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Energy Transition Now - Episode 22 with Zeke Hausfather

In this episode of Energy Transition Now David Linden speaks with Zeke Hausfather, the climate research lead at Stripe, to discuss the role of climate science amidst the real-world action on climate change. Hausfather is a climate scientist whose research focuses on observational temperature records, climate models, carbon removal, and mitigation technologies.


About Zeke

Zeke Hausfather is Climate Research Lead for Stripe. He is a climate scientist whose research focuses on observational temperature records, climate models, carbon removal, and mitigation technologies. Zeke spent 10 years working as a data scientist and entrepreneur in the cleantech sector, where he was the lead data scientist at Essess, the chief scientist at, and the cofounder and chief scientist of Efficiency 2.0. He also works as a research scientist with Berkeley Earth, is a science contributor to Carbon Brief, was the senior climate analyst at Project Drawdown, and the director of climate and energy at the Breakthrough Institute. He has masters degrees in environmental science from Yale University and Vrije Universiteit Amsterdam and a PhD in climate science from the University of California, Berkeley.

David Linden [00:00:19] Hello everyone. I’m your host, David Linden, the Head of Energy Transition for the Westwood Global Energy Group. And you’re listening to another great episode of Energy Transition Now, where we discuss what the transition really means for the oil and gas and the broader energy industry. We’re increasingly being urged to listen to the science or follow the science to make some real-world action on climate change. And so while we have touched on the science in this series before, we had the glaciologist Martin Siegert in the last series, as a great example of that. My very special guest today is Zeke Hausfather, who’s the climate research lead at Stripe. And you guessed it a climate scientist. So welcome, Zeke.

Zeke Hausfather [00:01:09] Thank you. It’s great to be here.

David Linden [00:01:10] Thanks. I think you are actually officially our first California based guest as well. So you get to wear that special badge for today as well. So thank you for that.

Zeke Hausfather [00:01:24] I wont to brag about our weather here this time of year.

David Linden [00:01:27] No, I was I was thinking about the weather. And I look outside my window at this time and it is rather pathetic in comparison. Sure. But. But you do have a heat wave in another way. I suppose you had a heat wave. So, yeah, so pros and cons.

Zeke Hausfather [00:01:41] Our challenge is we now have a smoky season. The wildfires have gotten so bad that there’s a good month or so of the summer where we have to keep all our doors and windows closed and can’t go outside as much as we used to.

David Linden [00:01:53] Interesting. Yeah. So you posted something about that. There aren’t actually necessarily more fires, it’s just that they burn for longer and I guess more intensity and there’s more smokiness I guess, as a result.

Zeke Hausfather [00:02:06] Yeah. So we actually have fewer fires here in California on an annual basis on average than we had 50 years ago. But the typical fire burns five times more area. And part of the reason is that, you know, we have both so much built up dead undergrowth and the forests and they’re so dry that it’s really a tinder box.

David Linden [00:02:25] Goodness. All right. Well, so I hope there aren’t too many this season at all. But look, I think it’s always nice to start off with these sort of podcasts introduce, you know, because we do quite a wide-ranging set of conversations with different people from different backgrounds. And I always like to do a bit of a kind of a basic intro as to what is it you do and how do you do it type thing. And I saw it’s quite interesting, I saw it on your Twitter feed and I saw it on my one, someone had noted it to me. But there was a cartoon that came out where there was this exchange of two people. One of them said, “I need to warn you about the future!”. And the other ones responded saying, “Holy sugar, you are a time traveller?”. And the guy responded, said, “No, I’m a climate scientist.”. And the other guys said, “boring!”. So I thought that was a pretty harsh critique of essentially your role. So I want you to take that as your challenge for today, as, you know, essentially defend climate scientists and the work that you do and work to dispel that notion. But yeah, I thought that was pretty harsh.

Zeke Hausfather [00:03:39] Maybe it’s our new communication strategy. We just need to pretend to be time travellers from the future.

David Linden [00:03:46] The matrix is back. Okay, so with that in mind and I guess essentially, you know, for folks who don’t know, you know, we’ve talked to a lot of people from the industry, we’ve talked to various academics, etc., but we haven’t talked as a said, to a proper climate scientist, although a glaciologist would argue, of course, they form part of the climate science community. But, you know, can you just maybe just explain to us what is climate science and what kind of role does it play for us?

Zeke Hausfather [00:04:17] So you sort of nailed it. You know, you said glaciology is part of the bigger community. You know, climate science is a very big tent within which there’s a lot of subdisciplines. So there’s atmospheric physicists who sort of study the radiative transfer of gases in the atmosphere. There is great glaciologists who study sort of ice sheets. There’s oceanographers who study, you know, ocean carbon cycles biogeochemistry, ocean PH. There are paleo climatologists who study climate proxies of the Earth’s distant past. There’s climate modellers who sort of build physics-based simulations of the climate future. There is observational climate people who collect all the data from ships and weather stations and try to stitch it together in the past in the most accurate way. And sort of every one of these is its own silo with thousands of scientists working within it. And we sort of have various community efforts like the Intergovernmental Panel on Climate Change, where you try to synthesise all of those different disciplines into sort of a single comprehensive picture of, you know, this is how the climate has changed in the past and this is how it may change in the future. And then, of course, feeding into that, there’s a whole separate world of energy system modellers who sort of develop models of what the future might look like in terms of our emissions and our energy mix.

David Linden [00:05:30] So are they essentially individuals that are looking at different parts of the climate, but from a quite a specific narrow lens or you know, because it’s like a glaciologist, I would say sounds like someone who’s looking at ice, but in trying to work out what that means globally. So they’re asking what’s the kind of general impact? Is that fair to say?

