The Physics of Climate Change Online Lecture with Lawrence Krauss

[00:00:00] Speaker 1: Hi, I want to thank first Susie Jamila and ThinkInc for helping us get the word out about the Origins Project Foundation lecture that you're about to hear. And I want to welcome you now. I'm Lawrence Krauss, and I want to welcome you to the very first Origins Project Foundation live interactive public lecture, which you're now watching. And it's very exciting for us to be able to do this. As you know, this lecture is being provided free online for all those who registered or anyone who happens to show up at the YouTube page or our web page right now. Also, after the lecture, for those who bought premium tickets, we're going to have a question and answer period, which will be an hour or so. And it'll begin about 10 minutes after the lecture ends, giving you time to go to the bathroom or whatever. And all of those who've signed up with premium tickets should have gotten an email by now with the Zoom link. And if you're so compelled that you want to purchase a premium ticket while I'm talking now, there are still some available and you can do that. And if you do that during the lecture, you'll get before the event begins a Zoom link so you can hook up and I'll be able to see you and you'll be able to see me and we'll be able to chat. And I'll answer questions about that and I'll answer questions about the lecture. OK, so now I guess I just want to go right away to to my slides and we'll begin the lecture now. So there we go. OK. One of the reasons I wrote the book that I did and one of the reasons we're having this lecture is this fact that if it isn't possible to explain the scientific principles and predictions associated with climate change in a straightforward and accessible fashion, then what hope is there for a rational public discourse and decision making on the subject? The Origins Project Foundation was created for many reasons to get people excited about the universe and about the real universe and not nonsense, but also to energize them to help address the challenges we face in the 21st century. And certainly climate change is one of those. And the idea is to provide people a basis for rational discourse. And really, a healthy democracy depends on the fact of having an informed electorate. So one of the reasons, as I say, I wrote the book and one of the reasons we're doing this is to give people information that that will help you talk to your friends and decide how to act. The scientific information, I'm not going to discuss policy at the end. I'll talk about possible policy issues, but really the idea is to provide you with the information you need to make it your own decisions about how important this issue is for you, your family and your community. I'm not a climate scientist, I'm a particle physicist and cosmologist by my training, but my feeling was that if I couldn't be able to translate it into a language that was understandable by everyone, having a lot of experience doing that with a number of books, then what hope was there? And of course, as I've had a lot of experience over the years, I've been tutored by many, many colleagues who are in climate science. I was chairman of the board of sponsors for many years of the Bulton the Atomic Scientists that ran the Doomsday Clock and we used to have a doomsday symposium every year where we'd talk about these issues and I'd hear about them. So this has been bubbling up in my own mind for quite a while. But where it really began for me is recently about a year ago, a little over a year ago, I took a group through the Origins Project Foundation to the Mekong Delta in Cambodia and South Vietnam. And this is a picture I took from our riverboat and it's it's it's it was a remarkable experience and it's a they're beautiful countries and the cultures are just amazing. And if you look at that picture, you could see on the left side a sand barge digging up sand from the from the river bottom. You know, and they're everywhere on the on the delta and we'll talk about later the impact that those are having on the river and exacerbating the effects of climate change. And and really what hit home for me was that South Vietnam in particular is kind of a perfect storm for climate change. And when we think about climate change, it often seems like it's out there and not where we are. But having visited that region and met the people and seen the wonderful cultures and how they've survived so beautifully after many, many problems in the 20th century wars and genocides and come out of it hopeful and happy. The thought that they will be exposed to potentially a more severe challenge, not of their own making, really hit home for me and and and and I'll return at the end of this lecture back to the Mekong to talk about that. Let's let's go to the next slide. In the modern era, the recognition that greenhouse gases could affect climate really began with Charles David Keeling, who was at the time a postdoc at Caltech working. He was a geochemistry postdoc and he was working on actually issues having to do with uranium, but he moved to his work to study the equilibrium chemistry of water, limestone and atmospheric CO2. And to do that, he had to build a detector of atmospheric CO2. So he did that. He constructed that and he decided to test it out in Pasadena, but everywhere he went to Pasadena, he kept getting different readings depending upon whether he was near an industrial site or far away from an industrial site. So he decided to take the detector farther away, went to Monterey and he measured a value of three hundred and ten parts per million for carbon dioxide in the atmosphere. Now, the question is, is that a big number or a small number? And with a single single number, it's hard to know. And what he did do right away, what surprised him, was he measured a different value during the day compared to during the evening. And of course, later on, he realized after meeting reading a meteorology textbook that that he was getting the local region, he was getting the air from plants around him respiring, taking up carbon dioxide during the day and in some sense releasing it at night. And so he saw that diurnal variation, which in some sense was convincing him that at least he was measuring things, but also convinced him that you really have to get away from that local pocket where he was in a valley to measure a global number. And around that time, a little bit afterwards, two oceanographers and meteorologists, Roger Revelle at Scripps and Harry Wexler at the U.S. Weather Bureau, approached him to do a project for the International Geophysical Year in 1957 to 58 to measure CO2 at the South Pole and at the Mauna Loa Station in Hawaii. And they collaborated to do that, built detectors there, and in March 1958 made the first measurement at Mauna Loa of 313 parts per million. That established what has become what is really an important day in human history for society because it's probably the most significant continuous terrestrial science project ever done. Every day since that day in March 1958, that observatory has measured carbon dioxide in the atmosphere for the last 62 years, almost 63 years now. In fact, this month, 63 years. And one of the things they discovered, which again was a surprise to Keeling, it's kind of fascinating. They measured that the carbon dioxide had a maximum in May and a minimum in October each year as they began to measure it and tried to understand that. And what, let's go back to the slides again, what, what he discovered as he described it was the earth was breathing in the Northern Hemisphere in Mauna Loa. Because the, what happens during the summertime plants are taking, and as plants are growing, plants are taking up carbon dioxide and then starting October, they begin to release it as, as, as they release their leaves and die down. And so really he saw, as he described it, the earth breathing. And since that time, well, he, that's been observed a number of times since then, but in that period from 1958 to 1960, it was observed in, in, in the South Pole that the number went up from 311 to 314 parts per million. Now that's not a lot. And given the uncertainties in, in, in various things, the question was, is that a significant reading of increase? Well, it wasn't clear at the time, but since then it's clear. And here is what has now become called the Keeling curve, which