, is when you model that ... So you start with the answer, I want 100 percent of this. You end up with a scenario where you're missing out on other pathways. And so, for example, to get to 100 percent, you have to, by definition, pass through 80 percent, for example. But the way you pass through 80 percent is very different to when you plan for, say, 80 percent. And I'm not using 80 percent as being the answer, I'm just saying that when you plan for a specific scenario that has an endpoint in terms of absolutely everything has to be this type of generation, you essentially are doing the equivalent of evolutionary dead end. You're saying, "This is the endpoint and I'm gonna evolve to that point regardless of what's around me."

And part of the issue with that is when you do that, you find the costs and difficulties in terms of integration and difficulties in terms of supply and demand get higher and higher as you try and push down that direction. As opposed to planning for a different set of scenarios with more technologies, for example, but also planning the grid in terms of planning out where to site and things like that, say, for an 80 percent scenario looks very different how you get there and there's more options or spur offs from that position than there is from aiming at the 100 percent scenario.

And so why it's important to me and why I spent my life career or a lot of my career trying to work on this problem is because the more options we have, the more chances we have of succeeding. And the issue is so big that I don't think failure can be an option in this case. And I see failure as an option as not reducing emissions, not reducing local pollution, not reducing poverty, or energy poverty in particular, and all those things have to be thought of together. And if you're aiming for 100 percent, you shut off large volumes of options right from the beginning and that becomes very difficult to reverse later on.

Stephen Lacey: But Jacobson would counter by saying, "We are factoring in a lot of other outcomes, health outcomes, security outcomes. That we're not just thinking about a renewable grid, we're thinking about local air pollution. We're thinking about the environmental consequences associated with uranium extraction and processing and nuclear waste disposal. We're trying to decentralize the grid with renewables to make it more secure." And so that's what he's trying to do here with these range of studies on 100 percent renewables.

Dr. Christopher Clack: Right, that's what he's claiming, but that's not what he's doing. He's starting with, "I want to find 100 percent renewable or wind, water, and sun solution," and then working back and calculating what jobs they create, what the pollution effects are, and other parts, but he's already pulled out lots of other technologies that could help. And yes, they've done some less agreeable analysis on that in previous studies as to why they disclude certain things. But the point is that the modeling I've done, for example, shows that some nuclear is helpful. Not huge amounts, but not zero either. And some natural gas with CCS does help, doesn't exist yet, but does help. But when we take it out, it does increase emissions when you don't have it and things like that.

And so my point is that they're automatically coming up with an answer and then thinking of the ... I'm sorry. They come up with the answer and then thinking of what the question should be to match it. And that supports his advocacy roles that he has and that's fine. I'm not against people doing advocacy, but my main discourse with this issue is that they think that they've solved the 100 percent renewable energy problem and they haven't done that with this paper. And when they're saying things like, "Oh, we think of all these other things, local pollution." Go and read any NREL study or our study or others and we all are considering those extra things, those externalities, but solving the climate issue solves all those issues pretty much as well.

So for example, in our Nature Climate Change paper, we showed that you could almost entirely eliminate sulfur dioxide emissions. We weren't doing that as a constraint, but that happens to be what happens when you remove all the coal from the fleet. We also showed jobs that were produced. And so these extra things do come with a transition, but it's not like it's unique to the 100 percent wind, water, and sun scenario is my point and to claim that it is is somewhat disingenuous. And I'm not saying he is saying that it is, but I'm saying that we need to be thinking about these things, but we have to have the end goal insight of we need to stop climate change and making it harder for ourselves just seems counterproductive.

Shayle Kann: I'm curious what you think the next steps for the academic literature on this topic should be. Am I right to assume that in your view at this point, nobody has done a comprehensive 100 percent clean energy, even including the technologies that Jacobson doesn't, so including nuclear and CCS full grid integration, taking into account all the big questions of plausibility, study. And if not, is that what needs to get done next? I mean, what do we need in order to figure out what you think a realistic pathway is to get to 100 percent?

Dr. Christopher Clack: Yeah. So I mean, I think there needs to be a change in the discourse in my opinion to zero emissions rather than 100 percent whatever. But I mean, that, again, is a language thing, but I think it's an important one is that 100 percent anything tends to be a bad idea. Just ask farmers whether they want every crop in the world to be grown as one type. So homogeneity is not what we're after, we want to zero our emissions and I include other emissions than just greenhouse gases. But there are studies out there that have done low emissions or zero emissions for different areas and all of them, unfortunately, come up with some, quote unquote, miracle or technology that has to take over to do it.

So, for example, there's this one from, I think it's a Swedish ... oh no, a Finland university that does grid modeling. It does a very, very reduced form of grid modeling. Does actually do some transmission lines, which is good. They do hourly data as well, but they assume that you have the power to gas conversion solved and fixed and do that at huge amounts to balance the supply and demand. But every region is different and so there needs to be more studies done on it and we still need to be deploying lots of renewables, but we need to have more analysis done at the zero emission, what is the best way to go to zero emissions looking at all sectors? And so we've done electricity quite a lot. We've done, in the company I run, some all economy look at it. When I was at NOAA, I did also do some fraction of the rest of the economy as well to look at what happens when you bring these things together and some of it is beneficial, so extra loads help, and some of them actually make it harder.

And we have to also keep in mind that there isn't a single final answer. The energy system and human population are constantly changing and so we need to have a system that's nimble. And this is why I say more technologies is better because when we get to 2050, the job isn't done. We have to continually update and improve the system as technologies get old and need to retire and new ones come along. It's a constantly evolving system that is gonna require nurturing forever.

