Introduction by John Mutter
John Mutter: To begin the final session, it's my great pleasure to introduce Professor Daniel Schrag. He's professor of earth and planetary sciences at Harvard University, where he studies climate and climate change over a very broad range of Earth's history. He's examined changes in ocean circulation and their consequences over the last several decades, and is one of a group who developed a curious notion of what is called the Snowball Earth hypothesis, proposing that a series of global glaciations occurred between 750 and 580 million years ago that completely encompassed the Earth in a glacial period. He's worked on theories of Pleistocene Ice-Age cycles, including a better determination of ocean temperatures during the ages that may have led to the evolution of multicellular animals. Dan is currently working on creating integrated models of climate change and economic stability and development in poor countries. He was recently named, in the year 2000, a MacArthur fellow, among other distinctions, which his bio in your information packet adequately describes. Please welcome Dan Schrag.
Daniel Schrag: Thank you John, and thank you, Jeff, and everyone at the Earth Institute. I should also say thank you to the administration at Columbia. I think the vision and the courage to create something like the Earth Institute deserves a lot of praise and a lot of credit. This is an unusual organization, and we should recognize that. You know, universities . . . we've heard a lot today about trying to save the world, trying to make the planet a better place. Universities are good for many things. They're mostly good at education and research. They're not necessarily the ones that we would pick to save the world completely, and yet universities can be exceptional catalysts for conversations and dialogue, and I hope that's what's going on here today. So that's really what the Earth Institute, I think, is about, and it's an exciting adventure.
I'm the fourth person today to talk about climate and climate change, so I'm not going to surprise you with anything radical that is completely different from all the other speakers. We heard Wally Broecker frame the problem of jabbing the angry beast, we heard Admiral Lautenbacher almost talk about climate change, and Bob Watson spoke about it in detail. My perspective is similar to most, I've been inspired by some of those earlier speakers, but I'm going to try to frame it a little bit differently, and give you a different perspective and talk a little bit about how we move forward in the future in thinking about this. I agree with most of what Bob Watson said, although I'm not as clear as he seems to be on where the future is. We have a major challenge and we need a lot of thought and a lot of work to figure out how to solve this problem.
Okay, here's the picture of the Earth, a good place to start at the "State of the Planet" conference. We think of the Earth as a complex system. The climate system has many different parts that we still don't understand very well. And an important perspective, I want to emphasize today, is that we don't have a very long history of observations about the Earth. The direct observations of Earth's climate, you know, of the ocean temperatures have been maybe for 150 years. Good observations of the atmospheric chemistry of cloud physics go back just a few decades. And so we really only understand the Earth in the context that we see it in today. And what we're doing to the Earth is really taking it into another realm. A poster child for climate change, and the observations that for me are most compelling that the climate really is changing have to do with tropical glaciers, made mostly by one of my heroes, Lonnie Thompson, from Ohio State University.
There was an interesting article last week in the "Science Times" in the New York Times about the debate about Kilimanjaro. Here is a perspective of Kilimanjaro from 1912, from 1970, and 2000, looking at the retreat of the glacier on top of Kilimanjaro, and the New York Times article talked about whether or not this was really due to climate change or whether it was just part of some sort of natural variability. No offense to Mr. Revkin, who might even be here, but this was a terrible article, because it failed to mention a couple of things that are very, very important here. It did mention the fact that indeed it really is melting—it's not just getting dried and ablating, it really is melting. Here's a collapse with a huge outpour of water. This glacier is melting. But in addition it isn't just Kilimanjaro in isolation. Lonnie Thompson's work for several decades has shown that all over the tropics, and near the equator in high altitude, which is a very stable part of the atmosphere, doesn't experience a lot of variability, it doesn't have a lot of weather. All over at high altitudes glacial ice is melting. And if we look at Peru, for example, here the Quelccaya Ice Cap in Peru, this ice cap not only is melting but because of the annual layers and even because of the plants that are left behind as the glacial retreats, the fossil plants, we know that this hasn't melted for thousands of years. So this isn't a hundred-year cycle or a several-hundred-year cycle. We're clearly seeing changes that haven't happened for thousands of years, coincident with our last rise in CO2. And some people might want to argue that that's a coincidence, but I think it's getting beyond the realm of coincidence. And that's an important perspective.