is the daily record of carbon dioxide concentration in the atmosphere at Mauna Loa every day between that period in 1958. And today, well, this, this, that was taken March 27th, 2020. And the reason that number is there is that the, that's the day last year that I wrote, finished writing the chapter on this particular subject. And so March 27th was the, was the snapshot. You can go to the Scripps Institution of Oceanography website and see every single day what the, what the carbon dioxide concentration is. It's now, as you can see, it's increased from about 315, 314 parts per million, all the way up to in excess of 3, 410 parts per million, at a peak of around 417 parts per million. In the last 60 years, it's increased by 30% alone in 60 years. Now, again, is that significant? Well, fortunately, it turns out while there wasn't a direct measurement of carbon dioxide in the atmosphere before that, we can get an indirect measurement. And that comes from looking at ice cores in, in Antarctica in particular. Ice cores are kind of like tree rings because every year snow falls gets compacted and you can see the seasonal variation and you can literally count years. And for deep cores, we now can go almost a million years back. And when snow falls and is, and eventually becomes ice, it captures little bubbles of air in the, in the ice. And those little bubbles, of course, contain carbon dioxide. So in those ice cores at each level, you can measure the carbon dioxide and get a record of carbon dioxide over geological times, not just over the last 60 years. And you can see this incorporates a combination of the ice core data before 1958 and the monolated data after 1958. They match, which is a good sign, means that things are in agreement. And you can see that at no period, certainly in the industrial age since 1750, has, has, has the carbon dioxide concentration approach anything near what it was already by 1960. And clearly not at the current time. Let's go back further back because the ice core data allows us to do that. Let's, we can go back, not just a few hundred years for, but in this case, 10,000 years. You can see local variations, but once again, the current time is unique in that 10,000 year history. And finally, if we go back in this case with these ice cores down to about 800,000 years back, you can see that there are variations. These variations are, are geological variations corresponding to the years where there was glaciation and, and when the glaciers went back. And so you can see the earth went through periodic changes and that's due to, to variations in the, in the earth's orbit around the sun. In fact, they took place on, on not on, not on century time frames, but in fact, on tens or, or, or 20,000 year time frames, as you can see. But again, during this entire period, during which there was glaciation and no glaciation, the, the carbon dioxide never, in the concentration, the atmosphere never really went above close to 300 parts per million. Whereas in the last 60 years, it's, it's gone up from 310 parts per million up to 417. Now, some people say, well, maybe that increases, it doesn't have anything to do with humans. And, and the point is there's a lot of evidence and I'll show you, unfortunately, we understand that it has to do with humans, but, but this is a looks at the, at the peeling curve and overlaid on it are certain periods in, in human history. You can see that the carbon dioxide growth in the atmosphere, right in the oil crisis in the early 1970s, it, it, it, it leveled off. And, and again, in 1980 decreased because of, of, of less fossil fuel usage by, by humans. Again, the global financial crisis in 2009, when, when there was less travel, when there was less transportation, caused a little dip. At the time of the Paris Agreement, maybe the, maybe the psychologically people started to use it a little bit less than, and, and, and there was a leveling off. And this ended in 2018, but you can actually see after the pandemic, there's again, another little dip, but just a little dip. So human activity is clearly affecting the monotonic rise of carbon dioxide in the atmosphere. For me, this is one of the, this is the time period that I find most fascinating from the year one AD to the current time. And you can see there were periods, there's a little mini ice age, um, uh, in, in, uh, in, in around 1600 or so. And you, so you can see that there were variations. And those variations were natural and geological and, and, and due to various things. In some cases, explosions of volcanoes, by the way. Um, but what's happened since 1960 is unprecedented in modern human history from, from the basically one AD in the last 20 centuries, 21 centuries. Um, you can see that now the world is in a place it's never been before, at least in modern human history. Okay. Now, people often wonder, especially deniers, ask the question, can you, can humans really have produced enough carbon dioxide to affect the entire global feature of the earth? And I think the first person to make a con, a convincing argument about that, as I was researching for the book, was a, was a Swedish geoscientist named Arvid Hogborn, who, uh, who in 1894 did a kind of wonderful calculation. It's kind of back of the envelope calculation. It's the kind I like as a physicist. He said, well, look, he knew roughly how much carbon dioxide was in the atmosphere. They wouldn't have made a specific measurement, but they knew it was around 300 parts per million. Um, uh, as I'll talk about by measurements made earlier, um, by other scientists. And Hogborn said, well, take all of that carbon dioxide in the atmosphere. What would happen if you liquefied it all or, or solidified it all? How thick a layer would it cause on the, on the surface of the earth? So if you, there was about 600 gigatons of carbon dioxide in the atmosphere in 1894, 600 billion tons of carbon dioxide, of carbon dioxide in the atmosphere. Uh, actually that's 600 billion tons of carbon in the atmosphere. I should point the other way, not carbon dioxide, but just carbon. And if you liquefied it, he showed that in fact, it would produce a layer about one millimeter thick on the earth's surface. At which point he said, clearly life can affect the carbon abundance in the atmosphere. Because if you look at the earth's surface, life is, is, is everywhere. Even in the oceans, a layer thicker than one millimeter. And began to speculate in fact, that maybe human industrial activity, after all, which is beginning to probe not just a life in a millimeter, but by digging down for fossil fuels, is actually extracting carbon from millions of years of living beings, can fear, can clearly affect the carbon in the atmosphere. And of course we have, as you'll see, and, and as you've seen already with the, the, the, the Keeling curve. Now, here is a, a, a, a block plot that I obtained from a colleague at Lawrence Berkeley lab, that shows roughly the, the carbon exchange in the atmosphere in various reservoirs on earth. So as I said, there's six, before in, by about, you know, somewhere between 1900 and 1960, there was about, let's say 1900, there's about 600 gigatons of carbon in the atmosphere. And regularly there's an exchange with the biosphere, with plants and the, and, and terrestrial soils. You can see, um, it's, it, about 120 gigatons go back and forth and, and 60 into the biosphere and, and, and, and 60 into the soils. There's exchange with the surface ocean, about 90 gigatons. And, and again, the surface ocean exchanges with the deep ocean, which is a huge reservoir of carbon of 37,000 gigatons. And, and that happens on a regular basis. Those are exchanged, uh, yearly. On top of that, there's a geological cycle, which has been around even before the existence of life, in fact. And that's, that as carbon in the atmosphere is dissolved in the water, it produces carbonic atmosphere, carbonic acid, which basically dissolves and produce carbon, calcium carbonate, which go, which goes down to the ocean floor. And it also produces shells and living things. That gets down in the, the carbonate sediment into the ocean floor. But as the global plates move and regions are subducted under the surface, that carbon gets taken into the mantle and into deep ocean earth reservoirs, and eventually builds up and is released by volcanoes. And over about a hundred million year period, that cycle equilibrizes. And, and you'll