News - Belfer Center for Science and International Affairs, Harvard Kennedy School

Climate Science Doesn't Support 'Doomers', Says Scientist Michael Mann

| Apr. 04, 2024

There's still time to avert catastrophic global climate change. The greatest threat to meaningful action is despair among those who care about the climate, according to renowned climate scientist Michael E. Mann. 

“I push back on doomism because I don’t think it’s justified by the science, and I think it potentially leads us down a path of inaction,” said Mann during a March 28 talk at the Belfer Center. “And there are bad actors today who are fanning the flames of climate doomism because they understand that it takes those who are most likely to be on the front lines, advocating for change, and pushes them to the sidelines, which is where polluters and petrostates want them.”

Mann’s lecture, “Can Lessons from Earth’s Past Help Us Survive Our Current Climate Crisis,” examined climate-driven extinction events in Earth’s history for insights into how we can combat our current climate crisis. He also sought lessons from more recent touchpoints: Carl Sagan, nuclear winter, and music by The Police.

Read the Harvard Gazette’s coverage of the event.


  • Read an edited and condensed transcript of Professor Mann's lecture

    Cristine Russell: It's really a privilege of mine to have been able to get Professor Michael Mann, one of the leading climate scientists in the world, to come up to the Kennedy School. He's going to talk about his latest book, Our Fragile Moment: How Lessons From Earth's Past Can Help Us Survive the Climate Crisis

    Dr. Mann is the Presidential Distinguished Professor in the Department of Earth and Environmental Science at the University of Pennsylvania, with a secondary appointment in the Annenberg School for Communication. And he directs the Penn Center for Science, Sustainability, and the Media. It is very, very special to have scientists who can not only talk about their science, but can talk about it in a way that a general audience can understand and appreciate.

    Many of you will have read of his recent legal victory in the defamation suit in which he was awarded $1 million in damages. That was a front page story everywhere. But it was a very daring effort for him to bring that suit, and he has always been willing to speak the truth about science. Thank you so much for being here.

    Michael Mann: Thanks so much, Cris. Thanks to the Belfer Center and to the Kennedy School. It's great to be here again talking about more or less the same problem, the climate crisis. It's been six or seven years since we talked about The Madhouse Effect here. And of course, we're much further down the road than we would like to be at this point. That's partly what makes this such a fragile moment. 

    I think we can appreciate that we are in a fragile moment in many senses right now: with respect to global democracy, and democratic governance here in the United States. For many of the problems that we care about, including the climate crisis, there is likely no path to addressing those problems that doesn't require global democratic governance. But there is no greater challenge than the challenge to maintain a livable planet.

    Part of what makes this moment so fragile in that sense is that we developed our modern civilizational infrastructure over the last 6,000 years or so. The first city-state emerged in Mesopotamia 6,000 years ago. And so we have had this remarkably stable global temperature curve. There have been regional climate changes that have had an impact on civilizations, but there was always somewhere you could move to escape from that. Today’s warming and its consequences are global. There is no place to escape to, and that's what makes this such a fragile moment. We are dependent on the stability of the climate during which we developed the global infrastructure that now serves more than 8 billion people on this planet, and we are rapidly changing the climate and potentially undermining that infrastructure.

    My book is about various episodes in our past and what we can learn from them with respect to the climate crisis and more. But let's first talk about where it all began nearly 4 billion years ago. Of course, our moment, in a sense, began when primitive microbial life emerged from the primordial ooze, but there were other moments that were critical.

    One important event is the boundary between the Paleocene and Cretaceous. We used to call it the KT boundary, now we call it the KPG boundary. For reasons I won't get into, the terminology has changed. But we're talking about the asteroid that struck earth and killed off the dinosaurs. Or let's be careful, the non-avian dinosaurs, because you can still see dinosaurs out the window if you look hard. But all of the other dinosaurs and any fauna that were larger than, say, a mid-sized dog perished during this cataclysmic event. But it created a niche for small mammals to emerge, and ultimately, those small mammals evolved into modern day human beings. So in a sense, what was bad for the dinosaurs was good for us. There were winners and losers, at least in this scenario. We'll come back to that.

