Aviation vs Climate: Can Sustainable Flight Take Off? with Sebastian Eastham

Can we have guilt-free flying?

David, Sara, and Ed chat with Sebastian Eastham, associate professor of sustainable aviation at Imperial College London, about the climate impacts of aviation and what we can actually do about it.

The conversation covers immediate levers like contrail avoidance and operational changes that don't require waiting decades for new tech—plus the real potential (and limitations) of sustainable aviation fuels.

It's a lively and at times blunt conversation, with sharp audience questions and limited patience for climate cosplay. You'll get the cosplay bit once you listen...

🎙️ TIMESTAMPS
00:18 - Introduction
01:15 - Webinar Start
46:00 - Audience Q&A

🔗 LINKS
Full show notes
Subscribe to our newsletter

About Our Guest

Seb Eastham is the Associate Professor for Sustainable Aviation at Imperial College London. An atmospheric scientist and aeronautical engineer, he seeks to understand what the true environmental impacts of aerospace activity are and what we can do about them. He develops and applies novel numerical models of the atmosphere, ranging from the scale of a single exhaust plume up to the global Earth system, to provide new understanding of those impacts and guide the development of new solutions to support a growing and sustainable aerospace sector. One of his current focus areas is to find robust strategies to reduce (or eliminate) the climate impacts of condensation trails, currently thought to be responsible for up to half of aviation's contributions to climate change.

Follow us on:
LinkedIn
Bluesky
X/Twitter
Instagram

Energy vs Climate relies on the support of our generous listeners
Donate to keep Energy vs Climate going

Produced by Bespoke Podcasts

Transcript

[00:00:00] Sebastian Eastham: There's a lever here where if we can pull it off, if we can predict where those controls are gonna form, then theoretically overnight you adjust your air traffic control approach, and now you've eliminated up to, let's call it, half of aviation's contributions to climate change. 

[00:00:18] Ed Whittingham: Hi, I'm Ed Whittingham and you're listening to Energy Versus Climate, the show where my co-host, David Keith, Sara Hastings-Simon and I debate today's climate and energy challenges. 

On January 14th, the three of us recorded a live webinar with special guest Sebastian Easton, associate Professor of Sustainable Aviation at Imperial College London. The climate impacts of aviation often don't get the attention they deserve, and in fact, we ourselves haven't dedicated the show to aviation since October, 2021. 

We set this episode up to focus on what levers are available right now. Including operational changes like contrail avoidance that do not require waiting decades for new aerodynamics tech, or innovation in sustainable aviation fuels. It turned into a lively and at times blunt conversation with sharp audience questions and limited patience for climate cosplay. 

You'll get the cosplay bit once you listen. So without any further ado, here's the show. Today we're talking about aviation and aviation emissions, a topic that we last tackled. Back in October, 2021 with MIT's Stephen Barrett. And a lot has changed since then. But one thing that really hasn't is that aviation from some perspectives remains an outsized and stubborn and too often overlooked part of piece of the climate puzzle. 

So today, you know, about four and a half, five years later, we are four and a half years later, we're returning to the topic with an updated lens on what can move the needle in the near term. And then what are the longer run technologies and where are they at? And, uh, we'll hit upon some of the themes we discussed in 2021. 

We're also updating our guest for the topic. So welcome to Sebastian Eastham. He is formerly a colleague of Steve Barrett's at MIT, and now he's an associate professor for sustainable aviation at Imperial College London. Seb is an atmospheric scientist, an aeronautical engineer, and he looks at aviation's real environmental footprint. 

Once you account for what happens in the atmosphere after a plane flies by, and that's something we'll get into. And what are the most practical ways to reduce, uh, those emissions? That's something that we'll get into is to give you a little preview, is subs work 

on contrails. They can drive a large share of aviation's warming, and because avoiding the worst of them may be one of the fastest levers available to decrease the impacts of aviation on the climate. 

Sub joins us today from London. Welcome. It's good to be here. Thank you. David and Z, anything that you want to declare off the top? I fly a lot. I'll confess that. 

[00:02:58] Sara Hastings-Simon: I'll say I used to fly a lot. I was once a platinum, whatever, uh, when I was back, when I was a consultant, and now I fly relatively little. 

[00:03:06] Ed Whittingham: That's good. I, and I fly a fair bit as well, but I certainly fly a lot less than I used to. So let's dive in and let's start by, uh, pardon the pun, flying back in time. So back in October, 2021, we asked our audience. The look ahead and guess where aviation emissions would be at? Where they would land by 2030. 

We ask them, would they be higher by 2030 than they were in 2019 and we use 2019 as sort of pre COVID disruption would be, would they be lower by 2030 than they were in 2019 or would they be largely unchanged? And about half of our audience thought that emissions would be higher than they were in 2019 by 2030, 12% thought they'd be lower and 40% thought they'd be unchanged. 

Seb, you've got the benefit of sitting here now in 2026. You can see what's happened since that episode, and based on what you're seeing in the data in the industry, was our audience right or wrong, and why?

[00:04:06] Sebastian Eastham: I'm gonna be a little frustrating and say, it depends. Sorry. I'm probably gonna hear a lot of that. 

Realistically I'd argue that the, uh, the half that said said it would be higher are right. The basic answer to this is that travel, if you measure it in terms of, you know, how many passengers get flown, how far that's already up over where it was in 2019. Um, and according to the International Civil Aviation organization, like KO 2024, CO2 from aviation, international aviation in particular, uh, matched 2019. 

So we're already there. With that in mind, it seems very unlikely that you're gonna end up with lower CO2 emissions. By 2030 from aviation than we had in 2019. The, it depends. Part of this is that in theory everything above about 85% and specifically 85% of the CO2 emissions that occurred in 2019 from aviation is covered by an offsetting scheme called cosier. 

So, so if you consider offsetting to mean a reduction in emissions, and I leave it to you and the audience to decide that, then you could argue that they will never exceed 2019 levels at least as long as Corsea holds. I 

[00:05:21] Ed Whittingham: would direct our audience, who our most popular show ever on offsets that we did as a live show a couple years ago, and partly because of the controversy. 

So I think if we put that question to the audience, our audience, it would split them maybe down the middle or maybe two thirds who would think that offsets are buying indulgences and a third who think they actually do something, some benefit for the client, for the climate. But let, let's just put aviation emissions in perspective. 

Like what kind of contribution does aviation make to annual emissions? Global emissions overall, like does do its emissions really matter in the grand scheme of things. 