see compared to, to the, the, the carbon exchange due to life, it's very small. It's 0.03 gigatons of carbon per year is cycled through the earth by volcanoes and, and, and sediment. So it's really the, the, the rest of life that's producing a significant amount more. That was before human industrial activity. But how have things changed since that time? Yeah. Well, here's what we're doing on an annual basis. We, and this was in 2018, but the number is basically the same now in 2021. We are producing and, and putting into the atmosphere, roughly 10 gigatons of carbon per year due to human industrial activity. Now that means that in the atmosphere now, there's not 600 gigatons of carbon, but there's 830 gigatons due to the increase, as you saw from that Keeling Curb. What happens to that carbon that with that 10 gigatons of carbon per year, we, we put into the atmosphere, about half of it goes back into terrestrial biosphere and to the surface ocean and eventually into the deep oceans. Half of it remains in the atmosphere. So about five gigatons per year remaining in the atmosphere. Every year, increasing the carbon into the atmosphere. Now let's talk about the effect of carbon in the atmosphere because this, this is the famous greenhouse effect, which is poorly named because the earth is not like a greenhouse. It's a poor usage of the word when it was first done. Because a greenhouse, of course, and a, and a car, if you're in a greenhouse, you can be much warmer because of course the sunlight comes in and, and the greenhouse holds in that heat. There's a few reasons the greenhouse holds in that heat. The rate, part of the radiation, the heat radiation that's in the greenhouse can't escape through the glass. But more equally important or perhaps more important in a greenhouse, there's a barrier. There's glass that stops heat from escaping. The earth doesn't have such a barrier. And people often, when, when they try to be skeptical of the greenhouse effect, recognize that difference. But the real greenhouse effect in the earth has nothing to do with that, that glass barrier, but rather to the other effect. The fact that sunlight coming in is not as easily radiated going out. And I want to, I want to go through those numbers right now for you. So the sun provides the heat that keeps the earth going. And for some people, it may be a surprise to learn that the earth is a sphere. Okay. If it were a disk directly parallel or perpendicular to the sun's rays, then the sun is depositing about 1314 watts per every meter squared of surface directly perpendicular to the sun's rays. But the earth is a sphere. And the sphere has four times the area of a disk. So the average radiation impacting on the earth from the sun is one quarter times, not 1314, 1361. So one quarter times 1361 is three, about 340 watts per meter squared, is the average energy of the sun hitting the earth each day. Now, what happens? Well, we've got 1361 watts per meter squared hitting each meter square of the earth. And then, of course, to understand the total heat absorbed by the earth from the sun, or at least impinging upon the earth from the sun, you multiply it by the surface area of the earth. In this case, sorry, the surface area of an effective disk facing the sun. That surface area is pi r squared. And you get the total energy impinging on the earth. Now, some of it is reflected right away. Some fraction, a, is reflected right away. So the amount of energy power coming into the earth is one minus a, the fraction that isn't reflected, times the total power coming from the sun. And when you work it out over the earth, you get about 10 to the 17 watts. Or about, about 100,000 gig, a terawatts. About 100,000 terawatts of power. Now, the reason I'm talking about terawatts is rather interesting to me. Humanity, all of humanity uses about 20 terawatts of power. And that means that the sun each day is, is sending roughly 10,000 times as much energy as all of humanity uses in solar radiation. One of the reasons that many of us think the sun is a good place to look for energy. 10,000 times as much energy is impinging on the earth's surface each day as, compared to that, total usage by human industrial activity. In any case, that's the power in. Now, the, the, the central premise of climate and physics is not, is not very difficult. It is that power in equals power out if nothing's going to change. So how much power is going out of the earth? In equilibrium, if the temperature is not going to change, P in has to equal P out. So, so if, if the earth is, is radiating as much out as is coming in, the temperature will remain the same. Okay. Now, the other piece of physics that you need to know, is that a hot body radiates as the fourth power of the temperature. So, we can just say, okay, the earth is radiating with a surface area of four pi r squared, times some constant times T to the fourth. And that, if it's not going to, if the temperature isn't going to change, has to equal 10 to the 17th watts. This calculation was first done by Joseph Fourier, a very famous mathematician and physicist, I think in 1824. And he did that calculation and said, what, and solved for T, said, what should be the temperature of the earth? And when he did, he found out the temperature of the earth should be 18 degrees below zero Celsius. And he was frigid, much colder than the polar vortex was, and for many, over most of the United States, and some of Canada. And, and it was 1824. He said, if this is true, the earth should be frozen solid. The temperature of the earth should be much lower than it actually is. The actual temperature of the earth is 15 degrees Celsius, okay? 33 degrees warmer Celsius than this simple calculation would, would, would predict. And so the answer is there had to be something else keeping the earth warm. And, and he began to recognize, and in fact, he was the first one to suggest what might now be called the greenhouse effect. And did some experiments saying maybe there's an insulating layer that's holding the heat in. And we can, we can understand this by looking at, at, at, at radiation coming in. The sun's radiation comes at a given set of frequencies in micrometers, less than one micrometer. It's, it's, if you look at the visible light from the sun, it's, it's in the range shown there, much less than a micrometer. And that's, and that, that, in that wavelength band, um, the atmosphere is transparent. But if you look at what would be the radiation emitted by a, a surface body at 15 degrees Celsius, uh, you see the curve that we, I show you for the earth. Generally, it'll be emitting in the, in the band that peaks around 10 micro, micrometers or microns, as we call it. A very different radiation band. And the atmosphere is transparent in the smaller radiation band, but isn't transparent in the, in the larger wavelength band. That's in the infrared. The smaller band is, is visible light. The larger wavelength band is the infrared. And, um, and you could, and the atmosphere is not transparent there. So, let's go through and do a simple calculation, a very simple model. This is what I showed you before. Some fraction of, of, of the sunlight is reflected in the surface of the earth. But now we, now we have this layer of atmosphere that's doing some absorbing. And so, say that now the radiation that gets out into space is not the radiation emitted from the surface of the earth, but rather some smaller fraction because some fraction of it is absorbed. So the energy, the power going out is one minus b times the radiation emitted from the surface of the earth, where one minus b is now a number less than one. And that means that if, that, that, that the power radiated by the earth is the power that gets into space divided by one minus b. But since one minus b is a number less than one, that's much bigger than the power out. So it means the earth can radiate much more than you, in order to get a power out that's equal to 10 to the 17th watts. The earth is actually radiating at the surface much more energy, but a lot of it's being absorbed. And therefore you get a temperature much, much greater than minus 18 degrees Celsius. And that, and, and this is a very simplified model because in fact the, it treats the atmosphere as one bulk medium. But as I'll talk to you about, it's vitally important that the atmosphere is colder at the top and warmer at the bottom, as you'll see when