    Another important event was the Paleocene-Eocene thermal maximum. The PETM was a period of rapid warming about 10 million years after the demise of the dinosaurs. In a geological sense, it was rapid. It occurred over tens of thousands of years. Of course, the warming that we're seeing today is occurring over tens of years, a hundred times faster than the most rapid event that we can find in geological history. It's important to keep that in mind. But the PETM warming actually created an expansion of rainforests, of tropical rainforests. Warming often leads to miniaturization, and so there was a niche in this very warm environment for the emergence of the first primates. Dryomomys, who you can see there, would fit on your fingertip. Tiny little primate, but it was the first primate, our distant ancestor.

    There are lots of other events that we can talk about, but both of those are interesting from a climatic standpoint as well. So we'll return to them, the KT or KPG impact event and the PETM. What can we learn from them?

    All right. "Mighty Brontosaurus: Don't You Have a Lesson For Us?" Show of hands, who gets the cultural reference? The Police. So there are a few people out there who get the cultural reference. I was a child of the '80s. I grew up listening to The Police and Sting. I'm going to play one of the tracks off of the album Synchronicity. That'll be important, synchronicity, we'll come back to that. 

    (“Walking in Your Footsteps” plays)

    Gordon Sumner, otherwise known as Sting, wrote the lyrics to this song on the island of Montserrat in December 1982. The timing will become important here. We'll forgive him for a little bit of poetic license: the KT event was actually 66 million years ago. And brontosaurus actually went extinct around 150 million years ago. We are closer to the KT boundary than brontosaurus was. But we will forgive a little bit of artistic license because there's a profound point that's being made here.

    As we know, an asteroid strikes the planet. We now know Chicxulub in the Gulf of Mexico was the site. What happens when a huge impactor strikes the planet with great force? There are actually simulations of the shock wave that would have traveled around the world. There would have been huge windstorms, firestorms, massive devastation. Just over the last few years, we have found direct evidence of that. There's a site, Tanis, in southern North Dakota, which was discovered some years ago. A few years ago they actually recovered the whole leg of a dinosaur. On the bottom there, you see the skin of a triceratops. There was a preserved egg with a preserved embryo of a flying pterosaur and a fragment of the asteroid. We've actually seen now the direct evidence of that impact event.

    This would've been devastating. In this case, there was what appears to be a torrent of water and mud, and all these creatures got caught up in it and ultimately preserved. So there would've been events like this around the planet, but that wasn't what caused the extinction of the dinosaurs. Alvarez and Alvarez in 1980 were starting to think about how there would have been a huge amount of dust ejected into the atmosphere. It would've blocked out some sunlight, leading to a decrease in photosynthesis. But it was actually a couple years later that Toon, Pollack, Ackerman, and Turco demonstrated that what killed the dinosaurs was likely a massive cooling event from all of that particulate matter reflecting sunlight back to space, chilling the planet. Anything that wasn't small enough to burrow and escape the cold perished. That's become the prevailing understanding. That was put forward in 1982.

    A year later, Turco, Toon, Ackerman, Pollack, and the great Carl Sagan showed that the massive detonation of nuclear devices would similarly eject large amounts of particulate matter into the atmosphere, reflecting away the sun, leading to global cooling, or what Sagan described as nuclear winter. It became very important in the debate over nuclear escalation because, suddenly, we had an impact that would be global. It wasn't just the physical destruction if you happen to be near a strike target or the radiation. Nobody could escape the global impact of nuclear winter. It played an important role, actually, in spurring policy progress between Ronald Reagan and Mikhail Gorbachev at the time.

    Turns out, though, there were actually other scientists who were onto this earlier. As far as I understand, our good friend here, John Holdren, was a co-author on the first scientific publication that hypothesized a nuclear winter scenario back in 1977. Sagan, Toon, and the others here brought a modeling approach, the same approach they had used to study the KT impact event that killed off the dinosaurs. They used a similar climate modeling framework to look at this nuclear winter scenario. So it was actually a quantitative estimate of the impact, and that was an important development here.

    Sagan felt it was important enough that he decided to basically initiate a publicity campaign to alert the world to the threat of nuclear winter, that we could not survive a massive global thermonuclear war. Nuclear winter would potentially be a civilization-ending consequence of the escalating arms race. He brought widespread attention to the issue of nuclear winter in late 1983. 

