Eric Chivian & Mario Molina, "Global Environmental Issues: Effects on the Atmosphere and the Biosphere” - Ford/MIT Nobel Laureate Lecture Series

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GRAY: I'm Paul Gray, professor of electrical engineering and President Emeritus. And it is my great pleasure to welcome all of you this evening to the fifth Ford Motor Company MIT Nobel Laureate Lecture. The Ford Motor Company has sponsored now four-- this is the third year-- these lectures. And we are much appreciative of that support.

As you know from the program announcement, our subject tonight is global environmental issues, effects on the atmosphere and the biosphere. Our first speaker is Professor Mario Molina. Professor Molina is an Institute professor at MIT. If you're not familiar with that title, there are, at any one time, fewer than 12 individuals who are elected by their faculty peers to be Institute professors. And they have the freedom of the house, so to speak. They are no longer confined to a department or a school, but may pursue their interests, wherever it leads them.

Professor Molina came to MIT in 1989 with joint appointments in the department of chemistry and in the department of earth, atmospheric, and other planetary sciences. He shared the 1995 Nobel Prize in chemistry for his work on the chemistry of the ozone layer and the effect of CFCs, Chlorinated Chlorofluorocarbons, on the ozone layer. His interests now involve the chemistry of air pollution of the lower atmosphere-- in particular, the problems of rapidly growing cities. And those of you who have traveled recently to Mexico City or Bangkok or Beijing will know what that problem is.

I should announce, if you didn't see it in Tech Talk today, that Professor Molina was a recipient of the Heinz Award just a few days ago for his work in understanding and mitigating effect, mitigating effects, on air pollution, and advocating changes in public policy as they bear on air pollution.

Our second speaker tonight is Professor Eric Chivian. Dr. Chivian was co-founder of the organization called International Physicians for the Prevention of Nuclear War, an organization formed some 20 years ago, about the time Dr. Chivian joined the MIT staff as a physician in our medical department. That group, the organization, received the Nobel Peace Prize in 1985. Dr. Chivian is now director of the Center for Health and Global Environment at the Harvard Medical School. And his interests include the human health consequences of habitat degradation, species extinction, and biodiversity loss.

Now, our plan for this program is that each of our speakers will speak for some time at the lectern. And when they are both finished, they will move to the table. And we will entertain questions from the audience. Please join me in welcoming Professor Molina and Dr. Chivian.

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MOLINA: Thank you. [INAUDIBLE]. Thank you.

Thank you very much, Professor Gray, for your kind introduction. It's a pleasure for me to be here tonight as part of this Ford MIT Nobel Laureate Lecture Series and to share the podium with my colleague, Eric Chivian. I would also like to thank all of you for being here in spite of the weather we have tonight. Maybe I'm presumptuous and you're all here because you got trapped with the snow.

[LAUGHTER]

But I'm an optimist.

I want to talk tonight about global environmental issues. So let me start with this overview of the sort of issues that we are concerned about. These are just examples.

What I want to point out is we have two types of issues. Depletion of natural resources-- that includes issues such as loss of biodiversity, and so on, disposal of hazardous waste, water pollution, air pollution, and so on. But we have another set of issues that I label global. And what's happening is that the first set of issues we normally consider to be local or regional.

What has been happening in recent years is that these problems are happening in so many places on our planet that they are beginning to acquire global proportions. The second set of issues are truly global in scope because they're consequences of changes in the composition of the atmosphere, truly on a global scale. So I'm going to say a few words about these aspects of environmental problems that have to do with the atmosphere. I think Eric will talk, perhaps, more about some of the biological effects.

To put that in perspective-- show you this picture of our planet from space. We're dealing with the atmosphere. And what you really see from the atmosphere itself is just the clouds. The atmosphere is transparent, as you know. But the point I want to make here-- it's very thin. It's like the skin of an apple. And that's why, on the scale of human activities, it-- we can explain how is it that we are changing the composition of this very important system.

Another reason why this is happening is that there are certain components of the atmosphere that we label trace gases that are present in parts per million or even parts per billion levels, very small amounts. But those are the ones that have important consequences for the behavior of the atmosphere itself. The bulk constituents, nitrogen and oxygen, are fairly inert in many of these physical and chemical respects.

