For the past decade or so, Anderson and many others have been attempting to measure precisely the concentrations of a host of chemicals that aren’t much more prevalent in the stratosphere than that drop of vermouth. The concentrations of these chemicals also vary widely in time and place. As for the reactions that need to be observed, some are very hard to see. “Chemically speaking,” says Anderson, “the stratosphere is a gigantic lowtemperature flame.” In the stratosphere, as in a candle’s flame, labyrinthine networks of chemical events occur. Substances appear and disappear rapidly, some so quickly that for a time there was doubt that they would ever be seen in action.
Anderson developed a technique for catching glimpses of even the most evanescent of the stratosphere’s chemicals. He has incorporated this technique into a number of small laboratories, hung those labs from large balloons, and sent them to the stratosphere. (His latest contraption is like a gigantic fishing rig; the balloon rises to the top of the stratosphere and then, by remote control, the laboratory hanging from it is reeled up and down through the stratosphere on a string twenty kilometers long.) Anderson is one of those who collect the facts and figures that theoreticians insert into their models of the planet. He feels very optimistic about the prospects for his quest. “Within five to ten years,” he says, “the stratosphere will become the first reasonably complex natural system that we will understandunderstand well enough to predict its behavior into the next century.”
Against that cheerful prospect, as Anderson concedes, stands the fact thatthe stratosphere is really very simple when compared with the other natural systems that affect it. The stratosphere seems forbidding enough, but the enormous tasks begin when carbon dioxide and nitrous oxide are thrown into the models. Anyone can make a reasonable guess about the amount of fluorocarbons that might rise to the stratosphere over the next century. Human industry makes fluorocarbons. Whatever quantities the factories produce are the quantities that eventually ascend to the stratosphere. Scientists now feel certain that none get lost along the way. No such simple equation applies to nitrous oxide or to carbon dioxide. Human beings and nature use nitrogen, and some of that nitrogen eventually turns up in the atmosphere as nitrous oxide. But the process is complex. Along the way, nitrogen is processed through the biosphere, and scientists don’t know in detail how the biosphere responds to increases in nitrogen. They can’t say how much nitrogen will lead to how much new nitrous oxide. They measure increases in nitrous oxide only after the fact. They can’t predict increases with any certainty. To gain prophetic power over nitrous oxide, they must learn a great deal more than they know now about how a very large part of the biosphere operates. The same injunction applies to theories about carbon dioxide.
To foretell manmade alterations in the atmosphere, and the consequences of those alterations, scientists must first understand how the world works in its natural state, and today some students of the atmosphere express a sense of urgency about this endeavor. Some fear that within a couple of decades human industry will have altered the atmosphere so much that it won’t be possible to distinguish what is natural from what is manmade.
Other mysteries bear on those mysteries, and these, too, look formidable. Is methane increasing in the atmosphere? Methane, it turns out, is a major source of the very scarce hydroxyl radical. So scientists need an answer to the question about methane. To get it they have to consider a number of sources, including termites in the tropics and the world’s many herds of cattle, which, improbably enough, produce important amounts of methane gas.
Scientists may soon answer the remaining questions about fluorocarbons to nearly everyone’s satisfaction, but even if that happens in five years, the investigation will have taken more than a decade of intense, well-financed research. If banning fluorocarbons in aerosols proves an insufficient remedy, an obvious, ultimate solution exists: quit producing fluorocarbons altogether. But the industrialized world has already largely given up the most dispensable uses of those chemicals. Total elimination of them would mean altering throughout the world almost all systems of cooling and refrigeration. Against such an eventuality, Du Pont has spent seven years and millions of dollars looking for another refrigerating medium, but hasn’t yet found a satisfactory one. Any complete solution would require international agreement, but so far nations other than America have taken the fluorocarbon theory seriously in inverse proportion to their domestic industries' investments in the chemicals.
Fluorocarbons are, nevertheless, a tractable problem compared with nitrous oxide and carbon dioxide. Those problems, if they are real, stem from a worldwide appetite for the most basic things—food and energy. It hardly seems realistic to think of cutting off either problem at its source.
WARNINGS ABOUT SPRAY cans seem to have initiated an era of alarms about the atmosphere. Respectable scientists, as jealous of their good reputations as Victorian maidens, nowadays offer propositions that one would expect to find in the tabloids or in the Bible. Even the scale of these hypotheses invites disbelief. The atmosphere is, however, the air shared by all living things, and modern civilization has already begun to alter the composition of the air, significantly and rapidly. About that, there is no doubt. The measurements are precise and unequivocal. The possibility does exist that some not-too-distant generation will witness the immersion of cities, or will have to carry umbrellas out into a sunshine that only the hardy cockroach is certain to enjoy. It might not turn out that way, but it seems incautious to allow these experiments in global chemistry to continue, and merely await the results.
Michael McElroy, the theoretical chemist, has been involved in the issue of ozone depletion from the beginning; he helped bring attention to the threat of nitrous oxide, and he wrote part of the National Academy’s latest report on ozone. McElroy was appointed a full professor at Harvard at the age of twentynine, and ranks as one of the most important scientists studying the atmosphere. One afternoon, in a ruminative moment, he offered a prescription for the problem of carbon dioxide. McElroy’s scheme involves no less than engineering of the atmosphere. Even small engineering projects can lead to a long chain of problems and repairs. This was global engineering, and it isn’t easy to imagine organizing the world in a grand, cooperative effort that doesn’t promise equal benefits for all. It isn’t easy to imagine even getting started on a plan like McElroy’s, but then again, it isn’t easy to imagine Manhattan under water.
"I really think that the biggest and most immediate problem is carbon dioxide,” McElroy said. “I don’t think you can go out and say, ‘Hey, let’s stop burning oil, let’s stop burning coal,’ because with the best will in the world you can’t make the switch in less than twenty-five or thirty years. But if you can control carbon dioxide you in principle control climate. And I don’t think that’s out of the question; and the way to control carbon dioxide in principle is to control a managed biosphere.
"Now, we do that on a small scale already. Take agriculture. If people had had to provide an environmental-impact statement for agriculture a hundred years ago, it would never have passed. If you proposed to take 10 percent of the land area of the earth and to control what it did, runoff and so on, well, you could never have written the statement. I think that we already do affect the earth on a global scale and I think we could go a bit further. I've been looking at what that entails. We've released—by burning fossil fuel over the past hundred years—about 100 billion tons of carbon that we have mined and kicked upstairs. If you want to pull 100 billion tons of stuff out of a diffuse global system, that’s a hell of a job. It would take quite a big vacuum cleaner. The only way you could manage it would be by using the biosphere. You try to grow more trees, which will then bind up that carboi. and bring it back into the biosphere. So you do a calculation. And it turns out that the amount of area you require is about the amount we use for agriculture. But that gets you into competition for land, with farmers and oil companies and so on. So you say, in principle can I grow forests where there’s now desert? I don’t see why not, if you really wanted to do it. If it were a global commitment. It might involve towing icebergs to the Sahara from Antarctica, or it might involve desalinizing seawater using nuclear power. But, in principle, it could be done.”
McElroy paused. “Now, if you do it, you're then managing a different planet. But that involves all kinds of controversial questions. Managing it for whose benefit? And I don’t want to get involved in that question. But in principle you could do it, or something like it.”
"In principle you could do it,” McElroy repeated. “And perhaps also, perhaps we’ll have to.”