Learning from the Eocene Climate
Okay. Here is what I consider one of the most important observations of our climate system, that is, the ice-core record of carbon dioxide in the atmosphere, this from the Vostok ice core from Antarctica. And it shows the carbon-dioxide levels over the last 430,000 years. And you see here changes—in the preindustrial period we're in about 280 parts per million, during the glacial period somewhere around 180 to 190 parts per million, and with fairly regular fluctuations between interglacial and glacial states. The important perspective here, though, from our discussion, is that never in the last 400,000 years has CO2 been higher than 300 parts per million. Now just last week it was reported that the measurements at Mauna Loa in Hawaii now have 379 parts per million. So we are way above that. We are already at a level that we haven't seen for we know 400,000 years, and indirect geochemical evidence suggests that it hasn't been much higher than that—we don't exactly know how much, maybe above 500 parts per million or so—for the last 30 million years. Now this is truly an amazing geological experiment we're doing with the planet.
Now the last time that we're pretty sure CO2 levels were really high—and when I say really high I mean maybe 1,000 parts per million, maybe a couple of thousand parts per million—was a time 55 million years ago. Now we don't have direct measurements of the atmosphere at this time, like we do in ice cores for the last 400,000 years, but we do have measurements of the climate, and it was quite a remarkable place. This painting is a picture from somewhere in the western U.S., showing palm trees and crocodiles. The idea was that the Eocene climate was warm, really warm. Palm trees flourished in Wyoming. Palm trees can't grow when there's cold winters, and palm trees were all over the western U.S., where the winters are very cold today. Crocodiles lived in the Arctic, all the way up in Ellesmere Island. Antarctica was a pine forest. And deep ocean temperatures which today are about one or two degrees in the Pacific were at least 12 degrees Celsius. This was a different world.
Now I'm not suggesting that the Earth is going to transform itself into an Eocene climate in the next few decades. That would be a gross mistake because it takes time for ice sheets to melt, it takes time for oceans to warm up, probably thousands of years. But we're doing an experiment that hasn't been done on this planet, and the last time it was done, there are some interesting and troubling observations. For example, when we try to simulate the Eocene by taking a climate model like the ones that Bob Watson showed that we use to predict the future, the next hundred years, and we raise carbon-dioxide levels, very high levels, we can't seem to get the Earth warm enough, especially in the wintertime. The wintertime gets cold at high latitudes. And the palm trees were there, they were in Wyoming. That's very troubling. It suggests to many of us that there's something missing from our models. Again, we are moving the Earth so far outside our experience that the models are only based on the observations we have. In Donald Rumsfeld's terminology, this would be the unknown unknowns. This is serious concern for worry. He was a very wise man.
So in general . . . and I'm not going to talk a lot about climate history, Wally Broecker talked about it a little bit this morning, and again there'll be a whole conference on climate and climate change in a few weeks. The important point is . . . and we could talk about abrupt climate change, which Wally Broecker has documented so beautifully, as well as many other people, and different times. In general I just want to say that my reading of the history of climate suggests that the climate system seems to be very sensitive to small perturbations. That is the angry beast that Wally Broecker was talking about.
And what we're looking at . . . the question is, Is this a small perturbation? This is now the same carbon-dioxide level from ice cores, now looking at just the last 60,000 years, but it actually includes from the preindustrial period observations of the atmosphere due to our burning of fossil fuels. And we're actually already off scale because now know that the CO2 level in the atmosphere is about 379 parts per million. And where it's heading is towards somewhere between 500 and 1,000 parts per million. And it may seem a little arbitrary, you know, 500, 1,000, what's the difference? There's a big difference there, and we don't want to be pushing that limit.
So the way I would frame this problem is that we're performing a grand experiment with our planet that hasn't been done in millions of years, and no one knows exactly what's going to happen. No offense to Bob Watson and the IPCCC—that represents the best state of our knowledge of how the climate system works, and there's a lot of insight in there—but there are also things that we don't understand and we must acknowledge that. And, as Bob explained, those uncertainties may cut both ways, and in fact I would argue that they probably cut the other way: things are more likely to probably be more extreme than what the IPCCC consensus has given us. And that should be a reason for concern.
