The Wizard and the Prophet2

by Charles C. Mann

  Eccentrics

  Was Margulis correct that we are fated by natural law to wreck our own future? History provides two ways of approaching this question. The first draws on the inspiring manner in which a group of scientific eccentrics and outsiders slowly built up today’s picture of climate change just in time to use that knowledge to halt its worst effects. The second focuses on the discouraging way that political institutions have been unable to grapple with the challenge and climate change became the subject of a cultural battle over symbols and values. The second approach leads to the conclusion that Margulis was correct: indecision and political tensions will give the opportunity for our wastes to destroy us. Only the first approach leads us to do something about climate change, following the path either of Wizards or of Prophets.

  The first approach begins, like most scientific tales, with someone asking a question. That someone was Jean-Baptiste-Joseph Fourier (1768–1830), the nineteenth child of a tailor in Burgundy. The tailor exerted his main impact on Fourier’s life by dying when he was eight. The boy and his many siblings ended up in an orphanage. Fortuitously for Fourier, a local rich person suggested that the town bishop enroll him in an academy run by Benedictine monks. Initially Fourier wanted to become a mathematics teacher at another Benedictine school. This required him to become a Benedictine. In October 1789 the French Revolution began. Fourier had not yet taken his monastic vows. Among the first actions of the new, anti-clerical government was to forbid any French person from taking monastic vows. Fourier, disappointed, returned to Burgundy, where he was arrested for insufficient revolutionary enthusiasm and sentenced to death. The revolution’s leaders were executed in 1794, while Fourier was still on death row. He was released and became a math professor in Paris, intending to work on equations for the rest of his life. Instead he and two hundred other savants were drafted by General Napoleon Bonaparte to accompany his invasion of Egypt. The scientists were to study the conquered land and identify objects worth stealing. In Cairo Napoleon appointed Fourier to his new Institut d’Égypte. Unlucky for him, Napoleon (1) noticed that he was an able administrator and (2) had in the interim staged a coup and become France’s sole ruler. When Fourier came home in 1801 the dictator made him head of a province in southeast France.

  Joseph Fourier, 1823 Credit 64

  The story goes that Egypt’s hot climate somehow damaged Fourier’s internal thermostat. Back in France, he was perpetually cold; late in life, he wore heavy overcoats in summer and refused to leave the fire in winter. His constant chill may account for his interest in the physical question of how heat spreads, which he studied between bouts of administration. His ambition was to become the Newton of heat, the man who set down the “simple and constant laws” that explained how “heat penetrates, like gravity, all objects and all of space.” He struggled with the work until the end of his life, his body so weak from neurotic cold that he often worked in a custom-built padded wooden box with holes for his head and arms.

  Around 1820 Fourier asked: Why doesn’t sunlight keep heating up Earth until it becomes as hot as the sun? Earth, he knew, reflects some heat back into space. But why isn’t all of it reflected? What keeps our planet cozily warm, Goldilocks-style, and not too hot or too cold?

  Fourier wrote up his conclusions four years later. Three different mechanisms account for Earth’s temperature, he said. First, the sun shines on the surface, heating it. Second, the ground is warmed by the planet’s molten core—leftover fire from Earth’s creation, in Fourier’s phrase. And third, heat could come in from outer space, which Fourier noted is irradiated by the light from “innumerable stars.” Fourier thought that the starlit warmth of outer space acted as a kind of Goldilocks cap, surrounding our planet and preventing it from radiating away too much of the sun’s heat.

  Much of this is wrong. The temperature of outer space is not, as Fourier thought, “a little below what would be observed in polar regions.” (It is actually a few degrees above absolute zero.) And Earth’s core has almost no effect on the surface. Still, Fourier got the basic idea right: Earth’s climate is a balance of constantly interacting forces.*2

  Clearer light was provided by an Irish researcher named John Tyndall. Like Fourier, he had a modest background: Tyndall, born in 1820, was the son of a cobbler. Despite having no money he was able to attend school and become a surveyor. In school he contracted the science virus. The infection worsened in adulthood until he quit his surveying job at twenty-eight and moved to Germany to study physics at the prestigious University of Marburg. There he acquired a new disease: mountain climbing. When he returned to England he became a professor at the Royal Institution in London. Combining his passions, he investigated glacial ice.

