Is climate change an impending existential threat, or a serious but manageable problem we can tackle with innovation and human ingenuity? Zeke Hausfather joins this episode of Faster, Please! — The Podcast to explain the basics of climate modeling and give a clear-eyed assessment of the risks we face and the measures we can take.
Zeke is a climate scientist and energy systems analyst. He is the climate research lead for Stripe and a research scientist at Berkeley Earth.
In This Episode
Human impact on the climate (1:11)
Global temperature forecasting (6:33)
Low-probability, high-risk scenarios (15:07)
Reducing carbon emissions (17:06)
Carbon capture and carbon removal (25:25)
Below is an edited transcript of our conversation
Human impact on the climate
James Pethokoukis: How do we know that our planet is warming? And secondarily, how do we know the actions of people are playing a key role?
Zeke Hausfather: That's a great question. In terms of how we know it's warming: We've been monitoring the Earth's climate with reasonably dense measurements since the mid-1800s. That's when groups like NASA, NOAA, the UK Hadley Centre, my own Berkeley Earth group, have been able to put together reliable global surface temperature estimates. And we've seen in the period…
That's since the 1980s?
1850.
1850. NASA was not around in 1850.
No. But enough measurements were being taken both at weather stations around the world and on ships in the oceans that we can reconstruct global temperatures with an accuracy of a couple tenths of a degree going back that far. We know that the world has warmed by about 1.2 degrees centigrade since 1850 with the vast majority of that warming, about 1 degree of it, happening since 1970. That isn't in much dispute in the scientific community at all. Now, going further back is harder, obviously. We only invented the thermometer in the early 1700s. There are a few locations on land that go back that far, but to go back further in time, we need to rely on what we call climate proxies: things like ice cores, tree rings, coral sediments, pollen in lakes — various natural factors that are in some way related to the temperature when those things occurred.
Those have much higher uncertainties, of course, but we do know using those reconstructions that current temperature levels are probably unprecedented in at least the last 2000 years and are at the high end of anything we've seen in the last 120,000 years or so. Certainly if current temperatures were to stay at today's levels for another century, they'd be higher than anything we've seen in 120,000 years. But it's harder to precisely make those claims because the time resolution of these indirect proxy measurements is very coarse when we go back further in time. You might have one ice core measurement reflect a hundred-year average period, for example, rather than a specific year. We know from the temperature record that the world has warmed. How do we know that human activity is playing a role? Well, we've known since the mid-1800s, due to pioneering work by folks like John Tyndall or Arrhenius, that carbon dioxide is a greenhouse gas and that greenhouse gases like carbon dioxide, water vapor, methane are critical to maintain a habitable planet. Without greenhouse gases in our atmosphere, the Earth would be a snowball and life would probably not exist.
We also know that the amount of carbon dioxide in the atmosphere has increased pretty dramatically. We have measurements from ice cores going back about 800,000 years of carbon dioxide in the atmosphere at a reasonably high resolution. And because carbon dioxide is well mixed, knowing it in one location in one ice core gives us a good picture of carbon dioxide for the whole planet. And we know that prior to the year 1850, carbon dioxide concentrations in the atmosphere varied between about 170 to 280 parts per million. They're lower during ice age periods; they're higher during warmer interglacial periods. But since the 1850s, that value has increased dramatically. The amount of carbon dioxide in the atmosphere has increased by about 50 percent. It's gone from 280 parts per million, which was over the last 10,000 years since the end of the last ice age, up to about 420 parts per million today.
And that reflects a huge amount of carbon dioxide in the atmosphere. I don't think people realize quite the magnitude we're talking about. The amount of carbon dioxide that humans have added to the atmosphere by digging up stuff from underground and burning it is roughly equal in mass to the entire biosphere. We took every single bit of life on Earth and burned it. That was about how much CO2 we put up in the atmosphere since the Industrial Revolution. Or to put it another way, it's equal in mass to all of everything humans have ever built: the pyramids, every skyscraper, every road. We took all that mass and put it up into the atmosphere. That's the amount of CO2 we've emitted. And so that's had a pretty big effect on what we call the radiative forcing of our climate, essentially the amount of outgoing longwave radiation — or heat, in common parlance — that gets absorbed and reradiated back toward the surface. And the estimate…
That’s the key mechanism we're talking about here, right?