So I'm going to start talking about one of those problems that relates to a layer of the atmosphere that we cannot see here, which is the stratosphere. Before that, I want to point out another feature of this skin, if you want, this very thin layer, and it is the timescales for mixing. There are certain chemical compounds that, when released to the atmosphere, are very rapidly removed from the atmosphere by the cleansing mechanism that we have. Many of them are related to the presence of clouds. For example, rain removes many pollutants.

There are, however, other compounds that last days, months, or even years in the atmosphere. The timescale for mixing within each hemisphere is of the order of months. That means if you release some compounds that are sufficiently stable to remain in the atmosphere for months of years, they will be rapidly mixed within each hemisphere. Mixing between the two hemispheres takes a little longer. The timescales are between a year or two.

So let me move on to this problem-- whoops-- this problem that-- the first one that I will deal with, which has to do with the ozone layer that our planet has. What we have here is just a typical ozone profile that shows concentrations of ozone as a function of altitude. And also on this ozone layer is-- exists in the stratosphere, which is the second layer above the earth's surface. The troposphere is below. As I just mentioned, mixing in the troposphere occurs in-- pretty fast-- horizontally, a timescale of months.

But the same thing happens on the vertical scale mix. If you release species close to the Earth's surface, it only takes weeks or months for them to be rapidly mixed throughout the troposphere. But in the stratosphere, mixing occurs much more slowly. And that's because temperature increases with altitude in the stratosphere, whereas it decreases with altitude in the troposphere. That's why as you go to higher altitudes-- gets colder and colder. So consequence of those temperature profiles is these timescales for mixing.

Now, we worry a lot about the ozone layer because it has several very important functions-- one, in fact, I just mentioned, the fact that temperature increases with altitude and sets up the properties of the atmosphere. That's a consequence of the presence of ozone, which, by the way, is one of those trace constituents I just alluded to. It's present only at parts per million levels, just a trace amount. Ozone is a very unstable species. But its presence there-- the consequences to give this increasing temperature profile-- and that's because ozone absorbs ultraviolet radiation from the sun that would otherwise reach the earth's surface and have very important biological effects.

Some of that ultraviolet radiation, at wavelengths between about 290 and 320 nanometers, what we call biologically UVB, or the biologically active ultraviolet region-- that penetrates to the surface, to some extent, depending on how much ozone you have overhead. But the point is that this is a very important component of a huge natural system.

Now, what we have learned just in the past few decades-- the research I started with my colleague, Sherrie Rollins, in the 1970s is that there are certain industrial compounds that we know as CFCs, chlorofluorocarbons. These compounds are not natural. They were developed industrially to replace toxic compounds, like sulfur dioxide and ammonia, for uses such as refrigeration.

And they have several sets of properties. One is that they can be readily converted from liquids to vapors. And that's what you need in a refrigerator. They are also useful to make, for example, plastic foam, like the one you're sitting on, or as propellants in spray cans. All these uses require, then, this conversion of a liquid to a vapor, and vice versa.

Second property is they are relatively simple to make, and hence relatively cheap. And that's why they could be manufactured in large amounts industrially. But the third property, which is also very important, is that they are chemically very inert. You can even breathe them. In contrast to the gases they've replaced, like ammonia and sulfur dioxide, you can breathe them, like you do when you use a spray can, or at least that's what used to be the case in the past.

Now, what we suggested in the 1970s is that the use of these gases would have important consequences, which are summarized in this cartoon here. What happens-- because of the chemical stability, these compounds are not removed by these natural cleansing properties that the atmosphere has. They not soluble in rain, and so on.

But they can actually move to the stratosphere. This is-- mixing here just takes a few months. But here, it takes several years. And eventually, when they move above the ozone layer, they find the type of radiation that the ozone layer itself shields. And that's what breaks the molecules apart, releasing very reactive compounds that we call free radicals and, for an amplification factor, catalytic cycles. They can indeed affect ozone levels.

So a single chlorine atom can actually destroy many tens of thousands of ozone molecules. And that's why even if you have only parts per billion levels of CFCs or of these compounds, you can have significant effects on ozone. So this was a prediction in the early 1970s. Many experiments were carried out. And eventually, it became clear that something indeed was happening to the ozone layer. And of all places, where the effects were most spectacular happened to be over Antarctica, as far as possible from the sources. These compounds were mostly released in the Northern Hemisphere.

And what we have here is a normal-looking ozone profile, very similar to the one I just showed you a few minutes ago. And that was measured with balloons early in the spring. The light was just coming out in this year over Antarctica after the long polar night. And on a timescale of a couple of months, you could see that you develop this [? breadth ?] profile. Maybe at some altitudes, more than 99% of the ozone was gone.