    Of course, Sting wrote the lyrics to “Walking In Your Footsteps” a year earlier, in December 1982. He would not have been aware, I think, of the science of nuclear winter. So it was oddly prescient in that the true relationship between these events - the meteor impact that killed off the dinosaurs and the threat of human extinction from a global thermonuclear war - was the cooling impact of the massive input of particulate matter. Comparing, as the song does, the demise of the dinosaurs to our potential demise is far more direct and rigorous than, I think, Sting and The Police realized at the time that that song came out.

    So here we have two events that are not causally connected. There's no causal relationship between the KT or KPG impact event 66 million years ago and the threat of nuclear winter in the 1980s. They are causally disconnected, but they're meaningfully related. There's a term for events that lack a causal connection, but are meaningfully related. Synchronicity, the title of that album.

    The difference here is that we can do something about it. The dinosaurs had no agency. They couldn't do something about their impending doom. There were no actions that they could take. They couldn't have understood what was happening. We don't have that excuse today. We are faced with the threat of climate change. Ironically, not a cooling impact, but the warming effect of increasing greenhouse gas concentrations. It drives home a key point. It doesn't actually matter the direction of that climate change. Massive cooling, massive warming, anything that takes you away from the climate that you're adapted to is a threat. There are a lot of interesting connections here. Here is an indication of the threat posed by climate change. Early generation climate models that were used in these nuclear winter calculations today have evolved to the models that we use to project the impacts of fossil fuel burning and human-caused climate change.

    One other event that I will talk about before I try to wrap this up: The Great Dying Wasn't So Great. This is the end-Permian extinction that happened about 250 million years ago. By far, the most widespread extinction event that is preserved in the geological record. As we go farther back, it's a little more difficult to estimate how many species, for example, were lost in a particular event. But 90% of all species perished, 90% of all species on this planet, and 96% of all marine species, of all ocean life, perished during this event.

    Why is it important? Is it an analog for human-caused warming? It's often been pointed to as one. There has been a suspicion that this event was driven by the massive release of methane from the warming of the oceans. Methane is a very potent greenhouse gas, at least on shorter timescales. It's been posited that this methane bomb is what was responsible for the very high rate of extinction. This is sometimes used as an analog for what's happening today. We’re warming the Arctic and the permafrost and methane is escaping into the atmosphere. That's no doubt true. It is what we call positive feedback: there's extra warming that is coming from that. But there's no evidence that it is the dominant cause of any warming we've seen thus far or any warming we're likely to see over the next several decades. The dominant cause of the warming today is carbon dioxide and carbon pollution from fossil fuel burning.

    The climate doomers say that we only have 10 years. This claim was made almost 10 years ago, so look at your calendar. Guy McPherson, a very prominent player in climate doomism, argues that this runaway methane event is already underway. We can't stop it, and it's going to cause exponential warming and lead to the extinction of all life on this planet. There are huge numbers of people who buy into this framing. There are climate advocates who buy into this framing, that it's too late, the methane bomb has emerged, and we know it can happen because it's what happened during the PETM. 

    What does the science actually tell us? First of all, part of the reason that there were such high levels of extinction in the ocean is the geochemistry was very different from today. It's very unlikely we would see the same sort of thing from warming today. Back then, there were lower levels of atmospheric oxygen. Deoxygenation of the ocean led to an increase in hydrogen sulfide from anaerobic bacteria. Hydrogen sulfide is what makes a stink bomb or the smell of rotting eggs. Basically, this was a global stink bomb, as my colleague Lee Compass has argued, that contributed to the massive die-off of ocean life. That's not an analog for anything that we think is happening or can happen today.

    What about the warming? We now know it wasn't a massive release of methane. We can determine using geochemical isotopes what the source of the carbon buildup was. It was carbon dioxide from massive volcanic eruptions in Siberia that happened not over tens of years, but over thousands of years. But still, a massive input of carbon dioxide into the atmosphere, the same greenhouse gas that we are producing much more rapidly today through fossil fuel burning.