  In northern Europe and America, geologists had uncovered gigantic, strangely placed boulders, inexplicable gravel ridges, and rock strata that had been scoured by something heavy. Slowly scientists had come to believe that these were signs of the growth and recession, eons ago, of continent-sized glaciers. To create such enormous amounts of ice, temperatures must have plunged across the globe for millennia. Nobody understood how this could have happened.

  Tyndall came to suspect that the atmosphere somehow must have been involved. By this time, physicists had established that the temperature of any substance is a measure of the average energy with which its constituent atoms or molecules move, vibrate, and spin. The faster they zip and whirl, the hotter the substance. Scientists also had learned that atoms and molecules can absorb or emit light, and that this increases or decreases the energy with which they move, which in turn increases or decreases their temperature. One type of light—infrared light, invisible to the eye—is especially associated with temperature; all warm or hot objects radiate it. (The see-in-the-dark goggles in old spy movies use infrared light.) Tyndall hypothesized that the atmosphere absorbed infrared light, that this absorption governed global temperatures, and that in some fashion it was responsible for the ice ages.

  John Tyndall, ca. 1880 Credit 65

  Fourier had treated air as if it were a uniform material. Tyndall looked at its constituent gases individually, suspecting that one of them was the agent that took in infrared light and warmed the atmosphere. To answer this question, Tyndall filled long tubes with each gas, one per tube—a tube for nitrogen, a tube for oxygen, and so on. At one end of each tube he placed a hot metal box. At the other end he put a thermopile, a device that converts heat into electricity. The metal box radiated infrared light through the tube to the thermopile. Along the way, some of the infrared was absorbed by the gas in the tube; the rest, by the thermopile, converted its energy to electricity. The more infrared taken in by the gas, the smaller the electric current. In this way Tyndall could find which gas heated the atmosphere.

  It didn’t work. No matter what Tyndall did, infrared shot through the tube as if the nitrogen or oxygen weren’t there. Together nitrogen and oxygen make up more than 99 percent of the atmosphere—everything else is less than 1 percent. Tyndall’s apparatus was telling him that more than 99 percent of the atmosphere couldn’t take in infrared radiation. If that were the case, most of the infrared radiation from Earth’s surface would shoot into space like a bullet through tissue paper. Our world would be a frigid snowball, almost as cold as the moon. The question would be not why ice ages occurred, but why the world would ever be warm enough for life.

  After weeks of bafflement Tyndall was about to give up when, in a what-the-hey moment, he tried coal gas, which by this time was piped throughout London and used for lighting. To his surprise, it soaked up “about 81 percent” of the cube’s infrared radiation. Coal gas was colorless; like a clear window, it allowed visible light to stream through. But for infrared light, coal gas was like a frosted bathroom window, blocking most of it.

  Excited, Tyndall tried a variety of other gases, including ether, perfume, alcohol vapor, carbon dioxide, and water vapor. All happily sponged up infrared radiation. Tyndall was particularly interested in the last. When he re
moved the water vapor from air, it absorbed about one unit of infrared radiation. But when he added just a small amount of water vapor back to the air, it “produced an absorption of about 15.” This finding, announced in 1861, allowed Tyndall to assemble the first roughly correct picture of atmospheric physics.

  As schoolchildren learn, the sun washes Earth with every imaginable type of light wave—X-rays, ultraviolet light, visible light, infrared radiation, microwaves, radio waves, you name it. About a third of the total is reflected from clouds. Another sixth is taken in by airborne water vapor. That leaves roughly half of the incoming light—most of which is visible light, as it happens—to pass through the atmosphere. Almost all of that half is absorbed by the land, oceans, and vegetation on the surface. (A little is reflected.)

  Having taken in all this solar energy, the ground, water, and plants naturally warm up, which makes them emit infrared light, radiating it into the air. Most of this secondary infrared is absorbed by airborne water vapor, heating it up. Usually water vapor comprises between 1 and 4 percent of the atmosphere by weight. (The exact number changes with temperature, wind, and surface conditions.) But this relatively small quantity—1 to 4 percent—packs a big punch.

