The Greenhouse Effect: An Interdisciplinary Perspective

Publication Source: The greenhouse effect: an interdisciplinary perspective. Population and Environment: A Journal of Interdisciplinary Studies 17: 459-489 (1996).

Note: Figures of original text are not included.

ABSTRACT: A recent, rather typical, essay argues that even if the greenhouse threat is real, even if temperatures rise and low-lying lands must be protected forever by an enormous system of dikes, such unlikely occurrences do not justify "imposing vast costs on the present generation rather than helping developing countries overcome the environmental problems that they are facing today." This review shows that anyone willing to cross disciplinary boundaries, or willing to listen to scholars who have taken this less-traveled road, can easily ascertain that this surprisingly popular viewpoint is mistaken. This review's interdisciplinary journey begins with an exposition of a few fundamental, noncontroversial, ecological insights. These are followed by a brief case study in environmental history: the CFC-ozone link. The natural greenhouse effect is then introduced, relying for the most part on comparative astronomical data and insights. The nature of, evidence for, and the largely uncertain consequences of, the enhanced greenhouse effect on Earth are taken up next. For argument's sake, a conservative and arbitrary estimate is adopted, assuming that the chances of adverse greenhouse consequences within the next century are 10%; of a cataclysm, 1%. Such chances, this review then conclusively shows, should not be taken, because there is no conceivable reason for taking them: the steps that will eliminate the greenhouse threat will also save money and cut pollution, accrue many other beneficial consequences, and only entail negligible negative consequences. Thus, a holistic review leads to the surprising conclusion that humanity is risking its future for less than nothing. Claims that the greenhouse controversy is legitimate, that it involves hard choices, that it is value-laden, or that it cannot be resolved by disinterested analysis, are tragically mistaken. Given the stakes of the greenhouse debate+the future of humanity+concerned scholars and citizens ought to understand this issue. This review provides an accessible, factual, holistic, and self-contained portrayal of the greenhouse threat.  

Now we can only wait till the day, wait and apportion our shame.

These are the dykes our fathers left, but we would not look to the same.

Time and again were we warned of the dykes, time and again we delayed:

Now, it may fall, we have slain our sons, as our fathers we have betrayed.

Rudyard Kipling

The journey leads . . . through . . . psychology and . . . evolution . . . Perhaps some readers, firmly entrenched on the humanist side in the cold war between the two cultures, will be dismayed by this apparent desertion into the enemy camp. It is embarrassing to have to repeat, over and over again, that two half-truths do not make a truth, and two half-cultures do not make a culture.

Arthur Koestler (1967, pp. xii-xiii)


A recent, rather typical, review of the greenhouse threat (Beckerman & Malkin, 1994) rightly reminds us that there is much poverty, hunger, and disease in the world. Yet the media, this review goes on to assert, choose to focus on such telegenic myths as global warming. There is, this review continues, much uncertainty about future rises in temperatures and sea levels. And, even if the pessimists are right, we can handily adapt to the projected increases. Moreover, even if we gloomily assume that world output declines by 10% as a result of future warming, this still does not justify "imposing vast costs on the present generation rather than helping developing countries overcome the environmental problems that they are facing today."

A similar situation exists, we are assured, in regard to rising sea levels. To begin with, the relevant projections keep going down. But even if we accept the extremely unlikely estimate of a 3-foot rise, humanity could build the needed sea walls at a one-time cost of $2 trillion+a trivial amount compared to the expected annual expense of freezing CO2 emissions at 1990 levels ($120 billion a year for the United States alone). And, after all, "the people in Amsterdam live below sea level." Besides, since far more land is being lost to soil erosion than is expected to be lost to climate change, we should conserve soil instead of implementing draconian cuts in CO2 emissions (Beckerman & Malkin, 1994).

We are also reminded of excellent economic and humanitarian reasons to discount the future so that "it would not be worthwhile taking steps to avoid $1,000 billion of damage in 200 years' time if the cost of doing so today exceeded only $8.7 million." Claims that cuts can be achieved at a profit are mistaken, for then one would have to believe "that firms are very stupid indeed." Hence, "if we really care about the welfare of our fellow world citizens," we ought to do little about the greenhouse effect, and a great deal about such issues as "better toilets and drains in the third world."1

Such, indeed, are the prevailing sentiments among economists and statesmen. Another well-known student of the subject begins his much-cited book with these words:

Greenhouse warming poses terrible dilemmas for those who care about both people and the world we inhabit. We do not now know how human activities will affect the thin and incredibly complex life support system that nurtures our civilization, nor can we reliably judge how potential geophysical changes will affect societies or the world around us. Should we be ultraconservative and tilt toward preserving the natural world at the expense of economic growth and development? Or should we put human betterment before the preservation of natural systems and trust that our ingenuity will find a solution should Nature deal us a nasty hand? (Nordhouse, 1994, p. ix)

We shall see below that this alleged dilemma between people and nature, or the avowed Procrustean choice between third world misery and global warming, involve a tragic misreading of the greenhouse threat: the facts of the matter are far rosier than such views would have us believe. In the real world, steps taken to remove the greenhouse threat would free enough money to vastly improve the quality of life not only in the third world but everywhere; not only now, but in the future.

Another representative review (Firor, 1994) states that "the literature surrounding climate change . . . includes puzzling discussions . . . on careful reading, they are revealed to be disagreements on values." We shall see below that such assertions reflect a profound misunderstanding of the greenhouse debate. They implicitly assume that scholars ought to stay out of "acrimonious" debates because such debates are "value-laden." But this assumption is mistaken, for it would have kept Galileo out of the Copernican debate, Zola out of the Dreyfus debate, and Bonhoeffer out of Nazi Germany. A second underlying assumption of such assertions is that the dispute boils down to a host of value judgments of the kind: "how completely should we attempt to manage the environment." This again involves a common, but nonetheless grave, misreading of the ethical aspects of this debate. At the core of this debate there are indeed two ethical principles+but these are nominally subscribed to by all sides. The first principle is this: one should not needlessly risk the future of humanity. The second principle is this: all things being equal, it is better to have less pollution in the air and more money in humanity's coffers. Once these two universal values are granted, and once the facts of the matter are calmly and dispassionately considered, the "controversy"+such as it is+disappears. To see this, one needs to venture a bit farther than physics, non-"acrimonious" sources, and discount rates.

A full account of the greenhouse debate requires an understanding of the environmental and economic situation as a whole, for in both natural and human affairs, everything is connected to everything else. A full account also requires familiarity with both ancient and modern environmental history, for we can only make sense of the present by remembering the past. In the nature of the case, then, no essay about the greenhouse effect can provide a complete picture, if only because environmental history is being written daily in every corner of this beautiful, blue and green, planet+burning Amazonian rain forests, cultivated Guatemalan mountainsides, smog-wrapped cities like Kathmandu, wilting German forests, slowly dying Scandinavian lakes.

Thus, those who write about such tangled subjects as the greenhouse effect can scarcely hope to capture all its interconnections to other environmental issues, to other fields, and to the past. They can only hope to portray their subject through a few rough, judiciously selected, strokes. To this end, I shall begin this survey of the greenhouse effect with a few lessons from ecology, followed by one brief historical case study.