Yeah. Sunlight comes in from the sun, which provides pretty much all the Earth's energy. It gets absorbed by the surface of the Earth and reradiated as heat. That heat goes back out to space. Ideally, those two things should be an equilibrium: The amount of energy entering the Earth system matches the amount that leaves the Earth system, and the Earth stays a happy, healthy temperature. What we've seen in the last century, and we can verify this over the last few decades directly through satellite observations, is the amount of heat entering the Earth system is larger than the amount of heat leaving the Earth system. So the Earth is out of thermal equilibrium and is heating up. Most of that heat is going into the oceans, about 90 percent of it. But about 10 percent of that heat that's trapped goes into the atmosphere, and that's responsible for the warming we've seen.
The climate is a hugely complex system, and when you're trying to project the response of the climate to our emissions, you're dealing with a lot of uncertainty around what we call feedbacks in the climate system.
Global temperature forecasting
Looking forward, various climate models, which is what we use to forecast what's going to happen next, look at what we've already put into the atmosphere and what we're continuing to put into the atmosphere, and they make a forecast about how that will impact temperatures going forward. Do I have that part right?
Yep.
Okay. So based on what these models are saying, what is reasonable to expect in coming decades as far as temperature increases and their impacts?
The amount of future warming we end up having depends largely on how much CO2 and other greenhouse gases we emit. If we keep emissions roughly at current levels for the rest of the century — we're emitting about 40 billion tons of CO2 per year — if we keep that steady, we don't increase it at all, we expect somewhere in the range of 3 degrees centigrade warming by the end of the century, so that would be a bit above 5 degrees Fahrenheit warming globally, relative to the pre-industrial period or 1850. We've already experienced 1.2 degrees C. We'd have another 1.8 degrees C or so on top of that by the end of the century. If we emit more, it could be higher than that. If we emit less, it could be lower than that.
That said, that's sort of the average estimate across the 40 different modeling centers around the world that do these sort of exercises. In reality, the climate is a hugely complex system, and when you're trying to project the response of the climate to our emissions, you're dealing with a lot of uncertainty around what we call feedbacks in the climate system. As an example: As we warm the surface, we get more evaporation and the atmosphere can hold more water vapor before rain falls out as the air is warmer. This is a fairly well-known physical relationship. And so for every degree of warming, you get about 7 percent more water vapor in the atmosphere. Now, water vapor itself is a greenhouse gas, and so that enhances the warming the world experiences. Because it's warmer, that water vapor can stay in the atmosphere — because usually the water vapor itself is very, very short-lived and can't force the climate by itself because it just rains out if you get too much.
There are also uncertainties in how clouds respond to our emissions. More water vapor in the atmosphere leads to more cloud formation in some regions. Higher temperatures and changing wind patterns lead to changing cloud dynamics. Our emissions of other things like aerosols, small particles from burning fossil fuels also affect cloud formation. And how that all pans out and how those clouds change the balance of heat trapped versus heat reflected varies a lot across models. And for all these reasons, we like to give a range of what we call climate sensitivity, which is essentially, how sensitive is the climate to our emissions? And we usually define that as, if we double the amount of CO2 in the atmosphere — which is roughly what we're on track for by the end of the century today, we've already increased it by 50 percent — how much warming do we get at equilibrium? And that value is generally around three degrees C per doubling of CO2, but with a pretty wide range. In the most recent IPCC report, we said it could be anywhere from 2.5 degrees C at the low end of the likely range to about 4 degrees at the high end, 2 degrees to 5 degrees is the sort of very likely range that we gave in the most recent IPCC report.
I recently watched an Apple TV+ miniseries called Extrapolations, and it looked at climate change and how it would affect us over the entire century. That was the number they really fixated on: 3 degrees Celsius. The environment they showed was pretty chaotic: lots of very, very bad heat waves, hurricanes, flooding. Civilization wasn't going to get wiped out or anything, but it seemed pretty nasty. So are we talking kind of really nasty climate effects from three degrees of warming Celsius?