Zeke Hausfather [00:05:50] Yeah, I mean, it depends a lot on the scientists. You know, one scientist may spend their entire career studying one glacier in Antarctica and be the world expert on that specific thing and, you know, have more knowledge than anyone else. Other scientists try to be a bit more generalists. They might not have quite that deep a subject area knowledge on any particular part of climate science, but they dabble in a lot of different areas and try to do higher impact things and sort of synthesise different parts of climate science together. I definitely tend to think of myself a bit, on the latter side, I like dabbling, but I also very much admire the specialists who dig super deep into one topic area.

David Linden [00:06:27] Yeah, I guess the difficulty I found when I first looked at the space was trying to work out who the expert is. Because you’re right, someone might know something very specific about an area, but trying to translate that and help people understand what that really means, are they looking at it too narrowly? Are they looking at just that area? And so, yeah, of course they’re going to make that statistical significant argument because essentially that makes sense of their world. But hang on, the guy over here is looking at a different part of climate science might completely disagree. And so how, is it someone like yourself who goes, okay, let me take all these different bits and pieces and put those together that that’s kind of needed? Or does that kind of just happen naturally, as you say, through the IPCC and places like that, where all these views come together?

Zeke Hausfather [00:07:18] So I think it’s a mix of both. You know, there’s a fair number of generalists. We’re sort of trying to put the pieces together all the time. But there’s also these, big community assessment processes like the IPCC, which happens every five years or so, seven years, but also there’s increasingly very robust national climate assessments operations. So the U.S., we have a national climate assessment that happens regularly in the U.K.. You know, my friend Richard Betts over there at the Met office and many others are involved in in the U.K. version of that. And European countries have their own. So, you know, it is a challenge because it’s such a big area with so many moving parts and so many complexities going from like socioeconomic and energy modelling to climate physics modelling to observational data to everything else that, you know, you do know no one person is going to know it all. And it’s good to have these big community processes to bring together thousands of scientists and synthesise, you know, tens of thousands of research papers in order to, you know, give us the best picture of what is going on, what we know and where the remaining uncertainties are. Because, you know, the Earth is a very complex system. And while we have a lot more confidence in what we know now than, say, 50 years ago, there still are some pretty big unknowns when it comes to the future of our climate.

David Linden [00:08:32] We’ll come back to that in just a minute, then. But what if I was to sort of be, let’s say, a non-scientist coming at this and sort of would say, okay, so what are the top five things that you’re looking at and you’re constantly focussed on this to sort of say these are the climate indicators we need to worry about? I mean, to me it sounds obvious. It’s something like temperature and carbon emissions, parts per million or whatever that you look at. But what are the kind of call that top five? You might have more. You might have less to sort of simplify the story for us all. But what is it essentially that, you know, that despite all these different specialisms, what are the top things that people focus on to give us an indicator of what’s happening to our climate.

Zeke Hausfather [00:09:15] Yeah. I mean, there’s a huge amount of climate data that we’re measuring, particularly in the last 30 years when we have satellite measurements, you know, monitoring the Earth in real-time. But there’s definitely a few things that stand out, both because, you know, they’re iconic, they’re long-term records, and they’re also some of the most physically meaningful in terms of measuring what’s driving a lot of the impacts we’re seeing. And the first is probably the one that gets the most attention, which is simply the global surface temperature record. I actually helped produce one of the four different global surface temperature records that are out there with a group called Berkeley Earth. But essentially what we do for that is we’re gathering all of the data from all of the land-based weather stations, the ocean ships, the automated buoys, you know, various other data sensors, and stitching them all together into a record of the Earth’s average temperature. And by looking at that, we see that, you know, the Earth has warmed about 1.2 degrees centigrade since the late 1800s. And most of that warming about one degree of it actually has happened in the last 50, 60 years.

David Linden [00:10:24] Okay.

Zeke Hausfather [00:10:25] So that’s one of the major indicators. Another that is a shorter record, but in some ways is actually more meaningful from a climate standpoint. Is ocean heat content because the atmosphere is actually not a very good store of heat. You know, air does not absorb much heat. And so because of that, the atmosphere can vary a fair bit in terms of how hot it is, whereas upwards of 90% of the heat that’s being trapped by greenhouse gases ends up going into the oceans. And so ocean heat content is a measurement of how the amount of heat in the oceans has changed over time. And nowadays we have this wonderful network called Argo of about 3500 little robotic buoys that every day they dive deep down about 2000 metres into the ocean and they slowly come back up measuring temperature, salinity, P.H., various other things. And then when they get to the top, they send that data up to a satellite called Jason, you know, Jason and the Argonauts. And so for the last 20 years or so, we’ve had this really robust network giving us near real-time measurements of ocean heat content. And the thing with ocean heat content is. You know, it pretty much sets a new record every year, like the surface varies a bit. You know, some years are warmer than others, El Nino years or warmer, La Nina years, which is a sort of mechanism that redistributes heat from the ocean to the atmosphere. But almost every single year sets a new record for ocean heat content. And that’s because that’s really where all the energy in the climate system is going. And so it’s really a very robust measure of the amount of heat trapped in the Earth’s system by greenhouse gases. I guess the third major indicator I’d point to is simply the amount of greenhouse gases in the atmosphere. You know, we started measuring CO2 in the atmosphere in Mauna Loa in the 1940s. Before that we have fairly robust measurements from both Greenland and Antarctica of the amount of CO2 trapped in bubbles in the ice, which you can use to get a sense of how much CO2 is in the atmosphere at various periods of time. The nice thing about CO2 in particular, CO2 is not nice for many reasons, but one of the nice things about it from a physics standpoint is that it’s well-mixed throughout the atmosphere. You know, the CO2 concentration in North America is going to be the same as, you know, plus or minus one or two parts per million as Antarctica or Europe or Australia. And so being able to measure it anywhere in the world gives you a good sense of what it is everywhere in the world, which is one of the reasons that even though we don’t have, you know, great modern observations of CO2 prior to the 1940s, we can actually be quite confident in what global values were, you know, for the past at least 4 million years or so, which provides a really good record. And we know from these measurements that today the CO2 concentrations, the atmosphere are far higher than anything the world has seen for the last few million years, at a minimum, and probably the last few tens of millions of years.