Nature is indifferent to the fate of individuals. It cares not when tsetse flies assail us. It shows little pity for a shrieking baby rabbit in a cat's jaws, for a squirrel run over by a car, for a beached whale, or for a rat in a sinking ship. At the individual level, nature appears capricious and unforgiving.

But as soon as we advance from transient individuals to species, ecosystems, and the biosphere as a whole, anarchy is replaced by orderliness, senselessness gives way to harmony, and scattered strands are transformed into a finely-woven fabric. Here we shall only touch upon a few features of the most intricate fabric of them all: the biosphere.

Interdependence. The biosphere is marked by the absolute dependence of every creature on others. In nature's design, there is no such thing as self-sufficiency. The honey bee cannot exist without flowers. To reproduce, many flowering plants depend on the springtime visits of insects. If all the organisms which find our various body secretions so appetizing vanish, we shall, in short order, ingloriously suffocate in our own wastes.

Complexity and Unpredictability. Ecosystems are complex and, hence, often unpredictable. Any tinkering with them may have unforeseen consequences. This point is essential to any informed discussion of such global environmental issues as the greenhouse effect, and needs therefore to be explained and illustrated.

First, an explanation. Ecosystems are comprised of numerous living and nonliving elements. We are often ignorant of the existence of some of these elements, and only partially comprehend others. All these elements, in turn, form an intricate web of interconnections and feedbacks, a web which often eludes our grasp. As if this is not enough, we have also good reasons to suspect that ecosystems often behave chaotically+a change in one or another of their seemingly insignificant components may, in the long run, profoundly alter them.

Second, illustrations. Over the years, my students have given me some fascinating examples of the complexity and unpredictability of ecosystems, but here I shall resort to less anecdotal examples:

1. Cats and Flowering Plants. Charles Darwin describes "how plants and animals remote in the scale of nature are bound together by a web of complex interactions." To his surprise, Darwin found that the number of certain flowering plants in an English countryside depends on the number of cats. Now, it is easy enough to suppose that April showers bring May flowers, but how could cats raise the numbers of plants? It so happens that these particular plants are pollinated only by humble-bees (=bumble bees). And the "number of humble-bees in any district depends in a great measure upon the number of field-mice, which destroy their combs and nests." At this point, the last link in this causal chain should be obvious, for the number of mice in any given region depends on the number of cats. The cat and plant populations experience the same ups and downs: with more cats there are fewer mice, more pollinating humble bees, and more plants. Thus, even in this simplified four-species network, we encounter features which could hardly be deciphered in advance.

2. Grass and Sea Gulls. "Alongside the runway of a certain airfield, the grass was allowed to grow tall in order to discourage gulls, which it did. But starlings increased; one set of nuisance birds was replaced by another. Moreover, the tall grass encouraged field mice, which in turn attracted raptorial birds. The grass also encouraged earthworms, which then crawled out on the airstrip on rainy nights and attracted gulls!" (Scheffer, 1974, p. 172).

Now, both examples involve crude subsystems. It goes without saying that some features of the biosphere+which is comprised of millions of species and their environments+are vastly more complex and unpredictable.

Resilience. Species, ecosystems, and the biosphere as a whole, are bouncy. Some environmentalists mistakenly talk about them as if they are exceedingly fragile, forgetting that all three are masterfully equipped to cope with disturbances and hardships. Take, for example, nature's response to such severe stresses as volcanic disruptions which destroy all life in their vicinity. Gradually, life in all its wonderful complexity and diversity re-establishes itself. Or take, as another example, humanity's war against agricultural pests and medical vectors of disease. With few notable exceptions, the best that modern technology can achieve is temporary containment, not eradication.

A Breaking Point? Our lives now are more affluent, comfortable, and disease-free than they have ever been. Most ecosystems, and the biosphere as a whole, seem to be in sound shape, suggesting, as we have just seen, remarkable durability. The various living and non-living components of an ecosystem balance each other's activities in a way which assures the stability of that ecosystem. Nutrient cycles, decomposition, predator/prey interactions, parasite/host interdependencies, illustrate this balance+each organism and species, while busily minding its own business, contributes to the stability of the whole.

But resilience and prosperity should not be confused with indestructibility. Dinosaurs, dodos, and passenger pigeons tell us that living species can cease to exist. Every unreclaimed strip mine, every barren mountain whose topsoil has been lost to logging, every desert that has once been a productive farmland, tells us that ecosystems can die too.

Often, it is only when a species or an ecosystem reach collapse that we perceive the balance that safeguarded their existence all along. One often-told example of this belated recognition involves the mule deer of the Kaibab Plateau of northwestern Arizona. Out of compassion, hunting was banned and natural predators were removed. In the absence of predators, the deer population shot up, local vegetation declined, and many deer died of starvation and disease. Another example involves fish deaths in acidified lakes. These examples suggest that, up to a certain point, most species and ecosystems can adapt to change. But adaptability should not be confused with invincibility; beyond that point, disturbances can cause irreversible damage.

All this raises some pressing, and controversial, questions. Does our species have its breaking point too or are we fundamentally unlike dodos and dinosaurs? Can people destroy the life support system upon which they depend, or can the biosphere withstand any human intervention? Can our actions permanently lower the quality of life on this planet?

Amidst this controversy, one thing is clear. Insofar as they believe that they can foretell future events, both pessimists and optimists are mistaken. The pessimists are wrong in saying that the biosphere will collapse if we fail to act; the optimists are wrong in assuring us that it will not. The future is no one's to see. We can only act on the basis of limited knowledge. Because most species that ever graced this planet are extinct today, it seems reasonable to suppose that our species may cease to exist too. Because most local ecosystems can observably collapse, it makes sense to suppose that the biosphere as a whole may reach a point of no return too. If it does, humanity would vanish. If it does not, we may continue to pollute and prosper forever. Like it or not, extremists in both camps need to learn to endure uncertainty.

We should not, however, let prophets of either earthly heaven or hell blind us to one indisputable truth: given the scope, novelty, and multiplicity of human encroachments on the biosphere, nothing less than the future of humanity is at stake.



Ozone is a naturally occurring substance made up of oxygen atoms. Unlike an ordinary oxygen molecule (which is comprised of two atoms and is fairly stable), an ozone molecule is comprised of three atoms and it breaks down more readily.

Most atmospheric ozone is found some 12 to 30 miles above Earth's surface (in the stratosphere). Stratospheric concentrations of ozone are minuscule, occupying less than one-fifth of one-millionth the volume of all other gases in the stratosphere. If all this ozone could be gathered somehow at sea level to form a single undiluted shield around the earth, this shield would be as thick as the typical cover of a hardcover book (one-eighth of an inch) (American Chemical Society, 1978, p. 231).

However, minuscule as its concentrations are, the ozone layer occupies a respectable place in nature's scheme of things. By absorbing more than 99% of the sun's ultraviolet radiation, stratospheric ozone shields life on Earth from this radiation's harmful effects (some scientists feel that terrestrial life could not evolve before this protective shield took its place). A depletion of stratospheric ozone might allow more ultraviolet radiation to reach the ground and disrupt natural ecosystems, lower agricultural productivity, suppress the human immune system, and raise the incidence of skin cancer and eye cataracts (American Chemical Society, 1978, p. 231).