When we say 3 degrees, it sounds like a very small number, especially to us Americans are used to talking about things in Fahrenheit. But even when we think about the temperature from day to day, it might change, let's say 5.5 degrees Fahrenheit tomorrow, and that's noticeably warmer; 5.5 degrees Fahrenheit is the difference between 85 degrees and a bit above 90 degrees, but it doesn't sound huge. But the problem is, that's a global average number and no one lives in the global average. In fact, the global average is mostly the ocean. It turns out that where people do live, on land, is warming about 50 percent faster than the world as a whole. So if we talk about 3 degrees centigrade — or let's talk Fahrenheit for a moment, let's say 5.5 degrees Fahrenheit — over land, increase that by 50 percent, so let's say 8 degrees Fahrenheit globally over land where we all live. Even higher than that in high-latitude regions like the Arctic. We have bigger feedbacks associated with snow melting and exposing darker surfaces, so some regions are going to see really big changes.
To put this number in perspective, the last ice age, which I think everyone would acknowledge was a very different planet than we have today, was only about 6 degrees centigrade colder than current temperatures globally. Obviously it was much colder in the northern latitudes, which were covered by ice sheets, but the tropics were not that much colder. And so it averages to about 6 degrees difference. So that would have impacts. Exactly what those impacts would be depends a lot on the systems we're talking about and the adaptive capacity of those systems.
The natural world, I think in many ways, is going to be the worst hit by these changes. There are a lot of plant and animal species that live in fairly narrow ecological niches. And particularly in a world that's very fragmented by roads and human habitation, it's a lot harder for those plant and animal species to migrate to more temperate regions to be able to survive. So certainly there's a concern around large-scale extinction of many plant and animal species that can no longer live in the ecological niches that they've adapted to over the last tens of thousands of years and can't migrate quickly enough to adapt to that.
In terms of impacts to human systems, there's a lot of different impacts from climate change and the degree to which those are catastrophic is going to depend a lot on how wealthy we are and how well we can adapt to it. If by the end of the century we're in a world that's similar to today, that has huge amounts of inequality with billions of people living at a dollar a day, I would worry a lot about the ability of people in those societies to adapt to more widespread extreme heat events, larger floods associated with more water vapor in the atmosphere, sea level rise, some of these other impacts. If we live in a world where we're all very wealthy and relatively equal on a country-by-country basis and within countries, then we have a much bigger ability to build sea walls, to have air conditioning inside, to genetically engineer crops to be more heat tolerance, the many other ways that humans can adapt to these changes.
And so I think in many ways I see climate change less as an existential risk by itself and more as an existential risk multiplier. If we are in a world of weak institutions, of failing governments, of high inequality, I see climate as something that could help push societies over the edge. But I don't necessarily think at least a 3-degree world would be one that is the end of civilization by any stretch of the imagination, if we get our act together on these other issues.
What is what you described as what is sort of the “business as usual” forecast, and then what is the, we really get serious about policy, and we can talk about what those policies are, that reduce carbon emissions?
The good news is “business as usual” has already been changing a fair bit. Nowadays, it looks like business as usual is global emissions staying relatively flat. A decade ago, it seemed like doubling or tripling global emissions by the end of the century would not be out of the question. Certainly if you extrapolated the trends from previous decades, that's where we were headed. Nowadays, global coal use has largely plateaued and arguably is going to shrink in coming years. We have cheaper alternatives. Electric vehicles are taking off. There are many other technologies that are being developed and becoming increasingly cheap. And so it's harder to imagine a world where we're still burning massive amounts of coal, oil, and gas in 2100.
We can reduce emissions, we can develop new technologies, and we can get them widely adopted. And if we do that and if we get emissions to zero by, say, 2070 or so globally, then we limit warming to below 2 degrees.
Low-probability, high-risk scenarios
Does that make the very worst-case scenarios that maybe we were talking about a decade ago just highly unlikely?
It certainly makes the worst-case emission outcomes highly unlikely. If we look at 3 degrees, for example, that could really end up anywhere between 2 degrees and above 4 degrees if we get unlucky because of the uncertainty in how the climate system responds to our emissions, because the Earth is such a complex system. Climate change is both planning for the central outcome but also trying to mitigate those risks. In some ways, we want to reduce emissions not just to get that mean down, but also as an insurance policy against the 5 or 10 percent more catastrophic potential outcomes there. I don't think we're necessarily completely out of the woods on a 4 C world by the end of the century if we roll sixes on all the proverbial climate dice, but I think we have made a lot of progress in making those outcomes less likely.