Inertia in the System
Now, what we mean then . . . hold on, is this working? So the response of our system, this is another problem that we have to work in. I want to talk a little bit about the carbon cycle and how we manage it. I'm not a technologist, I'm not an energy expert, but I know something about the carbon cycle, and I want to try to frame this problem a little bit for you in terms of how we think about managing the carbon cycle in the future, in terms of then what specific technologies Klaus Lachner and the panel on energy will talk about tomorrow. But one of the important constraints on this is that the timescale for this system is very long. Wally mentioned this already, but it's important to reemphasize, that not only does CO2 last in the ocean atmosphere system for a very long time, but also the lifetime of energy technology is long. A coal plant typically lasts fifty or sixty years, so energy choices we make in the next few decades are going to be with us for the rest of the century. This is a big supertanker—we're not driving a sports car, we're not driving a speedboat, and therefore long-term decisions, there's a lot of inertia in the system. And we have to think about that in terms of our choices. We can't just decide fifty years from now to change our behavior, it's not going to work.
So if we look at the IPCCC scenarios—Bob Watson showed this earlier—you see here various emission scenarios. Here would be a rapid-growth scenario. This actually isn't rapid growth, it's kind of business-as-usual, middle-to-high growth, where you end up with today something like, you know, six and a half gigatons—billion tons—of carbon emitted per year, and you're pushing 30 billion tons by the end of the century. On the other hand, a more extreme scenario would be us actually dramatically reducing emissions down to below the current levels by the end of the century. The difference between those scenarios is somewhere between 900 to 1,000 parts per million on the high end, and maybe 550 parts per million or so on the low end. And these choices unfortunately to many of us seem a little abstract. What do they actually mean? What are these scenarios and what kind of choices do they represent? There's good news and bad news here. The good news is that we actually are in control of our future, that reducing our carbon emissions really is a way to solve this problem. We can protect our national security, we have to think about it as an insurance policy in the event that climate change is much worse than we think. Now we're never going to find out, hopefully, if we follow this recipe, if we buy onto this, hopefully we'll never find out. I hope we never see a world with 1,000 parts per million CO2 in the atmosphere.
The problem is that we have to act now—because there's so much momentum in the system, the next few decades are going to determine our path for the rest of the century. So we have a limited time window in which to act.
Possible Future Scenarios
Now what I want to do here is a little bit of an exercise, just to run a few scenarios by you, just to give you a feel for the way the carbon cycle works and what some of the choices are, because I think there are some very important points here to make about how one moves forward on this climate agenda.
First of all, let's consider a simple economic scenario where global economic growth is at about 2.5 percent a year. That averages the lower growth of developed countries from the higher growth of developing countries, and a long-term constant at 2.5 percent a year, but we're going to assume that energy efficiency is improving at 1 percent a year, so that energy itself in terms of CO2 emissions is growing at 1.5 percent a year. And we're going to make a very conservative assumption that all energy sources are going to stay proportionally the same over the next century. Of course that's not going to happen. It's probably conservative because more than likely some of the petroleum and natural gas will be replaced by coal, which produces even more CO2 per unit energy, so this is potentially a conservative scenario.
Next, let's take a look at another possibility—that we actually in the U.S. really decided to do something about this problem, and that in the next ten years we decided to get rid of all SUVs. In fact, even more than that, let's get rid of all sorts of bad polluting vehicles and we'll end up doubling our energy transportation efficiency in the next ten years, by 2014. I don't think it's very likely, but let's treat that as a second scenario.
Third, let's go even more radical, that by 2024, U.S. becomes a carbon-free economy. We convert completely to nuclear and renewables, or potentially sequestration, and we don't put out any more carbon dioxide at all.
And then finally a more global scenario where the world decides to work together and we end up sequestering . . . by 2020 to 2040 we sequester all CO2 emissions from coal, and petroleum peaks in 2030 and starts to decline by 1 percent per year thereafter. Those are the four scenarios I want to look at with you, and we're going to plot here on the left the carbon emissions, measured in billions of tons per year, against . . . That's not supposed to do that, it's supposed to do one at a time . . . now it's completely gone. Could you start that again? Small technical problem. It was supposed to work so beautifully. Okay, there we go. Okay, stop there. Now this should work, right? Okay, why don't you just click for me. Click once more and click again. Okay, it's all there. And the frame is missing, so there seems to have been some translation problem, okay. Well, okay, we'll just deal with it.
What you see here is that in this top frame, that's the global economic growth. Again we are growing from 6.5 gigatons per year today up to about 30 gigatons per year by 2100. And what you can see [is] that even getting rid of all SUVs, doubling our transportation efficiency in the U.S., makes almost no difference at all. Even radical change—U.S. becoming a zero-carbon economy—makes a difference, but not nearly enough. And here is the more dramatic change where we . . . sequestering all carbon dioxide and putting it either underground or in the bottom of the ocean, or transforming it into some more neutral phase. But you see that the important point here is that no matter what the U.S. does, this is a global problem. And there's good news and bad news in that. Next slide . . . click again, please. Okay, again. Okay.