[00:05:57] Sebastian Eastham: If you just look at the raw numbers, aviation is responsible for maybe two to 4% of global climate warming. I'm saying climate warming specifically because the CO2 and non CO2 parts really matter and they matter distinctly. 

For aviation specifically, we think that maybe half of that comes from CO2 effects and maybe half of it actually comes from other things. So that's things like nitrogen oxides, which is NOS and condensation trails or contrails. A another complicating question there is that that's the global average is two to 4%. 

If you go and look at the UK's carbon budget, we are maybe more like 10% of our total. CO2 comes from UK attributable aviation. So the two to 4% number hides quite a lot. 

[00:06:47] Ed Whittingham: Got you. And, and sorry, just another question. Is there some clear data just suggesting which of that would be for personal travel and which of that would be for freight? 

[00:06:56] Sebastian Eastham: In terms of overall averages, freight is maybe 20%. So personal travel might be about 80%, 85% freight may be 15 to 20%. Freight is a little tricky to break out sometimes because there's a lot of dedicated cargo, but there's also a lot of belly cargo. So if you take a flight but you don't take any luggage, and then somebody else has freight in the hold, who's responsible for that cO2. And then the ICCT has a nice report on it. 

[00:07:25] David Keith: Ah, so I'm not doing any better if I take no luggage. It's your substitution. But a serious point, uh, just to, I think clarify, you, you are comparing the cumulative impact of CO2 from all previous aviation to the instantaneous. So it might be helpful to say the, the viewers, if that two to 4% figure if all aviation stopped tomorrow, the CO2 component would presumably still be 2%. 

[00:07:47] Sebastian Eastham: That's absolutely right. So I'm, I'm thinking in particular about a study that came out a few years back, actually probably around the time of your last podcast on this, which showed that sort of cumulative impact, and there's a important difference there about what the CO2 would do, which would stick around and some of those non CO2 effects, which maybe wouldn't to the same extent. 

You did also ask about whether or not it matters. That's a complicated question I'm willing to go into, but, uh, is, so just to elaborate on that a little bit, whether it matters, it matters to me in the sense that I'm consider myself to be in the aeronautic sector, right in aviation sector. And I consider that every sector has to try and address its own contributions to climate change and to warming. 

So whether or not it matters as a whole, as a separate question for whether or not it matters to me, and if I look forward into the future and expect continuous growth, I think that it'll matter to everyone. Gotcha. Okay. Well 

[00:08:42] Ed Whittingham: let's, let's just do a quick, uh, tour to tabla of some of the decarbonization pathways available to aviation. 

And I kind of think of a few categories. So I think of aerodynamics and tech, you know, like new propulsion systems, electrification and love to see. We are, not wholly enthusiastic about the prospects of electrifying planes. And we talked about it back in October, 2021. I'd like to know where things are at SAF and e fuels and the e of course, being electricity, uh, making synthetic fuels from electricity. 

And then lastly, and I'd love to spend a little bit of time on the operational approaches and specifically around contra avoidance. 'cause that's something that I've come across just in the past few months, and I know you've done a lot of work there. And it could have a positive or negative impact depending on where you fly the planes, what time you fly, the planes, et cetera. 

So back to you, Seb. Does that sound like kind of the rough right categorization? 

[00:09:41] Sebastian Eastham: Yeah, so let's start with electrification then. Electrification is a really exciting idea in aviation, but the basic problem with electrification is that you can't burn batteries. Um, what I mean by that is that you're replacing, let's burn some fuel and turn a fan with let's discharge a battery and turn a fan. 

So you start off with the problem of energy density, right? A good battery. Right now a lithium ion might give you 350 watt hours per kilogram, let's say 400. Uh, if we're really optimistic, that might get up to sort of 700 in the coming decades potentially. If I can compare that to just jet fuel. Jet fuel is about 43 megajoules per kilogram, which is 12,000 wat hours per kilogram. 

Now, even if I take an efficiency of a jet engine of maybe 50% of thermal efficiency, that's still 6,000 watts per kilogram compared to maybe 700 from the battery. And I only have to carry that jet fuel on average halfway 'cause I burn it and set and put everything that came outta that burning out of the back. 

So by comparison, a battery, I can't burn it. I have to carry dead batteries with me for half of my trip. So electrification is great for maybe short trips where you weren't getting as much advantage from burning the fuel anyway because it was a smaller fraction of your overall mass, but it really doesn't seem viable for long haul trips and it's long haul trips that generating most of our CO2. 

The second category you mentioned was, well, I think you actually had it first, was efficiency. And I would say that efficiency is great, right? Technological, um, opportunities to improve our aircraft, improve our systems so that we burn less fuel and produce less CO2. But it's also arguably somewhat baked in and I'm not really doing a service to the industry there, but it's true. 

We have a good track record of increasing efficiency over time and we have a very good track record of outstripping our efficiency gains. With increases in travel. So the increase that that has been in CO2 emissions in the aviation sector over the last decades is despite really impressive, uh, improvements in efficiency and reductions in the amount of fuel that we burn per passenger kilometer that we achieve, possibly the exception to that is more dramatic technological options. 

Things like the blended wing body, the Jet zero we're talking about. Um, but there are serious infrastructure and regulatory challenges around that that make that a, a, a difficult question. The third, uh, one was sustainable aviation fuel sac? I think so, yeah, briefly, SAF says, how about if we make jet fuel but without the fossils this time, the ways of doing that are either that you make biomass, turned that into liquid biomass, liquid fuel, or you, uh, actually extract carbon from the air and may fuel out of that. 

And yeah, I would defer to David quite a bit on that, to be honest. And I'd say the SAF is great. The problem is you need to make a lot of it. The, at the moment, we are making around 2 million tons of SAF globally per year, and that's less than 1% of global demand for jet fuel. Worse, it looks according to the, uh, air Transportation Association, uh, international Transportation Association. 

I, it looks like growth is slowing, uh, when it comes to staff scale up rather than accelerating. Um, the big problem here right, is how do you make that fuel at low cost? It's, it's really hard to do, and I would argue that it may be impossible to have staff reach cost parity with fossil jet fuel unless you count subsidies. 

And that brings political questions in about, well, why, what happens if someone withdraws those subsidies suddenly? What would you, if you're investing in saf, would you say right now that you wanna invest something which can only survive with subsidy? Um, subsidy, subsidies at infinite item. I should also mention here that I wouldn't usually call these sap, but I would give a shout out here to hydrogen and liquid natural gas as potential options for alternative fuels. 