we try and actually make some more realistic predictions. Here is, here is a, a, a, a picture, um, uh, actually, uh, provided by, uh, uh, uh, the U S government, NOAA, um, the, the National Oceanographic and Atmospheric Administration. The, uh, that actually shows the radiation coming in and what's happening. So a hundred, if you wish, is, is, is, uh, uh, is the number coming in and normalized to be a hundred from the sun. Some of it's absorbed by the atmosphere right off. Some of it's reflected 23% of it is reflected 19% absorbed by the atmosphere. Some more absorbed by clouds, about 47% of that radiation makes it down to the earth. Now, the atmosphere ends up emitting energy into space, but, but if the atmosphere is emitting a certain temperature, it's emitting in all directions. So 49% of what was originally incumbent is, is, is emitted into space directly, but then another 49% must be sent down to earth. But in fact, the earth isn't just radiating. It's exchanging heat with the atmosphere by other means, by convection and by, uh, uh, uh, uh, water vapor. Uh, and so the earth is actually dumping a lot more radiation in the atmosphere. You see, in fact, the earth is actually dumping about 104% of what the original solar radiation coming in, into the atmosphere. And only 12% of that is getting directly into space coming from the surface of the earth. Most of the radiation being emitted into space. And this is the key point. Most of the radiation being emitted into space is coming from the top of the atmosphere. But the atmosphere is actually due to that heat exchange from the earth to keep things in equilibrium is actually radiating down to the earth an amount equal to almost the entire incident solar radiation. About 98% of what was the value of the initial solar radiation is coming and being emitted by the atmosphere down to the earth. And we can make these predictions, but these are not just predictions. We can make measurements. Here is, uh, some data that I got from, from, uh, from a network in Billings, Oklahoma, that looked on a given day, some October 3rd to 5th, 1993. For it, it looked at the long wavelength, the infrared radiation coming down from the atmosphere. There was a detector. So it's looking at infrared radiation, not the radiation emitted by the sun, but the radiation emitted by the atmosphere. And you could see this is a mid-level range. So it's about the, uh, remember the average radiation coming into the earth, giving the curvature of the earth is about 340 watts per square meter. And you can see that the radiation coming down from the atmosphere, the long wavelength radiation is precisely almost the same value about 340 watts per square centimeter. So this picture holds together, but even more than that, it holds together for other reasons, because we begin to understand. The absorption by carbon dioxide in the atmosphere. And the first, this, this, the, the physics of this is actually quite interesting. Now the first, uh, uh, person to, to, to, uh, really begin to, the real father of climate change in some sense is Tyndall. Um, uh, I think a Scottish, I think he's Scottish or Irish. I can't remember. Um, scientist who in 1853 really began to do the first studies to measure the absorption of infrared radiation. That's all called dark radiation back then infrared radiation by carbon dioxide, built detectors to try and measure that absorption. And began to suggest that carbon dioxide was what we would now call a greenhouse gas, which absorbs infrared radiation and helps lead to that effect I talked about earlier. But the real father of the, of the greenhouse effect is, is a, is a Swedish chemist called Svante Ahurinius, who was an interesting guy actually. And, and I was fascinated for me to learn about him a little bit more. Um, he was, well, he was, uh, he, he seemed to have trouble with others throughout most of his life. His PhD thesis basically got a D. He barely passed. He then complained and protested. It got raised to a C. Eventually he somehow managed to be able to, uh, get on the faculty, um, in chemistry and in Uppsala. Uh, but was not particularly liked by, by his colleagues who barely voted him on. Somehow, in spite of that, he rose to the level of rector of the university, the head of the university, which again there was complaints when he became head of the university, but he did. Eventually, getting on to the Royal Swedish Academy of Sciences, squeaking in that election where he was elected to the Royal Swedish Academy of Sciences, which is the academy that gives out the Nobel Prize. And interestingly, three years later, he was the first Swede to win the Nobel Prize in chemistry in that case. And you might think that was a little bit of nepotism, and maybe it was, but happily, it turns out Arrhenius' contribution to chemistry were incredibly important, so he certainly deserved it. But Arrhenius, in 1896, released a very important paper where he basically laid the foundation of what we now call the greenhouse effect, argued that a doubling of carbon dioxide in the atmosphere would change temperature of the Earth. He argued, at the time, given the data that he had, and I showed the data in the book and talked a little bit about that, would change the temperature of the Earth by five or six degrees, which he thought was a wonderful thing. Living in Sweden, he loved the idea of the Earth getting warmer. And so he, and he began to speak publicly about this, about this, and he actually used, um, uh, Arrhenius' papers and translated them into English for the first time for other people. But Arrhenius' work didn't have the effect it might have because of another Swede, uh, Knud Angstrom, who, uh, I thought he was, there's a, well, one of the, a word for, for a unit of length in physics is the Angstrom. And I thought he was the Angstrom behind that, but that was actually his father, but Knud Angstrom, for a number of reasons, argued that Arrhenius was completely wrong in his arguments about what carbon dioxide could do. And I talk about some of these things at length in the book, one I want to talk about here. This is, this shows absorption by water and carbon dioxide in the atmosphere. Water is a greenhouse gas, and Knud Angstrom argued, look, carbon dioxide absorbs, if you look at the range between 10 and 20 microns there, carbon dioxide absorbs in a range that's similar to, to, to water. And therefore, adding carbon dioxide in the atmosphere isn't going to do anything because water is already absorbing. The problem is Knud Angstrom didn't realize, it wouldn't have the resolution and spectroscopy that we now have, to see that the, the water peaks were, there were, there were many, many peaks and troughs, whereas the carbon dioxide absorption peak is very broad and it can actually absorb between those hydrogen, those water peaks and can have an effect. But then he said, it doesn't matter because if once things are saturated, once you're absorbing a hundred percent, it doesn't matter if you increase the carbon dioxide abundance anymore, you can't absorb more than a hundred percent. And he was right and wrong because he didn't understand the nature of, of absorption peaks, which are not, always at a single frequency, but spread out. So here's a, just a, a, a, a schematic of one peak of absorption now in the IR band. So say in that peak, the abundance of carbon dioxide is sufficient that at an absorption rate of two in this normalized value, at an absorption rate of two, it saturates. Namely, all radiation in that frequency band is absorbed by carbon dioxide, okay, for, for absorption factor of two, but if I increase carbon dioxide in the atmosphere by a factor of four, of four, then all frequencies where the absorption factor is bigger than one half will now be absorbed. But as you can see, what that does is it increases the frequency range over which radiation is absorbed. So, of course, the region before where things were saturated is still saturated, but what Engstrom didn't realize is that you broaden the reason and you open up more frequencies that can be saturated. And this is a very important effect, as I'll show you. Now, in fact, let's go from theory to data, let's, this is some modern data taken, um, uh, I believe by a group in Wisconsin and it's up in the Arctic Circle. So, in fact, we have two different measurements, two different measurements, one, um, from a satellite or a balloon at 