Field Notes From a Catastrophe: Man, Nature, and Climate Change (5 page)

The phenomenon that Tyndall identified is now referred to as the “natural greenhouse effect.” It is not remotely controversial; indeed, it’s recognized as an essential condition of life on the planet. To understand how it works, it helps to imagine the world without it. In that situation, the earth would be constantly receiving energy from the sun and, at the same time, constantly radiating energy back out to space. All hot bodies radiate, and the amount that they radiate is a function of their temperature. (The exact relationship is expressed by a formula known as the Stefan-Boltzmann law, which states that the radiation emitted by an object is proportional to its absolute temperature raised to the fourth power: P/A= sT
^4*
.) In order for the earth to be in equilibrium, the quantity of energy it radiates out into space must equal the quantity of radiation it is receiving. When, for whatever reason, equilibrium is disturbed, the planet will either warm up or cool down until its temperature is once again sufficient to make the two energy streams balance out.

* P stands for power, in watts; A for area, in square meters; T for temperature, in degrees Kelvin. s is the Stefan-Boltzmann constant, 5.67 6 10
^–8
W/m
²
K
⁴
.

The world’s first ratio spectrophotometer, built by John Tyndall, was used to measure the absorptive properties of gases. Credit: Philosophical Transactions,
vol. 151
(1861).

If there were no greenhouse gases in the atmosphere, energy radiating from the surface of the earth would flow away unimpeded. In that case, it would be comparatively easy to calculate how warm the planet would have to be to throwback into space the same amount of energy it receives from the sun. (This amount varies widely by location and time of year; averaged out over all latitudes and all seasons it comes to some 235 watts per square meter, or roughly the power of four household lightbulbs.) The result of this calculation turns out to be a frigid zero degrees. To use Tyndall’s Victorian language, if the heat-trapping gases were removed from the earth’s atmosphere, “the warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost.”

Greenhouse gases alter the situation because of their selectively absorptive properties. They allow the sun’s radiation, which arrives mostly in the form of visible light, to pass freely. But the earth’s radiation, which is emitted in the infrared part of the spectrum, is partially blocked. Greenhouse gases absorb infrared radiation and then re-emit it—some out toward space and some back toward earth. This process of absorption and re-emission has the effect of limiting the outward flow of energy; as a result, the earth’s surface and its lower atmosphere need to be that much warmer before the planet can radiate out the necessary 235 watts per square meter. The presence of greenhouse gases largely accounts for the fact that the average global temperature, instead of zero, is actually a far more comfortable fifty-seven degrees.

Tyndall suffered from insomnia, which grew worse as he grew older, and in 1893 he died from an overdose of chloral hydrate—an early sleeping drug—that had been administered by his wife. (“My poor darling, you have killed your John,” he is reported to have told her shortly before expiring.) Right around the time of his poisoning, the Swedish chemist Svante Arrhenius took up where he had left off.

Arrhenius would eventually come to be regarded as one of the giants of nineteenth-century science, but his career, like Tyndall’s, began inauspiciously. In 1884, when Arrhenius was a student at the University of Uppsala, he wrote a doctoral dissertation on the behavior of electrolytes. (In 1903, he would be awarded the Nobel Prize for this work, now known as the theory of electrolytic dissociation.) The university’s examining committee was so unimpressed that it awarded the dissertation a fourth-class mark:
non sine laude
. Arrhenius spent the next several years bouncing from one foreign post to another before finally being offered a teaching position back home in Sweden. He would not be elected to the Swedish Academy of Sciences until shortly before winning the Nobel Prize, and even then his election faced strong opposition.

Why, exactly, Arrhenius became curious about the effects of CO
₂
on global temperatures is unclear; mainly he seems to have been interested in determining whether falling carbon dioxide levels could have caused the ice ages. (Some biographers have noted, although it’s hard to find any real connection, that his work on the subject coincided with his separation from his wife—earlier his student—who had taken their only son with her.) Tyndall had recognized the influence of greenhouse gas levels on the climate, and indeed had even proposed—presciently, but not entirely correctly—that variations in these levels would have been capable of producing “all the mutations of climate which the researches of geologists reveal.” But Tyndall never went beyond such qualitative speculations. Arrhenius decided to actually calculate how the earth’s temperature would be affected by changing CO
₂
levels. He would later describe this task as one of the most tedious of his life. He began working on it on Christmas Eve 1894, and although he routinely toiled for fourteen hours a day—“I have not worked this hard since I was cramming for my B.A.,” he wrote to a friend—he was not finished for nearly a year. Finally, in December 1895, he was ready to present his conclusions to the Swedish Academy.

By today’s standards, Arrhenius’s work seems primitive. All of his calculations were performed using pen and paper. He was missing crucial pieces of information about spectral absorption, and he ignored several potentially important feedbacks. These deficiencies, however, seem more or less to have canceled each other out. Arrhenius asked what would happen to the earth’s climate if CO
₂
levels were halved and also if they were doubled. In the case of doubling, he determined that average global temperatures would rise between nine and eleven degrees, a result that approximates the estimates of the most sophisticated climate models in operation today.