And I've spoken for a long time. Do I have a little bit to go into Contrares? Well, let's, 

[00:13:59] Ed Whittingham: we wanna unpack SAF a bit more, so let's spend a few minutes there and then we can talk about Contraras and spend a few minutes on it. I know. David, do you want to jump in? 

[00:14:09] David Keith: Sure. I mean, just to say maybe one obvious thing is it's, there's always a soft between. 

Do burning fossil fuels, burning oil and removing the carbon with some real permanent carbon removal versus making synthetic fuel. And both could potentially work, but the trade off between them kind of depends on the cost of carbon, the carbon price, and depends on the oil price. And in a world where we really expect oil prices to be low for a long time because the whale market's gonna peak or quite soon, I think that tips it towards the fact that it may be cheaper just to do carbon removal by enhanced rock weathering, by ocean, by Dak, whatever it is. 

So to me that is one thing that takes the wind out of SAF sails. There's one kind of SAF that I think for different political reasons never got traction that I could see being more practical. So, uh, Seb mentioned two things. One is you take biofuels in and you make fuel, which bioethanol stuff we know how to do. 

The other one is that, um, you start with hydrogen and CO2 from the aero synthetically make fuel, which can be done. There is a third option, which is you take biofuels and you add hydrogen that you got from solar or nuclear in a, uh, gas de liquids facility. And that's a kind of weird intermediate, but it's a weird intermediate that nobody ever quite supported, but it actually might be a cheaper niche in some cases. 

[00:15:30] Sara Hastings-Simon: Yeah, I just wanted to jump in 'cause both, uh, David and Sebastian mentioned cost, and I think that is you know, how, how we treat cost as a barrier or not is a big part of this question that I know we'll, we'll discuss more in the future, but I just wanted to fly it here in that is the challenge or the need to really reach cost parity with this potentially low, uh, as David was saying, low cost oil in the future versus, you know, uh. 

Decarbonization is critical for the airline sector. Therefore we have to increase the costs of travel in order to, you know, reach this net zero. And I don't wanna brush aside the political challenges with doing so. I'm not saying that that would be necessarily easy, but it's not at least a technical barrier to say that well, because this is more expensive, we can't do it. 

Right. You have I think in some ways it's one of the easier sectors to impose those kinds of constraints because you don't have as many clear substitutes, especially when we talk about long distance travel compared, you know, compared with others where, you know, you could have some kind of agreement that we just have to do this and you know, it's gonna cost a bit more to fly over long distances. 

So I think that's worth, uh, mentioning as well. 

[00:16:39] Sebastian Eastham: And, and I, I just wanna jump on that if I can. Second to agree wholeheartedly actually that when I say staff will never reach cost priority with. Fossil jet fuel without subsidies, which I, I do believe, um, that's not the same as saying we shouldn't, therefore shouldn't think about it so much as like, I get frustrated with claims like, oh, we'll just keep, we'll just keep technologically improving SAF until it's cheaper than fossil fuels and that No, 

[00:17:03] David Keith: I mean, and, and as aircraft get more efficient, the fuel cost contribution is smaller per seat miles. 

So, no, I I think it's completely plausible. No, no question. The aviation world could switch to SAF and I think there's a lot of reasons to believe SAF would beat, well, definitely beat batteries for long haul. 'cause I think batteries are hopeless for long haul. But I think that the question for climate policy is, is that the right climate policy effort compared to other places to cut emissions? 

[00:17:27] Ed Whittingham: Yeah. And I want one example and, and Seb, I would love to get you to comment on e kerosene in particular because I hear much about e kerosene. And to your point, you know, batteries are heavy and planes are stubborn and physics are hard. And you know, you don't want to carry those batteries, those discharge batteries, half your trip e kerosene, you can drop into existing fuel systems. 

So it seems plausible as a way of decarbonizing long haul aviation. But, uh, I think the knocks against it, the energy losses are pretty brutal. And if the electricity is dirty in the first place, then it's kinda like climate cosplay and then using that electricity you're competing with other end uses of that electricity or, or the clean power. 

But I'd love, I'd love to get your take on it. 

[00:18:10] Sebastian Eastham: I'm, I'm currently teaching a, uh, undergraduate module and compuls into a machinery. I'm definitely stealing climate cosplay as a term. I love it. But I, I mean, I think that you are getting to a really, a couple of really important and more granular questions that we've stated over here. 

One of them is the question of drop in, right? So the first, the first one I think really was this, you know, e kein as power to liquid is, but I think of as e kein. And the second one is drop in, right? What does SAF mean? There are many different kinds of saf, even if you just take biomass to liquid, just, um, brain, that there are still many different kinds of saf and there's drop in SAF and there's non drop in SAF IE SAF that you can in theory use. 

Immediately and SAF that you just can't, you need to adapt your aircraft. Even now, you can only mix SAF in of any kind up to 50%. The standards require that you do not go to a blend of more than 50% SAF relative to fossil fuels, uh, out of concerns for the aircraft itself. So even with a sort of what you'd call sort of a drop in, in this case, you say that's the limit. 

So you do need to produce something that is compatible enough, which everyone agrees is compatible with all of the aircraft currently into service, which gets you back to this problem of aircraft saying service for a really long time. Right? So you need to make your, your fuel compatible with aircraft that are 50 years old potentially, and then that still doesn't address the other part that comes from, there are many different kinds of staff, which is, I think you brought it up nicely, that you can make saf, which is dirtier than fossil fuel, right? 

It's not actually very hard to do, but it's quite easy comparatively. So you do actually, if you want to get all those benefits, you have to make it clean. Yeah. The other 

[00:19:49] Ed Whittingham: analogy I've heard is just taking clean electricity when using that for saf. It's like turning champagne at the tap water and paying extra for it. 

So not the best end use, uh, in addition to climate cosplay. You're welcome to use that, Seb. That's, uh, that's shareware. Let, let's leave SAF behind. And now let's dive into Contraras. And so maybe just off the top, what should listeners understand about CONTRARAS and non CO2 impacts and why is it that Contraras could be one of the, and, and where you fly planes and some of the international agencies that govern aerospace, getting them to cooperate might be one of the fastest levers available to actually reduce the climate impacts of aviation. 

[00:20:36] Sebastian Eastham: So I'm gonna come into this out of the operational bet that we didn't quite get to because, um, I think one of the things that is often forgotten is that there are actually simple operational levers, which might be exercised, things like airspace optimization, uh, to make flight routes more efficient. And I, I want to give a, a quick shout out to my postdoc, Merrick Trav, Nick, who's done a huge amount of work on investigating how air spaces are organized and whether or not that actually results in inefficiency. 