David Linden [00:13:17] So just as a quick one there. So that’s kind of your top three. I like that so far. But why is it… to me, it’s really the first time I’ve heard that we’ve got such good measurements on ocean heat content, and it’s actually far more important in some respects in terms of explaining what’s going on. Why is it in some respects I’ve not heard about it as much, and I’m hearing much more about CO2 concentrations, and 1.2 degrees and all those sorts of things. I mean, if you think about any of the kind of groups that are out there, like, you know, is it because it’s kind of what Paris hooked on to everyone hooks on to what Paris said. And so it’s the 1.5-2 degree thing. And therefore then it’s about, you know, measuring and then coming up with plans aligned with that just seems easier rather than trying to work out what’s happening to the ocean or.

Zeke Hausfather [00:14:08] And it’s a good question. I think one of the main reasons we don’t care as much about it is we don’t live in the oceans, we live on the surface. And so the surface temperature is what tends to get all the attention. But also, it’s the record is reliable for surface temperatures back to the mid-1800s, you know, maybe plus or minus a 10th of a degree or two. For ocean heat content, you know, we really only have very high-quality records since the early 2000. You know, there are there are a lot of different groups that have produced reconstructions going back to the 1950s or so or even before in a few cases. But the uncertainties are much larger with that. You know, we can we can definitely see the direction it’s going. You know, there’s no possibility that ocean heat content was as high in the 1950s as it is today. You know, it’s not that it’s uncertain, but it’s not nearly as precise when you go back more than two decades. And so for that reason, I think a lot of people have treated the surface temperature as a much more iconic indicator. And in a lot of ways, you know, surface temperature maps better with the sort of the impacts that we see, you know, in terms of heat waves, extreme weather events, all those sort of things. The ocean heat content tracks very closely with sea-level rise. So. Yeah. Different drivers of different things.

David Linden [00:15:25] And if we come back to the idea that. I think from what I can see from you, that is we’ve essentially started to get better at A measuring, and B, understanding what’s happening to our climate. And, you know, I guess you also said that there still a lot of unknowns. Maybe it’s worth just dealing with that question there for a minute. How much of an unknown are we talking about here? I mean, there’s lots of things that we don’t understand in our world. Obviously, it took us a while to work out everything from gravity to whatever. Right. But is this a… Science will always have unknowns, of course. But how big of a field of unknown is there out there?

Zeke Hausfather [00:16:10] Hmm. That’s a great question. And it’s useful to go back a bit in time. You know, scientists first postulated the idea of CO2 as a greenhouse gas in increasing the atmosphere, causing warming in the late 1800s with Arrhenius, Tyndall, Fourier. And that sort of languished a bit, particularly after some papers that were published that suggested, “Oh, wait, maybe it’s the atmosphere saturated. So adding more CO2 doesn’t actually have much of an impact”. Turns out those ones are wrong, but they really led to not much focus on the field for about 50 years. And so the 1950s, the issue was sort of rediscovered in the scientific world, especially as we started getting these records of atmospheric CO2, suggesting it was increasing. And then it was really in the late 1960s, early 1970s, we started seeing an explosion of and really the birth of what we call modern climate science with sort of the first physics-based climate models, huge investments in increasing the number of observations we have, and specifically going back and collecting all these historical observations, all these handwritten ship captain logs of temperature measurements from 1890 that had been sitting in a basement somewhere in London for 80 years. And then, you know, in the early nineties, the IPCC was started to sort of help synthesise and bring together the scientific community and, you know, coordinate a lot of the modelling work that was done as well as the scenario planning. And so, you know, over time we’ve gotten a lot more confidence and a lot more understanding of these systems and a lot better ability to model them and measure them. And so today there’s a few things that are pretty incontrovertible. Like even a lot of the scientists who are sort of sceptical of the severity of climate change would agree on the basics. And that is, you know, CO2 in the atmosphere is increasing. That increase is due to human activity. You know, the amount that’s in the atmosphere very closely matches the amount of oil and gas we burn. That CO2 is a greenhouse gas. It traps heat. You know, without CO2, the earth would be much, much cooler. Life would not be possible, most likely in most places. And that, you know, if we keep burning fossil fuels, the world will keep warming. So that’s what we all agree on. Where there’s some disagreement is exactly how much the earth will warm in the future. And that really comes down to a question of what other factors change as CO2 increases that will either enhance or reduce the amount of warming we’d experience. So if we were to ignore everything else in the earth system and only increase CO2 in the atmosphere, if we doubled the amount of CO2 in the atmosphere, the Earth would warm about one degrees C, which is not that much. I mean, it’s obviously it’s a decent amount, but it’s not.

David Linden [00:18:56] Yea, that’s right some areas hit more than others, etc., etc..