20 kilometers looking down to the earth, looking at the, at the frequencies of radiation that are emitted by the earth, and another with a detector on the earth. Now, if you look at those dashed curves, what are they? Those are called black body curves. Namely, if you had a black body at a certain temperature, you can see one there, 260 degrees Kelvin, um, uh, which is, uh, zero degrees Celsius is 273 degrees Kelvin. And so, if you, 260 degrees Kelvin is below zero Celsius. But if you had a, uh, a black body, the earth radiating at that temperature, it would emit radiation with that kind of general curve. And what you can see, if you're looking down, is that in the regions where carbon dioxide isn't absorbing radiation, you'll see radiation from, uh, from effectively the surface of the earth. This is in the Antarctic, below zero. You can see it's following that curve. But right there around, around what, uh, a wavelength, a wave number, in this case of a little over, uh, a thousand to 50, that corresponds to around 10 microns. That's where carbon dioxide is absorbing. And there's a lower frequency where it's also absorbing. You see the characteristic temperature that it's now experiencing is crossing a curve that's much colder. Why is that much colder? Because now, because carbon dioxide is absorbing all that radiation, now it, the atmosphere is emitting that radiation for much higher than the earth's surface. And it's much colder up there. So you're now seeing radiation emit, being emitted from a surface, which is maybe 30 or 40 degrees colder than the surface of the earth. And that will be an important effect. Also, if you're at the surface of the earth, if you look at the lower curve, again, if you, if you're looking in the regions where, where carbon dioxide is not absorbing. Then you're looking at radiation directly from space and you're seeing how much, how much colder you're seeing around, you know, 800 to a thousand. It's much, much colder. It's falling a curve of 160 degrees Kelvin. But right there in that peak where carbon dioxide is absorbing, you're seeing it's now much warmer, but now characteristic around 230 degrees Kelvin. And that's because now that, that region of frequency, the radio, the atmosphere is absorbing the radiation. You're not seeing it from space. You're seeing the radiation being emitted from the surface, the atmosphere down. And that's why it's, it's warmer than space itself. So you're seeing the effect I, I, I described, namely the fact that the atmosphere is absorbing in that frequency band. And that's the frequency band that's ultimately producing what we now call the greenhouse effect. Now here is, here are our theoretical curves based on the best atmospheric models you can have of what happens if you start out with 300 parts per million of carbon dioxide, which is, of course, much less than there was even at, at, at, at, in the, uh, turn of the century, last century. And you can calculate, and you can see how much in that, in that, uh, orangey red curve, um, you can see that there's a, that there's a trough where the, where the carbon dioxide is absorbing, um, some of the radiation that would otherwise go out into space, and, and you're seeing that basically the earth is emitting around 260, uh, watts per meter squared out into space because of that absorption. But if you double the carbon dioxide, you, what you can see is the wings of that trough are a little bit broader. You know, the curve I showed you earlier, the schematic curve was, was a much exaggerated version, but by increasing the carbon dioxide, you're increasing the frequency range of absorption. In this case, just by about one or two percent, but it's enough to lower the radiation emitted into space by 3.39 watts per meter squared. And that produces an imbalance because it says beforehand, when things were equal, when the power in equal power out, the temperature was, was remaining constant. But now when you add carbon dioxide in the atmosphere, the power you're emitting is 3.3 watts per meter squared less than it would be otherwise. And that's radiation that heats up the Earth. And 3.3 watts per meter squared may not seem like a lot, but when you multiply it over the entire surface of the Earth, it's a lot of heat. It's a lot of heat, and that is basically the fundamental quantity that is relevant for understanding climate change. It's called radiative forcing. We can measure it and we can predict it, and it's a few watts per meter squared. Now this is really how carbon dioxide heats up the surface of the Earth. Really the action is at the top of the atmosphere. So originally, let's say we have 600 gigatons of carbon in the atmosphere in 1900, and we have a temperature in balance and the radiation out is equal to the radiation in. And the length of that little squiggly line is the power that the Earth is emitting into space. And in equilibrium, that power is equal to the total amount of radiation coming in. So things are in balance. What happens if you double the CO2? What happens is because CO2 is absorbing the atmosphere, the point in the atmosphere where you can where radiation is now free to go into space is higher up because more of the atmosphere is opaque. So the atmosphere is emitting radiation from higher up, but at a higher altitude, it's colder. So the atmosphere is emitting at a colder temperature. And since the radiative power goes to the fourth power of temperature, that means the atmosphere is emitting into space less radiation than would be otherwise, and the gap is what we call radiative forcing. Now eventually, if nothing else changes, eventually you get to an equilibrium again, where basically the top of the atmosphere will be hotter than it was before, and you'll be emitting as much radiation as you were before. But if you look at those curves, the lines, if the top of the atmosphere is hotter than it was before, then the surface of the Earth is hotter than it was before. And that's the effect of the greenhouse effect, so really the greenhouse effect is really an effect that's occurring at the top of the atmosphere, and first what it does is produce an imbalance where more energy is stored in the Earth than it's radiated, and the Earth heats up, but eventually the Earth heats up, so the top of the atmosphere heats up, but so does the bottom of the atmosphere where the Earth is, and that's the substance. Now, this is measuring basically the effect of radiative forcing due to different greenhouse gases. Carbon dioxide is just one of them, there's methane, nitrous oxide, other gases including water, and you can see how over the period from 1980 to 2015, that radiative forcing effect gone up from about 2 to almost 3 watts per meter squared due to just those quantities. Now, the Intergovernmental Panel on Climate Change produces regular reports, and this is one of the more recent reports, I think this one's from 2012, but it might be from 2018, I forgot which one I picked for this image, and it measures the radiative forcing, which is the key effect, and you can see that carbon dioxide is by far the largest impact here in the radiative forcing. This is the relative radiative forcing compared to 1900, compared to what it was when it was basically 600 gigatons of carbon in the atmosphere, and you can see that carbon, the increase in carbon dioxide between then and 2012 has produced that radiative forcing, but there are other, there's methane, nitrous oxide, various halocarbons, there are other effects. For example, some land use reduces, you know, causes reflection of light if you wish, and reduces the absorption of radiation of the earth, so do clouds. But when you include all of these effects, the net anthropogenic, the net radiative forcing produced by humanity averages around 1.6 watts per meter squared at this time, and that has produced a temperature change, which in fact, if you actually describe in the book how we can kind of calculate this, but ultimately, it turns out there's more or less a linear relationship between the radiative forcing and temperature change. And the factor is about 0.75, so if you multiply 1.6 by 0.75, you get, you predict about 1.2 or 1.3 degrees of warming since 1900. What have we seen? Well, if you look at it since 1900, where we're in that curve, you see the global temperature was that about minus 0.4, it's normalized to be 1960 to be zero. So it's about 0.4 degrees Celsius