Today we're headed toward, as I mentioned earlier, about 3 degrees of warming if emissions stay relatively constant, or a little bit below 3 degrees. But we can do much better than that. We can reduce emissions, we can develop new technologies, and we can get them widely adopted. And if we do that and if we get emissions to zero by, say, 2070 or so globally, then we limit warming to below 2 degrees. If we get emissions to zero by 2050, which is going to be a much harder lift given the amount of infrastructure in place today that relies on fossil fuels, then we could limit warming to maybe about 1.6 or 1.7 degrees. And if we build lots of machines to remove carbon from the atmosphere, plant lots of trees, do other things to actually get negative emissions, models suggest we could get temperatures down to 1.5 degrees, only 0.3 degrees above where we are today, by the end of the century.
We are really on this acceleration of private sector and government spending on these technologies. But I think government does play a role here. I think most economists would acknowledge that what we're dealing with here is an externality.
Reducing carbon emissions
When I look at what our responses might be, I tend to think, what will happen to emissions in a world where our responses will be constrained by our low collective tolerance for suffering and pain and deprivation and sacrifice? To me, that's a pretty important constraint. If there's one lesson I think we learned from the pandemic, it’s people don't like shortages. We don't like to rough it in any way. In a world where, at least in the West, that's our attitude, how do we get emissions down in a somewhat timely manner?
I think a lot of it relies both on the combination of human ingenuity and governments playing a role in catalyzing that ingenuity and allowing these technologies to scale. We've seen the biggest successes in mitigating climate change in technologies that slot in nicely to replace things that we enjoy today. We don't talk about it much, but Texas is the renewable energy capital of the US today, because it's cheaper to generate electricity with the wind and sun there than it is to burn coal and gas. Similarly, we've seen an explosion of electric vehicles in places like China and Europe, and the US is catching up, not necessarily because everyone there is a tree hugger, but because they're really fun to drive and they perform better and are lower cost in some cases than conventional vehicles. The more we can follow that model of developing new technologies that don't involve sacrifice, that don't involve necessarily giving up things we enjoy today, I think the more successful we're going to be.
And that's led to a lot of money being spent on these things. In the last year, the globe spent about $1.1 trillion on mitigation technologies: renewable energy, electric vehicles, nuclear power, heat pumps, all that sort of stuff. That's up from $200 million a year or so a decade before or 15 years before. And so we are really on this acceleration of private sector and government spending on these technologies. But I think government does play a role here. I think most economists would acknowledge that what we're dealing with here is an externality. And by an externality, I mean it's something that has a social cost, but no one individually pays for it when they put carbon dioxide or other emissions in the atmosphere.
So there has to be some role of internalizing that externality, either through (as economists would like to do) a price on carbon, or in a world where you can't do that for many reasons, subsidizing the good stuff to essentially account for the benefits it has of displacing fossil fuels, both in terms of their affecting climate change, but also conventional pollution. I think we discount a lot, particularly living in a place like the US, which has done a lot of work on this, how disastrous fossil fuels are for public health. There's somewhere in the range of a couple million people dying prematurely globally from pollution, particularly outdoor air pollution. And if you go to a place like India or China and walk around outside, it's pretty catastrophic some days in terms of the brown soup that is the air. We get a lot of co-benefits by cleaning up these conventional pollutants, particularly in places like Southeast Asia or South Asia, as well as reducing emissions of greenhouse gases.
Reducing emissions, going to zero emissions, pulling emissions out of the air: Do these scenarios work with just renewable energy sources or is this a world that's using nuclear energy in some form far more than we currently are?
So I think we necessarily need a variety of energy sources here, and there's been a lot of work done in recent years by the energy modeling community on this front. Renewables are great. Solar is super, super cheap; to be honest, a lot cheaper today than any of us thought it would be a couple decades ago. Wind is increasingly cheap. But they're also intermittent. The sun doesn't shine all the time; the wind doesn't blow all the time. Batteries are part of the solution to deal with that, but they're not a perfect solution. We tend to find that you get a much lower cost in scenarios where you also have a sizable chunk, maybe 20, 30, 40 percent, of your energy coming from what we call clean firm generation. Things like nuclear, like enhanced geothermal, potentially fossil fuels with carbon capture and storage, though those have some challenges in implementation, to support large amounts of renewable energy on the grid.