CFCs (chlorofluorocarbons) were invented in 1930. As the name suggests, these human-made substances consist of chlorine, fluorine, and carbon. Gradually, these nontoxic, odorless, inert compounds came to be used as coolants (in refrigerators and air conditioners), as foam-blowing agents (in such things as takeout food trays and cups), as propellants in spray cans, and as cleaning agents of computer chips.

In 1974 scientists began to suspect that these long-lived creations reach the stratosphere and destroy ozone. Their concerns were dismissed out of hand by governments, CFC makers, and their paid experts. A heated controversy followed, and by 1978 only the United States, Canada, Sweden, and Norway banned the use of CFCs--and only in aerosol sprays. So atmospheric CFC levels kept inching upwards. Unexpectedly, by 1985, and thanks only to the fortuitous presence of permanent scientific stations in Antarctica, alarming temporary reductions in springtime ozone levels over Antarctica were reported. By 1986, the CFC/ozone link was reasonably established. Later, less massive depletions of stratospheric ozone were detected throughout the globe. Nonetheless, corporations still engagedsuccessful--in delaying tactics. As a result, by 1990 the world's nations did agree to stop production of CFCs--by the year 2000.

By 1992 the global shield had lost 5% of its ozone. By then, the world's nations agreed to advance the virtual phaseout date (1996 for rich countries, 2006 for poor; Houghton, 1994, p. 143) and to replace CFCs with somewhat (Asimov & Pohl, 1991, pp. 129-133) less destructive materials. In some cases, CFCs might even be replaced with readily available, cheaper, and environmentally benign substitutes (for instance, reusable glass cups instead of CFC-containing styrofoam cups; ammonia as a refrigeration agent instead of CFCs, cf. Ross, 1994). By March 1995, ozone concentration above Europe and the United States fell by 10% to 20% below 1979 levels (Monastersky, 1995). Ozone levels are expected to reach their lowest levels over the next decade, and to fully recover by 2066.

In the next fifty years, 240 million human beings might contract skin cancer as a result of ozone depletion, of which 4 million might die. Eighty million might develop eye cataracts, of which many might become blind. Other possible effects are suppression of the immune system, threats to the Antarctic food chain, damage to ecosystems and agriculture, and extinctions of some wild species. Some of these effects are already being felt, especially in southern countries like Australia and Chile.

Struck by the unprecedented nature of the global phaseout decision, some people see the ozone saga as a remarkable victory for human rationality. We are, they say, at the dawn of a new age.

Others see the exact same events as proof of collective misconduct (e.g., Asimov & Pohl, 1991). They question the advisability of letting these Frankenstein monsters (CFCs) loose on the environment in the first place. They wonder about the 22-year lag from indictment (1974) to partial lockup (1996) and about the 11-year interval from discovery of the Antarctic hole to the partial ban. They note that CFCs have not been indispensable to the world's economy or to average quality of life. They frown upon the unremitting use of CFCs in such things as coffee cups despite the availability of cheap substitutes (and despite the unpleasant taste of hot drinks in styrofoam cups). They draw attention to CFCs' well-known and decisive contribution (second only to CO2) to a second major environmental threat (enhanced greenhouse effect), and to the prospective legacy of one-third of a billion needless tragedies left in the wake of this "victory for scientific rationality acting in the realm of human affairs" (Hobson, 1993, p. 11).

Such skeptics find the closest parallel to the ozone tale in science fiction. For instance, in Karel Capek's humorously pessimistic War with the Newts, exceptionally clever and prolific salamanders are encountered in some far off bay. At first their discoverers offer them knives and protection from sharks in exchange for pearls. Gradually, however, many of the world's nations avail themselves of these creatures for other purposes, including war. In a few years, the salamanders run out of living space. To accommodate their growing numbers, they flood countries, one at a time. To do this, they need supplies from countries elsewhere and from merchants of the soon-to-be ravaged country itself. Needless to say, the salamanders have no trouble securing everything they need. At the end, humanity is on the verge of sinking and drowning; not so much by the newts, but by its greed, shortsightedness, and colossal stupidity.

This and other tales (e.g., Capek's R.U.R, Kurt Vonnegut's Cat's Cradle) imply that the world is not a wholly rational place. Indeed, the place and date of publication of War with the Newts+Czechoslovakia, 1935+throw some light on the origin of this tale. At that time, or a short time earlier, a few English, French, or American divisions could have invaded Germany, sent Hitler into early retirement, and saved humanity from disaster. Others besides Capek appealed for preemptive action. But Western politicians worried about the next elections and disregarded the more distant future. They remembered their petty quarrels and forgot their common, and far more sinister, foe. Without trying to resolve this historical controversy about ozone abatement and human rationality, let us shift our focus to the greenhouse effect.


For reasons that will become clear shortly, students of the greenhouse effect are interested in climatic and atmospheric conditions on Earth's nearest planetary neighbors, Venus and Mars.

Being closer to the Sun than Earth (7/10 the distance), Venus receives more intense sunlight. Owing to its thicker cloud cover, a smaller fraction of this received sunlight reaches the ground on Venus than on Earth. Early astronomers felt that the more intense sunlight and thicker cloud cover would balance each other and keep Venus' temperatures within a livable range. However, space travel disclosed harsher realities. The surface of the entire planet turned out to have kiln-like temperatures. At 900F, lead would melt and mercury boil. Life as we know it was but a dream on Venus, except perhaps as an afterlife inferno.

Venus' atmosphere is about 90 times denser than Earth's. That is, if we took two identical steel tanks and filled one with uncompressed Venus' air, the other with Earth's, and weighed both on Earth, the contents of the Venusian tank would be 90 times heavier.

Owing to the incredible density of its air, Venus' slow-moving surface winds are more powerful than Earthly hurricanes. Measurements showed that Venus' atmosphere is approximately 97% carbon dioxide (CO2) and 3% nitrogen. Its thick clouds are made of water and highly corrosive sulfuric acid.

Let us move on to Mars. At the close of the nineteenth century, astronomers imagined they saw canals on Mars' surface. One famous astronomer theorized that these were the irrigation canals of a technologically advanced civilization. This popular belief is captured in H.G. Wells' War of the Worlds, which depicts a Martian invasion of Earth. Although we were no match for these aliens, they were fortunately wiped out at the end by an epidemic. When a dramatization of Wells' book was first aired on a radio show, large numbers of Americans mistakenly thought it was a news report and fled in terror.

Space travel disproved once and for all the existence of artificial canals, and it showed that Mars is even colder than had been believed. The average surface temperature is -63F+too cold for life as we know it. Mars' atmosphere, which is mostly made up of C02, is thin: 1/100 that of Earth; 1/10,000 that of Venus.

Venus then is closer to the Sun than Earth; its atmosphere is denser and richer in CO2; and it is many times hotter. Mars, on the other hand, is farther, has a thinner atmosphere, and it is much colder. Why does Earth enjoy a habitable climate while Venus and Mars do not? Calculations convincingly show that something other than mere distance from the Sun accounts for these temperature differences. That additional factor is the atmosphere; it is our planet's unique atmosphere which moderates its temperatures and makes life possible.