So this is the consequence of these type of catalytic cycles. I was mentioning it. And these altitudes coincide with the presence of polar stratospheric clouds. I won't have time to go into the details of the chemistry that are very, very interesting. But let me just point out that this very spectacular effect occurs mostly at high latitudes-- also, of course, over the Arctic, although perhaps not quite as spectacular. But it became clear that ozone was being depleted not just over the poles, but at mid-latitudes as well.

And what happens-- what happened as a consequence of these findings and the scientific community working together and making a very strong scientific case-- namely, that the CFCs were decomposing in the stratosphere and, in turn, decomposing ozone-- there were some international agreements called the Montreal Protocol, first enacted in 1987, but then strengthened. That led to a total ban in the industrial production of CFCs by the end of 1995, this ban happening only in the industrialized countries, but even somewhat longer time table for the developing countries to eventually ban the CFCs as well.

So this is the first instance of a truly international agreement that we believe has actually worked. And we can show that here. This is a set of measurements from one of the CFCs, CFC-11, by this ALE/GAGE program, which is coordinated by my colleague, Ron Prinn, and the EAPS department. And you can see here this very rapidly industrial growth of industrial production of these compounds lead to increasing atmospheric concentrations of these compounds until it became clear that the Montreal Protocol was going to take effect. And around this time, then, industry essentially stopped producing these compounds except for these smaller amounts in the developing countries. And so you could see how it's-- the concentration is slowly coming down.

What happens is it will take quite a few decades for these concentrations to come down because of the stability of these compounds implies that they will remain in the atmosphere for many decades. Because of this, we do not expect the ozone layer to recover immediately. It would take several decades more before we see, for example, the ozone hole over Antarctica disappear. But anyhow, this turning around in what is a global property of the atmosphere, a consequence of an international agreement-- this is the first instance that we have of such an impact.

I'll come back briefly to this problem if I have time. But first, I want to discuss briefly yet another problem, which has to do with climate change and perhaps make some analogies with the problem of ozone depletion. And the problem of climate change-- we're worried about it also because the chemical composition of the atmosphere is changing, truly, on a global scale.

The problem has to do with the energy balance of our planet. And what we know that happens in terms of energy is that our planet receives energy from the sun. But it's essentially a steady state-- has been so for millions of years. It loses essentially the same amount of energy as it receives from the sun. And those amounts of energy in this chart here are represented by the areas under these curves, which have to do with intensity of the radiation as a function of wavelength, or color, or if you want. So we receive energy from the sun, a good fraction of which is invisible. That's why our vision developed to have maximum sensitivity for visible light. But our planet loses this energy at much longer wavelengths in the ultraviolet.

Now, I have here several equations which I will not explain in much detail. But I put them here for historical reasons. These equations-- those of you that are physicists or chemists or engineers will probably recognize them-- they were developed at the beginning of the 20th century. They were extremely important. There was a revolution in physics that led to the development of quantum mechanics and so on that names such as Albert Einstein or Max Planck are associated with these equations. So they have an enormous impact on the development of science. But it just so happens that Planck's equation also describes the shape of these curves.

So this is very fundamental science. And in principle, we can use these equations to predict what should be the temperature of our planet. All we have to know is how much energy we receive from the sun, how far is our planet from the sun, and essentially, also, the color of our planet. And if we do this, realizing the sun is around 5,700 degrees [? Centigrade, ?] we calculate that the earth should be at minus 18 degrees [? Centigrade. ?]

Again, these are very fundamental equations. In principle, there's nothing wrong with them. But there's something wrong with the number. If we really have an average temperature in our planet of minus 18, the oceans would be frozen. We wouldn't be here. So there's something that requires explanation.

But as experimental-- is we can see what else is going on in our solar system. The moon, on the average, is about the same distance from the sun as the earth. And indeed, the moon, on the average, is at minus 18 degrees [? Centigrade. ?] So the calculation was all right.

However, if you look a little bit more in detail, it turns out that on the sunny side, the moon is about 100 degrees [? Centigrade ?] on the dark side at minus 140 degrees [? Centigrade. ?] So on the average, it's indeed minus 18.

[LAUGHTER]

Nice weather.

Fortunately, the earth, back here, has an atmosphere. So the atmosphere plays a very important role in terms of distributing this energy. But that still doesn't explain the average temperature [? which you'd ?] have.