Yes. Is the answer. You can also talk about things like making planes slower, could make them more efficient. Would it be popular? No, it wouldn't. Not at all, but you could do it. But yes, Contraras are this potentially huge opportunity when it comes to an operational lever. So, uh, in case anyone isn't aware, uh, Conrail is a condensation trail. 

It's the white cloud you see coming out the back of an aircraft quite often. There are ice clouds that form in aircraft exhaust. And they matter when the ice cloud sticks around for a long time. So if you ever, if you ever watched an aircraft go past, sometimes you see nothing, it's just a nice blue sky. 

Sometimes you'll notice that there's like this little exhaust trail that just follows the aircraft or doesn't stick around for very long, but sometimes if the conditions are right, that ice valve will persist. And that basically comes down to was the atmosphere around the aircraft told enough and was it humid enough? 

And this can really only happen frequently at those cruise altitudes the aircraft operate at, but the game has been given away here in terms of what you can do about them by that first part that they only turn up sometimes, you know, maybe 5% of the time. Uh, do you get these persistent contraras? Because those rare persistent contraras we currently think are responsible for maybe 20 to 50% of aviation's overall climate impact. 

They're really, really situational. But when they're there, they trap some outgoing, uh, thermal radiation and produce a sort of greenhouse effect. We now know that those corn trails form in ice supersaturated regions, that was the cold and humid enough. But those regions are pretty broad, that you can often be so hundreds, maybe thousands of kilometers across, but maybe only a kilometer deep, maybe even 500 meters deep. 

So the theory is, well, we're pretty good at moving aircraft up and down. We've gotten very experienced out over the last 50 years. What if you just looked for where you think control controls are going to form and moved underneath that layer that is supersaturated inspect to ice. It means that you would avoid ever forming the control. 

And the current expectation is that if you could predict where those contrails are. Accurately enough then for maybe a 5% increase in the amount of fuel you burn. 'cause you know, anytime that you add maneuvering, you are inherently adding an inefficiency for 5% increase in your fuel and therefore, CO2, you might be able to eliminate 90% of your contra trails. 

And if your controls are really half of your overall diamond contribution for aviation, then that's a great trait that therefore implies that there's a lever here where if we can pull it off, if we can predict where those control controls are gonna form, then theoretically overnight you adjust your air traffic control approach and now you've eliminated up to, let's call it half of aviation's contributions to climate change. 

But there's a lot of uncertainties and a lot of questions that go in before that. Got you. So. 

[00:24:15] Ed Whittingham: Exploratory research I know has some of it's been undertaken in the US and Europe, but no government that I'm aware and, sorry, we're segueing a bit into policy. We will come back into to tech and behavior, but no government, I'm aware is yet kind of advanced contra mitigation as a political or as a diplomatic priority. 

Why is that? Like, what's it it, it seems that it is one of those solvable parts, imminently solvable parts of the climate problem in aviation. What's standing in the way? 

[00:24:46] Sebastian Eastham: So I'll challenge actually your basic assessment there. The European Union has actually brought non CO2 impacts or non CO2 emissions, if you wanna call it that, into their monitoring, reporting, and verification framework. 

As of January 1st, this year, airlines have to report contributions to non CO2, including contra trails. Now that's not the same as saying that they have to do anything about it, but they do actually have to report it. So that to some extent is actually an action, um, on in that respect. But the question of then why hasn't there been more is really 

[00:25:27] David Keith: about un uncertainty. 

Tell us a bit specifically about what they have to report. Like do they report their NOx emissions or their flight trajectories, or do they themselves report some estimate which they come up with or what the radio forcing is? And if so, one Earth is doing this, and what about manipulation? 

[00:25:44] Sebastian Eastham: And then this is honestly a big question at the heart of the MIB, it's one of the reasons that right now it's reporting and it's not doing anything about it, to be perfectly honest. 

Um, with regards to Contraras, if I recall correctly, it's, there's a protocol in, in place for estimating what the contra formation likely would've been and what the ral impact likely would've been from the flights, uh, that their loans taken. And there's been a fair amount of development modeling work to try and figure out what that ral impact would be in a sort of robust fashion. 

But it's, it is modeling. This is not satellite, uh, estimates of emissions. And, you know, compared to CO2, right, CO2, you basically wave the plane when it comes in and compare it to when it went out. And you'll get the answer as long as you know how much fuel you burned. Not the same for contrails. 

[00:26:31] David Keith: I really worry about gaming here. 

So if I'm the airlines, you know, it's not very hard to hire PhD atmospheric scientists who are really smart, who would tend to produce a higher or lower estimate for relatively low salaries, especially 'cause some are getting laid off of US federal institutions. Just be blunt here. So I could get a, a pretty credible person to kind of make my number higher or lower if I'm somebody airline. 

And kind of interesting to think about it, do I want to get it to be higher in the near term so that I can get more credit for reducing it? And how am I gaming this? 

[00:27:03] Sebastian Eastham: It's an excellent question. And I, and that's I think is part of the reason there has been so much internal discussion about how to set up this protocol. 

To their credit, they've been quite clear about it, that this is a first protocol for es, um, estimating this and that. I think they are expecting that a lot of the early questions are gonna be about gamesmanship and also though uncertainty and verification. Because I would argue that a critical next step here is going from purely model based assessments to something that actually has observational uh, verification. 

[00:27:39] Ed Whittingham: You know, Seb, you challenged the premise of my question around governments, and I really, I'd be remiss if I didn't give a shout out to the Canadian government because in the Canada's aviation climate action plan, there is an acknowledgement of the non CO2 impacts of aviation and a call for the development of a, uh, an atmospheric modeling tool by ECCC environment Canada and climate change to try to figure out in the, the airspace that Canada controls, contra pro zones that, uh, was the phrase that you used the, the Sta super ice supersaturated reasons. 

But just before I move on, David, and, you know, uh, just out of curiosity, so contrails, they. They have that, that heat trapping disc benefit, but I would think they'd also have a sunlight reflection benefit as well. So as we've talked about with cleaning up air pollution, say from coal-fired electricity, would, are there any and unintended consequences that we should be aware of if you eliminate all s tomorrow? 

[00:28:38] David Keith: Well, basic fact for, for those who are guilty about flying is you'd better to fly during the day than during the night. Because during the day you get the reflection from the contrails, which is cooling the world and you get the heating. But during the night you just get the heating. 

[00:28:49] Sebastian Eastham: And, and that's actually something that I love to bring up. 