below that in 1900, it's about 0.9 degrees above it in 2020, you add the two, you get 1.3 degrees Celsius, you get exactly what you'd predict, essentially. Now, this is really important, because people often point out, and I often point out, that correlation is not causation. And therefore, correlating temperature to carbon dioxide themselves doesn't show you that carbon dioxide is responsible for heating the atmosphere. But if you have a theoretical prediction that tells you why you should have that correlation, then correlation may be causation. And this predicts bang on exactly what you see. And if it walks like a duck and quacks like a duck, it's probably a duck. I mean, you could argue that maybe there's some conspiracy that many other things that cancel out everything completely, can't make, that cancel out all the predictions that we make, and something else is responsible. But here, a simple, basic calculation, which is really based on 150-year-old physics. Nothing, you know, high school level physics, as I discuss in the book, developed sometimes accidentally by scientists over that period, predicts exactly what we're seeing. Too often, because, of course, the details of climate change, how climate is going to affect currents and temperatures across the globe, which I talk about in the book, too, that requires supercomputer models of the atmosphere and the Earth. And people think, well, I don't trust those. Those predictions are not believable. But in fact, the fundamental prediction of the global temperature rises is, it doesn't require supercomputers, it just requires basic physics. And the physics agrees with observations. Okay. If you don't, if you think it's an accident, here's a curve I got from Jim Hansen, a very well-known climate scientist. And this is just looking at the observations of temperature, because you can actually measure, by looking at isotope ratios in ice cores, you can also measure the temperature over periods of the Earth. Going back 400 or 800,000 years. And just taking the observed carbon dioxide and multiplying by 0.75, a very rough thing, you can see what good agreement you have. So if you don't believe what's happening now, you can see that over a 400,000 year period, understanding the forcing produced by carbon dioxide in the atmosphere and comparing it to the observed temperature gives you a pretty good agreement. And again, it tells you the physics is working. And it's unlikely that there's some hidden conspiracy going on that's canceling out the well-known physics. Now, the next thing I want to talk about is the Las Vegas effect. What I call the Las Vegas effect. Namely, what happens in the atmosphere stays in the atmosphere. And the really important thing that is important for us today is that the carbon we're putting in the atmosphere, the abundance of carbon in the atmosphere we put in there will remain up there for not decades, but centuries. Here's a calculation, and there are many different calculations that have been done that say, look at carbon in the atmosphere. So let's say we turned off all carbon in the atmosphere right now around 450 parts per million, 440 parts per million. What would happen? Well, carbon dioxide, individual carbon dioxide molecules get exchanged with the ocean, as I told you, and they have lifetime of just years, but the net abundance doesn't change. The fall off is, if you look at it, about 60%, even a thousand years later, about 60% of the carbon abundance in the atmosphere that we've put up there will remain there. So if we're at 417 parts per million and we turn it off in a few years at 430 or 440, about 60% of that, about 300 to 400 parts per million will be up there still a thousand years from now. And that's the reason there's some urgency to this, because people often say, well, we can wait. Maybe it's going to produce financial hardships now to do something about it. But every year we wait exacerbates the situation. By the way, this is the same computer calculation for what the global temperature warming is. You can see that if we turn it off now, the average warming compared to sort of 1800 or 1900 is about 1.3 degrees. That warming is going to stay there. There's nothing we can do. Even if we stop producing carbon dioxide right now, unless we take carbon dioxide out or do something more dramatic, that's going to change that. That warming is written in stone. And we'll come back to that because I think it's really important when you talk about the predictions of climate change to talk about what's written in stone, what's firm, and what's more speculative. And you can see if we continue business as usual and don't reduce our carbon production in the atmosphere, we're going to have about four degrees of warming by 2100. And that's going to remain that way for a thousand years. Now, the Copenhagen dialogue about 30 years ago produced what was called the ski slope curve. I call it the slippery slope. Basically, it says, let's say we have a target. We want to limit global warming to two degrees Celsius. It's an arbitrary number. It's not as if the world is going to end if it's 2.1, but it's a target. You can say we don't want things to increase more than two degrees Celsius above the 19th century value. What are the emission pathways to give a 67% chance of limiting global warming to that? Well, if we basically started turning the curve over 10 years ago, we would have had to reduce our emissions by 3.7% per year. But now, because we haven't turned the curve and we've been producing more and more each year, in order to reach that goal, we have to reduce it by 9%. Reduce it by 9% per year. And therefore, the requirements on us to do the same thing are more dramatic. Every year we wait. Every year we wait, we're adding 10 gigatons of carbon in the atmosphere, 5 gigatons of which it stays there. And that's 5 gigatons that's not going to go away. And you can see it's gotten even worse. That was a plot done in 2010. But here's a plot today. You can see that today, basically, if we don't turn things around by 2025 or 2025, or 2030, there's nothing we can do. We'll have already dumped enough carbon in the atmosphere that we're going to have a 2 degree temperature change. But if we want to try and limit things, as the Paris Accords wants to do, every year we wait, what we have to do is more dramatic. Here, by the way, just to give you a sense, remember there was 600 gigatons of carbon in the atmosphere before the industrial times. If we turn things around around 2030 and follow that lower curve, the net abundance of carbon in the atmosphere, by the time we basically produce zero carbon emissions, will be about 1200 gigatons of carbon. We'll have doubled the amount of carbon in the atmosphere before humans started spewing carbon into the atmosphere beyond their breathing. If we don't, if we consider business as usual to 2100, if we don't lower things by then, the total amount of carbon we'll have added in the atmosphere is 5000 gigatons. Almost 10 times more carbon that was in the atmosphere in the turn of the industrial era and for recorded Earth's history back for at least a million years. We're dramatically changing the climate that way. Now, the last thing I really want to talk about before I go back to the Mekong, I think, is this fact that it's not rocket science. And I wrote a book about rocket science. Well, imaginary rocket science, the physics of Star Trek. But people often think that a lot of these predictions require serious detailed models and they're not believable. Well, here's a prediction that doesn't require anything but high school or middle school science. Namely, we have dumped heat into the ocean. In the last 25 years, due to radiative forcing, we've dumped heat and I'll tell you how much. That heat gets equilibrated in the ocean. It takes a little while to do it. And you can see two curves here from predictions. One assuming we turn off carbon production around 2010 or 2020. The other saying we turn it off around 2100. That heat heats up the oceans and when water is heated up, it expands. And we can see that roughly 20 centimeters, two tenths of a meter of sea level rise will happen by 2100 or so. Close to that. Just independent of glaciers melting or what happens in the Arctic or ocean currents or anything else. Just because the sea level is going to heat up and rise. It's not due to anything similar, more serious. If we continue