    If you compare proxy evidence for the warming that occurred and you try to fit climate models to it, what you find is that the warming that we estimate happened at that time is entirely consistent with what models predict the warming should be, given that input of carbon dioxide into the atmosphere. Around three degrees Celsius or five and a half Fahrenheit for doubling of CO2 concentrations. We call this climate sensitivity. It's a measure of how sensitive the climate is to our carbon emissions. The PETM actually reinforces our understanding of the relationship between these two things. It reaffirms the models that we use to project climate change today. So no, the PTM doesn't indicate that a runaway methane bomb has commenced and there's nothing we can do about it, it actually reaffirms our understanding of the relationship between CO2 and temperature.

    But we see a lot of headlines these days. Just last week, a colleague of mine wrote a piece in Nature implying that we don't quite understand what happened in 2023, how it got so warm. The world is warming faster than scientists expected. I've been pushing back on that.

    These are the latest state-of-the-art models used in the last IPCC report called CMIP6. The red is the observations. You can see the spike at the end from the recent El Nino event. We're already turning around, headed in the opposite direction, towards La Nina. We'll see how long it takes to happen. It looks a lot like what happened in 2016, actually. Big El Nino event, warming spike, then cooled back down. If you look at the overall trajectory of that red curve, it's right in the center of the model projections. The observations are entirely consistent with the model projections, and that's bad enough. The truth is bad enough. Because if you look at the impacts of continued warming along this trajectory, they will be devastating. The consequences of that warming will be devastating. We don't have to exaggerate the science to make an argument for urgency. It's already there.

    I push back on doomism because I don't think it's justified by the science, and I think it potentially leads us down a path of inaction. If you really think you have no agency in addressing a challenge or problem, then you might just give up. There are bad actors today who are fanning the flames of climate doomism because they understand it takes those who would be most likely to be on the front lines advocating for change, and pushes them to the sidelines, which is where polluters and petrostates want them. 

    My good friend, Harvard professor Naomi Oreskes, has done much of the work in exposing what the fossil fuel industry knew. This is a graph that appeared in a report back in 1982 that correctly projected the increase in CO2 and the warming that would result from it. Decades ago, it was spot on. It wasn't the IPCC, it wasn't me, or a calculation by John Holdren or any of our colleagues. This was from an internal report by ExxonMobil's own scientists. Now, these aren't my words, these aren't Al Gore's words, these are the words of ExxonMobil's own scientists, who describe the potential consequences of business as usual fossil fuel burning and the warming that would result. They used the word catastrophic. 

    And of course, ExxonMobil publicized that report and raised... No, of course they didn't do that. They buried the report, they fired the division, and spent tens of millions of dollars, along with other fossil fuel companies, in attacking the science and attacking scientists who were coming to the very same conclusion that their own scientists had internally come to. It's not an old tactic. We saw the tobacco industry do this and we see the fossil fuel industry do this.

    This ski slope diagram depicts what we would have to do with our carbon emissions if we had acted two decades ago, back in 2000. You can see we could have brought our carbon emissions down pretty gently. That's a bunny slope. I can handle that. Now what do we have on our hands if we're trying to keep warming below truly catastrophic, one and a half Celsius, three degree Fahrenheit warming? We've got a black double diamond slope on our hands. We've got to bring carbon emissions down by 50% this decade and down to zero by mid-century. That is the opportunity cost of decades of relative inaction thanks to ExxonMobil and other bad actors.

    But that isn't a reason to give up hope. We have made some significant progress in recent years. If every country makes good on the commitments it made at COP26, that will keep warming likely below two degrees Celsius. There are two caveats there. Two degrees Celsius is still too much. We really want to keep warming below 1.5 Celsius. And these are promises made, not yet promises kept. There are reasons to be a little disappointed, for example, in the last conference of the parties and the lack of progress that we've seen since COP26.

    But it's not too late for us to take the actions to keep warming below one and a half Celsius. The obstacles at this point aren't physical, they are not technological, they are entirely political, and political obstacles can be overcome. College students have played and continue to play an important role in some of the great social movements. In fact, here at Harvard, students have organized to help encourage the administration to divest of fossil fuels, and that is now propagating through the Ivy League. It'll eventually reach Penn, I'm pretty sure. We're still waiting on that.

