Can Earth’s Past Climate Help Us Understand Today’s Crisis?

17:14 minutes

Dara Ancient City. Mesopotamia. Mardin, Turkey. Dara Ancient City, one of the most important settlements of Mesopotamia.
Ruins from the Mesopotamian city of Dara. Credit: Shutterstock

A combination of factors led to Earth’s climate being able to support life. And changes in the climate some 6,000 years ago created the conditions for human civilization to flourish. It’s a delicate balance on the verge of collapse, due to our reliance on burning fossil fuels. 

Ira talks with paleoclimatologist Dr. Michael Mann about his forthcoming book Our Fragile Moment: How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis, about the importance of understanding our planet’s climate history, and strategies to get policymakers to take action before it’s too late to reverse some of the worst consequences of climate change. 

Mann is a professor of earth and environmental science and director of the Penn Center for Science, Sustainability and the Media at the University of Pennsylvania, based in Philadelphia, Pennsylvania. 

Read an excerpt of Our Fragile Moment.

Segment Guests

Michael Mann

Dr. Michael Mann is the author of Our Fragile Moment: How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis, a professor of Earth & Environmental Science, and the Director of the Penn Center for Science, Sustainability and the Media at the University of Pennsylvania in Philadelphia, PA.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. It’s climate week in New York, complete with lectures, demonstrations, and climate protests. I would venture that perhaps no public figures, save Al Gore, is associated more with our climate crisis than climatologist Dr. Michael Mann. And according to Mann, understanding our planet’s climate history shows us that it’s not too late to take action to reverse some of the worst possible outcomes of the climate crisis.

And that is good news. And it’s all in his forthcoming book Our Fragile Moment– How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis Dr. Mann is professor of earth and environmental science, director of the Penn Center for Science Sustainability and the Media at the University of Pennsylvania in Philadelphia. Welcome back to Science Friday.

MICHAEL MANN: Thanks, Ira. It’s always great to be with you.

IRA FLATOW: Nice to have you. I want to start with the title of the book– what is Our Fragile Moment?

MICHAEL MANN: Yeah. We now have more than eight billion people living on this planet. And we have this massive societal infrastructure that we’ve created to support that global population. And that infrastructure was built over a period of several millennia, where the climate, the global climate, was remarkably stable.

And so that infrastructure is sort of dependent on the stability of the climate. And what we are doing right now is, of course, we are creating instability. We are dramatically warming the planet at rates unlike anything we’ve seen in the past. And that’s what makes this moment so fragile because, if we leave that envelope of variability within which our infrastructure can exist and continue to function, if we leave that range of climate variability during which we built our civilization, then that threatens our civilization.

And we’re getting closer and closer to the point where we’ve warmed up the planet and created climate impacts, extreme weather events, wildfires, heatwaves, floods, superstorms like we’ve seen this past summer. That threatens this fragile moment that we are still in, where, if we can get the problem in hand, if we can rapidly reduce our carbon emissions, we can still remain within that envelope that supports us and a global civilization of more than eight billion people.

IRA FLATOW: Now, you’ve brought up a very interesting question there. You used the word if we can do these things. How do we get people to do these things? We’ve seen climate activists ramp up their tactics recently. Earlier this week, protesters blocked the Federal Reserve Bank, calling for an end to banks lending to fossil fuel companies.

Climate activists disrupted the US Open semi-finals. One person glued their feet to the floor. Are these kinds of tactics effective in change and ringing alarm bells, getting governments to implement more aggressive climate policies? You’ve been talking about this for 20 years. Isn’t it frustrating? How do we get people to actually act?

MICHAEL MANN: Yeah. It is frustrating at some level that we haven’t seen the sort of action that we had hoped to see. And yeah, I’ve been at this now for, I guess, two and a half decades, two and a half decades ago when we published the now famous hockey stick curve. And that sort of thrust me into the center of this larger debate.

And I had hoped that we would get the problem in hand that policymakers would be listening to the scientists and that would lead them to pass enlightened policies that would help us decarbonize our economy. Part of the problem is there are some powerful vested interests, fossil fuel industry, that profited greatly from our reliance on fossil fuels. And they’ve pushed back quite a bit.

And at a time, when we are just witnessing these unprecedented extreme weather events, it’s actually quite difficult for polluters or those promoting the fossil fuel agenda to deny that something’s happening. So we’ve seen them turn to various other tactics to keep us addicted to fossil fuels. And doomism is key among them because, ironically, if we become convinced it’s too late to do anything about the problem– and as you allude to, young folks in particular are vulnerable to that because they’ve seen so little progress. And they are the ones who will inherit the worst impacts of our carbon emissions today. They are the ones who will bear the brunt of the climate change that we are generating.