business as usual till 2100, you can see that we're going to ultimately produce one meter of sea level rise over the long run. As that heat gets equilibrated in the ocean just due to the expansion of water. And you can see that the heat, the sea level rise corresponds to the temperature increase in water as measured there. Now, if you want to get a sense of what's happened in the last 25 years, the average temperature of the oceans has increased by 0.75 degrees. That may not seem like a lot, but a Japanese collaboration turned that into another number, said it's the equivalent of having exploded 3.6 billion Hiroshima level bombs into the ocean over the last 25 years. Four atomic bombs worth of heat every second, 24 hours a day for the last 25 years. And that, as I say, is written in stone. No matter what we do now, that's the kind of sea level rise we're going to get, some fraction of a meter, a fair fraction of a meter. And that can be significant. By the way, just to show you, this is measurements that were done up to 2008. This is the sea level rise, measured sea level rise. And thermal expansion corresponded to about half of that. Half of that came from mountain glaciers and Greenland and ice, and the Arctic ice melting. Now, Greenland and Antarctica are melting faster. Here's the amount of, the gigatons of, that are, of ice in Greenland. And you can see that the Greenland ice sheet is melting. And in fact, if I put one more curve on here in 2019 and it's melting, it turns out that melting is accelerating. And we can see that. Here's the average cumulative number of melt days. And you can see in the white and blue is a low number. And as you get to green, I think I'm colorblind, you can see the number gets higher. And if you take the average between 1979 and 2007, there's very little green. But already in 2012, there's a lot. And 2012 is a big year. 2019 is an equally big year. There's a lot more ice melting. And this is maybe, this is a standard index to show you. Again, if you look at that, it's clear that Greenland ice is melting at an accelerating rate. Now, you can do some predictions and say, well, how much, in the year 3000 AD, this, in 2000, 370 parts per million, that's the amount of ice on, in Greenland. How much ice will be in Greenland in 3000, a thousand years, if we do business as usual, and we turn things off at 2100 at about 500 parts per million? Well, the Greenland ice sheet will have, will have decreased by that amount, which will have, if you look at the sea level rise, it will have corresponded to, that will be around several meters. If we increase it to 750 parts per million by 3000, then, then more of it will have, have, have melted. And you can see now you've got three or four meters, ultimately, of sea level rise. And it turns out, we know for certain, that if we go up to somewhere between 750 and a thousand parts per meter, there's a, there's a tipping point, that nothing you can do is going to stop the Greenland ice sheet from melting. And, and over a several millennia, the Greenland ice sheet will melt. And if the Greenland ice sheet melts, that's seven meters of sea level rise. And it's happened before, it's happened more than once before, as I'll show you. Let me just go to Antarctica before I show you some of these, before I try and summarize. This is the average temperature change in Antarctica. And you can see the West Antarctic ice sheet has heated up a lot in recent times. And, and my wife and I were fortunate enough to go there. This is a picture I took from our boat. This is a small iceberg, you can see. And the effects of global warming are significant in Antarctica for the following reason. This is, this shows you, there are these big, there are these big, the, the icebergs calve off these large ice sheets floating on the ocean. Now, when the ice sheets, when the ice sheets calve off into an iceberg, sea level doesn't rise because the, the, the ice sheet is already floating. But what happens is as warm water melts that, that ice sheet itself disappears and a huge, basically all of that ice shelf disappears. And we've seen that happen a few times in Antarctica in recent years. And when that happens, there's nothing to hold glacial ice black. It was flowing, but it was buttressed before by the ice sheet. Now it's not, and then it flows and that, and it flows and that flow has been accelerating Antarctica. And when that ice goes into the ocean, that raises sea levels. And unfortunately we're seeing that happen in, in, in a variety of places. And in fact, it's quite the, people argue we're already at a turning point where the ice sheets are disappeared. And these large glaciers are going to flow into the water and could produce over the course of a centuries, a two to three meter sea level rise. You can see here is a summary of, of, of the mass change in, in, uh, Greenland and Antarctica. And the summary of the two, and you can see that basically it's accelerating. It's melting down. And here is a summary now from the National Academy of Sciences of basically what we expect for sea level rise. It's built in no matter what we do, basically what we've done already, the heat we've already put in. Thermal expansion is going to produce about 0.23 of a meter. Glaciers and ice caps will do 0.37. If the current acceleration of melting that we see in Greenland continues at its current rate, it's going to produce 0.16 meters about. And similarly, and I talked together, the total you get is about 0.8 meters. So more or less close to a meter of sea level rise is built in. This is not speculative. It's going to happen somewhere between a half a meter and a meter. Now that may not seem like a lot. I'm half a meter, a meter sea level rise by 2100. Why are we worrying about that? Well, it depends where you are. It's all relative. If a meter may not seem very high, but if I take a bowling ball and hold it a meter above your foot, it seems pretty high. And this, before I go back, I want to say that this meter is one thing. If Greenland melts, we'll see seven meters. And sea levels have already been known to change by much more than that over even thousands of years of history. You can see around 15,000 years ago, as we left a glacial period and heated up, there was a huge meltwater pulse. And actually sea levels rose by 20 meters over the course of several centuries. So sea level rise that's large can happen over centuries. And to give you this, I want to show you a curve that really woke me up about 10 years ago when I started to think, how serious is this? This is what I showed you earlier. This is basically a correlation between the carbon dioxide and temperature as measured from ice cores down to 400,000 years ago. Now let me exchange for that from the Red Sea measurements of sea levels. And you can see a correlation between those things. And sea levels on earth changed by not one, not 10 meters, but 120 meters as temperature and carbon dioxide changed. So we're talking about a change that's unprecedented in the amount of carbon dioxide in the atmosphere. Temperature changes that are unprecedented potentially in the last few 400,000 years. And one meter may in the end seem like it's very small compared to what might happen. And this was the figure that made me, reminded me of that Clint Eastwood movie where he says, are you feeling lucky kid? Okay. Because ultimately, when you ask yourself, what are the likely risks? What's possible? And what can we do? Well, you say, well, this kind of thing may not be written in stone. One meter is written in stone. But is it worth the possibility that we may have something much more severe? Or is it worth thinking of innovations that can get rid of that? Now, let me, as I wind down here now, let me end by, by, um, um, talking, returning to, to the Mekong River, because, uh, uh, I just want to summarize what's going to happen there in the near term. The Mekong is the richest density of freshwater fish in the world in that river. Over a thousand species of fish expected, some not yet discovered and some extinct. It supports a population of over 14 million people directly and then rice growing, you know, even more. A greater volume of freshwater fish is harvested from that Mekong than all the rivers and lakes in the United States combined. Now, here is the problem. There's a large tide, it turns out once a day, and at the beginning of the Physics of Climate Change book, I