    But really, it's about acting before it's too late. It's about the future that we want to leave behind for our children and grandchildren. We could leave behind a truly degraded planet or we can leave behind a still thriving vibrant planet. It's in our hands. It's up to us. Thank you. 

    (Fireside chat with Cristine Russell begins)

    Cristine Russell: As journalists, we often write stories about bad thing happenings because of climate change. How are you an optimist about the global effort to slow down global warming? Or are you an optimist?

    Michael Mann: My friend, Christiana Figueres, who's the former head of the UNFCCC, describes herself as a committed optimist. She refuses to be a pessimist as long as there's a window of opportunity. So I would reiterate the point that I've made. If the physics was such that we could no longer keep warming below catastrophic levels, then as a scientist, I would have to say so. I have to be truthful to what the science says. I'm not an expert on technology, but I follow the experts in this field. John Holdren has done a lot of important work. People like Mark Jacobson at Stanford and others have looked at whether the transition is possible. And it is, so the limitations are not physical, they're not technological, they're political.

    The danger here is that this becomes a self-fulfilling prophecy. We decide that it's too late to do anything. If we decide that, then we will not garner the political will to take the actions that are necessary. Moreover, we start to become desperate. When we become desperate, we start talking about things like geoengineering. We talked about the role of aerosols, particulate matter that cools the planet. Well, maybe we should just shoot huge amounts of particulate matter into the stratosphere to try to cool the planet. What could possibly go wrong? Maybe we should play around with ocean ecosystems to try to change the uptake of ocean biota, carbon fertilization. It turns out if you were to study some of these schemes, they could end up, for example, favoring red tide algae that caused massive deoxygenation events in the ocean.

    We're talking about toying with a planet that we do not understand perfectly. To me, that is deeply unethical because there is no planet B. There is no other planet we can go off to if we screw this one up. The idea of “Let's just colonize Mars” - there are some very powerful and influential people today who are pushing in that direction, almost as if it doesn't matter if we screw up this planet because we'll just screw up another planet.

    Cristine Russell: How would you evaluate the Biden administration and its efforts to do something about climate change?

    Michael Mann: I actually think that they've done quite a bit, given the obvious constraints, by passing the Inflation Reduction Act. A lot of us would've liked to have seen somewhat more teeth in the IRA in particular. There's a fair amount of carrots for renewable energy, but there should be some stick for the fossil fuel side. We've got to de-incentivize fossil fuel infrastructure. Some of that stick was negotiated out of the agreement to secure the 50th vote in the Senate from a coal state Democrat, in name only.

    The IRA was the strongest bill that, I think, the president could have negotiated through Congress and signed. Republicans are going to try to throw every monkey wrench that they can, but if it's implemented in full, it would lead to about a 40% reduction in carbon emissions. That's significant progress. And that's mostly by incentivizing renewable energy. It's not enough progress. 50% reductions is what we need globally. By the way, the legacy polluters like the United States have to do more than the global average because we've had a greater role in the carbon pollution thus far.

    Cristine Russell: Is the Biden administration’s big push for EVs and hybrids going to make a difference? Already, it's been politicized by people who think that it's taking choice away. What's your sense of EVs? Do you have an EV?

    Michael Mann: We have a hybrid and our next one is going to be a full EV. By the way, we elect to pay a little extra and get all of our electric power from renewable energy. So when we power up our electric hybrid, we're powering it off of wind and solar. You shouldn't have to pay extra for that. That's part of the problem. The incentives should actually be for us to make decisions that are better for the planet, better for the climate. That's why we need policy. Individual action and choice alone aren't going to do it.

    That gets us back to automobiles. Sure, crocodile tears will always be shed by polluters or their agents, those promoting their messaging. Of course, they're going to make up fake stories about whales offshore that are being supposedly killed by wind turbines. That's entirely manufactured. It's a myth that was created by polluters and the plutocrats to try to defeat renewable energy, which is the primary threat to their business model, which is continued fossil fuel dependence. Same thing here. A lot of the arguments that you see against electric vehicles are disingenuous. Transportation is the largest sector of carbon emissions in the American economy. I think something like 26% of our emissions, even more than electric power. We've got to electrify transportation, and then we've got to decarbonize the grid so that electricity is coming not from carbon, but renewable clean energy.