IRA FLATOW: Some of them have gone to court, though, right?

MICHAEL MANN: Well, yeah, so absolutely. And so the youth climate movement has been so critical. The Montana court case, youth climate activists brought a case against the state, which was not supporting the needed climate policies. And the court found in their favor. So they’ve been a game changer.

And what I worry is that they will– some of them or many of them will fall victim to doom, like, oh, you know what? It’s too late to do anything about the problem. And you see some of that. You feel some of that out there today.

And so one of the things that I try to do with the book is to make it clear that the paleoclimate record, the past climate events, past extinction events, if you understand in detail what drove them, they do not tell us that it is too late today we do not necessarily. Have to be part of the next great extinction event. But there’s a shrinking window of opportunity. And the paleoclimate record speaks to that at well. It speaks to both the resilience that the climate system has to appoint and the fragility of the climate system once you go beyond that point.

IRA FLATOW: Well, let’s talk about that paleoclimate record. Let’s focus on a few important moments in our planet’s climate history. In the book, you talk about another period in our planet’s warming due to a CO2 release. But this one was way before human causation, right?

MICHAEL MANN: Yeah. So one of the episodes that I talk about, for example, is the end-Permian extinction. It was the boundary between the Triassic period and the Permian period about 250 million years ago. It’s actually the largest recorded extinction event in geological history. 90% of all animal species died off. 96% of all marine species in the ocean died off.

And so some people look to that event. And they say, oh, it was driven by a massive release of methane from the seafloor as the planet warmed up, started with carbon dioxide venting through volcanoes. It was a natural injection of carbon dioxide into the atmosphere through heightened volcanic activity that tapped into carbon-rich geological reservoirs. And of course, we are increasing carbon dioxide today through fossil fuel burning at a much faster rate, mind you.

And the argument goes that in that caused the seafloor to warm up and release the methane that was stored there. And methane is a very potent greenhouse gas. So this created an almost runaway effect, where the methane made it into the atmosphere. It warmed the planet even more. And some of the sort of doomers, as we call them, say and that’s what’s happening today because we’re warming up the arctic. And we’ve released methane gas from the permafrost. And it’s a runaway warming event that we can’t do anything about, and it will cause all life to go extinct within a decade no matter what we do.

Now, that is not true at all. And what troubled me was that I was seeing the paleoclimate record, these past events, misrepresented not by climate change deniers, which is something that we’ve confronted in the past. Here, it was those who argue for inevitability, for doom, who were misrepresenting the science.

And so I go through that episode. And it turns out that there wasn’t a massive release of methane from the seafloor. What warmed up the planet is the same thing that’s warming up the planet today. It’s CO2 that we are generating even faster from fossil fuel burning.

IRA FLATOW: And so that’s one of the reasons why you say we have hope, right?

MICHAEL MANN: Yeah, that’s right. And so what the science tells us today, when we use climate models, comprehensive Earth system models, what they tell us is, yeah, the warming is caused by the CO2 we’re producing primarily. And that warming will continue until CO2 emissions cease. Now, that’s a really important point because, Ira, you probably remember in the past there was this notion of delayed warming or committed warming. If we stop carbon pollution now that the planet would continue to warm up for decades.

IRA FLATOW: Right. Right. Right. Yes.

MICHAEL MANN: And that’s half of the story. But we weren’t getting the other half of the story, which is that the oceans are actually absorbing carbon dioxide from the atmosphere. So if we stop adding carbon pollution to the atmosphere, CO2 levels actually start to drop in the atmosphere. And that offsets the committed warming.

So the result is you get a flat line. In other words, when you stop adding carbon pollution to the atmosphere, the surface of the planet stops warming up almost immediately. And so we have agency. It’s not too late for us to prevent that warming.

IRA FLATOW: That is good to hear. You also write about the role of climate change in the rise and fall of ancient civilizations. What can we learn from human civilizations, let’s say, in Mesopotamia that you talk about?

MICHAEL MANN: Yeah. It’s really interesting. So civilization, human civilization, arose about 6000 years ago in Mesopotamia. It was the first city-state. Where Mesopotamia is located today, it literally means the plain between the two rivers, and those two rivers are the Tigris and Euphrates rivers.

