A WELL-DESIGNED MACHINE?

What A World!(Freeman Dyson, New York Review Of Books V. 50, No. 8, 5/15/03), reviewing The Earth's Biosphere: Evolution, Dynamics, and Change (Vaclav Smil, MIT Press, 346 pp., $32.95).

[T]he major theme of Smil's book . . . is the difficulty of understanding the behavior of the biosphere on a global scale. Even the nonliving processes governing weather and climate are difficult to understand. The living processes governing the fertility of forests and oceans are even more difficult. As an example to illustrate the difficulties, I look at the effects on the biosphere of carbon dioxide in the atmosphere. This is one of the subjects in Smil's book, but it is the reviewer, not the author, who is responsible for giving it emphasis here. As a result of the burning of coal and oil, the driving of cars, and other human activities, the carbon dioxide in the atmosphere is increasing at a rate of about half a percent per year.

Everyone agrees that the increasing abundance of carbon dioxide has two important consequences. First, carbon dioxide is a greenhouse gas, transparent to sunlight but partially opaque to the heat radiation that transports energy from the earth's surface into space. Second, carbon dioxide is an essential nutrient for plants on land and in the ocean. The increase in carbon dioxide causes changes, both in the transport of energy through the atmosphere and in the growth and reproduction of plants. Opinions differ on two crucial questions. Are the physical or the biological effects of carbon dioxide more important? Are the effects, either separately or together, beneficial or harmful? In his last two chapters, Smil summarizes the evidence bearing on these questions, but does not presume to answer them.

The physical effects of carbon dioxide are seen in changes of rainfall, cloudiness, wind strength, and temperature, which are customarily lumped together in the misleading phrase "global warming." This phrase is misleading because the warming caused by the greenhouse effect of increased carbon dioxide is not evenly distributed. In humid air, the effect of carbon dioxide on the transport of heat by radiation is less important, because it is outweighed by the much larger greenhouse effect of water vapor. The effect of carbon dioxide is more important where the air is dry, and air is usually dry only where it is cold. The warming mainly occurs where air is cold and dry, mainly in the arctic rather than in the tropics, mainly in winter rather than in summer, and mainly at night rather than in daytime. The warming is real, but it is mostly making cold places warmer rather than making hot places hotter. To represent this local warming by a global average is misleading, because the global average is only a fraction of a degree while the local warming at high latitudes is much larger. Also, local changes in rainfall, whether they are increases or decreases, are usually more important than changes in temperature. It is better to use the phrase "climate change" rather than "global warming" to describe the physical effects of carbon dioxide. . . .

Roughly speaking, half of the contiguous United States, not including Alaska and Hawaii, consists of mountains and deserts and parking lots and highways and buildings, and the other half is covered with plants and topsoil. Just to see how important an unmeasurable increase of topsoil may be, let us imagine that the increased root-to-shoot ratio of plants might cause an average net increase of topsoil biomass of one tenth of an inch per year over half the area of the contiguous United States. A simple calculation shows that the amount of carbon transferred from the atmosphere to the topsoil would be five billion tons per year. This amount is considerably more than the measured four-billion-ton annual increase of carbon in carbon dioxide in the atmosphere. So the increase of carbon dioxide in the atmosphere over the entire earth could be canceled out by an increase of topsoil biomass of a tenth of an inch per year over half of the contiguous United States. . . .

Another environmental danger that is even more poorly understood is the possible coming of a new ice age. A new ice age would mean the burial of half of North America and half of Europe under massive ice sheets. We know that there is a natural cycle that has been operating for the last eight hundred thousand years. The length of the cycle is a hundred thousand years. In each hundred-thousand-year period, there is an ice age that lasts about ninety thousand years and a warm interglacial period that lasts about ten thousand years. We are at present in a warm period that began twelve thousand years ago, so the onset of the next ice age is overdue. If human activities were not disturbing the climate, a new ice age might begin at any time within the next couple of thousand years, or might already have begun. We do not know how to answer the most important question: Does our burning of fossil fuels make the onset of the next ice age more likely or less likely? . . .

Since we are confronted with two plausible arguments leading to opposite conclusions, the only rational response is to admit our ignorance. Until the causes of ice ages are understood in detail, we cannot know whether the increase of carbon dioxide in the atmosphere is increasing or decreasing the danger.

The biosphere is the most complicated of all the things we humans have to deal with. The science of planetary ecology is still young and undeveloped. It is not surprising that honest and well-informed experts can disagree about facts. But beyond the disagreements about facts, there is another deeper disagreement about values. The disagreement about values may be described in an oversimplified way as a disagreement between naturalists and humanists. Naturalists believe that nature knows best. For them the highest value is respect for the natural order of things. Any gross human disruption of the natural environment is evil. Excessive burning of fossil fuels, and the consequent increase of atmospheric carbon dioxide, are unqualified evils.

Humanists believe that humans are an essential part of nature. Through human minds the biosphere has acquired the capacity to steer its own evolution, and we are now in charge. Humans have the right to reorganize nature so that humans and biosphere can survive and prosper together. For humanists, the highest value is intelligent coexistence between humans and nature. The greatest evils are war and poverty, underdevelopment and unemployment, disease and hunger, the miseries that deprive people of opportunities and limit their freedoms. As Bertolt Brecht wrote in The Threepenny Opera, "Feeding comes first, morality second." If people do not have enough to eat, we cannot expect them to put much effort into protecting the biosphere. In the long run, preservation of the biosphere will only be possible if people everywhere have a decent standard of living. The humanist ethic does not regard an increase of carbon dioxide in the atmosphere as evil, if the increase is associated with worldwide economic prosperity, and if the poorer half of humanity gets its fair share of the benefits.

I have a real affection for the entire Dyson family, if for no other reason than the fact that Dyson Spheres are such a cool idea. I also agree with the admission that we don't even know what we don't know about the theory of climate change and, if we did understand the theory, we still wouldn't be able to measure the effects with any certainty. I like the way Dyson draws the distinction between naturalist and humanist, as it makes clear that humanist is the only rational position to take and allows me to say, in only this special case, that I am a humanist. Finally, I find the idea that nature and man have found a stable equilibrium in which each can correct the problems of the other, to be both intuitively attractive and philosophically congenial.

Yet, there is quite a bit here for conservatives to be wary of. This is not the best of all possible worlds and we must be on guard against being mislead by our natural American optimism. Moreover, the fact that we don't know what's happening is not good news. The Earth may be healing itself, but it might not be and we don't know whether we are speeding towards a cliff or, if we are, are we at the top or the bottom. We must also be concerned about the other side of the humanist coin, what Dyson (and apparently Smil) refer to as the "noosphere," defined as "a planetary ecology designed and maintained by human intelligence." What is this but a somewhat more attractive Gaia hypothesis that puts man in the center of creation? Attempts to replace G-d with man are always with us, but they always end in desperate horror. Posted by David Cohen at June 17, 2003 12:57 PM