explain how you can get a once a day tide instead of a twice a day tide. That would spell disaster if it wasn't held off by the river, because if it, if it produced in a brackish water, if it, if there was saltwater coming in, that richest rice harvesting region in the world would become brackish. And instead of having a rice bowl, you'd have mangroves. What prevents the disaster is the power of the mighty Mekong. This is not from my book. This is a book called Mekong, Mad About the Mekong, about an, of the first time the Mekong was, was, uh, mapped in the 1860s by a French group. And the problem is sea levels are rising. Philip Minderhud, uh, was the first person to basically realize that the actual elevation level in, in South Vietnam has two problems. First of all, it's subsiding due to water usage and due to the fact that the, the Mekong River is being, uh, is a lot of is being, the depth of the Mekong River is going down because sea, uh, because sand is being taken up. He shows with his hand where the zero level was when that, at the time that, that pumping station was built, and you can see it's much lower than that now. But he also realized that satellite data of the elevation of South Vietnam was wrong. And in fact, 95% of South Vietnam is less than one meter above sea level. So that if you look, this is a paper that came out in Nature early in the year. If you look at the, uh, in the dark regions here, our regions, the amount of South Vietnam that'll be more than half a meter below sea level if there's one meter sea level rise. 95% of South Vietnam will be below sea level. And interestingly enough, independently, another group looking at satellite data and realizing that satellite data of the surface of the Earth was wrong, was systematically in error. Um, gave new estimates of the elevation of much of the Earth's surface. And then they came up with a number that's exactly the same as Minderhud in South Vietnam. And they said more than 20 million people, one quarter of the population of Vietnam will live on land that's going to be inundated by 2050 in high tides. Much of Ho Chi Minh City, where we visited last year, will be below sea level, of course, unless we do something. But this isn't just South Vietnam. If you look at it, if we turn things around and don't emit much carbon dioxide in the atmosphere, stopping it around 2020 to 2030, 190 million people around the world currently occupy global land that's going to be below high tides in 2100. And if we don't stop things in the next decade or two, we have business as usual. Then up to 630 million people live below land, on land below sea levels in 2100. This is a global effect. No place is an island. And it's sad that the most significant impact is going to be in probably in places that are least likely to be able to do something about it. South Vietnam is now getting richer, maybe with enough anticipation they can build dikes to put this back. After all, much of Holland is below sea level. But a lot of the world's population won't have the resources unless the industrialized world helps. And when I was a kid, my parents had a little store and there were trinkets and I used to work there. There was a sign saying, "If you break it, it's yours." And in some sense, the carbon that's already in the atmosphere was produced by the industrialized world. And maybe you could argue we have an ethical motivation or maybe obligation to help those regions of the world that are going to be affected because of the built-in effects of climate change. Now, I don't want to end this on a downer. There are some various impacts, but technology allows us a great deal of possibility. Technology can help us. We can make transitions to sustainable energy. We can do infrastructure improvements in South Vietnam and other places around the world if we want to. There are already climate refugees in South and Central America that are coming up to the United States because of the likely effects of climate change. But one of the ways we can help stop that flow of immigrants is to provide agricultural tools that we already know how to grow more with less. In the industrialized world, if we export those techniques, then we can mediate the effects of climate change a lot. One possibility that has been suggested is geoengineering, and that is to basically put aerosols in the atmosphere that will potentially absorb or reflect sunlight. It used to scare me a lot, but my friend Dan Schrag, who I did an Origins podcast with, who's a climate scientist, has pointed out to me that those aerosols are remaining in the atmosphere only about a year or so. So even if we screw things up, it'll only last for a year. Or maybe we could try global carbon capture. I know that Elon Musk has made a big prize, and I've been involved earlier at my last university in a project looking at global carbon capture. It's quite a challenge. And maybe in the question and answer period, I'll talk about what a challenge it is. But I've already gone an hour and six minutes, so I want to end up here. But what we can do is slow, inevitable changes. If we decrease the rate of carbon increase in the atmosphere, we can stave off sea level rise. We can stave off Greenland melting for not just centuries, but millennia, giving us time to react. So technology is not the problem. The problem is probably politics, and that's the reason I'm giving this lecture. That's the reason I've written this book. Understanding the science of climate change and its likely impact is the first step. And informed and willing policymakers will then need to weigh the safety, socio-political, and economic risks associated with future amelioration challenges versus the challenge of enacting potential preventative measures now. And politicians don't lead. They follow. And the only way they're going to act is if we all demonstrate that this is a serious issue in the voting booth and in the other things we do. So what I wanted to provide you was the science. You can decide how severe you think the problem is, but you can see that the science is fundamental, understandable, and certain things are inevitable. I talk in the book about Charles Dickens' goals to Christmas past and the Christmas future, the future as it might be versus the future as it must be. And there are a lot of potential things that are much worse than one meter sea level rise, but they're more speculative. The question is, are we feeling lucky? One of the reasons, one of the ways you want to educate Congress, the foundation that I lead has just started and we're planning to, we've just got the books here. We're planning to send copies of the Physics of Climate Change, which is a science, to every member of Congress. And we're trying to raise money to do that. We've raised 3,000 or the 6,000 we need to do that. We're hoping people will continue to donate. We hope in the next couple of weeks to get those 600 books to members of Congress, not to lobby them for policies, but just to educate them and hope that they open them up or hope that their staffers open them up at least. And you can go to the GoFundMe site looking for climate education for Congress, if you want to contribute. The epilogue of the book is called Fortune Favors the Prepared Mind. It's a statement by that great scientist, Louis Pasteur. And fortune does favor the prepared mind. It's one of my mantras. It doesn't guarantee us. It makes no guarantees about the future. It just offers better odds. And I'll take those odds. So knowing what the science is will give us better odds to act accordingly to make a better future for us and our children. Thank you. And that's the end of the lecture. And now, it's now 7:15 by my watch. And we're going to take a break. Is that right, Corey? We're going to take a break for about how long? Ten minutes. Ten minutes. And some of you I'll see in a Zoom, and I'll actually get to see you, and we'll have a discussion. And we'll go on as long as you want. An hour, an hour and a half, or maybe ten minutes if you don't have any questions. So I hope this has been informative. We will be recording this and eventually streaming it and putting it on our YouTube podcast channel, which is part of the foundation. Thank you very much for having put up with me for the last hour and ten minutes or so. And I hope we'll do more of these. Take care. [01:12:29] Speaker ?: Take care. Thank you. Take care. Take care. Take care.