And what happened was the climate was slowly getting drier. And that has to do with changes in Earth’s orbit relative to the Sun, which shift rainfall zones and drought zones slowly over time. And over thousands of years, the Middle East was getting drier, and it was getting more and more difficult to support agriculture.

And so you needed some sort of technological innovation, for example, irrigation, where there wasn’t much rainfall. But if you could tap into the water supply from these two rivers, then you could continue to maintain viable agriculture. And so civilization basically arose out of the need to have specialized workforces, including those who could engage in these massive water engineering projects, that would allow the continuation of agriculture.

Our ingenuity, our engineering capability, in this case irrigation, allowed us to continue to maintain a large population by being very clever about how we made use of water resources in a drying climate. And that provided stability, having specialized workforces provided so that you could move water and food around within the civilization from where there was a surplus to where there was a deficit.

And so I sometimes liken civilization– it’s like a catamaran. A catamaran is very stable the presence of relatively small waves, more than a single-hulled boat. But it becomes completely unstable for large-enough waves. And so civilization is the same way. It provides stability to a point. But you hit it hard enough, and that hit came in the form of a massive volcanic eruption about 4,200 years ago, which created a sudden drying in that region, which put far more stress on water resources.

And all of a sudden, you had parts of the empire– this was a very large empire with divergent needs and divergent resources. And the parts of the empire that were driest, there was conflict between them and the wetter regions over those water resources. And so climate change created conflict over water. And there was even a wall that was built to keep part of the population out, those who were suffering from the climate-related water stresses. If that sounds like a cautionary tale for what we’re seeing today, it’s because it is.

IRA FLATOW: This is Science Friday from WNYC Studios. If you’re just joining us, I’ve been talking with climate scientist Michael Mann about his new book Our Fragile Moment– How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis. As we run out of time, I want to make sure we hit some of the points that are very important. And one of those things, those points, is politicians.

You sort of talked about how no one can deny what they’re seeing with the way that the weather has reacted to the climate. And obviously, no one’s going to be walking in with a snowball into the Senate like–


IRA FLATOW: –the senator from Oklahoma did years ago and say this is just not happening. As you point out in your book, you actually quote an anecdote I said years ago about senator Muskie wanting a one-handed scientist instead of having, on the one hand, there’s this. On the other hand, there’s that. Are they still looking for these one-handed scientists in government?

MICHAEL MANN: [LAUGHS] Yeah. It’s a great story. And I love telling it, Ira, because I thought you laid it out so well. We often say, scientists, we tend to lead with uncertainty because that’s where the interesting science is taking place, at the horizons of our knowledge, at the limits of our knowledge. And so we spend all of our time in the areas where there is uncertainty.

And it’s easy for us to lose track of the wealth of information that is well established. And when we’re communicating to the public, of course, we need to lead with what we do know. And it’s important to couch that in uncertainty and caveats and to provide nuance.

But we lead with what we know. That’s what policymakers need to hear. And sometimes there’s unavoidable uncertainty. And so you know you’re not going to find that one-armed scientist. You’ve got to look on the one hand and on the other hand because there is uncertainty.

And uncertainty is not our friend here. And I’ll just give one example. One of the major developments in climate science over the last decade and a half has been our ability to better model ice physics. And so our ice sheet models, the models of the Greenland ice sheet and the antarctic ice sheet, are far more comprehensive and realistic than they once were. And as our models become more comprehensive and we start to remove some of the uncertainty that existed when our models were cruder, what are we finding?

We’re finding that ice sheet collapse can actually happen faster than we thought, not slower. So when you hear a politician, including that senator who appeared on the senate floor with a snowball in Washington DC in the middle of the winter to somehow disprove climate change, when you hear a contrarian, a politician who favors an agenda of climate inaction, when you hear them say, well, there’s uncertainty, so we shouldn’t act, it’s just the opposite. Uncertainty is actually a reason for more concerted action because, if anything, as we’ve learned more, as our models have become more comprehensive, we’ve found that ice sheet collapse can happen faster.

Sea level rise can happen earlier. And the weather events that we’re seeing are more extreme already than we expected them to be at this point.

IRA FLATOW: So much to talk about. I wish we had more time. I want to wish you a good success with the book. It’s a great read.

MICHAEL MANN: Thanks so much, Ira. It’s always a pleasure to spend any time with you at all, and I look forward to the next opportunity.

IRA FLATOW: Always happy to have you with us. Dr. Michael Mann, author of the forthcoming book Our Fragile Moment– How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis, he’s a professor of earth and environmental science and director of the Penn Center for Science Sustainability and the Media at University of Pennsylvania in Philadelphia.

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