So here is the same . . . this is now carbon-dioxide level in the atmosphere against year, and what you see here again is the growth towards about a 900 to 1,000 parts per million for the business-as-usual scenario. We're only at maybe 850 parts per million if the U.S. radically removes all of the carbon from its economy, and we're down to maybe about 550 parts per million if we phase in complete sequestration from coal by 2040. And by the way, this means that we're sequestering over ten billion tons of carbon a year by the end of the century. So this is a rather massive problem.
How we get here is not really clear to me. As Bob Watson said, China probably is going to burn its coal, and there's not a lot we can do to stop it. And the question is, How do we convince them to sequester the carbon dioxide from it? That's a really challenging problem. And if we think we can do this alone we're wrong. We can solve this problem, but the U.S. can't do it in isolation. It's going to have to work with others because their decisions determine our fate. We have to start thinking that way.
Now as soon as you think that way you have to look at the world. And here's a map of global carbon emissions. This is from 1996. It looks quite a bit like a map of GDP per capita, except there are a few European countries that are low carbon emissions, like France, partially because they have so much nuclear power. But you see, you know, Africa, a poor spot, very low carbon emissions, and Australia and the U.S. are the major emitters.
It is true that over the next hundred years most of the growth in emissions is going to come from Asia, from China, from India, from Southeast Asia, but how politically we're going to convince them to sequester the CO2 from the coal they burn, how we're going to actually encourage them to buy more expensive technologies that don't put CO2 into the air when we're producing so much carbon dioxide, that's a real political challenge. And so, you know, the objections to Kyoto of the U.S., that China and India aren't really involved, that's really a fallacy. If we don't start ourselves, we don't show some leadership, the rest of the world isn't going to follow.
At the same time, I worry that Kyoto calling for a 10-percent reduction may not actually put in place the sort of mechanisms we need to have more radical change in the next few decades. We don't have a hundred years to do this—we can't reduce by 10 percent and then wait another twenty years for reduction by another 10 percent. We have to do something radical by about the middle of the century, and the question is, What are the political and economic mechanisms and technological mechanisms to put us in the best place of being able to do that? And hopefully that's something that Klaus Lachner's panel is going to talk about tomorrow.
Equity and the Impacts of Climate Change
Okay. When you talk about this map, you have to talk about equity, and when you think about equity you have to think about the impacts of climate change. And the impacts of climate change are going to be felt everywhere. Bob talked a lot about this. Certainly, you know, France lost something like 12,000 people in a heat wave last summer. You couldn't attribute it directly to climate change, but it certainly made people in Europe wake up to this concern. If we lost the equivalent, which would be about 60,000 Americans in a heat wave in the summer, you can bet that there would be some political action in Washington.
If we look, however, at the sort of impacts, there is some part of this discussion that troubles me. A lot of the impacts are talked about in economic terms. People try to calculate what it costs to move houses or move cities. Here is an example. This is for a sea-level rise of 1.5 meters, which is about three times what is predicted for the next hundred years, although that prediction doesn't include melting of glacial ice, so there's a big uncertainty on that. I think what we see here in Bangladesh—1.5-meter sea-level rise, 17 million people affected, and total land area affected, 22,000 square kilometers. The problem I have with this is, How can one actually argue that only 17 million are affected? These are 17 million people who are underwater. The whole society is affected. What is the economic cost of removing 15 or 20 percent of the land area, which is where people are living? How does one actually do that calculation? You just calculate the cost of homes? What sort of political disruption will it lead to, what sort of instability, what some of famine and disease? This is the interaction between many different disciplines that needs a lot of study. And this is actually something to take note of, this is another thing universities can provide, and are actually doing that now.
Here is, for example, a picture from 1997 in Indonesia—the large fires during El Niño. There is no clear evidence that this El Niño was caused by climate change. El Niño is a part of [the] natural cycle of climate variability, and yet there's a group at Columbia, the International Research Institute for Climate Prediction, run by Steve Zebiak, that works on trying to understand how to use climate prediction to make it useful to people in developing countries. But one of the other things that's important about their studies is trying to understand how human society is coupled to climate systems. That knowledge will ultimately lead to better understanding for adaptation purposes. Helping people to adapt to climate change means understanding how the complexities of a social system are coupled to a complex natural system. And that is one of the grand challenges here because again, as Bob Watson said, climate change is going to happen anyway, we're just trying to make it as little as possible, but it is still going to happen, even at 550 parts per million. And there are lots of other examples.