Stephen Lacey: So Dr. Clack, let me kinda channel the sentiment from supporters of Jacobson's 100 percent renewable energy scenario and I think what Jacobson himself has implied that you and your colleagues are supporters of nuclear and CCS, that you want political preference for those technologies, and you're upset that this scenario doesn't factor them in. And then you're not necessarily sort of paid by the nuclear industry, but you and your colleagues have spent your careers with a political preference for those technologies and that, somehow, he's getting attacked because they're not factored into his analysis. Respond to that.

Dr. Christopher Clack: Well, I mean, sometimes I feel like when people respond like that, it sort of shows their allegiances more than other people's. I mean, I am a bit disappointed in that being thrown ... Rather than talking about substance, they decide to divert attention by saying, "Oh, you're advocates for fossil fuels," or anything like that. I mean, I think our record speaks for itself. If you go and look at the work I've done, I've worked at NOAA, worked at the University of Colorado, worked for the National Academy of Sciences, and now started a company to try and incorporate low cost low carbon generation assets into the grid to try and put more help in that modeling arena for that. I've never taken any money from fossil fuels or nuclear. Nobody on the paper, apart from one person, received any funding to do the paper whatsoever. We all did it as part of our scientific duty, we felt. The one person that did receive funding got it from the Rodel Foundation, an educational foundation, because they needed to spend time on it and they were doing consulting in between jobs.

And so I can't speak for all my co-authors, I don't know exactly what all their intentions are. I think it's strange that someone would claim to know what our intentions are without actually speaking to us about it. But my intentions were very clear from the beginning was to correct to scientific literature. I have no support or emptiness to any technologies other than what benefits and disadvantages they have to the grid. I try to be agnostic in terms of technology, apart from when they do harm. And so when they're in the model, if we are constraining something, for example, greenhouse gas emissions, some will be favored by the model than others. But if we do a least cost scenario, we just look at what the cheapest options are regardless of my preference. I don't have a preference. I'm not a supporter of nuclear in any way. I don't support CCS. I don't do anything of the sort. I try to do good modeling and good science and try to educate the public and the broader community on that.

And I believe for my colleagues, it's the same, but I can't categorically answer for every single one what their 100 percent intentions were, but what I can say is that they all come on to the paper to want to correct the science. And if you look through the authors list, you will see that they all work heavily and supported renewables for a long time. And I want to clear up that we declared no conflict of interest at all in our paper. Somewhat bizarrely, we had to fill out a funding analysis of what we had ever been funded on by for PNAS, which is unusual for PNAS or any paper to be specific. But we did that out of transparency, but we had no conflict of interest. We weren't supporting any technology and we were clear in it that we don't support technologies. We're saying that more technologies help, not less.

Stephen Lacey: So where do you think we go from here? You identified what may need to happen from a modeling perspective, but what about in the public discourse? How do we have a say in conversation about this?

Dr. Christopher Clack: Yeah. I mean, I think we, as co-authors on our paper, have very specifically not attacked Mark or his co-authors in any way on a personal level. We just want to talk about substance. I think it's very telling that they constantly were attacking us personally of our motives or whether we're supporting this, that, or the other, or wanting fame and things like that rather than talking about substance. They did a little bit, which is good. But essentially, talking more about the substance. People need to listen to all sides of an argument when people actually are working in this field for a long time. I know everyone's entitled to opinion and you wouldn't get anywhere, but we have all been working on this a long time and been thinking about it a long time and we want to get to zero emissions just like Mark. We want the public to be educated in it.

With terms of the public discourse, I think that people need to just cool down a little bit, have a read of the paper again, and see that what we're trying to do may come across at first, if you support Mark, for example, as attacking Mark. But actually, if you look at it and you go, "Actually, there was a mistake with the modeling," and they've admitted that as such. They may have called it an assumption, but it was a mistake 'cause it wasn't put in the paper. And so that's now in the public discourse and they can talk about it and we can now move forward and do more work on it. What we're trying to do here is to say that we could be putting lots more renewables on the grid and we should be, but we should be supporting a goal that does what we want it to. The 100 percent renewables has got sort of semantically tied to zero emissions, but, really, what we care about is zero emissions at low cost and quickly, which is the third constraint, unfortunately, that we can't get around anymore.

And so if we focus on that, we can get more people behind it and we can drive not just innovation, but deployment. We can think about smarter planning. We can work with the utilities and the public to do this. Because one of the things I noticed with working with industry is there's a big disconnect between the public perception and the industry's understanding of how the grid works and how difficult it is to integrate very large percentages of renewables. And so they feel sometimes like they're the bad guy because they're saying actually this is harder to do than people are saying. And we want to support them and help them change their business models and help them adapt and help them provide low cost energy that's not polluting because we want to have a clean environment.

And we have to do this all in 32 and a half years, give or take, and the faster we do it, the more time we give ourselves to get rid of the last remaining parts of emissions that are very, very hard, like land use change and things like that. And that's where I want it to drive towards. I want us to be thinking about the future of how to reduce emissions, save lives, and make the economy strong.

Stephen Lacey: So let me distill that down. Get the hell off Twitter and actually read and listen to what people are saying because there's a lot of nuance to this and the discussion is quite interesting and robust. And I think it's pretty clear that this is not an attack job, that we are working through some pretty complex problems here. So Dr. Christopher Clack, thank you so much. We really appreciate your time for adding some more context to your critique here and for helping us thinking about what comes next.

Dr. Christopher Clack: Thank you very much. I appreciate being on.