Yeah. It's cutting edge science in the sense that could it evolve any, um, and it will evolve all the time. But I try and tell people if you can, if you fly in the morning, in summer and you make sure that you're on a and as I possible, make sure you're on a flight where you're going to sort of stay in the morning as you travel. 

Right. You know, whether you're going east or west or west or east, that changes how hard that is. It means that the con trails you form are gonna be there when you get that sunlight reflection benefit. Whereas if you're taking a flight where the contra trail, if you imagin, a contra trail could last for, let's call it three to 12 hours. 

If that contraras gonna be there only during the night, then you are maximizing the downside, that trapping effect, and you're getting no benefit. So there are actually opportunities if, if you feel like you need to take a flight, if you have any control over the time of day you fly and the season you fly in, you may actually be able to, uh, significantly mitigate your 

[00:29:48] Ed Whittingham: overall impact. 

Interesting. It's a fascinating topic, and along the way I've learned that there are these air navigation service providers like Nav Canada and the in Canada or Nats, that have a tremendous amount of authority over the, the control areas. You know, Canada's got Gander and, and the UK's got the, uh, the, the shandwick oceanic control areas. 

So, but they also remain in the shadows and from personal experience, hard to talk to. But let's, let's move on. I'd love to know, get your take and, and we'll all jump in here, but like, what changes can we realistically expect the industry to make between now and let's say 2035? Over the next 10 years, and we've got challenges. 

You mentioned that the airplanes are 50 years old. You've got, you know, slow capital, stock turnover, you've got the usual barriers to new tech, new tech companies. You've got these, uh, you know, I said these regulatory authorities in the background that are hard to get to. So with all that as caveats, what, what can we expect in the next 10 years? 

[00:30:49] Sebastian Eastham: Honestly, I don't know. I would say that on the tradi, what I would call a sort of more traditional side, I think there's going to be incremental improvements in electrification. Uh, there are some really exciting companies making these sort of regional, uh, electric aircraft, but that's not gonna take a big chunk out of overall CO2 to be honest. 

SaaS scale up is always the question, but I think in, if we call it by 2035, I don't honestly expect that we will hit the sort of 10%, 20% the mandates are looking for us to get to. But I'd love to be surprised on that. I would personally be really excited to see a big push on hydrogen and liquid natural gas towards cryogenic fuels, but that is probably in a big way because I am an engineer and I get really excited about gnarly engineering problems and it sounds really cool. 

There are sort of a, a lot of technical aspects there, which would be really fun to work on. But you are then talking about infrastructure changes and you are running into the safety veto, uh, in aviation, which is a, the fact that we have a really well earned reputation for safety, generally speaking. And so if you do anything that is going to take a long time to bring in and which could be looked at and said, well, is that gonna compromise safety? 

It's gonna have a really hard time because anyone can at any point say, well, realistically, there's a safety risk here. We, we don't wanna tolerate it. On the other hand, I'd say that contral avoidance is an area where we could really see something happening by 2035. There's a paper which has just been accepted by, uh, led by Jesse Smith at Cambridge, which explicitly, uh, lays out it using just some, some pretty basic client modeling. 

How delaying a trial of contral avoidance at scale is a, a big miss, right? You can start it early and try and learn quickly from rolling out contrare avoidance. And if you delay that, you just lose the opportunity to have not made contrares for five or 10 or 15 years. At the same time, if you believe that we can learn quickly, then you could start tomorrow. 

Do very poorly, but take advantage of the fact that contraras are something we can see and observe, right? More than CO2, you can see a contra trail, so you can then learn from how poorly you are doing and do better and actually get to a position where you are succeeding. Now it's a personal question. 

Whether or not you believe that we can learn fast enough? I think we can. 

[00:33:25] David Keith: So is it your, I mean, if, if you were voting or recommending, is it right to say that you would recommend that governments push forward pretty quickly to figure out a way to, to begin to incent airlines? To reduce res 

[00:33:36] Sebastian Eastham: I wouldn't necessarily do it at the airline level, to be honest. 

I would recommend the government's push forward with looking at cold trail avoidance as a, you know, call it a technology, but really it's a policy. I really like the idea of trials and even implementation being led actually by those air navigation service providers that you were talking about at the a NSPs. 

We've had trials led by airlines. They are great, but we don't necessarily learn as much from them. We may well learn more if we are instead designating air spaces and saying, you know, these are forming regions. These, please avoid them if you possibly can. Uh, and I, I would honestly like to see that moving forward as a potential uh, implementation approach. 

[00:34:17] Ed Whittingham: And, and Contraras are, it's something that Canada, I think could be unusually relevant in the grand climate scheme because of the geography and the, the airspace control story. It's my understanding, correct me if I'm wrong, Seb, that most of the warming contrails form over the North Atlantic corridor and you've got, as I mentioned, Canada's gander airspace. 

You've got the UK Shandwick airspace over that route and it's, it's managed by these two authorities. So Nav Canada and Nats, as I mentioned, Canada now has this ECCC forecasting tool that I think, and given that we've got politically, a Prime minister who, uh, used to be the governor of the Bank of England, has visited the UK a bunch of times, is married to a Brit and is looking more to Europe than to the United States for a bunch of geopolitical reasons that we probably don't need to name. 

It seems that there's like, it's ripe for collaboration between Canada and the UK on some kind of trial. 

[00:35:18] Sebastian Eastham: I would love to see that. I should, however, before I get too out over my skis, uh, mention that a big factor in all of this is uncertainty. It is possible that 10 or 20 years from now we decide the contrares are maybe a quarter or a 10th of the importance that we think they are now, that is still within the uncertainty balance. 

Now what Jesse's paper argues is that it's still worth working on it even in, even despite that because of how much of a, uh, small CO2 cost you pay for the amount, the benefit you can get. But there are absolutely atmospheric scientists who argue the opposite way. To your question, though, yeah, I, I would love to see a UK EU Canada collaboration on this topic, and I, I have a few thoughts on that, that maybe we can get to you later, but. 

[00:36:12] Sara Hastings-Simon: So I'll take us in a slightly different direction over the next, you know, 10 year time horizon and say something kind of outlandish, but then bring some data to back it up. You know, in theory we could cut global airline emissions by 30% just by reducing flying. And so when I look at, I, I, I looked at some numbers, um, from a recent paper looking at the history of emissions. 

And that comes back actually to this cost question. And then the distribution. So airline emissions from air travel have grown almost seven times over the period of 1960 to 2018. Um, and actually global CO2 emissions. Only grew four time, four x during that time. So airline emissions, despite, you know, all of the, um, growth that we have in CO2 emissions from all kinds of sectors, they are really growing much faster. 