But we have another example. In this case, we go to Venus. Venus is, as you know, closer to the sun. This is a picture of Venus in the ultraviolet because in the visible, Venus is very white. That's why you can see it so bright in the sky.

So it turns out that the amount of energy absorbed by Venus, the amount of energy coming from the sun, is smaller than the amount of energy that our planet absorbs. In spite of that, the surface of Venus is very much warmer. It's around 470 degrees [? Centigrade, ?] warmer than a hot oven. And so this is because the atmosphere of Venus, in contract to our atmosphere here on Earth, is very heavy. And it consists mostly of carbon dioxide.

So what we understand now is what happens is Venus has a runaway greenhouse effect. And so let just me explain briefly then what this greenhouse effect is. The atmosphere-- I already mentioned a very important function, to distribute this energy going from the sun. But another important function is that it functions as a blanket. It's transparent to the visible radiation coming from the sun except for the presence of clouds. But it's not transparent to that energy emitted by the surface of the planet at much longer wavelengths. So it's-- that's why it functions like a cover, a mantle, around the planet. And that's what explains this enormous temperature difference in Venus. And that's what explains why, in our planet, the earth's surface is actually at plus 15 rather than minus 18 degrees [? Centigrade. ?]

So that 33 degrees difference is what we call the natural greenhouse effect. And in fact, the minus 15 degrees [? Centigrade ?] temperature that we calculated is correct, except that it's not the temperature of the surface, which is what we care about. But it turns out to be the temperatures, roughly, 6 or 7 kilometers above the Earth's surface.

So the greenhouse effect, from the point of view of fundamental physics, is very well understood. But here is what worries us. The gases that absorb this infrared radiation that I was alluding to are the so-called greenhouse gases. Their concentrations, for some of them, are being affected by human activities. And we can see here how carbon dioxide-- its concentrations has been changing with time.

So there is a different nomenclature that we normally use. We refer to the greenhouse effect. We label that whatever is changing as a consequence of human activities, what I just explained before, what happens in Venus and this 33 degrees difference in-- on our planet is a natural greenhouse effect. But just the greenhouse effect-- normally, we use that phrase in connection with these changes resulting from human activities.

Now, why is carbon dioxide increasing? First of all, you'll see these natural oscillations. And that's because it's biologically active. Respiration releases carbon dioxide. And photosynthesis absorbs it. So you see here the summer/winter variations in the concentration. The more pronounced ones are in the Northern Hemisphere, which is where the bulk of the landmass exists in our planet, and the less pronounced ones in the Southern Hemisphere, where there is less biological activity.

But what jumps out here is this steady increase. And we know now, of course, where this is coming from. It's essentially from burning fossil fuels. Roughly half of the carbon dioxide, which is a result of combustion of these organic materials, ends up in the atmosphere. The other half is captured partly in the oceans, partly by land and plants and so on.

So let me give you another perspective for these changes. I discussed carbon dioxide now. But if we look back for a whole millennium, the year 1000 to 2000, and we look at the concentration, in this case, of three greenhouse gases-- here is carbon dioxide, here is methane, and nitrous oxide-- methane you can see also increasing very recently. Where does it come from? Turns out that methane is produced by anaerobic processes, [INAUDIBLE] processes. So a large source of methane comes from ruminants, from the guts of cattle, but also from growing rice. You have rice paddies that are flooded with water. So this is indirectly a consequence of human activities. And it's all very recent.

Nitrous oxide is, to a large extent, produced by using fertilizers, nitrogen fertilizers. But the striking thing is that these curves have a similar shape. And the changes began then with the Industrial Revolution.

Well, there is one more curve that has a sort of similar shape. What we have here is temperature, temperature in our planet. And this is the average, the mean surface temperatures. You have to measure it in many places and then average it.

The red line indicates direct measurements. But if we go back a whole millennium, there were no direct measurements. But there are ways to infer what the temperature was from tree rings, from corals, from ice cores, and even from historical records. So using our best understanding of all these pieces of information, one can reconstruct what the temperature was. Here, it's actually constrained to the Northern Hemisphere, where we have data. But what is quite clear is that you have this very recent temperature jump.

So if we look at all these sets of figures, we could-- we might suspect that there's a connection between all of them. Well, but that connection turns out to be rather complicated because the climate system is complicated. So what I'm going to do is merely summarize it. And I'm going to use some of the conclusions of these so-called IPCC group, the Intergovernmental Panel on Climate Change. You can get here a little bit of information, convened by the United Nations, and so on, which, by the way, was established in a very similar way to the way we dealt with the ozone layer problem. There was an international community of scientists that provided assessments that were meant to advise politicians. And that's how the Montreal Protocol came about. This is a similar process.