Zeke Hausfather [00:18:59] But in reality, given all of the complex interactions, the Earth system, we think that if we double the amount of CO2 in the atmosphere, the earth will warm closer to three degrees. And the reason for that is because of what we call climate feedbacks. So the biggest one of those is water vapour. Water vapour itself is a very strong greenhouse gas, but it’s also very short-lived in the atmosphere. If you get too much water vapour, it falls out as rain. But the amount of water vapour that can be in the air before it rains out is determined by the temperature of the air. So a warmer world is one where the air can effectively hold more water vapour, which means that there’s more heat being trapped by that water vapour. Since water vapour itself absorbs certain frequencies of outgoing long wave radiation, it’s a greenhouse gas. And so that water vapour feedback by itself, you know, adds roughly doubles the effect of CO2 warming. On top of that, there’s large changes in the reflectivity of the air surfaces associated with warming. So, you know, as snow and ice melt, that gets replaced by darker surfaces, you know, trees, vegetation that absorb more of the sun’s light. As sea ice melts, it gets replaced by darker ocean water that absorbs more of the sun’s light and bounces less back up to space. That enhances the amount of warming. There’s other feedbacks that can work the opposite way. So the warmer the surface gets, the more energy goes back out to space. In fact, the amount of energy going back out to space from the surface is the fourth power of the temperature of the surface. And so that’s a big factor that prevents sort of climate from running away and spiralling and sort of out of control warming is that you sort of get much, much more energy going back to space as the surface temperature increases. And then there’s just some big unknowns around things like clouds and  exactly how they will respond, you know. Some types of clouds, particularly those that are higher up in the atmosphere, tend to be better at trapping heat. Other types of clouds, such as those that are lower, closer to the surface, tend to be better at reflecting the sun’s rays back to space. The mix of high and low clouds you get as the earth warms. And exactly how that change changes is an area of pretty big uncertainty. And so we’re not going to know precisely, you know, how much warming we’re going to get until we get better measurements and better models of those things. There’s another big uncertainty around what we call aerosols, which are not spray cans, but rather little floating particles in the atmosphere, things like sulphur dioxide that, you know, are reflective. So they’re like slightly shiny. So some of the sun’s light bounces off them, goes back to space. They can also serve as cloud condensation nuclei. So you need certain amount of bits of dust and aerosols in the air for clouds to form readily. And so the more you have, the more clouds you can form. And then clouds have their own complicated climate effects. And so you know exactly how aerosols are impacting the climate and our emissions of them are going to change over time. We’ll also have a big impact on, you know, the degree of climate change we’re going to get. And then the final big area of uncertainty is our own emissions. You know, we could have a world where we double CO2 by the end of the century, or we could have a world where we kind of close to zero. And obviously that’s going to be a huge effect on the results. But if we sort of back up a little bit and look at what we expect to happen in the future, there’s a metric that climate scientists like to use that I alluded to a little bit earlier that we call climate sensitivity. And the way we usually define climate sensitivity is if we doubled the amount of CO2 in the atmosphere, say, from pre-industrial levels to it. So it actually doesn’t really matter that much where you start, how much warming we expect to experience, you know, over the next few hundred years, if we just double it and hold it there. And, you know, for a very long time, that range has been pretty wide. So back in the late 1970s, the first real estimate of this was the Charney Report. And they said, if we double the amount of CO2 in the atmosphere, the world will probably warm somewhere between 1.5 degrees centigrade and 4.5 degrees centigrade. Now, flash forward nearly 30 years in the 2013 IPCC report, they said if we double the amount of CO2 in the atmosphere, the world will probably warm somewhere between 1.5 and 4.5 degrees centigrade. So the fact that we hadn’t really reduced that uncertainty substantially in, you know, nearly 30 years was not great. I mean, to be honest, the original estimate was probably too precise. But we have had some good news in that particular area. The most recent IPCC report that we published this past year actually narrowed that range substantially for the first time in 30 years. And they say now that if we double the amount of CO2 in the atmosphere, the world will likely warm somewhere between 2.5 C and 4 C. So it’s getting much more.

David Linden [00:23:36] Good news on the narrowing. But actually the bad news is the lower boundary’s gone up.

Zeke Hausfather [00:23:44] But the upper boundary is going down. So now it’s, you know, two, 2.5 to 4 instead of 1.5 to 4.5. So there’s a silver lining there.

David Linden [00:23:52] But sorry, I was being very gloomy.

Zeke Hausfather [00:23:57] But you’re right. It does mean that, you know, we’re less likely, or at least it seems now that we’re less likely to get lucky and have, you know, climate sensitivity end up being low and much less warming than we expected.

David Linden [00:24:09] Okay. But I guess part of it’s down to the as you suggest there is it’s just a better understanding of what’s going on. Ability to measure our ability to forecast. It just got better. And so you can start to narrow that range of uncertainty going forward. It just seems like a natural pathway to go down.

Zeke Hausfather [00:24:28] Yeah, you know, we’re getting better measurements of these things. We’re getting higher resolution models and faster supercomputers. Models are an interesting area. You know, climate models are far from perfect. You know, the earth is an incredibly complicated system. You know, it’s hard to get everything right. But at the same time, they’ve really improved by leaps and bounds over the last few decades. We, I actually led a group of scientists on a research project two years ago now. We published a paper looking at all of the climate models that have been published since the first one in 1970, that said, “we think this is going to happen to the world by this date”, you know, some sort of a concrete prediction of what would happen to global temperatures, global surface temperatures. And so we looked at all of those models published between 1970 and the mid 2000s and then compared them to what actually happened after they were published. And what’s interesting, you know, most models actually did a pretty good job of predicting the warming that occurred. You know, 11 of the 18 models that we found. You know, we’re pretty much spot on there indistinguishable from the observed trend in temperatures in the real world. And of those that, you know, didn’t perfectly match, I think four had slightly too much warming, three had a bit too low warming. But by and large, these models did a good job of predicting the future after they were published. So, you know, out of sample, so to speak. And that’s particularly impressive for the early models, the ones published in, say, the 1970s, when we didn’t really even know that the world was warming. We didn’t have a great collection of historical temperatures back then. We hadn’t gone around the world and digitised all these old ship logs, like most scientists in the 1970s, thought that global temperatures had been flat or even slightly cooling for the last few decades, in part because our records are almost entirely based on weather stations in the Northern Hemisphere, on the land, which did show that they didn’t have any ocean data. And so to be able to say that like, hey, the world has been cooling, we think, for the last three decades, but that’s going to reverse. And we’re actually going to see 0.6 sea warming by the year 2000, as Wally Broecker did in his paper in science in 1975, was pretty remarkable. And what’s more remarkable is we saw exactly that 0.6 C warming by the year 2000 relative to 1975 when we published that paper. So the performance of, you know, these old climate models, which were much more basic than the sort of supercomputer models we have today, you know, the fact that they could get it right is definitely encouraging that our current models are not too far off.