And they are really concentrated more, even more so. So the top 1% uh, economically of, of people around the world are responsible for about 50% of commercial aviation emissions. Uh, I think then based on this paper, if you add in the private jets, you get to like 54%, um, but over half. And then similarly, that top 1% is only responsible for 16% of global emissions overall. 

So, you know, we're, we're used to these statistics, I think of the idea that emissions are growing and that they're very concentrated among the richest and air, the air traffic is a sector for which that's even more so true. So, you know, 90% of people around the world don't fly every year. Okay. But let, let's look at a sort of more, a region that's more similar to us. 

We look in the us, half of the people in the US don't fly every year. But actually there's some more interesting things in the, in the other half. So 35% take somewhere between one to five trips a year, and tho they are together responsible for 30% of flights taken. So the top 12% of flyers in the US that are taking six or more trips are actually responsible for 68% of all flights. 

And I see David cheering here. Uh, and you know, there's, there's, uh, there's all kinds of flight shaming and stuff that come into this, but I think that there's two things that I take from this one actually coming back to that cost piece and the staff. If you know, yes, it may be a higher cost way than some other levers we could pull in the near term, but aviation is overwhelmingly used by the richest, and so I think there is a reasonable argument to say it is actually reasonable to impose some even higher costs there. 

The other is. It's not a question of we would actually have to stop, you know, everybody would have to stop flying. Overall, you know, as I mentioned before, I live far away. We live far away from family on both sides. And so when we go visit our family, we have to fly. That's the only way we, we can get there, really. 

Um, I guess we could take a boat, but, uh, the only, only practical way, let's say, but it's, there's a world of difference between saying, okay, you're not gonna fly at all ever. And saying, you know, if we got those top 12% to move into the one to 5% trips per year, my quick and dirty back of the envelope math tells me that would. 

Cut flights by half. So, so there's a big world I think, between these two. And there's interesting discussions about how to do that. There's a fun, uh, ad campaign. I wish I could show it 'cause it's just like, the pictures are so nicely done. It's done of course, by the train company in Germany. So, you know, they have their own reason for this, but it's called the No Need to Fly campaign. 

And they basically took a bunch of pictures of places in Germany and then found kind of famous places around the world, or I suppose the other way around, found famous sites, people go to visit around the world and then found places where you can like, make the same picture in Germany and get the same, you know, view as, as taking your international flight for your vacation. 

So I do think that we need to more seriously have that conversation. And this is not, you know, I wouldn't pick specifically on airlines only, you know, I think this comes through whether we talk about consumption, emissions and other sectors and stuff as well too, but. It is true that with aviation, we are talking about a sector that is, you know, doing worse than than others in terms of the growth. 

And as much as I also think that, you know, obviously I'm someone who's lived places around the world and that was a hugely enriching experience for me to, you know, really be immersed in other cultures. So it's not an easy thing to just say, well, people should completely stop flying and, and stay home. 

But I do think that there is a lot that can be done here with some thought about how we reduce those emissions and how, you know, when people go and experience other cultures, they do that maybe once every few years and they spend more time there really, you know, being a part of that and learning that rather than just, you know, going to get the photo and, and so forth. 

So that's my, uh, soapbox spiel for this one. But in interested to hear, to hear reactions, 

[00:41:19] Sebastian Eastham: I, I'd love to jump on that quickly because. I really appreciate that distinction, right? Who it is that's actually getting to take advantage of the service. I think a, a couple of things that are interesting to me, one is how you would design, not you, how one would design that restriction. 

And I had a great conversation with, uh, a tax academic about whether or not you could structure a tax, which acts like, um, you know, income tax in the sense of being higher cost, the more flights you've taken a year, um, maybe the more flight kilomet does you take a year. But I think the o the other part is to turn that around a little bit and ask what it is that we're penalizing. 

A conversation that we were having, uh, earlier was how efficient is an aircraft now? And it is comparable with ground transportation. So, and, and you know, sorry, you said it specifically, right? It is not actually that you get to go to these places anymore and you just take a different mode. It is actually, you don't get to go to them. 

Unless you have an ev charged from a solar panel, you may not have an option that gets you to that place without really burning much less fuel than you would've on the aircraft if the aircraft is fully loaded. So the conversation has to be, are we, how do we charge access to the things that aviation gives us access to? 

[00:42:40] Sara Hastings-Simon: Yeah, I think, I think that's exactly right. And just really quickly add on that you know, I think there's, there's a penalizing part of it, but there's also looking at, you know, what has driven this demand for it, right? And there's a paper we've talked about, I don't have it handy, but a, a while back that talked about how kind of. 

The increasing ability to see what people are doing and also how a certain segment of the population sort of drives what is normal, right? And what is considered normal for a successful, you know, comfortable family. How many trips do you take a year? How far do you go? All of these kinds of things that are really about societal norms rather than somebody saying you are or aren't allowed to do this. 

I think that also is part of the conversation of like, what is cool? You know, is it cool to go? Is it expected? I, I experienced this quite a bit, kind of over this last year that I've been sick where, uh, you know, very common conversation is like, oh, well where are you going for the summer? And you feel almost strange as like a person of a certain social class to be like, oh, we're not going anywhere. 

We're just. Staying home, you know, like it almost feels shameful or like you're doing something wrong. And I think those are the kinds of societal norms that, you know, granted, it's very tricky, right? Like I'm not gonna say that we can go and legislate them, right? That would be problematic in a lot of ways. 

But I do think that climate, you know, people working on climate in addition to the technological side, we need to be thinking about this side as well. 

[00:44:06] David Keith: I agree. I no, I totally agree. I want one short thing, maybe I've said it before, that I do think there's this other hard to count social value of long distance sort of social relationships or even family relationships that I think make it less likely the countries go to war, they connect up countries more. 

And I think that's not a nothing burger, but it's hard to know how to think about it and how to think about it versus class and wealth. 

[00:44:31] Sebastian Eastham: And I, I think that there's a missing evaluation here. Uh, I say that, I mean part, 'cause I've been wanting to do it for a long time. Where does aviation fall? If you take an inclusive wealth approach? 

And that is things like, you know, the capital, the different falls of capital that are generated from, because I, I don't think that valuation really exists at this point. I, 

[00:44:50] Ed Whittingham: I want to get us to questions, but I do want to give a shout out and, and to your point, Seb, about your conversation with the tax prof. 