And this is one of the conclusions they reached-- comes from calculations like the ones I'm going to describe briefly here. One way to look at the climate is through models, models of the climate, that have to take into account all sorts of complications-- the way the climate functions-- difficult models to build. That's only one tool. There are several other tools.

But with those models, one can compute temperature changes. And this is done for the last-- since, I'd say, in this calculation-- from 1850 to the year 2000. And the lower line here is what is calculated to happen if you do not take into account these changes in the chemical composition of the atmosphere that I just showed you.

If, however, you take that into account, then you get, instead of this lower curve, this other curve. And the upper line are the observations. So it's clear that these calculations fit the observations much better if you make a connection between those changes in the composition and what we expect to happen to the climate.

If you have established or suspect, at least, this cause-effect relationship, then you can take one more step. And then you can predict what should the temperature do in this century once you make a connection between those two sets of observations. And what happens to the temperature in this century will depend on different scenarios. It depends how society evolves, how the economy moves, and whether society imposes restrictions of emissions of carbon dioxide and other greenhouse gases or not. But what is striking here is that we have very significant temperature changes compared to what has happened in the last 1,000 years and, for that matter, in the last tens of thousands of years as well.

So what do we do about this? First of all, we have to ask the question, so what? What happens if temperature changes? I will not discuss this in any detail, but just show it to you. There are, in fact, some beneficial impacts of a warming of the earth's surface, like you might have longer growing seasons for some crops in some parts of the world. But overall, the effects tend to be negative.

I've just talked about temperature. But rainfall will also change quite significantly if, indeed, these greenhouse gases have the effects that the scientific community is assuming. Sea level rise is yet another effect. So you have a multitude of potential effects held-- in fact, that's one of the expertises of Dr. Chivian.

But then you have agricultural impacts and water resources impacts. Obviously, if you change rain patterns, the consensus is that you might get, because of this temperature increase, more extreme events. When it rains, it pours. Otherwise, you have more droughts. So it's-- that's a logical consequence of having more moisture in the atmosphere.

At this point, I should mention that water vapor itself is a very important greenhouse gas. So human activities will not directly change the amount of water in the atmosphere. But if, through changes in carbon dioxide, the temperature changes, you have an important feedback effect. This water vapor will, in turn, enhance the greenhouse effect. And that's taken into account in these calculations.

So you have other impacts. Sea level rise, of course, is very worrisome. Certain countries will disappear completely, the small island countries.

What I'm doing here-- I'll go through this very briefly, just summarize what I've said so far in terms of climate change. We have certain-- I should-- I would label these facts. The climate is clearly changing. Very few people doubt that.

The atmospheric concentrations of greenhouse gases and other gases are clearly changing [? all. ?] So that's very well-established. But what is perhaps less well-established, but certainly very logical, is that these changes have a connection and that human activities are at least partly responsible for this temperature increase. And this last point just tells you the magnitude of these changes, between 1 and 1/2 and probably 6 degrees in this century, and some changes in the way this temperature is distributed.

Let me ask a question here. With this information, what should society do? Should society do something about this problem-- I recognize that there are uncertainties-- or is it premature? Is it a matter of opinion?

Well, let me clarify, at least, my own thinking here. What scientists can do is to provide this type of information. But the actual answer to that question does not lie within the realm of science. It depends on your value judgments. It depends how you assess risks. But science can go at least one step further. And I'm showing you here the results of some very interesting calculations done by our colleagues here at MIT by the-- in the Center for Global Change Science, led by Professor Prinn.

What they have done is calculated probabilities. Since these changes in temperature are rather uncertain, you can at least assess-- it's a little bit subjective. You cannot do this experiment. We have only one planet. But you can calculate probabilities based on what you think you know about the system.

And here are the results-- two curves, one assuming that society does something, even if you-- to take actions right now, you will have a temperature change because we already changed the composition of the atmosphere. But if you continue just with business as usual, you will have much larger changes.

And then you can analyze this in any way you want. For example, there is one chance in 40 that the changes will be larger than 5 degrees. Those would be very, very large changes. They begin to be comparable to the changes within an ice age and an interglacial. Our planet would really look very different. Do you want to take that risk? Again, we only have one planet.