Before exploring the atmosphere-temperature link, we need to say a few words about radiation. Each type of radiation has its own characteristic wavelengt--what we call "red," for instance, has longer wavelength than what we call "yellow." Under certain conditions, one type of radiation turns into another. Sunlight can go through the atmosphere+that is why we see the Sun. Sunlight then warms the ground and lower atmosphere, which then emit heat, a form of radiation one can feel but not see. In physical terms, heat radiation has a longer wavelength than visible light. On the spectrum it falls just below visible red, hence it is called infrared radiation.

Now, CO2 and a few other greenhouse gases in the atmosphere of all three planets allow most sunlight to go through them. When this light reaches the ground or lower atmosphere, it is converted in part into heat which is then reflected back towards space. On Venus, CO2 and other greenhouse gases trap much of this heat and irradiate some of it back to the ground, thereby delaying its escape into space. On Earth, less heat is trapped, and on Mars, still less. This sharply varying greenhouse effect is the chief reason for the hellish temperatures of Venus, comfortable warmth of Earth, and sub-Antarctic conditions of Mars.

Earth, then, is livable thanks to its naturally occurring greenhouse gases: water vapor, carbon dioxide, methane (natural gas), nitrous oxide (laughing gas), and ozone (Hare, 1993, p. 11). The same fundamental process which accounts for temperature extremes in our planetary neighbors explains the comfortable temperatures on Earth. Like the glass of a car with rolled-up windows, these gases trap more heat than light. Our planet is thus a sleeping giant, comfortably blanketed by its own set of greenhouse gases. Without these atmospheric gases, Earth would be 60F colder than the current average of 59F, hence lifeless. "The natural greenhouse effect+so called because the gases act in some ways like the glass in a greenhouse+is thus essential for life on earth" (Hare, 1993, p. 11; Houghton, 1994, pp. 27-28).

The link between atmospheric CO2 levels and global temperatures receives further support from the historical record (Fig. 1).

+Insert Fig. 1 here


Can there be too much of such good things as water vapor and CO2? Venus tells us that there can be, and both Venus and Mars caution us that levels of greenhouse gases must fall within a narrow range. Yet, it is possible that Earth is imperceptibly moving in the Venusian direction. It is this putative move, its possibly momentous implications, and the desirability and nature of proposed remedies, which are at the heart of the greenhouse debate.

The chief culprit in changing Earth's greenhouse balance is CO2. Recall for a moment the link between Venus' CO2-rich atmosphere and its hellish temperatures. The dense CO2 helps to trap the much smaller amount of sunlight which Venus receives, thus generating far higher temperatures on Venus than on Earth. Earthlings, it turns out, may be creating their own CO2 problem. Our civilization is burning enormous quantities of coal, gas, oil, and wood, thereby releasing CO2 into the atmosphere. Forest burning similarly releases CO2 and transforms trees from longterm consumers of CO2 to short-term producers. As a result, since 1860 CO2 levels have gone up by 25% (Cherif & Adams, 1994, p. 30), with more than half of this increase taking place since 1959! (Brown, Kane, & Ayres, 1993, p. 68).

+Insert Fig. 2 here

In the future, other factors may further exacerbate this problem. For instance, ozone-related increases in ultraviolet light (Smith, 1995), as well as rising pollution levels, may reduce the capacity of the world's oceans to sustain small, floating aquatic plants, thereby further disturbing the CO2 balance on Earth.

As we have seen, human-made CFCs are still being discharged into the atmosphere, and CFCs trap heat too. Although their role in the natural greenhouse effect is minimal, CFCs contribute to suspected additional warming. Other important enhanced greenhouse gases are methane and nitrous oxide. In absolute terms, the increase in CFCs, methane, and nitrous oxide has been comparatively small, but pound for pound, some of these gases are more powerful heat absorbers than CO2. Their combined warming effect is equivalent to that of a 15% rise in CO2. So the Earth's atmosphere contains now the equivalent of 40% more CO2 than it did in 1960 (Beckerman & Malkin, 1994).

In summary, the above-normal atmospheric levels of greenhouse gases are traceable to the burning of coal, oil, natural gas, and firewood, and the consequent release of carbon dioxide (7 billion tons each year; Zimmer, 1994, p. 28) and nitrous oxides; further release of the same two gases from deforestation, burning of forests and fields, desertification, reductions in biodiversity (e.g., turning a prairie into a corn field); further release of nitrous oxide through other agricultural practices such as fertilization; the production and use of synthetic CFCs for sprays, coolants, packing materials, and cleaning solvents; the release of methane from pipelines, drilling operations, coal mines, rice paddies, livestock, from burning forests, firewood, and charcoal, from sewage, and from garbage dumps (Heilig, 1994; Houghton, 1994, p. 38).

Besides documented rising levels of CO2 and other greenhouse gases in the atmosphere, besides the documented (1F) global warming in this century (Hare, 1993, p. 13), and besides the apparent acceleration of this warming trend (1990, 1991, and 1994 are the first, second, and third warmest years on record), other developments can be seen as harbingers of global warming (Kerr, 1995). These include unusual weather extremes in recent years (more numerous and severe storms, floods, and droughts, cf. Houghton, 1994; Monastersky, 1995); since 1940, a possibly unprecedented rate of change in the timing of the seasons in the Northern Hemisphere (Thomson, 1995); melting of Arctic and Antarctic ice; retreat of the Antarctic ice shelf (Beardsley, 1995); retreat of some Alpine, Himalayan, and Chinese (Guoan et al, 1994) mountain glaciers; northward migrations of warm-climate fish and trees; spread of tropical diseases (Stone, 1995); destruction of coral reefs; rising ocean temperatures (Regalado, 1995); steadily rising levels of water vapor in the stratosphere; and rising sea levels (Nerem, 1995).

These continuing trends would likely have some favorable outcomes. For instance, because low CO2 levels currently limit the pace of photosynthesis, all other things being equal, rising levels of this gas may increase the productivity of farms, forests, and marine systems in some regions. Likewise, Siberians, Greenlanders, and other northerners might welcome a warmer climate.

The best scientific bet, however, is that, on balance, the effects would be troublesome. Temperatures may have already risen by about 1F, explaining perhaps the unusually hot summers and weather extremes of recent years. In fifty years, if we continue the unbridled release of greenhouse gases into the atmosphere, temperatures might go up by some 6F. This increase may lead ocean water to expand and rise. Ocean water may rise, as well, because higher temperatures may melt the polar ice caps. Sea levels may thus rise by 17 inches by the year 2070 (Brown, Kane, & Ayres, 1993, p. 68) and submerge low-lying areas such as Louisiana. Unable to cope with the unprecedented pace of climatic fluctuations and change, some wild species might perish (Gates, 1993). Climates may shift, perhaps converting once-prosperous agricultural areas into deserts. Higher temperatures, weather extremes, flooding of coastal areas, regional changes in rainfall patterns, and an unstable seasonal cycle (Thomson, 1995, p. 66) may reduce agricultural, forest, and natural productivity (Manning & Tiedemann, 1995; Rosenzweig, 1994). Tropical climates and diseases may spread and summer heat waves may become more common (Stone, 1995). Oxygen levels in the atmosphere and oceans may decline. Humanity may be visited more often by devastating storms, droughts, and other weather extremes. History likewise shows that, at times, global and regional temperatures profoundly affect human affairs; climatically, economically, or politically stressed societies are especially vulnerable (Brown, 1994).