David Linden [00:26:58] Very interesting as people are. I guess people can take a bit of, call it hope or take a view on the fact that, look, things have got better, they’re more accurate, but essentially the picture or the outlook is still the same. Right. It is essentially a world that’s getting warmer, etc., etc.. But and, you know, they’ve been some effective, whether it’s the hockey stick kind of diagram that’s come out around, you know, well, temperatures or forgot the who came up with that image if that were changing colour bars as well.

Zeke Hausfather [00:27:38] Ed Hawkins and the Climate Stripes.

David Linden [00:27:40] Yea, that’s the chap. Yeah, absolutely. I think we’ll see that on, I think Greta’s new book is coming out, so all of the different essays she’s collected soon as well. But you know, that sort of imagery is, you know, you always get this is the way that people will ultimately consume some of this. And it’s been a lot of activity, a lot of noise, we’ve had COP 26, etcetera, and others before that have made all these warnings and let people know that you need to change, etc.. What is it in your mind, though, that isn’t getting people to maybe make enough or to take that seriously enough? Because if we did take it all seriously, right now, every country in the world and every person in the world and every company in the world would be committed to saying, “Okay, actually, sorry about that. Let me just recognise that we’ve done a very good scientific, you know, backed up study here. And this tells us over many years of a multiple studies, thousands of scientists, etc., etc., who globally all agree that this is the problem”. Why are people not responding to this kind of thing is, I guess, the kind of question I am trying to ask?

Zeke Hausfather [00:28:53] It’s a big question. I mean, I think it’s important to emphasise that we are responding, you know, not necessarily as quickly as we’d like, but we’re we are starting to see real movements, particularly in the last two years. We’ve started to see more and more countries around the world, including India, China, the EU, the U.K., the U.S., Brazil, Japan commit to get their emissions down to net zero by the middle of the 21st century. In fact, countries representing over 75% of global emissions have now made those commitments. And if they followed through on all those commitments, we would actually succeed, most likely at least in limiting warming to below two degrees, if not 1.5. So I think we should emphasise that there is there are some things moving in the right direction. You know, clean energy is getting cheap. Global coal use likely peaked back in 2013 and is probably in structural decline, electric vehicles are 14% of global vehicle sales in the last quarter. You know, there’s a lot of trends moving in the right direction. They’re just not happening quickly enough to meet our most ambitious climate goals. And, you know, it’s easy for politicians to say they’re going to do something in 30 to 50 years. It’s a lot harder to actually take concrete actions today that put us on a pathway to meet those goals. So, you know, I certainly think we should treat those net zero commitments, you know, in 2050 with a proverbial boulder of salt, particularly, you know, for those of us not in the U.K. who don’t have the sort of thing, you know, actually legally mandated and have governments that, you know, can get stuff done to put us toward that direction. But that said, you know, it is a good question of why we’re not doing it faster and why there isn’t more impetus around these things. And, you know, there’s a couple of different answers to that, right. One is that we as a society are just really bad at dealing with long-term problems. You know, our election cycles are short-term. The issues we tend to focus on day to day are short-term or on the economy or crime or those sort of things. And so while a lot of people care about climate and in the abstract, you know, they see it as an issue that’s less pressing right now than all these other things that are facing them. And so it’s hard to keep people’s attention on it for a long period of time. Now, that’s starting to change a little bit as we’re starting to see more and more extreme events that are, you know, at least in part, attributable to climate change. You know, here in California, for example, as I alluded to earlier, you know, we now have a smoke season which has a pretty big impact of climate change staring us in the face. Or, you know, my home here was built in the 1970s, never had any sort of air conditioning. We had to put it in last summer after enough days of, you know, close to 40 C. And so, you know, there are definitely changes that are getting to be big enough that people are starting to see them. But it’s just hard to break through relative to all these other priorities people have. The other challenges that it’s become, at least in some countries, a very political issue. You know, particularly in the US, Canada and Australia, there’s a very big left-right split, not just on the preferred solutions to climate change, but even the extent to which it’s a problem that requires addressing. And while I think it is very good to have public policy debates around the solutions, you know, I think when the science itself becomes politicised, it, you know, can lead to big problems for society.

David Linden [00:32:11] Interesting, I know, is a difficult one. Is it a technical problem? Is it a political problem? Is it a social problem in terms of moving things forward? I guess that’s almost like a circular debate there because it kind of just depends on where you are in the world as well. But you alluded to some of the kind of the progress points that we have made. And he sort of listed a few just quickly there. But maybe we could just quickly revisit some of those if we were to sort of take our heads out of the doom and gloom, you know, the path we were on is not the path that we want to be. And we got to be sceptical about some of the, I would say politicians, but essentially that’s a commitments we’re making. What is it in your mind that we have achieved that is actually a very positive thing that, you know, leading us down the right path.

Zeke Hausfather [00:33:01] Yeah. So. So to borrow a term that was popularised in COVID, you know, we really have bent down the curve of future emissions in a way that wasn’t true a decade ago. A decade ago, it certainly seemed plausible the world was headed toward a 21st century dominated by coal. With, you know, four, even five degrees warming by the end of the century of global coal use that almost doubled in the previous decade. You know, China was building a new coal plant every three days. And today we’re in a very different world. Coal use has plateaued globally and even, you know, mostly plateaued in China. They’re still building new plants, but the utilisation of those plants is way down. You know, we are in a world of increasingly cheap, clean energy alternatives. Renewables have become much cheaper, much faster, than I think anyone anticipated a decade ago, you know, we’ve seen huge drops in the price of batteries. We’ve seen electric vehicles become much more cost-competitive. We’ve seen LEDs take off in the lighting market, which used a fraction of the energy of conventional lighting. So I think we’ve we’ve sort of lucked out in some ways on the technology front. Now, technology alone is not going to save us. You know, we need policy as well. But I think we underestimate. A bit. The extent to which technology enables policy, you know, the fact that we are seeing the Chinas and the Indias of the world commit to ambitious net zero goals is in large part due to the fact that they now see a pathway to achieve those goals that doesn’t come at a cost to their development priorities and their economic growth. And so to the extent that we have made clean energy cheap, I think it enables us to have more ambitious policy because the costs of that policy are more palatable. You know, a world where solar power is ten times cheaper than it was a decade ago is one where countries are a lot more willing to commit to building, than if there’s sort of this huge premium that they’re having to pay to transition away from fossil fuels. That then also comes at the expense of other priorities they have.