Let me just close here. The important point is that from a geological perspective we really are at a crossroads. This is an experiment on the Earth's climate, on the Earth's atmosphere, that hasn't been done for millions of years, and the choices we make in the next few decades are really going to determine how far outside the bounds of human experience we are going to push our planet. I really hope we don't end up at 1,000 parts per million carbon dioxide because I think there are going to be many surprises there that none of us are going to be able to predict. But most importantly the uncertainty—the fact that we don't understand exactly how a planet works at 1,000 parts per million—that is the problem. It's not a reason for inaction. That is the whole reason for doing something about it, because we don't want to try this out. We only have one planet that we can live on. The view from the rovers on Mars is pretty interesting, but it's no place I would like to spend any time.
So there's much we can do, mitigation and adaptation, but the problem is that the price for our inactions and actions is going to be paid by all of us, it is going to take something from all of us, but most importantly the people who are already at the edge, the people that Jeff Sachs talks about as the "poorest of the poor," they don't have anything to pay. When you are sick with malaria, when your parents have AIDS, when you're living in extreme poverty, and then climate change comes and hits you in some way—perhaps a drought in your area, perhaps a heavy rainstorm that leads to a huge outbreak of malaria—you don't have many options other than to just die. And that's what we're talking about here. The cost is going to be paid in human lives, and so the economic coldhearted analysis of the cost needs to be balanced a little bit by some sense of global equity.
Question 1: About Carbon Sequestration
John Mutter: Dan, thank you so much. We have time for a few questions. Same drill, two microphones, one either side. Please remember to identify yourself. We're taking names.
Woman: Thank you very much for the wonderful presentation. I'm Pastor Nancy Wright from a church in Brooklyn and very concerned about these issues. And as a layperson, could you help me by explaining a bit more what sequestering the carbon would do, how would we go about that in relation to China, and so on?
Daniel Schrag: Yeah. Basically when we talk about carbon sequestration we mean that ultimately it comes from the idea that it's unlikely we're going to be able to turn completely to renewable energy sources, and so we are still going to depend on coal and oil and gas. But one way to solve the problem of climate change is to take the carbon dioxide coming out of a smokestack and store it somewhere. You could either put it deep underground where it would hopefully stay for a very long time. You could put it deep under the ocean perhaps, or perhaps you could chemically transform it to something inert, like calcium carbonate. So there are variety of technologies and ideas that people are thinking about how to do this. On geological timescales of hundreds of thousands of years, the Earth is going to neutralize it all anyway. The problem is that we have the next sort of several hundred years to several millennia to deal with for human society, and the Earth isn't going to speed up to accommodate us, so we may have to technologically speed that up. And it is possible right now to use coal gasification processes to concentrate the carbon dioxide coming out of a coal-burning power plant, and then at least you have a concentrated effluent of carbon dioxide that you could sequester. Exactly where and how you do that and who's going to pay for it is not yet determined. But hopefully Klaus' panel will talk about that tomorrow.
Question 2: Thinking Beyond an Election Cycle
Woman: I had a quick question. Do you think it is the science and technology's progress that has caused this monster climate change? Because, you know, at one hand we are at this, you know, threshold of amazing discoveries, and at one hand we are in this dilemma as to how to deal with climate change and we don't know how to deal with it. And so are we waiting for some kind of an emergency to happen to deal with it, some breakdowns? Like you mentioned, you know, there were some people who died in some countries, that's the reason why they caught attention, you know, and small island developing states they are all sitting on bombs if their sea levels rise, their houses are displaced. So there are, you know, there are some parts of the world who are sitting on the climate-change experiences on their times every day, and on one hand of the world people are not ready to accept, you know, and debating in the senates. So how do you deal with this dilemma? I mean I completely agree that we are at a crossroads in human history, but we don't want to wait for an emergency to happen and deal with the situation where it's too late. Thank you.