An even worse specter cannot be altogether ruled out. As the Earth heats up, more water would turn into vapor, and vapor is a greenhouse gas. Stored CO2 might likewise escape from ocean rocks and shells, and stored methane might escape from vast permafrost regions (Cherif & Adams, 1994, p. 30). Beyond a certain point, the process may get out of control. Venus tells us how far such a runaway process can go+hellish temperatures, enormous surface pressures, and a distorted landscape:2

Until recently, we have been lucky. Earth has just as much carbon as Venus, but most of it is still locked away harmlessly in rocks. . . . Is it possible that we will someday destroy Earth's good health and turn our home into a runaway greenhouse? Will the human volcano heat Planet Earth until all the seas go dry and lead melts in the sunlight? Are we already on the downhill path to Venus? We simply do not know enough yet about Venus, or even about Earth, to be sure of the answer. But judging by our neighboring world, we are playing with fire (Weiner, 1986, p. 174).

But can humanity really have such an appreciable impact on something as colossal as its home planet? The answer is still: nobody knows. To show that human-caused global warming here on Earth is conceivable (but not that it is probable or certain), we need to examine a scientific proposal for transforming another world.

In brief outline, this proposal calls for the construction of a nuclear power plant on Mars. The energy thus produced would be harnessed to mine raw materials and convert them to CFCs. The CFCs would then be released into the Martian environment, where they might trap solar heat and raise temperatures by about 7F. From that point on, a runaway global warming may take over. The elevated temperatures might vaporize some of Mars' vast stores of frozen CO2 (dry ice), which in turn would further warm up the planet, releasing more CO2, warming Mars still more, and so on, until all the frozen CO2 is vaporized and Mars is 126F warmer than it is now (Chandler, 1994). Now, if serious scientists believe that humans could conceivably raise Martian temperatures by 126F, it is hard to see why a similar runaway greenhouse process+albeit unintentional+could not in principle overtake Earth.


Owing to the complexities of Earth's biosphere and climate, all predictions are shrouded in doubt. It could be that, as I revise these words, our planet's temperatures are imperceptibly rising. For argument's sake, let us arbitrarily say that there is a 1 in 2 chance that this is occurring. If this warming continues, in a few decades it may lead to adverse (say, 1 in 10), beneficial (say, 1 in 10), or neutral (say, 8 in 10) consequences for the quality of life on this planet. Finally, there is the specter of consequent extinction of life on Earth in a few centuries as a result of human-caused, unchecked global warming (say, 1 in 100). Amidst all these uncertainties and arbitrary numbers we can be sure of one thing: the uncertainties will remain. Should we then cross our fingers, allow present trends to continue, and let chance decide our fate?

Given the stakes, some people would argue that we should act to avert the possibility of disaster, regardless of cost. Others might argue that we should act only if the requisite policies do not divert resources from even more urgent tasks. No one, however, would openly argue that we should do nothing if the requisite policies not only avert the greenhouse threat, but if they also have many other beneficial environmental, public health, and aesthetic consequences and if they can save our species billions of dollars every year. If such policies were shown to exist, the greenhouse debate would, in principle, come to an end. Who could oppose beneficial and remunerative policies? Uncannily enough, although such policies have been readily available for decades, they are not being followed!

As we have seen, CFCs contribute to as much as 24% of the expected warming. Because they are also the chief culprit in the ozone layer tragedy, they will be soon partially banned. Over the next century, their concentrations in both the lower and upper atmosphere will decline.3 Tardy or not, the CFC ban would slow down the suspected warming trend.

The needed additional steps have been championed for decades by many writers. Among the most indefatigable, articulate, and insightful advocates of this sustainable-earth path is Amory Lovins. Here is a typical refrain:

Global warming is not a natural result of normal, optimal economic activity. Rather, it is an artifact of the economically inefficient use of resources, especially energy. Advanced technologies for resource efficiency, and proven ways to implement them, can now support present or greatly expanded worldwide economic activity while stabilizing global climate+and saving money. New resource-saving techniques+chiefly for energy, farming, and forestry+generally work better and cost less than present methods that destabilize the earth's climate (Lovins & Lovins, 1991, p. 433).

Such steps, sustainable-earth advocates say, could cut emissions of CO2 by more than 60%, of methane, by 17%, and of nitrous oxide by 75%. Such claims are usually dismissed by politicians and journalists, by scientists and other academics who believe that the greenhouse threat is a chimera requiring no action whatsoever, by reputable economists who believe that it might cost as much as 4 trillion dollars to avert the greenhouse danger (Schneider, 1990, p. 188)4 and also by many informed science writers who are committed to removing the greenhouse threat. Here is one example out of dozens:  

Despite the uncertainties, even many scientists who understand that the global warming theory has not been proved believe that humans around the world should act to reduce those activities that contribute to accelerating the greenhouse effect. This is, after all, unexplored climatic territory, and by the time the theory is proved, it may be too late to act. Expensive as actions may be, the costs of not taking them may be even greater in the long run (Franck & Brownstone, 1992, pp. 145-6; italics added).

Such widespread beliefs seem to make a mockery of Lovins' claims that increased energy efficiency can solve the greenhouse problem and save money. Are his claims absurd? My answer to this is simple: these claims are not absurd, but entirely correct.

To begin with, assertions of combined savings and safety are supported by many other researchers.5 Also, the worst greenhouse offender+the United States+does not use energy as efficiently as some other equally prosperous countries. By catching up with existing Swedish standards, for instance, the United States could vastly reduce greenhouse emissions, save trillions, and begin to heal its citizens and trees, fields and streams, water and air.

A similar point concerns history. Compared to real energy expenditures in 1973, and thanks to conservation measures implemented since then, energy conservation is already saving the United States at least $100 billion a year.6 Twenty years ago many economists opposed energy conservation for 1001 reasons.7 They have thus managed to slow down this historical process, but common sense, and the logic of a mixed economy, tilted the balance and proved them wrong.

Thus, the sustainable-path position boils down to nothing more outlandish than a plea to all nations to accelerate this salutary historical trend, in part by following the proven examples of prosperous, energy-efficient, countries like Sweden and Japan.

The sustainable-earth package is comprised of numerous measures. To be sure, this package is neither complete nor flawless. But here we are only concerned with the large picture, and can let independent experts and experience settle the rest. So we can safely set aside such questions as: Would sustainable-earth measures save $100 or $200 billion a year? Would they reduce carbon emissions by 50% or 70%? Would they cut future additions to the acid rain problem by 90% or 98.9%? To make our case, we need only show that, taken together, such policies can save money, avert global warming, and help heal our planet. To achieve this limited end, we only need recount a few typical steps:

1. "Removing a 75-watt incandescent lamp [the familiar household light bulb] and screwing into the same socket a 15-watt compact fluorescent lamp will provide the same amount of light for 13 times as long, yet save enough coal-fired electricity over its lifetime to keep about a ton of CO2 out of the air (plus 8 kg of [polluting and acid rain-causing] sulfur oxides and various other pollutants). . . .Yet far from costing extra, [in the long run each lamp] . . . saves tens of dollars more than it costs" (Lovins & Lovins, 1991, pp. 437-8; see also National Academy of Sciences, 1994, pp. 217).