There is a group called the Premium Flyers Solidarity Coalition that came out of the Global Solidarity Levies Task Force. Nine countries are members of this. Uh, it was launched back in June, 2025 and what they proposed is applying progressive levies to private jets in premium class tickets. So that the rule is those who, you know, have the means that, and they're having the greatest impact. 

They contribute more and so they're doing great work and got some more traction at COP 30. The irony is when I was, I had a couple conversations with the government of Canada. About Contraras and about these levees. It was in the last budget when the Carney government took away a luxury tax on private jets and private yachts on the manufacturer of them, because, I don't know, apparently it was depressing the private jet, private yacht market. 

So we're saying, sure, okay, you've made it more affordable now for the super rich to buy the private jets and private yachts, but let's consider this levy and make it progressive, and you blend it into the cost of the ticket and no one's gonna bat an eye. 

[00:46:11] David Keith: Do the math. Quebec politics matters. Bombardier is located where, and Bombardier status, the maker of global public of, of, of private jets is what? 

[00:46:20] Ed Whittingham: Exactly, exactly. So, yes, that math adds up pretty quickly, David will said. Okay, we're gonna turn to our usual our number one questioner. Standby. Robert Tremblay. Rob, uh, the Floor's, yours. I know you proposed a couple questions. We're gonna leave it up to you to decide which one you want to ask. 

[00:46:40] Robert Tremblay: Sure. 

Thanks, ed. Um, I'll just go with the first one. Uh, um, so, uh, Dave alluded to this earlier, I think, but on, um, ESAP specifically, so if SAP is being made from electrically derived carbon, so from Dak and same for hydrogen, then does, does it make sense energetically to make the SAF at all instead of just sequestering the carbon in the first place? 

'cause with the SAF, you're just putting the carbon back in the atmosphere to take it out later. Um, just to make more saff. 

[00:47:08] Sebastian Eastham: I'd love to hear David's perspective on this because I almost see the answer is ideological. Whether or not, you know, what's the difference between taking out fossil fuels and burning them but sequestering the same amount of carbon versus reusing that carbon? 

If you reuse the carbon but it's more expensive, then yeah, why not just sequester the same amount of carbon, uh, and keep using the fossil fuels? I imagine that there are some questions about whether or not you can account, perform the accounting reliably enough. I do honestly believe that there is also just an, I see a sort of ickiness about continuing to use fossil fuels, um, and sequestering a's place. 

Whether or not that is actually a good enough reason to not do it. I dunno. 

[00:47:50] David Keith: I think my answer, I really agree with Seb. I think this is an ideological question. I think with all respect, the way you asked it is to me not the right environmental and social way that is, the world doesn't have a fixed amount of energy. 

I don't really care how energy efficient it is. The issue is environmental impacts and cost avoided carbon and you're not comparing the same energy sources. So the point is we have, and we'll have even more access to enormously cheap solar during the day in sunny places. And if you can turn that into a transportable liquid fuel, that might be really beneficial, even if it's not very efficient because of the fact that that's. 

Energy that you get with no carbon and pretty low environmental impacts. So to me, it's really a trade off with the right questions to ask from my perspective are what are the environmental impacts of this pathway of doing aviation and what are the costs of it? What are the environmental impacts? 

Include land use and other things. 'cause all these ways of removing carbon, having environmental impacts and they have costs. 

[00:48:48] Ed Whittingham: Um, Irwin Dreesen, Hass got a question and it kind of, it's uh, references back to the conversation we just had about the solidarity, levies, levies a 2026 paper in nature communications, earth and Environment makes a big point of attributing emissions to classes of passengers. 

Is that even relevant? 

[00:49:07] Sebastian Eastham: I would argue that, uh, I'm the wrong person to answer this. So I, I would direct you to a fantastic former colleague of mine, Florian Rogan, who I believe would give you a very deep and comprehensive argument about how it is relevant and is not relevant on the basis that you can do that attribution and Absolutely. 

Right. Right. Now we do attribute more CO2, uh, to premium classes than to economy, but you then have to engage with the question of, well, what would that mean from an airline economics perspective, right? In the sense that if the premium passengers are paying for the flight to occur in the first place, and the economy of passengers are mostly marginal, then who's responsible for this flight and who should be attributed to it? 

So I really struggle with these attribution questions. It's honestly one of the reasons I mostly look at a total flight level. 

[00:50:00] David Keith: And the substitution with freight is really interesting. I hadn't thought about this enough before. So the point is, if I buy super, super premium service where I'm the only person in the cabin and I don't weigh very much, and, and so then if you think about it, your first thought is, oh my God, there's enormous amount of CO2 emissions associated with my flight. 

But if the airline then fills up the hold with all sorts of very dense cargo, so the actual fuel burn and mass is the same, what I've done is just cross-subsidize the cargo transport, but not change the CO2. 

[00:50:27] Sara Hastings-Simon: Yeah, I was gonna add there. I mean there's a time dimension I think in all of this that's important. 

When you talk about that attribution, right, and the sort of counterfactual, because I think it's true, like in the very short term, you get one set of things that happens, and in the longer term you get a difference set. And I think it's very hard, honestly, to know which way it goes, because I could also imagine. 

The inability of the airlines to have the, you know, business class passengers subsidizing the flights means that flying is less cheap for everybody and therefore you have less flying that happens overall. So, you know, I can tell a sort of causal link story that it's not about the fact that they're taking up more space on the plane and therefore they are responsible for more of the emissions. 

I actually think the, in some ways, the more important driver is probably this longer term, you know, dramatic lowering of the costs of travel. 

[00:51:26] Ed Whittingham: Yeah. Sorry to cut you off, Sara. The first 10% of seats in an aircraft, you know, like the business class pay for something like 80% of the revenue of any kind of flight. 

Thus this very strong incentive to have business classes. Just as a side question, Seb, while we're on it, you know, there are all these carbon footprint calculators out there for flights and so I say I'm gonna take an economy class flight from. My nearest airport, Calgary to Toronto, and it spits out, ed, you're, you're responsible for, you know, 0.76 metric tons of CO2 and here's how you can pay five bucks a ton to offset it. 

Can you just give us a very quick sense what goes into calculating that number? 

[00:52:06] Sebastian Eastham: Yeah. Um, so it'll depend on the exact calculator to use. Although there is a standardized methodology, you can get the information from IKO in fact which says, you know, well this is how we're going to divvy it up, but. I would say the basic answer comes down to figure out how much fuel that aircraft is going to burn, which gives you the CO2, right? 