David Linden [00:34:59] Okay. I mean, it’s an interesting point around the technology side of things. There is clearly different camps who say, technology will solve everything. So don’t subsidise anything. Don’t get involved. Politics, the market will sort itself out because there is a problem, which is climate change. You go in and you’ll solve all the problems. What in your mind, if you were to sort of look at the different cooling pathways, for argument’s sake, what are the actual pathways that we can take to try and reach our target called at 1.5 for argument’s sake, or at least below two degrees going forward. You know, are there certain technologies that we will have to go if we want to take the technology angle? Or are there sort of certain other levers that we’re going to have to pull that are going to get us there while we are way too late, in fact? And actually, look, sorry, David, to be very optimistic here and asking for things that, you know, you just can’t pull out of the bag, unfortunately.

Zeke Hausfather [00:36:00] I mean, I think it depends a bit on the pathway. Right. You know, I would argue that we’re, to be honest, probably too late for 1.5 degrees, at least in the absence of a world where we get very, very lucky with, you know, planetary-scale deployment of carbon removal technologies later in the century, which, you know, I work on this from my day job at Stripe. So hopefully, hopefully that’s a future we could see. But, you know, I think we also need to not bet on that. Like the challenge with 1.5 degrees is we’re at 1.2 today. You know, we have this vanishingly small remaining carbon budget to limit warming to 1.5 degrees. And in the absence of net negative emissions of removing more from the atmosphere than we’re emitting, we’d have to cut all global emissions to zero in the next 20 years or so to avoid passing 1.5 degrees. You know, if you allow a lot of negative emissions, like pretty much all of our models do, you can, you know, say we need to get to net zero globally by 2050 or 2055 even. That is not consistent with the pledges that most countries have made today. So I just don’t see much indication that there is the political will globally to make the degree of cuts needed to limit warming to 1.5 degrees. A particularly stark statistic as so a few months ago, the IPCC published its Working Groups Three Report, which they report on mitigation pathways and they looked at 230 different scenarios that had been run to limit warming to 1.5 degrees by the end of the century. And of those 230, 221 of them, so 96% passed, 1.5 degrees on the way there and then brought it back down. There are only nine scenarios in the report that did not overshoot 1.5 degrees.

David Linden [00:37:35] So these are the overshoot type scenarios.

Zeke Hausfather [00:37:37] Yeah. So I think that, you know, barring some sort of dramatic public awakening around climate globally in the next few years, you know, we are going to be in a world of overshooting 1.5 degrees. At the same time, you know, the distance between 1.5 and two is actually pretty huge in terms of its emissions implications. So again, without any net negative emissions, without any net carbon removal, we’d have to get global emissions to zero in the early 2040s to meet 1.5 degrees. We’d have to get global emissions to zero in the 2070s to limit warming to, you know, well below two degrees or at least a two in three chance of avoiding two degrees warming. So a best estimate of like 1.8 degrees or so. And so, you know, I have a hard time imagining global net zero in 2040 or 2050 for that matter, but I can definitely see pathways to get us there in 2070 if we get our act together. So I think that, you know, we’re definitely a world where we can limit warming to 1.7, 1.8, maybe even 1.6. I think the ship might have sailed at 1.5. We got took too long to get our act together. In terms of how to get to these well below two degree goals, though, you know, there’s a few things that come to mind. The right one is that it’s important to realise there’s very much a floating order of mitigation. You know, coal goes away first. It’s the least cost-competitive day, it’s the most dirty and carbon-intensive. You know, they’re the most mature alternatives to coal. You know, electricity generation is in many ways easier to transition in other sectors because you’re dealing with a much smaller number of plants. The economics are much better for, you know, prematurely retiring them. You know, the next sort of thing on that chain is oil. Again, we’re having, you know, more cost-competitive electric vehicles, say, or oil’s the second most carbon-intensive fossil fuel. There’s going to be some sectors like aviation that are going to be tough to fully eliminate. But we have alternatives, you know, in the pipeline that are cost-competitive for a lot of others. And then the final thing that’s sort of the hardest to eliminate and that we see in our models is sort of the last thing that you get rid of is natural gas. You know, it is the least carbon-intensive of the fuels. It is used in applications that have, both tend to be a lot harder to replace things like industrial heat. Even gas for electricity generation is dispatchable in a way that other sources find challenging and, you know, gas for home heating. While we have increasingly cheap heat pumps, the turn over time for our housing stock is very long, and the economics of prematurely retrofitting and removing functional gas equipment to replace with electric heating is, you know, it’s a lot harder to make that pencil out than, say, if you’re doing it at the point of building new homes. So from a both utility and capital turnover time, it’s a lot harder to get rid of gas. And so, you know, we should sort of target our policies accordingly, I think, in terms of really prioritising today getting rid of coal as quickly as possible and, you know, prioritising new gas or new applications that use electricity instead of gas and sort of letting that the sort of fleet of installed buildings and technologies turn over their. And then in terms of the policy side, to help push those, you know, I think. We need, like as I mentioned earlier, I don’t think technology alone is going to save us. And again, I think a big part of that is that the benefits of carbon emissions are privatised and the costs are socialised, and that is that the cost of climate change to society is not reflected in the market price of goods, and there’s no mechanism outside of government intervention that can leave that to happen. And so there’s been, you know, a basis for having governments. Intervene in prices to internalise externalities in the economics discipline for 100 years. You know, Arthur Pigou, you know, famously posited the idea of the Pigouvian Taxes and that have had a lot of buy in from mainstream economists and critics, including folks like Gregory Mankiw at Harvard, who is the economic adviser for the Bush administration here in the U.S.. You know, he started a Pigou Club of economists who want to internalise the cost of climate change in the price through carbon taxes. So, you know, there’s a lot of good reasons from an economic standpoint to do that. It’s proven a lot more politically challenging in practise in many countries, particularly here in the U.S., where it turns out it’s a lot easier to have carrots, than sticks. It’s a lot easier to pay things that are good rather than penalise things that are bad. And those are, you know, not necessarily as economically optimal. You run into problems of governments picking winners. But there’s also a ways to design sort of technologically neutral subsidies for clean energy, for example, that can, you know, if not quite as effective as a price on carbon can at really get you close. And so I think that, we are going to need to do some of that. Otherwise, we’re sort of, setting up an implicit subsidy for fossil fuels that’s not enjoyed by clean energy. You know, the fact that they cause all these societal harms that they don’t have to pay for and clean energy, on the flip side is at least currently in most countries not subsidised for its, for not cause of those harms. And so we need at least one of those two to really drive the level of adoption of the sector that would be, you know, society and economically optimal.