2. A 1989 study by the U.S. Department of Energy describes "15 proven, readily available, improvements in car design. These, plus two more equally straightforward improvements," would not involve any changes in car size, safety standards, or acceleration, yet they could reduce fuel consumption by 35%. And this is a mere drop in the bucket. Already available prototypes such as the Toyota AXV (89 mpg city; 110 mpg highway), prove that cars more than three times as efficient as the world's fleet can be at least "as comfortable, peppy, safe, and low in emissions as today's typical" new car (Lovins & Lovins, 1991, p. 446).

3. According to the National Academy of Sciences, "a consensus is emerging in the engineering, utility, and regulatory communities that, even when past efficiency gains and projected population and economic expansion are considered, an additional, significant reduction can be made in U.S. residential and commercial electricity consumption. This reduction is not expected to sacrifice comfort levels and will cost less+in many cases, substantially less+than the purchase of new sources of power" (1992, p. 204). The savings in both carbon emissions and dollars can be readily accomplished through such simple steps as adding triple pane windows to existing buildings and improving the design of hot water tanks. For the United States alone, such measures would cut total CO2 emissions by some 18%, and would save some $56 billion per year (National Academy of Sciences, 1994, p. 240). By itself, this figure is striking from the economic standpoint, if from no other: every year, the average American household could save hundreds of dollars through this step alone.

4. Recycling paper saves money, energy, trees, pollution, water, landfill space, and methane emissions. Indirectly, such recycling also reduces carbon dioxide and nitrous oxides emissions otherwise incurred in the production and transport of paper (Lovins & Lovins, 1991, p. 474; Miller, 1994, p. 402).

5. Cogeneration entails production of two useful types of energy from a single process. For instance, waste heat from industrial processes can be converted into usable electricity, instead of letting it dissipate through the smokestack. A more familiar example comes from personal transportation+cars need no heaters because they are built to recycle waste heat. We are ready for another astonishing statistic from a 1994 ecology text: American "industries that use enough high-temperature heat or steam and electricity could save energy and money by installing cogeneration units . . . By 2000 cogeneration could produce more electricity than all the U.S. nuclear power plants, and do it much more cheaply" (Miller, 1994, p. 450).

6. Methane losses by the petrochemical and coal industries are "primarily due to technological inefficiency . . . lack of 'good-will' among those responsible. It is well documented that simple and cost-efficient measures could substantially reduce methane emission from these sources. Even if population growth (and spreading industrialization) were to require an increase in fossil fuel exploration, the total methane emission from these sources could decline in absolute terms with better technology and intelligent process design" (Heilig, 1994, p. 131).

7. "According to the U.S. Army Corps of Engineers, retrofitting abandoned small and medium-sized hydroelectric sites, and building new small-scale hydroelectric plants on suitable sites, could supply as much electricity as forty-seven 1,000-megawatt power plants" (Miller, 1994, p. 464).

8. Many efficiency measures entail renewable sources of energy. Consider, for example, solar cells (=photovoltaics), which convert sunlight to electricity without producing any greenhouse gases, and which, as far as we can tell, incur comparatively small environmental costs. By 1977, a task force of the U.S. Federal Energy Administration proposed direct government intervention to speed up the development and commercialization of this benign technology (Commoner, 1979, pp. 35-38), a step that would have, over twenty years, saved the government money, cut pollution, and created a major new industry. Needless to say, governments paid little attention (for the same reason, probably, that Lovins, as far as the world's decision makers are concerned, remains a voice in the wilderness), thereby needlessly slowing down the large-scale use of this benign technology. Nonetheless, the price of solar cells has been steadily going down, and they are expected to become truly competitive in a few years. For instance, solar cells are already used in most hand-held calculators. If the true economic costs of nuclear power are included,8 solar cells already outperform nuclear power plants as net producers of electricity. Governments genuinely concerned with the health of the planet would at long last heed the advice of one of their own task forces and shift a fraction of their coal and nuclear subsidies to this sunnier technology:

Today's solar photovoltaic technology already achieves every [failed] dream of nuclear technology research: the solar resource potential is unlimited, its energy source is fusion (with a self-containing "reactor" located a comfortable 93 million miles away), it is [comparatively] clean, it needs no fuel, it is passively safe, its waste and safety problems are relatively minor, it comes in all sizes from rooftop to utility-scale, and the necessary materials are effectively infinite (sunlight and sand). The only thing left to do is to bring down the cost, which will not be difficult according to informed assessments by the United States Department of Energy (Keepin, 1990, p. 316).

A similar situation applies to many other solar technologies: "Contemporary solar engineers [believe that] solar power is not only possible but eminently practical, not to mention more environmentally friendly. Alas, once again, just as the technology has proven itself from a practical standpoint, public support for further development and implementation is eroding, and solar power could yet again be eclipsed by conventional energy technologies" (Smith, 1995, p. 40). "Solar technology already boasts a century of R&D, requires no toxic fuel and relatively little maintenance, is inexhaustible, and, with adequate financial support, is capable of becoming directly competitive with conventional technologies in many locations. These attributers make solar energy one of the most promising sources for many current and future energy needs. As Frank Shuman declared more than 80 years ago, it is "the most rational source of power" (Smith, 1995, p. 47).

According to two of this century's most distinguished interdisciplinarians, the case for solar and renewable technologies is even more convincing when government policies are taken into account. To begin with, we must bear in mind that while the U.S. government spent "some $40 billion a year in the 1980s" on energy research, 90% of that money went to fossil-fuel and nuclear power and only 4% went to renewable energy. At the same time, the fossil-fuel and nuclear industries lavished "immense fortunes on political lobbying and influence-buying" (Asimov & Pohl, 1991, p. 226). Moreover, these authors believe that, when all concealed costs are taken into account, consumers pay less for some renewable energy sources than they pay for fossil fuels and nuclear energy. The alleged extra cost of some renewable energy sources, they say, "is a fiscal illusion, if not an actual fraud practiced on all of us." (p. 230; see Asimov & Pohl, Chapter 15, for details)

Scoffers at the sustainable-earth position often treat the greenhouse problem in isolation from everything else that ails our planet and species. They forget that while academia can be gainfully fragmented into disciplines, the world cannot: reality is a web, not a collection of parallel lines. We have seen already that the prospective CFC ban would markedly aid both the ozone depletion problem and the greenhouse threat, but this combined effect is a mere peanut in Santa Lovins' famous briefcase. Besides averting the greenhouse and ozone threats, the proposed measures would entail worldwide savings of untold billions of dollars and countless natural resources. They would improve our material quality of life, reduce pollution, cut severe environmental and health impact of coal use (e.g., black lung disease, land subsidence), improve human health, eliminate future acid rain problems (which are currently aging buildings and monuments, damaging forests, and killing fish in thousands of lakes and streams). Furthermore, these measures would diminish urban smog and help clean up our air, water, and food. They would reduce the incidence of tragic and costly floods, storms, and, perhaps, other natural disasters. They may improve the quality of topsoil and farmland, thereby increasing longterm agricultural productivity. They would gradually lead to the elimination of costly and unsafe nuclear power. "In sum, informal estimates (of EPA) . . . suggest that most+perhaps around 90%+of the problems EPA deals with could be displaced, at negative cost, just by energy efficiency and by sustainable farming and forestry. That is a pleasant by-product of abating global warming at a profit" (Lovins & Lovins, 1991, p. 518). Moreover, the sustainable-earth path would considerably slow down the worrisome prospect of massive species extinction. It would raise economic competitiveness (for instance, greater energy efficiencies partially explain low production costs of Japanese cars). And they would reduce dependence on foreign energy supplies.