Basically a factor of three on the amount of, uh, fuel that's burned. That's the amount of CO2 you're gonna get. And then make a decision about how you divvy that up between the passengers. There will be some premium factor applied for passengers, um, who are taking, you know, first class business class, uh, which is related somewhat to floor space, but not exactly, and then the rest gets divided amongst, uh, the economy class. 

It, it's the basic answer there. Now, if you go to say Google Flight and use their travel impact model, they will also tell you we think that the contr impacts from this are gonna be low, medium, or high, and that's a totally separate calculation based on some work they've been doing over the past few years. 

In general, what you're usually seeing is just this, uh, straightforward e estimation of total CO2 emotions, um, being divided up again amongst the different passengers, depending on their class. 

[00:53:19] Ed Whittingham: Gotcha. I think we have, uh, time for about one more question. One came in from Karen Grecki. It's got a preamble, then a question I'll read both. 

I can't help but think about our society's inability to accept a carbon tax to ground the conversation around making the rich pay for their flying. I wish it weren't so, but beyond voluntary avoidance of flying, I did not think it is at all politically a viable to ask those to fly to pay more. Okay. 

So Karen's not supportive of the, uh, the premium levies, but her question contra avoidance seems like an easy win. However, if there is a question around the inability to accurately quantify these emissions, do you think that this may link to a lack of policy will, specifically that question around accurately quantifying emissions? 

[00:54:07] Sebastian Eastham: I would say that there is a fight going on right now about exactly this. I think this has really gone to the heart of it. There is sort of a, a three different groups who are fighting around chondral avoidance. I would argue that the first one is atmospheric scientists who have, you know, heart attack levels of anxiety about this maybe not being a big enough deal, right? 

That this, what if this isn't real? What if we have overestimated the impact of these contrails? Uh, and you know, I see a lot of skepticism associated with that and I understand it. I do, I think you've then got sort of the modelers who say, how do we predict this accurately enough? And you've got then industry saying, well, how do we implement this safely? 

All of these questions result in this fight where some people, and I found myself amongst them, argue that we can learn quickly through trials and therefore we'll push to engage with governments to try and fund these trials so that we learn, you know, basically put our money where our mouth is. And if we don't learn, we don't lose that much. 

Again, we're talking two to 5% CO2, right? There's one year of aviation growth. The other side of this fight is saying this is a huge distraction. This is just preventing us scrum acting on CO2. And I understand that side entirely. I don't know who's going to win. Um, and it, it all comes down to whether or not the, the idea we will learn quickly enough that it will outweigh the uncertainty can win out against, no, no, these uncertainties are too large. 

Stick to CR two. 

[00:55:40] Sara Hastings-Simon: It's hard not to see this whole, you know, airline and emissions as sort of a microcosm of the broader emission challenges, right? We've been talking technological solutions that may and may not work. How the policy you implement them, what to do with the kind of social aspect. And so as much as like, I would've loved to finish this show with like a clear plan, we'll implement X, Y, Z and do this, you know, it, it, that, that feels in some ways further away. 

Although the, the technologies are maybe closer. So I guess as my grandpa used to say, we'll just muddle along and kind of try our best going forward with all of the levers we have. 

[00:56:15] David Keith: On the one hand, I mean, in a kind of rational world run by some utilitarian, uh, it seems like trying to learn how well contral avoidance works is a clear win. 

It doesn't have any obvious bad environmental impact and it would reduce swarming, but I am very worried that it will effectively get used in some bargain with the aviation industry so that they basically give way on this kind of cheap thing to give way on contral avoidance and don't do so much on CO2. 

There's some kind of implicit political saw there, and that's CO2 that has the long run climate consequences. I guess the other thing that you know, connects to my day job is I think contrail avoidance is, is a very interesting way, a kind of slippery slope into solar geoengineering because if it becomes a really built in piece of climate policy, uh, in, in some regulatory respect, then it's maybe the first place where countries are beginning to explicitly. 

Have policy or maybe whether it's full regulation or not, we'll see around radio forcing that is the amount of reflectivity the earth has as opposed to around long relived greenhouse gases. 

[00:57:22] Sebastian Eastham: That's a a, that's a reason I think that there's a bit of a distinction between what I call cultural avoidance, which is about finding robust strategies to avoid controls as far as I'm concerned, right? 

Saying s on average are a problem, so can we find a robust strategy to just avoid forming them versus control, control management, which I think does unfortunately slip in that direction, making it well, what if we only avoid the warming ones and make a net cooling? But I would also argue, I, I just wanted to plug this idea. 

There's a great opportunity for collaboration here between the UK and Canada because we're at the same latitude, more or less. And one of the big challenges around s is observing them from, uh, space with geostationary satellites in the UK is a little tricky 'cause we're such high latitudes. We got a bad angle. 

Well, Montreal and Heathrow similar angles in fact. The many of the challenges that are gonna face us here in the UK as we develop will also face, uh, contral avoidance strategies in the, in Canada. So maybe there's an opportunity there. 

[00:58:18] Ed Whittingham: Well, I think we've had a robust discussion on robust strategies to avoid contraras, and I couldn't agree more that I think, uh, the time is right for bilateral work between Canada and the uk. 

I, I will also note that IKO is based on Montreal, so there's kind of that natural hook as well. Seb, thanks so much. Uh, fascinating discussion. We talked about contrails plus plus lots on aviation, decarbonization, and, uh, it was too long. It we, for us, it took us too long to revisit the topic. You're the great expert and a wonderful guest for us to do that. 

Thanks so much. 

[00:58:54] Sebastian Eastham: Thank you. It was really, really a pleasure to be here. Really appreciate the time and the opportunity to talk with you all. It was a lot of fun. 

[00:59:01] Ed Whittingham: Thanks for listening to Energy Versus Climate. The show is created by David Keith, Sara Hastings-Simon and me, Ed Winningham, and produced by Amit Tandon with help from Michael Edmonds. 

Our title and show music is The Windup by Brian Lips. This season of Energy Versus Climate is produced with support from the North Family Foundation, Consecon Foundation, Trottier Family Foundation, and you are generous. Listeners, sign up for updates and exclusive webinar access energyvsclimate.com and review and rate us on your favorite podcast platform. 

Really does help new listeners find the show. If you enjoyed this episode, check out our earlier aviation conversation from October, 2021 with MIT Steven Barrett, where we explored the long run technology pathways for Decarbonizing flight, we'll be back later this month with a live in-person show in Calgary on January 27th. 

Check out energyvsclimate.com for details on the show. See you then.