David Linden [00:43:04] Okay. And I guess that’s a politically tough choice always, of course, to make, because if you talk about the cost of that transition, will you be almost arguing there is the how do you effectively pass on that cost to consumer? And then people don’t always understand the, I guess, carbon taxes because essentially carbon tax gets connected with then gets redistributed effectively, right? That’s how it should work. But when the minute you say the word tax, people do not like that.

Zeke Hausfather [00:43:31] Yeah. And again, we don’t need to be a slave to what is economically right. If we’re in a second best world where we’re just subsidising clean energy for, you know, the fact that it’s not causing pollution, that itself is good or, you know, we’re in a more regulatory regime where we’re restricting, you know, both conventional and greenhouse gas pollution from fossil fuels and one way or another, you know, can help drive adoption. So, you know, I originally came from a world of climate economics and, you know, I was very much into the perfect optimal model there’s sort of market outcomes back as a grad student in college but the more I spend time I spend in the real world I realise that sometimes, you know, the second or third best world is still better than the world we’re in today.

David Linden [00:44:20] That’s an interesting outcome there. Alright. Okay. Very interesting indeed. And just as a quick one on natural gas, there’s an interesting one there around how it came, kind of came third order in your in your list of coal then oil and natural gas. Just because of the reality around how these things work is one of the dangers the world that we have right now. I’m sitting here in Europe right. So we have a particularly acute need to switch out one particular country’s fuel for another one. And so it’s a rush to LNG as an example. Right, which is encouraging other countries, you know, further afield obviously, you know, including us, but I’m thinking of as far afield as in Mozambique and Australia, etc.. So we will, let’s actually sanction all these big projects that are going to be around for 20 to 30 to 40 years producing more LNG because, you know, essentially the world now needs that. But these things are sanctioned on the basis they’re going to work for 20 to 30 to 40 years. Is the danger there that this is a short-term thing that we’re seeing in Europe, but actually longer term, where the climate kind of well, how we’re trying to change the world is is that those projects essentially and we all talk about stranded assets and those sorts of things do become stranded because that’s where the world is having to trend or is because natural gas isn’t as hard hit as coal and oil in the grand scheme of what the problem is, you know, essentially, you know, look there space here for some additional LNG to come into the world as in I’m just making one example, right, there are millions of different arguments made all over the place for different projects, whether they’re they should be coming on line or not. But just specifically of the world we’re in right now, the dilemma that Europe faces, security of supply and in encouraging other countries to essentially sanction new projects to feed them, is that a realistic solution in that sense, or should we be looking at the world in a different way?

Zeke Hausfather [00:46:26] I mean, it’s definitely a sub-optimal outcome in many ways, though I don’t think any of the alternatives right now are particularly great. You know, another option is to and which is already happening to extent is, you know, to double down on coal use in Europe, which is, you know, from a climate standpoint, considerably worse. But there is this question of infrastructure, right? If you are building these big LNG terminals, they’re going to be around for many decades. How do you deal with that? Are you locking in future gas use in a way that you wouldn’t otherwise if you weren’t building things? And I think there are some ways to mitigate that. One is to make sure that all of the new LNG facilities are also designed with hydrogen in mind. Because, you know, we may have a global hydrogen economy where we’re shipping hydrogen rather than methane in a low carbon future. But also there’s this question of where we’re aiming, right? It is very hard to justify any new gas developments in a 1.5 C world, or at least net gas development. It could have potentially lessened North American more in Africa. But if you’re talking about a 1.8 degree world or a 1.7 degree world, then, you know, maybe it’s a little less than consistent as long as we’ve pretty much gotten rid of it all by 2050. Or so. Right. And so it’s sort of this question of where we’re aiming at in terms of what degree of long-term fossil fuel use we can have. But I think the important thing is that, you know, while we might be diversifying our supply of gas, we’re also as quickly as possible, reducing our reliance on gas and other fossil fuels that are, you know, in many ways been equally impacted. Your price of coal has skyrocketed, price of oil skyrocketed. And I think that those all send powerful, both market and policy signals to countries that there is a need to reduce our exposure to price risk around these things. You know, clean energy technologies have their own challenges around intermittency and other issues, but, you know, at least they’re reasonably reliable in terms of long-term pricing. You know, you’re not going to have the price of electricity from solar suddenly triple or increased tenfold as gas has. So, you know, there’s definitely a strong incentive to diversify and to invest more in clean energy as fossil fuel prices become high. And I think at the end of the day, the overall climate impact of this entire, you know, geopolitical challenge that Europe is facing right now might end up being, you know, positive for the climate simply because it is accelerating this transition in a way that, you know, was harder when fossil fuels were cheaper.

David Linden [00:48:59] Super Zeke. So, look, I think we’re coming close to the end of our time, as is always the problem with these conversations.