But you don't have to go all the way to 5. What is most likely to happen is something above 2 degrees-- remind you that we already seen half a degree change. And we see all these consequences already.

But there is one chance in 20 that you're going to be between 3 and 4. These are the sort of risks that we normally don't take. If I tell you there is one chance in 10 that you will be stuck if you drive in the snow, only some of you might want to drive. But if I tell you that there's one chance in 10 that you're going to have a bad accident, you probably won't do the driving unless you have a very strong reason to do that.

So again, this is not within the realm of science, considering we're dealing with a planet and we're dealing with these very important risks, and considering how many millions of people will be affected. In my own personal opinion, this is certainly enough reason to start doing something now, because the risks are just too large.

And just to highlight one more point very briefly, I talked about the average temperature changes. But the changes are not evenly distributed with latitude. You see that at the poles, you have some very large changes that would have very important consequences, for example, in terms of melting of the ice caps. Again, these are results from the group here at MIT.

I'm going to transition now to the last problems that I will deal with. Let me try to do that fast. But I'm still talking about climate change. And here is just a representation of the forcings. That means how much do we expect, on a relative basis, different factors do affect the climate. And one factor is the changes in the concentrations of greenhouse gases, which-- for which we have a relatively high level of scientific understanding. And the magnitude is reflected by this bar-- CO2, methane, N2O. That's what I talk about. The halocarbons are the CFCs. Those are regulated because of the stratospheric ozone problems, anyhow.

And then on the other extreme, we have changes in the intensity of solar radiation that we can do nothing about, or in between-- we also have stratospheric ozone. But in between, we have all these other effects. It turns out that they have to do with pollution. They have to do with air quality. So it's interesting that climate change is actually connected with pollution.

So what do we know about pollution? Air pollution-- considered normally just a regional or local problem. We had pollution like the episodes in London that had to do with the sulfur and coal that we knew was very damaging to people. Many people actually died from the pollution events in the generation of sulfuric acid, and so on.

But the pollution that we are more accustomed to in recent years is what we call photochemical air pollution. That was really first unraveled in Los Angeles. And we know about the ingredients of pollution are hydrocarbons, like from gasoline, that are either directly emitted or gasoline that's only partially burnt, nitric oxide, and sunlight. The combination of the three generates this type of pollution, which we know part of it is ozone, the same molecule that protects us in the stratosphere. It's actually nasty if you have to breathe it because it's very active. And it irritates your lungs. And besides ozone, the other components of pollution are suspended particulate matter that we also know has very important health effects.

So just in passing-- I know I have very little time left. But let me nevertheless just allude to the program that we're heavily involved with that has to do with air pollution in Mexico City. We're worried about pollution in megacities of the developing world, again, because there are many cities now. So pollution is happening in many parts of the world.

And this particular program-- what is interesting about it is it doesn't deal just with the science and technology of the problem, but we know that we have to deal with social, economic, and political issues, as well, to solve these real-life problems. In this case, the science itself is not in question. We know where the pollution comes from. We still have to do a lot of science to refine our recommendations to the government. But it's very important to work very closely with the governments in these developing countries to make sure that some improvements actually take place. And that has been the case in Mexico City. It's no longer the most polluted city in the world. But there's still a long distance to go.

But what I'm talking about, recall, is the context of global issues. What we have to do is to add to this pollution coming out from many cities. Recall that roughly half the population of the world now is urbanized, lives in cities. And the trend is increasing there.

But we have to add another source of pollution, the same type of photochemical pollution, that comes from things like forest fires, but also agricultural practices, such as slash-and-burn agriculture. Anytime you burn organic matter, you're going to generate hydrocarbons and nitrogen oxides that will contribute to this, making smoke and making the ozone in the atmosphere.

Now, what we know now-- I'll just show very briefly some satellite views of what happens to this type of pollution. In '98, we know there were some forest fires in Mexico. You can see the plume from satellite clearly reaching the southern part of the United States.

There were some large pollution events in Asia, again, from forest fires in '97. And the health effects were extremely large in many parts of Asia-- in this case, in Kuala Lumpur.

Let me show you a more recent event. This is just this year, in the end of January. This is West Africa. This red dot-- this is the satellite picture. But these were some individual fires. And you can see the smoke really moving over the ocean very clearly here from these satellite pictures.