Needless to say, not all proposed sustainable-earth steps save money; in the short term, for instance, the shift to energy-efficient appliances or to renewable resources will involve a net economic loss. Similarly, while conservation measures would benefit society, they may create genuine hardship for many people (e.g., coal miners, nuclear utility executives). Moreover, the political and psychological barriers against these measures may well prove insurmountable (Nissani, 1994). Here, however, I should like to focus on just two protracted problems+population and deforestation+and on their impact on the sustainable-earth path.

Large and rapidly growing populations make decisive contributions to the greenhouse effect and to other environmental problems. In the long run, then, efforts to curb the greenhouse effect depend in part on our species' ability to roll back its numbers. It is, for instance, sobering to recall that for every eleven human beings alive now, only one was alive in 1650 (Hollingworth, 1995, p. 285; National Academy of Sciences, 1992, p. 415):

The world's population is growing rapidly. If there is no significant reduction in fertility rates, the population may reach 14 billion [28 times its 1650 levels] before stabilizing. . . . at any given rate of greenhouse gas emissions per capita, a smaller population will mean less total emissions, as well as less stress on the environment in general. . . . Greenhouse gas mitigation is thus well served by well-designed family planning, health, and education programs. It is furthered by broader economic development programs if they complement population reduction programs and enable earlier and more complete demographic transition. . . . as of the year 2020, carbon emissions will be about 15 percent lower for the lower-middle- and upper-middle income countries than they would be without family planning. Strong family planning programs are in the interest of all countries for greenhouse gas concerns as well as for broader welfare concerns (National Academy of Sciences, 1992, pp. 421, 422, 811; see also Ehrlich, 1994).

As one illustration of the longterm impact of population on the greenhouse effect, consider the case of that potent greenhouse gas, methane:

Contrary to carbon dioxide, methane is not primarily emitted from the production and consumption sectors of affluent societies. Significant sources of atmospheric methane are in developing countries, where high population growth is projected for the next decades. . . . [humanity's] emission of methane to the atmosphere would stagnate or even decline, if population had stabilized at its 1990 level. Through its link to food production, third world population growth is a key factor of future methane emissions. By the year 2025 (third world) population growth could increase methane emission by between 22 and 230%, as compared to a constant 1990 population (Heilig, 1994, pp. 131-131).

Let us move to another longterm problem: the state of the world's trees. By releasing into the atmosphere carbon dioxide, methane, and nitrous oxide, deforestation accounts for some 20% of the enhanced greenhouse effect (National Academy of Science, 1992, p. 424). Owing to rapid population growth, poverty, and other factors, many third world people are forced to move into, clear, burn, or cultivate tropical forests. Moreover, the productivity and general health of the world's forests is threatened by such things as the greenhouse effect, ozone layer depletion, airborne pollution, and acid rain.

Deforestation presents a more daunting challenge than energy inefficiencies. Partial remedies include easing population pressure on tropical forests through effective investments in family planning efforts and through education of the third world's people. Moves towards participatory democracies, and a greater measure of economic sufficiency may also help to stabilize the numbers of the world's people and trees (Harrison, 1987, but see also Abernethy, 1993). Another remedy would involve greater efficiency in the use of wood products (enforced perhaps through a special tax) and recycling. Another measure would provide financial incentives for preserving forests and for sustainable forestry (National Academy of Sciences, 1992, pp. 425-428). Still another promising+but in the short term costly+step would involve massive tree plantings of abandoned deforested lands, and of unused lands elsewhere (e.g., in cities, and along riverbanks, highways, and railroad tracks). Reforestation will in turn have the added benefits of conserving biodiversity, pristine wilderness, topsoil, and homes for indigenous people, and of minimizing desertification, flooding, and regional declines in rainfall (Houghton, 1994, p. 101).

In summary then, both population pressures and deforestation are intimately connected to the greenhouse effect and both defy short-term solutions. So far, both have received far less attention than they deserve. In the meantime, until humanity finds the gumption to deal with these two political minefields, we can more than offset any temporary greenhouse setbacks in these two important areas by vigorously moving forward with the more tractable components of the sustainable-earth path.

At any rate, alongside the all-important efforts to curb population growth and deforestation, and despite the many drawbacks of, and political barriers to, the sustainable-earth path, it is undeniable that, for the coming years, this path would check the greenhouse threat and save money.9 Indeed, because this path is associated with so many benefits, it should be undertaken even if the greenhouse threat disappears tomorrow.

Such then are the facts which lead Lovins to conclude:

The assumption that saving fuel costs far more than burning it simply ignores the enormous body of empirical experience flatly to the contrary. . . . It is this [mistaken economic] attitude, so foreign to commonsense and everyday experience, that has propagated as fact the falsehood that saving large amounts of energy will cost money instead of saving money. It led [the Bush Administration] . . . to estimate costs of up to $200 billion per year for the US economy. . . the amount may in fact be about right but . . . the sign wrong: such an efficiency-gain would save the US economy roughly $200 billion per year. . . . it is generally cheaper today to save fuel than to burn it. The pollution avoided by not burning the fuel can, therefore, be achieved not at a cost but at a profit+so this result can and should be widely implemented in the market-place (Lovins, 1990, pp. 220-4).


The question of uncertainties rears its head often in the greenhouse debate (e.g, Nordhouse, 1994). As we have seen, scientists are good at predicting such things as the return of Halley's comet but poor at forecasting such things as tomorrow's stock prices. The greenhouse effect belongs to the second category (see for example, Eastwood, 1991). Some scientists insist that the higher temperatures of the last decade have nothing to do with the greenhouse effect. Others are convinced that the oceans might be able to absorb the excess amounts of CO2, with no consequent warming and disasters. Others argue that the warming effects of rising levels of greenhouse gases would be neatly counterbalanced either by the chilling effects of rising levels of dust and smog, or by the next ice age. Others put their hopes in expensive and elaborate technological cures (e.g., Chakma, Mehrotra, & Nielsen, 1995; Seifritz, 1995). Still others claim that Mother Nature can withstand any onslaught we puny humans can visit upon her. Each and every claim could turn out to be true. Still, it would be as frivolous to say that they imply a wait-and-see attitude as it would be to suggest that uncertainty about the outcome of your next cross-country trip implies that you should not buckle up (cf. Houghton, 1994, chapter 9). Time magazine, not particularly known for its radical views, felt forced to put the situation in the following terms:

Unfortunately, scientists cannot agree on how much global warming has occurred, how much more is on the way and what the climatic consequences will be, giving policy makers an excuse for delay. But no one disputes the fact that the amount of CO2 in the atmosphere has risen and continues to increase rapidly and that the human race is thus conducting a dangerous experiment on an unprecedented scale. The possible consequences are so scary that it is only prudent for governments to slow the buildup of CO2 through preventive measures, from encouraging energy conservation to developing alternatives to fossil fuels.10

This is a reasonable enough position: "better safe than sorry" seems to be eminently applicable here. And one must not forget that+as in the case of the ozone layer+uncertainty cuts both ways. That is, current middle-of-the-road scientific projections might either overstate or understate climatic conditions half a century hence. Scientists were shocked, for instance, by the ozone hole, as they were, in the early 1980s (Nissani, 1992, p. 57) by nuclear winter projections. The best bet, despite the uncertainties, would be to refrain from experimenting with Earth's climate; the best cure, to do everything we can to stabilize it.