    Cristine Russell: How much do you think climate is going to be an issue in the presidential election? 

    Michael Mann: This is a defining election for climate, in my view. There's no progress in climate that doesn't go through preservation of democratic governance. Without a functioning democracy, we're not going to be able to do anything on climate. Without American leadership, we're not going to be able to take global action on climate. This election couldn't be more important. It really is about the path we follow with our planet and our civilization.

    I think climate is an underappreciated issue, especially among younger voters. When you poll younger voters, climate often ranks number one. In the last election, climate was ranked number one by democratic voters. There's actually a lot of energy and passion. One of the things you need is voter intensity. You need young people in particular to have a reason to turn out, and climate is one of the dominant reasons. As a university professor, I interact with undergraduates at Penn, and I know it's true here at Harvard as well. There is great passion and great concern, great anxiety. In fact, we've invented a term, climate anxiety, to talk about how young people are troubled about the peril that they face. We have to get young folks energized.

    If the Biden campaign makes climate an important part of their messaging and does emphasize the real progress that they've made, and touts the achievements that they've made in the face of pushback from Republicans in Congress and conservative courts that have tried to overrule some of the executive actions the administration has tried to take, they can get that message out. They can energize young voters. If young voters turn out, then we will elect a climate friendly administration, and maybe the House and Congress as well.

    Cristine Russell: There’s been a concern among young people that’s it’s too late to do anything. So are you going to go on the campaign trail?

    Michael Mann: I've done that once before. I don't plan to do it again. In that case, I campaigned for a governor who was running against a former attorney general who had tried to subpoena all of my emails in the State of Virginia. We were successful in that venture. Ken Cuccinelli was defeated. He went off to actually help run an oyster farm in Tangier Island, which is an island in the Chesapeake that is slowly succumbing to the effects of global sea level rise. That's where climate change denier Ken Cuccinelli... You can't make this stuff up. 

    Yale and George Mason University have been doing polling on public opinion on climate. Dismissives number about 9% or 10%, so there's actually a fairly small fraction of the public that are emphatically climate change deniers, and yet they have a very loud voice. There's a megaphone in the conservative media that amplifies that messaging. But it's not worth wasting your time trying to convince that 9% or 10% of climate deniers. Their heels are dug in. They come at this from a tribal standpoint. It's about the allegiance to the canon of the Republican party, which is to deny climate, or at least oppose climate action. That's not where the challenge is. The challenge is energizing people.

    One of the real problems is that young folks, as I mentioned, and not just young folks, but a lot of people concerned about climate, have come to believe that it's too late to do anything. There is quite a bit of social science research that suggests that doomism and despair can lead to disengagement, which is the opposite of what we need. It turns out that righteous anger, on the other hand, can be a very energizing emotion. We should be righteously angry about the predicament that we find ourselves in. So I think that's the right emotion to be emphasizing. We do need to convince folks that it's not too late because the science tells us it's not too late.

    (Audience Q&A begins)

    Karim Bardeesy: I know you've been critical of degrowth in the past. I'm just wondering about your take on it, and, for those of us who maybe disagree with degrowth, how to respond to people who are espousing degrowth theories.

    Michael Mann: Certain language is very easily weaponized against action. The critics have tried to portray environmentally minded people as radical extremists. We've seen certain framings emerge, often before important elections. Phraseology hashtags. Things that make progressives, environmental progressives, the climate conscious, sound just a little unhinged to middle America, who are critical in winning these elections. Russia, in particular, has been engaging in PSYOPs on social media to try to radicalize certain groups to make them look extreme, to make their messaging look unpalatable to middle America where these elections are won.

    I think we have to think very carefully about terminology. Degrowth, to a lot of people, is going to sound radical when, in fact, the underlying point is not so radical. It's self-evident that the continued extraction of finite resources is incompatible with a sustainable existence on this planet. That's an important point to get out. The fact that we talk about the importance of clean energy, electric vehicles, wind turbines - all of these things require resource extraction. In the end, we do have to find a way to get away from an ever-growing extraction-driven global economy because it just doesn't work in the end. That's a conversation we need to have, but we need to make sure it doesn't get framed in a way that's easily weaponized by bad actors. And unfortunately, that's happened a lot in recent years.