One more-- you can see it here, Asia-- of course, Japan, Korea. Somewhere here is Beijing. And Shanghai, I guess, is somewhere around here. This gray color is pollution. So there are large amounts of pollution. And I believe this is the same area. You can see here again Beijing and Shanghai somewhere here covered by that. So except for the clouds, all this gray mass is pollution. This is what's-- leads to the so-called brown cloud that-- there are worries that it reaches the American continent as well.

How do we know that? Well, it turns out there are other events that are also very easily observed from satellites. In this case, it's not directly pollution, like the one I was describing, but dust storms. And their origin in these cases, like the Gobi Desert, which is also indirectly being affected by human activities-- the Gobi Desert is increasing in size relatively fast. So desertification is another of those problems that contributes to these global issues. And you can see here the timescale for these, the dust clouds, to reach the American continent from Asia is about six days. It's just how fast these things moves.

And one last [INAUDIBLE] here in terms of these pollution issues-- it's also very interesting finding-- in this case, come from this so-called [INAUDIBLE] experiments. These were measurements of the composition of air. In this case, we're showing measurements about 1,000 kilometers away from the Indian continent in two air masses that are relatively close to each other, but one is in the Northern Hemisphere-- namely, this one-- and one in the Southern Hemisphere. And if you recall, as I explained earlier, the two hemispheres are-- do not mix well.

So this represents pollution coming from India, in this case. You can clearly see the difference. You don't even see the horizon. It's pollution that has traveled 1,000 kilometers. But the effect that is really highlighted in this paper is cloudiness.

[INAUDIBLE] important component of this pollution is soot, these black carbon particles, that turn out to-- when they are incorporated into clouds, they heat them. And the clouds evaporate. So this is an example of an indirect effect of pollution. Clouds play a very important role in this energy balance of the planet. And you can either make more clouds with haze, like [INAUDIBLE] sulfuric acid droplets, or change their properties in such a way as to compete with the greenhouse effect, or else, like in the case of soot, you can add to the greenhouse effect in terms of decreasing cloudiness and increasing the amount of energy that reaches the surface of the planet.

So all these I can label as a global air quality problem. What I have here is just a summary of-- I chaired a few years ago the National Academy panel, which we label global air quality, to highlight these types of issues, the connection between air quality and climate change. In this particular report, we just made a point that we don't have enough observations in our planet to understand clearly how these problems come about. So we should do more about it.

So I'm close to the end, but want to remind you about these curves I showed at the beginning of constant methane, constant carbon dioxide, and then suddenly increasing. There is another curve that you all probably know about that has a similar shape, human population. In this case, I go back many millennia. But we are now close to six billion people, or a little bit above. And this has all happened very recently. Fortunately, it's leveling off. It's not increasing at this rate anymore. But clearly, all these dramatic changes that I [AUDIO OUT] to show you are a consequence of this increasing human population.

So let me just finish by coming back to the ozone problem. I want to give you an example to see you how we deal with these problems. As I mentioned, we dealt with the stratospheric ozone problem rather successfully. Here is an example dealing with one CFC, one that happened to be used in the past to clean electronic boards, CFC-113.

When we first suggested in the '70s that these compounds had to be banned, the electronic industry got very worried. Japan was not willing, initially, to sign the Montreal Protocol, and so on. But it turns out that societies were inventive. So many patents came about to develop these boards in different ways, to clean them, even, with water and soap rather than with these more sophisticated, but excellent, solvents. But the most interesting technology, shown here, is one in which you make clean electronic boards to begin with. So you do not need to use any solvents.

So let me end up with this view, again, just to highlight how thin is our atmosphere and just to summarize a perspective on all this. Of course, we know that people in the developing world-- that they have to increase their standard of living. They have the right to do that. And so their economies need to grow.

But it's clear that they should not grow their economies the same way that we have done it in the industrialized countries so far because our planet is not large enough to absorb all these unwanted side products of our activities. We have to learn to do it in different ways. And so that's why it's imperative that we all work together-- the industrial sector, the academic sector, environmental organizations. That's how it happened with the stratospheric ozone problem. All these sectors work together. But we have to do it once more because these new technologies will not come out of the developing world. They don't have the resources. But at least with the ozone story, we have shown that it can be done. So there is light at the end of the tunnel. Thank you.

[APPLAUSE]

CHIVIAN: That was a wonderful talk, Mario. And it's a great honor to be on the program with my friend and colleague, Mario Molina. I want to thank Paul and Priscilla Gray for inviting me to be back at MIT, where I worked for 20 years, until about two years ago, in the medical department.