But, as we have seen, the Procrustean choice between costly prevention and lucrative impotence is strictly imaginary. Virtually all the actions needed to abate global warming should be taken anyway to save money and cut pollution:

These "no-regrets" actions are about enough to solve the problem if it does exist, and are highly advantageous even if it does not. The problem with global warming is not decision-making under uncertainty; it is realizing that in this instance, uncertainty is unimportant. . . The real choice is not balancing uncertain future benefits against daunting present costs, but rather making the investment as wisely and quickly as possible in order to achieve both the uncertain future benefits and the guaranteed financial savings (Lovins & Lovins, 1991, pp. 521-2).

As we have seen, much has been made, on both sides, of the expenses of abatement. It is of some interest to try to trace the origins of this misconception. For this, one need go no farther than Newsweek:

During the early Bush Administration, estimates batted around for greenhouse reductions ran from $100 billion to a mind-bending $3.6 trillion. Such calculations contained an astonishing omission. The way to control carbon emissions is to make energy use more efficient. The big numbers took into account the capital costs of new conservation technology, but not the value of the fuel saved. Factor in the energy savings, the analysts Amory and Hunter Lovins showed in a landmark 1991 study, and . . . it becomes possible to imagine cutting greenhouse gases at a profit. . . . Currently the [Bush] White House is pushing its National Energy Strategy [which fails to see] that resource conservation, pollution control, lower energy prices and a hedge against global warming might be achieved simultaneously by a comprehensive commitment to improved fuel efficiency. . . . [Moreover, seen in light of population growth and worldwide improved standards of living] significant improvements in energy efficiency are imperative whether the thermometer is going up, down or sideways (Newsweek, 1992, pp. 32-3).


Humankind's greenhouse policies defy common sense. If the technical solutions are so easy, profitable, and beneficial, why are they not adopted? Why did President Clinton, when announcing his administration's greenhouse position in late 1993, agree to do virtually nothing? Is it mere ignorance on the part of politicians, as Lovins & Lovins suggest (1991, p. 525)? Is it greed (humanity spends one trillion dollars a year on coal, oil, and gas alone; cf. Leggett, 1990, p. 4)? Is it yet another manifestation of Garrett Hardin's (1968) tragedy of the commons? Is it inertia? The answers to these important queries+answers which rival in number and ingenuity Lovins' energy-saving gizmos+cannot be explored here (cf. Hardin, 1968; Nissani, 1990, 1992).

In the meantime, it would appear that the greenhouse threat is real; the recipe for health and wealth simple; the wisdom to use it, absent. To justify their faith in humanity's luck, the optimists can rightly cite the historical record. But to maintain their faith in humanity's rationality, they must show that the probability of disaster is close to zero and that the costs of prevention are well above zero. Until this feat is accomplished, skeptics would go on insisting that all but the details of humankind's environmental follies had been predicted long ago in Capek's War with the Newts.

The last chapter in humanity's greenhouse saga remains to be written, perhaps long after cacti have grown over our cheeks. Until then, one's future projections depend less on science and more on one's temperament: on whether one sees the world as turning towards dawn or dusk. Who knows? We may continue to emit greenhouse gases forever and remain as cool and comfortable as we have ever been. We may come to our senses in time, act, and vanquish the threat. Inadvertently, we may remove the threat. We may sweat and survive. Or we may sink and drown.



I thank Donna Hoefler-Nissani, Virginia Abernethy, Ronald Aronson, and students of ISP 601 for generously and competently criticizing this review. For permission to adapt figures, I am grateful to Wadsworth (Fig. 1), Lion Publishers, Human Sciences Press, and Wilfrid Laurier University Press (Fig. 2).



1. For similar views, see Singer, Revelle, & Starr, 1993; Moore, 1995.

2. George Woodwell concurs: "The continued habitability of the earth is clearly in question" (1995, p. 4). W. S. Broecker: "We can state with some certainty, however, that the climate system provoked with our greenhouse gases might turn into a raging bull rather than a quiet lamb!" (1994, p. 18). Jeremy Leggett: "In a poll of 400 climate scientists . . . 45 percent . . . said that a runaway greenhouse effect is possible" (1992, p. 30).

3. It is unlikely that CFCs would be replaced by substances which would neither damage the ozone layer, nor serve as a greenhouse gas, nor possess other, unforeseen, negative environmental impact: in environmental politics, there is always the danger of jumping out of the ultraviolet pan into the greenhouse fire.

4. Similar claims still persist, e.g., Beckerman & Malkin, 1994, p. 10.

5. See, for instance, Blair & Ross, (1993, especially p. 151); Gates, 1993, p. 251; Flavin & Lenssen, 1993; Miller, 1994; National Academy of Sciences, 1992, pp. 60-64; Sinyak (1994, especially p. 50). In 1979, the energy project of the Harvard Business School found that Conservation "should be regarded as a largely untapped source of energy. Indeed, conservation+not coal or nuclear energy+is the major alternative to imported oil. It could perhaps 'supply' up to 40 percent of America's current energy usage" (Stobaugh & Yergin, pp. 11-12).

6. National Academy of Sciences: "The average net annual savings . . . from 1973 to 1986 . . . from efficiency amounted to $100 billion (1992, p. 201). See also Flavin & Lenssen, 1993, p. 566.

7. For instance, the unabashed post hoc ergo propter hoc claim that growing national economies require corresponding growths in energy consumption.

8. Excluding massive government subsidies and including long-term safe disposal of radioactive wastes and of the huge buildings which house the reactors.

9. Sir John Houghton, long-time chair of the Science Working Group of the Intergovernmental Panel on Climate Change, concludes: "Many studies have shown that in most developed countries energy savings of 20 or 30 per cent can be achieved at no net cost or even at some overall saving" (1994, p. 175).

10. "To wait for the climate forecasters to become more confident and precise could be to delay dangerously" (Brown, 1994, p. 22).



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Figure Captions

Fig. 1. Correlations between global surface temperatures and CO2 levels over the past 160,000 years (adapted from Miller, 1994).

 Fig. 2. (a) Rising atmospheric CO2 levels since 1700 A.D. (adapted from Houghton, 1994). (b) Rising CH4 levels from 988 A.D. to 1988 (adapted from Heilig, 1994). (c) Rising world's surface temperatures since 1860 (shown as departures from the 1951-1980 mean; adapted from Hare, 1993).

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