    Audience Member: What do you think about the term climate change? Why do we call it change?

    Michael Mann: We could have a long conversation about the history of this. Republican pollster Frank Luntz some years ago was encouraging his clients, basically fossil fuel industry Republicans, to use the term climate change, to favor that over global warming, because it sounded less threatening, based on his polling and his focus group work. But the irony is that climate scientists would largely agree that climate change is the more comprehensive term to describe what we're talking about, the warming of the surface of the planet. Global warming is just one aspect of human-caused climate change. But there is the danger that you use language that deemphasizes the urgency. One of the themes that I repeat is urgency and agency. There's great urgency in acting and it's not too late to act.

    There are terms like climate emergency, climate crisis, that convey the threat. What you have to be careful about is there are scientific contexts. In a journal, you're not going to describe model projections of the climate crisis. It's just not an appropriate scientific term. So don't tell scientists not to use the term climate change. That's going to alienate scientists. But when you're talking about the impacts of climate change and the threat of climate change, then why not characterize it as a crisis, even an emergency? So it's context dependent, which I know is always an unsatisfying answer. But certainly in the public realm, when we're speaking to the public and policymakers, we do want to use wording that conveys the urgency while, again, avoiding wording that might work against the notion that we still have agency.

    Cristine Russell: Human-caused climate change is a lot less neutral than just climate change. Oftentimes, that's not put in news articles. I think that's something, as a journalist, you should repeat when you're writing about this.

    Audience Member: There's been some discussion today about electric vehicles, and also wanting to eventually move away from resource extraction. I often hear a lot about electrifying vehicles, and that implies people are going to continue having cars. I wonder if you have any thoughts on why we don't hear as much about investment in public transport and designing our cities differently?

    Michael Mann: We should be talking more about that. I was derelict in my own responsibilities not to talk about that dimension of the problem. That's absolutely right. Other countries have done a good job of moving away from individually owned vehicles. I live, I'm happy to say, in the city. Well, I go back and forth. My family's back in State College. I'm there sometimes, but most of the time, I'm in Philadelphia, and I don't own a car there. I can walk to pretty much anywhere. And if not, I can hop on the trolley. So I'm living the dream right now when it comes to decarbonizing my own footprint. But not everybody is in that situation.

    In fact, I'm teaching a course in climate communication right now. One of the projects students have been presenting, for example, looks at the fact that the University of Pennsylvania doesn't subsidize public transportation for their students. They should be doing that. They do it for faculty and staff. There's a little bit of myopia there. We need to think about ways, as institutions, that we can incentivize choices that do move us away from reliance on gas-guzzling vehicles.

    I think cities are trying to do that, states are trying to do that. We also have groups like ALEC, funded by the fossil fuel industry, that are doing everything they can to oppose that, because they want a lot of people out there using a lot of fossil fuels. Anything that moves us in a different direction, to them, is a threat. That's part of why the solution to so many of these problems comes down to us turning out and voting, and voting for climate friendly politicians and voting out the ones who are just rubber stamps for polluters.

    Russell DeGraff: I wanted to ask about bridge technologies like ethanol that are less than perfect, but could be cleaned up and made much better, and the environmentalists who are fighting them instead of trying to work to clean them up, and your take on that.

    Michael Mann: I'm not sure I have a simple answer because it's a delicate operation when you're talking about bridge technologies. If they facilitate the movement away from more carbon-intensive, energy-intensive technologies, that's good. But if they're crowding out investment in even better carbon-free solutions, how do you strike the right balance? I don't think there's a one size fits all answer. I think you have to look in detail at the policy and try to really figure out how it will change incentives for individuals. Will it move us in the right direction or could it end up backfiring? I think we just need to think about the complexity of those things.

    Kate Cell: When you talked about anger, one of the things that I'm seeing is an unholy alliance between fossil fuel front groups and environmentalists in the case of the offshore wind circumstance that you cited, and a lot of other land use challenges that we're seeing around solar, et cetera. I'm curious what you see as the role of scientists and science communicators when we're dealing with those local land use unholy alliances.