I must confess that I have not started using PowerPoint. I'm reluctant, as you'll see, to part with things that have worked so well for me. I'm still using 35-millimeter slides. And for years, I must confess, I continued typing on my IBM Selectric when others were using word processors. And I still drive a 1986 Saab with over 200,000 miles on it.

There was a slide that, I believe, Professor Molina may have dropped out of his tray. This is from that peer-reviewed journal called the Weekly World News.

[LAUGHTER]

Couldn't resist that, Mario. We can turn off the slides. I'll get back to them in a minute.

A minister in Montana was tired of working on his sermon. And he decided to go bear hunting. And so he drove to some nearby mountains and hiked a trail and sat with his gun loaded. And after some hours, a large brown bear emerged and began to run towards him. The minister aimed his gun. And he pulled the trigger. But the trigger jammed. And in a panic, he began to pray. And he said, oh, Lord, I have always been your faithful servant. Please, Lord, please, please, make that bear a Christian. And at that moment, the bear came to an abrupt halt. And it put its huge paws together. And it looked up at the sky and said, dear, Lord, I thank Thee for the gift I am about to receive.

[LAUGHTER]

Now, I tell this story because, as you'll see, I'm generally rooting for the bears and-- because bears are totally unique and remarkable creatures that hold enormously important secrets for medicine, as I'll talk about shortly.

Now, when I was on a flight from Washington to Boston a couple of years ago, there was, all of a sudden, a great commotion around me. It turned out that a large brown moth had somehow gotten onto the plane. And people, being very startled and afraid when it landed on them, wanted to kill it, even the stewardesses. Everyone was in a real frantic mood.

Somehow, this unfortunate animal had wandered into the high-tech, relatively sterile world of humans, where it didn't belong. And people were very frightened of it, even though it was totally harmless. And everyone was very surprised when suddenly, I stood up and insisted that we catch the moth and let it go.

I announced this very loudly. And I must confess, I surprised myself because I didn't realize I would do this. And I didn't have a very good idea of how I was going to catch the moth. But then I thought of the vomit bag in front of me. And I blew it up. And I went after the moth. I banged a fair number of heads in the process. And I released it after we landed in Terminal B at Logan Airport, where the buses were spewing their diesel fumes. I'm not sure how much of a favor this was. But I was, as you can imagine, savoring one of those few moments in life when people ask, who was that masked man--

[LAUGHTER]

--or perhaps, in this case, who was that mad man? But I tell this story because it illustrates, it seems to me, how separated we've become from the environment in which we live, so disconnected from the natural world which increasingly exists as we become more and more urbanized and zoos and aquaria and botanical gardens-- so disconnected that true nature, like the moths, seem to many an alien creature, as a hostile force to be conquered and exploited and even killed, that the environment has come to be, for many people, an infinite resource that exists for our use alone, that we can take as much as we want from, or as an infinite sink that we can dump as much as we want into, that somehow, we can alter and degrade the atmosphere and the oceans and the forests and soils, endangering, perhaps, millions of species we share this planet with, some of which have been on Earth for hundreds of millions of years longer than we have, like sharks and dragonflies and horseshoe crabs and frogs, as if, somehow, these alterations had nothing whatsoever to do with us at all, as if we were totally insulated from them. And it seems to me that this lack of connection to the environment, this fundamental failure to understand that our health and lives depend on the health of the global environment-- that this problem is among the most important problems we face in the years ahead.

Now, what prevents us from recognizing the threat that global environmental change poses for us? For one, it's too abstract. It's too hard to relate to. As you heard Professor Molina talking about the atmosphere and the globe, it occurs over too large a scale. It evolves too slowly over time. It's outside our everyday experience, especially for those of us in rich nations, like this one, not living at the margin of survival, as large numbers of people in developing countries do all the time, at the mercy of every cyclone or crop failure.

Global environmental change is also too frightening. The specter of floods or drought or fires or famine or epidemics of infectious disease-- they're too overwhelming to contemplate. They're biblical in their proportions. And for the most part, the problems seem too large to solve, making people feel frightened or helpless or hopeless. And they'd rather just as soon think about something else.

They're also very complicated and technical. The science is very complicated. And then it's made worse, it seems to me, by scientists, and also people in public health, who write and speak in jargon-filled languages, unable to communicate with policymakers or the media or the public. So people find it generally hard, too hard to understand.