Zeke Hausfather [00:49:06] It always goes by too fast.

David Linden [00:49:09] It does, becuase I still have a list of questions in my head now actually around various topics, but I’ll ask you a very big question, I guess. And I mean, look, you mentioned this earlier in terms of pathways you mentioned and your role of what you do at Stripe as well in terms of what your company focuses on as well. We’ve talked a lot about mitigation. We didn’t talk that much about carbon removal as a concept. Now it’s a whole podcast in itself. Appreciate that. So let’s not open the whole can of worms around that area. And could you maybe just share a little bit, though, around, how important is carbon removal as such of what we’re talking about here? How important could it be? I’m talking about how important is it now and how important could it be? Because clearly someone like Stripe either has taken the lead in some of this, you know, in terms of getting involved in it. But we are you know, it’s a tiny, tiny industry right now relative to many other industries we might be talking about. So, you know, it’s a very big question I’m asking you here. But in terms of the things that we’ve talked about, you know, how important is it now? How important can it be or should it be, do you think, in your mind in the future? And maybe if you’ve got anything around, you know what you’re working on that Stripe that you want to throw in in terms of the role that you’re taking on there that I’d be interested to hear as well.

Zeke Hausfather [00:50:36] Yeah. So the short version of it is that, you know, carbon removal, particularly permanent carbon removal, putting CO2 back into the ground or turning into rocks is a tiny industry today, you know, something like 10,000 tons that’s been delivered since last year globally. And we know we’re going to need millions of tons for it. So it’s an area where we can have an outsized impact because it’s so nascent and sort of we know where it has to go. At the same time, you know, we’re always going to be in a world where it’s, you know, upwards of 90% mitigation, reducing our emissions and probably only 10% or so carbon removal. But the reason we know we’re going to need a decent chunk of carbon removal, at least a few billion tons of carbon removal a year, which is a very big number. Yeah, particularly compared to 10,000 today is for three reasons. One is that there’s going to be some sectors or some long-tailed emissions that’s hard to fully eliminate. You know, we might be able to get global emissions down 90, 95%, but that still leaves us with a couple of gigatons of remaining CO2 emissions per year. The second is CO2 is not the only game in town. There’s other greenhouse gases, particularly methane and nitrous oxide. And it turns out those are much harder to fully eliminate than CO2, in large part because of their sources from agriculture. You know, we can probably if we get rid of all fossil fuels, if we employ the best technologies, if we shift people’s diets, if we do all that, we can probably cut their emissions by two thirds or so. But that leaves the remaining third of methane and nitrous oxide emissions that need to be counterbalanced by something. And so we need at least a few billion tons a year of carbon removal just to balance out those. And then the final piece of the puzzle is that. One area that the science has gotten much clearer about in recent years is what we call the zero emissions commitments associated with CO2. So the good news is our best estimate now is if we get CO2 emissions down to zero, the world will stop warming pretty quickly. There’s not a huge amount of warming sort of in the pipeline or that’s inevitable. The bad news there is, though, is even if we get emissions to zero, the world doesn’t cool back down for many centuries to come without net negative emissions, without carbon removal. So the only way to deal with overshoot, the only way to ever bring temperatures back down at least over timescales relevant to human beings, is to remove carbon from the atmosphere. And so for those reasons, you know, we know we’re going to need it. We know that we’re going to need it in a world where we’ve, you know, already or where we’re already reducing emissions. You know, it certainly isn’t a replacement for reducing emissions. There’s no world where we’re sucking up 40 billion tons of CO2 from the air, which is what we’re emitting today. That would be bonkers. And God knows how many trillions of dollars. But, you know, we know that if we succeed with the mitigation side, we’re also going to need a lot of removals. And right now, it’s an area that we’ve underinvested in that we’re sort of still playing catch up to. And so that’s one of the reasons why Stripe is focussed there. And increasingly, you know, a number of other scientists and funders not to take resources away from the much needed mitigation, but to complement them by also investing in this. And, you know, we have a decade or so to figure out the space, to start scaling it up, to figure out what works, what doesn’t work, because we’re going to need these billions of tons per year by 2050 or so. We’re not necessarily need them today. And so for that reason, you know, we really want to cast a wide net. We want to try to explore a wide variety of different approaches. We want to fail fast, but we also want to be willing to fail so we can learn what doesn’t work. And to that end, you know, we recently launched this new initiative called Frontier, along with Google, Meta, Shopify & McKinsey, where we committed to spend $1,000,000,000 over the next nine years to sort of kickstart permanent carbon removal technologies, to fund, you know, a wide variety of early stage companies, to do bigger offtake agreements going forward with those that successfully deliver so they can scale up. And then to couple all of that with very rigorous monitoring, reporting and verification so we can actually track where that carbon is going and figure out, you know, does kelp sinking actually permanently reduce carbon emissions that end up back in the atmosphere in one way or another? Those sort of questions.

David Linden [00:55:02] I wish we had another hour. No, it is a fascinating topic in itself, and I’ve listened to many other people talk about it, and I’d love to maybe get you back another time to talk about that, because it certainly, you know, another whole area that people spend a lot of time talking about. But as you rightly said, it’s small now but has a huge potential and can certainly add a lot to the opportunity set of how we can reduce the temperatures on the planet. But for now, thank you so much for taking the time that you have, for not making it boring in the slightest. I have a very interesting indeed and for sharing essentially what a climate scientist does with what you guys focus on and the breadth of things there and the complexity, but also sort of, you know, looking at the pathways. And I, you know, as I think as you rightly said, that the optimistic side of things as well and what we can do to achieve it. So thanks very much, Zeke. I really appreciate it.

Zeke Hausfather [00:56:05] Oh, it’s great to be here.

David Linden [00:56:07] And thanks everyone else for listening as well. If you enjoyed that, which I’m sure you did, please do hit subscribe. Give us a great rating and share with your friends. Talk to you next time.

Zeke Hausfather [00:56:18] Thanks.



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