Arrhenius was also responsible for a key conceptual breakthrough. Allover Europe, factories and railroads and power stations were burning coal and belching out smoke. Arrhenius recognized that industrialization and climate change were intimately related, and that the consumption of fossil fuels must, over time, lead to warming. He was not, however, terribly concerned about this. Arrhenius thought that the buildup of carbon dioxide in the air would be extremely slow—at one point, he estimated that it would take three thousand years of coal burning to double atmospheric levels—mostly because he believed the oceans would act as a vast sponge, soaking up extra CO
₂
. Perhaps owing to the age he lived in, or perhaps just because he was Scandinavian, he anticipated that the results would, on the whole, be salubrious. Addressing the Swedish Academy, Arrhenius declared that rising levels of carbon dioxide, which at the time was referred to as “carbonic acid,” would allow future generations “to live under a warmer sky.” Later, he elaborated on this notion in one of his numerous works of popular science,
Worlds in the Making
:

By the influence of the increasing percentage of carbonic acid in the atmosphere we may hope to enjoy ages with more equable and better climates, especially as regards the colder regions of the earth, ages when the earth will bring forth much more abundant crops than at present for the benefit of rapidly propagating mankind.

After Arrhenius’s death, in 1927, interest in climate change dropped off. Most scientists continued to believe that if carbon dioxide levels were rising at all, they were rising very slowly. Then, in the mid-1950s, for no particularly good reason, a young chemist named Charles David Keeling decided to work out a new and more precise way of measuring atmospheric CO
₂
. (Later he would explain his decision by saying he was “having fun” trying to assemble the necessary equipment.) In 1958, Keeling convinced the U.S. Weather Bureau to start using his technique to monitor CO
₂
at its new observatory, eleven thousand feet above sea level, on the flank of Mauna Loa, on the island of Hawaii. These same CO
₂
measurements have been taken at Mauna Loa nearly continuously ever since. The results, known as the “Keeling Curve,” may well be the most widely reprinted set of natural science data ever collected.

Presented in the form of a graph, the Keeling Curve looks like the edge of a saw that is being held at a tilt. Each tooth on the saw corresponds to a single year. CO
₂
levels fall to a minimum in the summer, when the trees of the Northern Hemisphere are taking up carbon dioxide for photosynthesis, and rise to a maximum in the winter, when these trees go dormant. (In the Southern Hemisphere, there are fewer forests.) The tilt, meanwhile, corresponds to the rising annual mean.

The Keeling Curve shows that CO2 levels have been rising steadily since the 1950s. Credit: Scripps Institution of Oceanography.

The first full year that CO
₂
levels were recorded at Mauna Loa—1959—that mean stood at 316 parts per million. By the following year, it had reached 317 parts per million, prompting Keeling to observe that the reigning assumption about CO
₂
absorption by the oceans was probably wrong. By 1970, the level had reached 325 parts per million, and by 1990, it was up to 354 parts per million. In the summer of 2005, the CO
₂
level stood at 378 parts per million, and by now, it has almost certainly risen to 380 parts per million. At this rate, it will reach 500 parts per million—nearly double preindustrial levels—by the middle of this century, which is to say, roughly two thousand eight hundred and fifty years ahead of Arrhenius’s prediction.

Chapter 3

Under the Glacier

Swiss Camp is a research station that was set up in 1990 on a platform drilled into the Greenland ice sheet. Ice flows like water, only more slowly, and, as a result, the camp is always in motion: in fifteen years, it has migrated by more than a mile, generally in a westerly direction. Every summer, the whole place gets flooded, and every winter, its contents solidify. The cumulative effect of all this is that almost nothing at Swiss Camp functions anymore the way it was supposed to. To get into it, you have to clamber up a snowdrift and descend through a trapdoor in the roof, as if entering a ship’s hold or a space module. The living quarters are no longer habitable, so now everyone at the camp sleeps outside, in tents. (The one assigned to me was, I was told, the same sort used by Robert Scott on his ill-fated expedition to the South Pole.) By the time I arrived at the camp, in late May, someone had jackhammered out the center of the workspace, which was equipped with some battered conference tables. Under the tables, where, under normal circumstances, you would stick your legs, there were still three-foot-high blocks of ice. Inside of the blocks, I could dimly make out a tangle of wires, a bulging plastic bag, and an old dustpan.

Konrad Steffen, a professor of geography at the University of Colorado, is the director of Swiss Camp. A native of Zurich, Steffen speaks English in the lilting cadences of
Schweizerdeutsch
. He is tall and lanky, with pale blue eyes, a graying beard, and the unflappable manner of a cowboy in a western. Steffen fell in love with the Arctic when, as a graduate student in 1975, he spent a summer on Axel Heiberg Island, four hundred miles northwest of the north magnetic pole. A few years later, for his doctoral dissertation, he lived for two winters on the sea ice off Baffin Island. (Steffen told me that for his honeymoon he had wanted to take his wife to Spitsbergen, an island five hundred miles north of Norway, but she demurred, and they ended up driving across the Sahara instead.)