Daniel Schrag: Well, thank you. I mean this is a classic problem in politics, which is how does one actually plan and think about something that occurs in longer than an election cycle? Has science and technology led to the climate-change problem? Energy technology has. Burning of fossil fuel has led to the climate-change problem. And it was started a long time ago, and we continue to be dependent on it, and until we find a cheaper form of energy, or one that we're willing to pay more for in terms of the reduced environmental costs, we're not going to solve this problem. But I think the problem comes when you try to motivate people to act on something for an effect that you can't guarantee they'll see in the next two to five years. And therefore, unfortunately, we may have to see some really terrible catastrophes before governments are pushed by public pressure to do something about it. It was very interesting, if people noticed the interesting debate over this rather silly Pentagon piece that was written on abrupt climate change. It was a rather ridiculous scenario from a scientific perspective. It talked about all sorts of doom and gloom, and yet it received enormous attention by Republican senators. No, it's a very interesting lesson, which is that, you know, decades of testimony by top scientists in this country to Congress has convinced fewer than half of the senators that climate change is something to worry about, or even a real problem. And a single Pentagon report is enough to get them all up in arms. So the credibility of science is something to worry about here.
Question 3: The Possibility of Another Ice Age
Man: Seamus Moran, African Rainforest Conservancy. I'm fundamentally optimistic, and I think that . . .
Daniel Schrag: As am I.
Seamus Moran: . . . the biggest climate threat to humanity is actually the return of the Ice Age, and in some odd way our pumping of carbon dioxide into the atmosphere may postpone that. What do you think?
Daniel Schrag: Well, I would argue with you on that. I would say that the return of the Ice Age poses no threat to humanity. The Ice Age, the glaciation occurred over a very long period of time, thousands to tens of thousands of years. And on those sort of timescales I'm kind of with the economists. Any discount rate you assume, we can adjust to that. So yeah, climate change could happen. It's a question of how fast. There are certain places where we worry about abrupt climate change even towards colder conditions because of sea ice amplifiers that Wally talked about in the very beginning, and it might affect a few regions, perhaps northern Europe around England and Scotland, but in general I don't think humanity is threatened by the Ice Ages, I think humanity is much more threatened by very abrupt changes caused by our own actions.
Question 4: The Costs of Climate Change
Woman: Hello, I'm Jessica Flagg. I'm one of the cofounders of a group called New York Climate Rescue, and our goal is to get New York become the zero-carbon emissions city. We're looking at getting pieces of legislation passed along those lines. But anyway, one of the things that really has bothered me so far is the lack of discussion about the alternative technologies, and then you made a statement which got me up here to the microphone about the cost of alternative energies in the face of the cost of the current technologies. And there's false accounting going on here. And I want to go on the record, and I think this group needs to address it, when you're talking about the cost of energy and you're looking at things from . . . I've heard, you know, nuclear energy referred to several times today, which is really troubling, because we can't deal with our nuclear waste, and if we understand the cost of carbon emissions, then we need to be costing everything that we produce that results in carbon emissions very differently. We have diseases and we have the cost of what it is going to mean in terms of those 17 million people are likely going to die in that one city. That's just one city. Now if we were going to cost things accurately, I bet business would switch over to alternative technologies pretty quickly, because you know what? It wouldn't be cost effective for them not to. And there is a false costing going on. What about the cost of this war in Iraq? What about the cost associated with the degradation of people's lives all over the world because of our egocentric consumption of a fuel that is pumping death into the atmosphere?
Daniel Schrag: Thank you for that. Let me answer it this way. I think there's a lot of very interesting work in economics to do to think about climate change because I agree with you that the costs of climate change have not been properly accounted for. No question if we included the cost of our military expenditures in the Middle East, even half the cost, into the price of gasoline, there would be a huge incentive to drive more efficient vehicles. And in addition, for example, the cost of maintaining the freeways, the highways, on our national transportation system also should go into the cost of transportation, which right now is being subsidized, so there are all sorts of externalities. But you know what? What I was talking about earlier with this carbon-cycle problem goes even beyond this, unfortunately. Because even reducing, even using more efficient technology, still if you look at the energy experts it's very hard to imagine weaning ourselves of fossil fuel entirely in the next century.
Jessica Flagg: But we need to make a start.
Daniel Schrag: Yes, we certainly need to make a start, but we need to do more than just make a start, and therefore what I'm calling for is even more radical than that.
John Mutter: I'm going to call a close to the session. Thanks again, Dan, appreciate it. Thank you to the speakers. Dan is going to be around for the remainder of the afternoon, so if you have more interesting debating with him I'm sure he'll be happy to engage.