You end up with a much more expensive system if you try to shoehorn in 100 percent renewables, and to be honest, it's pretty unnecessary. So I think we are going to see, and we're already starting to see, bigger investments in things like next-generation nuclear. I think we just need to figure out how to build them on time and on budget. The biggest problem with the nuclear industry in the US — certainly regulations have contributed to it — but I think it's just our inability to build these giant, bespoke megaprojects. Nuclear goes super over budget for the same reason the “Big Dig” in Boston does: You have this 10-year-long, many, many billion-dollar megaproject that has construction delays and all these other problems. The more we can learn from what renewables have gotten right, make things small, modular, pumped out in an assembly line, and less contingent on these giant construction projects, I think the better outcomes we'll see for things like nuclear.
There's an economist, he passed fairly recently, Martin Weitzman from Harvard, and he wrote about the economics of climate change. And there's one quote that always sticks in my mind. He wrote that “Deep structural uncertainty about the unknown unknowns of what might go very wrong [with the climate] is coupled with essentially unlimited downside liability on possible planetary damages” and a “non-negligible” probability of a “collapse of planetary welfare.” He's talking about, you can't write off the possibility that we get some very bad outcomes. And I guess that's what worries me: If we're doing something to the atmosphere that we've never done before, what if the models are wrong and we get something really catastrophic, that really becomes a true existential risk? How much should I worry about that?
I think we're all worried about unknown unknowns. For me, the odds of those happening, which are somewhat unknowable by definition, increase the more we push the Earth out of the climate we've seen for the past few million years. Right now we're around the range of what we saw in the Last Interglacial Period, about 120,000 years ago. If we get temperatures up to 3 degrees centigrade globally, we will be out of the range of anything we've seen for the last two million years or so, if not further back. And we know if we go further back into the Earth's history, there's some scary stuff back there. There are periods where we see very rapid increases of temperature associated with 90 percent extinction of all life on Earth, like the Paleocene/Eocene Thermal Maximum. And we don't have great explanations for all these things. A good example is, for warmer periods in the Earth’s past, we think there's a mechanism where if temperatures get high enough, maybe 5 degrees above where they were in the pre-industrial period or a bit above 4 degrees above where we are today, suddenly all the stratocumulus cloud decks that cover much of the Earth's oceans disappear. And that leads to another 4 degrees warming on top of that. That sort of behavior seems to help explain some of these rapid warming events in the Earth's more distant past.
Now, we think we're pretty far from experiencing something of that today. But maybe our models are wrong, or maybe the Earth is much more sensitive than we think. And again, rolling sort of sixes on the climate sensitivity and carbon cycle feedback dice leads us into those sorts of conditions. And so Marty Weitzman, who I did have the pleasure of knowing before he passed, had a great phrase to sum up that quote, which is that “when it comes to climate change, this thing is in the tail,” which is a very nerdy way to put it: The tails of these probability distribution functions, the low-probability but high-impact events, are really what should drive a lot of our concern around this and push us to reduce emissions more than we otherwise would if we were just planning for the most likely outcome.
But whenever we talk about carbon dioxide removal, it is always important to emphasize that this stuff is expensive and it only makes sense to do at scale in a world where we're already cutting emissions dramatically.
Carbon capture and carbon removal
People will say, “What if the models are wrong?” and they assume they're only going to be wrong to the benefit of humanity. Maybe they're wrong to the detriment of humanity.
We talked a little bit about reducing these emissions. You have carbon capture, where you pull it out of the air. How close is that technology to being something that can scale?
When we talk about carbon capture, that's often a different thing than when we talk about carbon removal. Carbon capture generally means taking an existing fossil fuel plant…
That could be trees too, right?
Yeah, but carbon capture is mostly taking an existing fossil fuel plant like a coal, oil, and gas plant, sticking a unit on that captures the carbon coming out of it, and putting that underground. And there's a lot of funding for that in the new Inflation Reduction Act. The record on that over the last few decades has been a bit mixed. It's been hard for folks to make the economics work in practice. It's really complicated technically, but a lot of folks are confident that we can get there with some of those technologies. If a coal plant with carbon capture is going to be cheaper than a nuclear plant or renewable plant is a separate question. And I'm a lot more skeptical on the economics of carbon capture there.