  When water vapor molecules take in infrared light, the extra energy kicks them into an “excited” state—their electrons go into a new, higher-energy configuration. (Here I am using modern language that Tyndall wouldn’t have recognized; electrons weren’t discovered for another three decades.) Left to their own devices, water molecules typically release this energy back into space in a few thousandths of a second in the form of infrared light. Then, like middle-aged suburbanites recovering from a fling, they settle into more stable, lower-energy states. If this was all that occurred, the atmosphere as a whole would absorb no infrared light and there would be no effect on temperature. But that isn’t what happens in the air—molecules there aren’t left to their own devices. Instead, a typical molecule in the atmosphere collides with one of its neighbors about 10 million times a second. In the few milliseconds before water molecules would release their extra energy, they may collide with nitrogen and oxygen molecules thousands of times. In those collisions, they transfer the extra energy they have picked up from the infrared radiation to the nitrogen and oxygen molecules, and thus increase their temperature. Another way of putting this is to say that a water-vapor molecule is like a machine that feeds infrared energy indirectly into nitrogen and oxygen molecules that can’t take it in directly.

  Every second of the day, the Sun emits almost every form of light—radio waves, ultraviolet light, visible light, X rays, gamma rays, microwaves, you name it. Most of it is visible or infrared light, though. Credit 66

  Almost a third of the light that comes to the Earth is reflected by clouds, dust, and the surface. Some is absorbed, notably by the ozone layer that soaks up dangerous ultraviolet light.

  The rest is absorbed by land, water, and vegetation. All heat up and release most of the light energy as infrared light—a good thing, as otherwise the planet would become unbearably hot.

  The nitrogen (N2) and oxygen (O2) that make up 99% of the atmosphere don’t react with infrared light. But water vapor (H2O) absorbs it—a good thing, as otherwise the infrared energy would shoot out of the atmosphere and the planet would get unbearably cold. Water vapor doesn’t absorb all the infrared energy. Instead it lets a few frequencies pass by—that lets just enough energy escape to keep the air from getting unbearably hot.

  Unfortunately, carbon dioxide (CO2) absorbs just those frequencies—a bad thing, because it closes the escape valve. Even though there is very little CO2 in the air, there is just enough to slowly warm the Earth.

  Some water-vapor molecules do emit infrared light, the waves bouncing down to Earth or up to the sky, only to be re-absorbed and re-admitted, or re-absorbed and the energy transferred, and re-re-absorbed and re-re-admitted, and so on. And nitrogen and oxygen molecules do dissipate their heat slowly into the cold upper atmosphere in another ramosely complicated snarl of interactions. Adding up all the pieces, the whole system ends up with just enough infrared energy being stored in the atmosphere, second by second, to keep Earth tolerably warm—and just enough leaking into outer space to prevent Earth from getting too hot. And this, Tyndall realized, was the answer to Fourier’s question. Water vapor is the master switch that controls the climate. The ice ages, he thought, must somehow have been set off by changes in water vapor. These were, in Tyndall’s excited, italicized words, the “true causes” of “all the mutations of climate which the researches of geologists reveal.”

  Tyndall paid next to no attention to carbon dioxide, because so little of it was in the air. At the time, carbon dioxide comprised about .03 percent of the atmosphere by volume (the level has risen slightly since then). If somebody collected ten thousand scuba tanks of air, the carbon dioxide in them would be enough to fill up three tanks. It was hard to credit that anything so tiny could be important—as if a child’s toy bulldozer could knock down a skyscraper. Carbon dioxide, Tyndall thought, was too inconsequential to have any real effect.*3