    Michael Mann: It's complicated because what you have are bad actors who are creating these framings and memes. There's a front group that was funded by the Koch brothers and the Heritage Foundation. They are trying to create a wedge within the environmental community. They've been trying to do that for years. Russia tries to do that online, creating a wedge within the community of climate, getting us fighting with each other. Divide and conquer. That's what this is about.

    But people get caught up in it. Many of them are good, honest people who have been hoodwinked by that framing. And so we need to provide a path for them that doesn't alienate them or portray them as villains - they're victims - while calling out the villains. We need to expose the bad actors. Sometimes we call it inoculation in the communication world. People talk about righteous indignation. When you expose the fact that somebody has been intentionally lying to you, it can create a very powerful response on your part. So it is important to expose the bad actors while not alienating the victims of their actions.

    Jason Baldock: In another discussion with a conservative commentator, who can't be named under Chatham House rules, they were very confidently pointing to economic modeling, especially from large insurance agencies, who are very serious about risk modeling where the economic forecast of unmitigated climate change wasn't really all that compelling. Can I get some comments from you about whether you see a consensus in the scientific community about the impacts, and how that may or may not be penetrating into modeling about how it's going to affect the U.S. economy in this particular instance?

    Michael Mann: I talked about some of these front groups and think tanks that produce bogus economics numbers that can be cited by Republican senators in congressional hearings, et cetera. There's a lot of that. I testified at a Senate hearing. James Inhofe, who was a well-known climate denier, cited some economic report from the Heritage Foundation or something and asked me to comment on it. And I said, "It's the Heritage Foundation. This is not an objective..."

    There's a lot of room for baking the answer you want into these economic modelings. A lot of it has to do with what's known as the discount rate. Using economic discounting, what's the yield on a 30-year bond? If you treat climate impacts the same way, if you say the impacts are discounted over time because, just like you'd rather have $10 now than $10 30 years from now, it's more important to have climate mitigation now for us, than climate mitigation 30 years from now.

    Implicit in the whole idea of social discounting, of parlaying that into climate policy, is that you're discounting the lives of your children and grandchildren. More than one economist has pointed out that that is not a valid assumption. That there is a deep, ethically dubious assumption that's made when you use this sort of social discounting. If you use that discount rate of 6%, your model will tell you, “Don't bother doing anything about climate. Just grow the economy.” The reality, of course, is even that argument doesn't work because we're seeing far more damage from extreme weather events and the disruption of the supply chains and distribution systems. The cost of inaction is actually greater than the cost of action.

    Contrarians love to talk about the cost of climate action, and they'll talk about investment in fossil fuel energy. Wait a second. Why is one a cost and one an investment? Again, it's language. But the calculations behind that are often very dubious. They assume very large discount rates. Back when I was at Yale, there was basically one person doing this, William Nordhaus, who was using a very high discount rate. He did some of the early projections. His view was the optimal warming of the planet is more than three degrees Celsius, which would be catastrophic. Because he was discounting the future.

    Today, there are a whole bunch of other economists who point out that, for one thing, these linear models of just some smooth impact of climate change ignore the fact that there are potential tipping points, and they ignore the tails of the distribution. The small but finite possibility that the impacts could be far worse than the models predict actually leads you from a risk-averse framing to invest even more. So uncertainty is a reason for even greater action, not less action, not the way that contrarians have framed it. So I would have to see the specifics of what this person was... But my guess is that they were buying into a very flawed framework that is all too common in the simple cost-benefit analysis that conservatives love to cite.

    Cristine Russell: I think we are going to stop there. Thank you to the audience for coming, and thanks to Dr. Mann and his brilliant book. Buy the book.

    Michael Mann: She gets a cut, by the way. Thank you.

For more information on this publication: Belfer Communications Office
For Academic Citation: Hanlon, Elizabeth. “Climate Science Doesn't Support 'Doomers', Says Scientist Michael Mann.” News, Belfer Center for Science and International Affairs, Harvard Kennedy School, April 4, 2024.

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