Now, carbon dioxide removal is a slightly different thing. And there we're talking about technologies that don't stop emissions from coming out of a smokestack, but instead take carbon that's already in the atmosphere and pull it back out. And most of our models suggest that we are going to need a lot of that down the road, in part because we can't fully get rid of all of the emissions from all of the parts of our economy. And the real challenge with climate change, or what I like to call the “brutal math” of climate change is that as long as our emissions remain above zero, the Earth continues to warm. CO2 remains in the atmosphere for an extremely long period of time; it takes about 400,000 years to fully clear out a ton of fossil CO2 we emit today through natural processes. So we end up needing a lot of carbon removal to both balance out what we call residual emissions and potentially to deal with overshoot. If we figure out that we really don't want temperatures to go above 1.5 degrees, but they're headed toward 1.7, we're going to have to pull a bunch of carbon out of the atmosphere to bring temperatures back down. It's only a small part of the solution. Maybe 10 percent of the solution to climate change writ large is carbon dioxide removal. But for a problem as big as climate change, 10 percent still matters a lot since solar is probably 20 percent, electric vehicles are probably 20 percent, heat pumps might be 10 percent.
And there's a lot of technologies people are developing to do that. Direct air capture is the one that gets a lot of press: the sort of big fans that suck carbon out of the air, though they're incredibly energy intensive. But there are a lot of ways that leverage natural processes as well. Planting trees is a good one, though it has a lot of challenges in keeping the carbon in those trees in a warming world, particularly as we see more wildfires, more pine bark beetle outbreaks that used to die in cold winter temperatures and don't anymore. And so it's hard to justify planting trees as a way of permanently taking carbon out of the atmosphere, but it's still quite valuable. There's also a lot of interesting work being done around using biomass to sequester carbon, so taking residues from commercial timber operations, burning them, and putting their carbon content underground. Something called BECCS, or bioenergy with carbon capture and storage, that a lot of people are excited about.
Then there are other interesting ways to leverage the natural carbon cycle. For example, over long periods, the weathering of certain types of rocks like basalt or olivine drives a lot of atmospheric CO2 absorption over the course of millions of years. And so a lot of scientists are trying to figure out ways to speed that up. If you take rock dust and spread it on farm fields, it can help manage the pH of soils, it can add some nutrients. And it turns out that as that basalt dust weathers, it absorbs carbon to the atmosphere, it turns it into stable bicarbonate and then flows out to the ocean and eventually forms limestone on the bottom of the ocean. Stuff like that, or adding alkalinity directly to the ocean to counteract ocean acidification, can also lead to more CO2 uptake from the air, because the amount of carbon dioxide the ocean absorbs in the atmosphere depends on how acidic the surface level of the layers of the water are.
Scientists are working on tons of different technologies here. And actually my day job these days with Stripe and Frontier is helping support companies to do that. So there's lots of exciting stuff there. But whenever we talk about carbon dioxide removal, it is always important to emphasize that this stuff is expensive and it only makes sense to do at scale in a world where we're already cutting emissions dramatically. If you keep burning fossil fuels willy-nilly and spend a ton of money on a bit of carbon dioxide removal, it's not going to make any difference.
Why are you interested in this subject?
I think it's an underexplored area. Certainly until the last few years, no one was really putting any money or resources into it at scale. And it's something that is going to have to be an important part of the solution in the next few decades, and so I think this is the decade that we should be spending resources to figure out what works and what can scale for decades to come. We probably should spend about 1 percent of the money we spend on reducing emissions, but historically we've been spending a lot less than that.
And why are you also more broadly interested in the entire topic of climate change rather than, I don't know, tax policy or something?
I come to it from a scientific background. I just find the Earth's climate fascinating. It's super complex. It's hard to fully understand. We've really made leaps and bounds in progress over the last few decades, but there's so much we still don't know. And so it's just a fascinating area from a scientific standpoint, but it's also one where the importance to the society is quite large. I try not to wade too much into the policy solutions to it, but certainly helping understand the likely impacts of our actions affects a lot of choices that policymakers and others make. There's no one right answer. To your question earlier, people debate renewables versus nuclear and all these other things. Knowing what the impacts of climate change are, what the risks are, and how we can actually get to certain outcomes based on our decisions, I feel like is really important to set the stage for people to use the science in the real world. And it's exciting to work in an area of science where there is a practical, real-world application of it. And not just studying one plant species that lives on top of one mountain in a remote part of the world. We're looking at these big questions that affect everyone over the next century.
🌎 My chat (+transcript) with climate scientist Zeke Hausfather