  For the rest of the nineteenth century researchers followed Tyndall’s lead. Few thought airborne carbon dioxide to be of any interest. Among those few, though, were two Swedish scientists, Arvid Högbom and Svante Arrhenius. Both born in 1857, they both studied at the University of Uppsala. In 1891 both joined the Stockholm Högskola, a private think tank that later became the University of Stockholm. But their paths to the institution were different. The charming, urbane Högbom was such a successful student at Uppsala that upon receiving his doctorate he was immediately hired as a professor. The impulsive, emotional Arrhenius produced a thesis bubbling with so many novel but undeveloped ideas that his exasperated supervisors almost flunked him. Convinced that his low marks had put an end to his career, Arrhenius spent the next two years bewailing his fate and sleeping on his parents’ couch. Eventually he picked himself up and took temporary jobs in German laboratories while he worked out what would become some of the fundamental ideas of physical chemistry. When these were published, Arrhenius’s reputation soared; he was able to return to Sweden and take a job at the think tank with Högbom.

  Högbom, a geologist, was interested in the origin of limestone. When carbon dioxide comes into contact with the ocean, it dissolves into the water. Seawater is also replete with dissolved calcium. The dissolved calcium and carbon dioxide combine to form calcium carbonate. Shellfish, coral, foraminifera (single-celled protozoa that usually live in tiny shells on the seafloor), and other aquatic organisms use this calcium carbonate to make their shells. Over time the shells pile up in drifts that are gradually compacted and turned into stone—limestone. Limestone, Högbom realized, is a storehouse for atmospheric carbon dioxide. But there were huge deposits of limestone in the earth and very little carbon dioxide in the air. Where did the carbon dioxide for limestone come from?

  The biggest source of carbon dioxide that Högbom knew of was volcanic eruptions, which belch out the gas from molten limestone, coal, and petroleum. If the eruptions were really big, Högbom realized, they could jack up atmospheric carbon dioxide levels substantially. Similarly, without volcanoes carbon dioxide could become scarce in the atmosphere because it would be taken in by the sea and turned into seashells. From this he concluded that “the probability of important variations in the quantity of [carbon dioxide] must be very great.” In less academic language: the air could have held much more—or much less—carbon dioxide in the past than today.

  Arrhenius was intrigued. Having won a cozy academic sinecure in Stockholm, he had lost interest in slaving over test tubes in experiments. Instead he had taken to lofty speculation about other people’s data. In this way he came up with new theories of the formation of the solar system, the age of the universe, and the inner mechanics of the sun. All of these were later proven wrong by people who actually did experiments. Learning of Högbom’s work, Arrhenius wondered if his carbon dioxide data could
explain the ice ages. Could the glaciation have been set off by lower carbon dioxide levels?

  To answer the question, Arrhenius decided to estimate what the effects would be if the concentration were doubled or halved. The calculation was laborious. Because of their differing latitudes and cloud covers, different parts of the world receive different amounts of sunlight at different times of the year. Arrhenius ended up calculating the average for each season in seven-hundred-mile bands from the equator to the poles. A U.S. scientist had measured which light wavelengths are absorbed by water vapor and carbon dioxide, and which pass through. (The wavelength is the distance between successive crests of a light wave.) Different wavelengths have different energies, which means that they affect temperatures by different amounts. Arrhenius had to include this factor, too. Snow, water, and soil don’t reflect the same amount of light; Arrhenius plugged these variances into his calculations. Et cetera, et cetera—one complicating factor after another.

  Svante Arrhenius, 1909 Credit 67

  He began his “tedious calculations” on Christmas Eve of 1894. He had just married his laboratory assistant; she left him, pregnant with their child, while he was still bent over his desk, and went to live alone on a remote island. Tens of thousands of calculations later, Arrhenius finished in December 1895. “It is unbelievable that so trifling a matter has cost me a full year,” he complained to a friend. He didn’t mention his wife.

  The results were worth the effort, if not, perhaps, the marriage. Arrhenius believed that he had established a remarkable fact: tiny changes in airborne carbon dioxide could cause an ice age. Indeed, he said, halving the level of carbon dioxide—reducing it from .03 percent to .015 percent—would cool the world by about 8°F, more than enough to set off the glaciers. Högbom had pointed out that burning fossil fuels must be increasing atmospheric carbon dioxide. Arrhenius estimated that doubling carbon dioxide levels would increase Earth’s average temperature by as much as 11°F, enough to turn most of the planet into a desert.