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The fallibility of long term predictions

Until the 1960s i t was widely held that this was the chief limitation on science's ability to predict the longterm behaviour of fluids, and, in particular, of atmospheric flows and the weather. More recently, a second factor has been recognized, a more fundamental one. I t appears, simply, that the motion of fluids can be intrinsically unpredictable. As in the breaking wave, fluids may become unstable. In other words, very small factors can have large results, a tiny push can send things into a tailspin. This fundamental aspect of fluid flow was developed mathematically, in the weatherforecasting context, by a number of people in the 1960s and 1970s, notably by E.N. Lorenz of MIT. In physical terms, the message is simple: unexpected atmospheric instabilities may occur anywhere, at any time, to upset our predictions. A small cloud, somewhere, grows suddenly into a thunderhead; dust particles seed a rainstorm; and, it has been said, the flap of a seagull's wing could affect next week's weather. The last may, or may not be, an exaggeration; the spirit of the statement, nonetheless, is correct: beyond a certain point, chance rules.

Indeterminism in the large, in the macroscopic world, is not rare; yet i t is not always easy to recognize. Take climatic change. The earth has a long history of climatic swings; periodically glaciers have invaded Europe, North America and parts of Africa. The time scales are variable — millions of years in ancient, geologic times, tens of thousands of years in the more recent past. Not so long ago, the musk ox and the woolly mammoth roamed the plains of France, Germany and Russia; during balmy, semi-tropical interglacials the hippopotamus and the lion inhabited the South of France. The recent picture, during the last million years, is one of climatic oscillations — cold periods followed by warm. Yet we don't know when the next glaciation is due. We don't have a predictive theory for these cycles. There are hypotheses, of course, but none are entirely satisfactory. We know, for instance, that astronomical factors play a role — small, periodic changes in the earth's orientation as it spins its way about the sun (the Milankovitch theory). We suspect, too, that the great eras of glaciation in the earth's more distant past correlate with long-term galactic effects: the solar system, i t appears, sweeps periodically through the dust-laden arms of our galaxy; this, it is said, influences the sun's radiation, the earth's heat budget and thus the climate. These are some of the outside factors which have, possibly, triggered climatic changes. We don't know i f there are 126

others; we have no reliable, quantitative theory. For all we know, the problem may not have a solution — not, that is, in traditional deterministic terms.

Tampering with the weather

This casts a disturbing light on current worries about mankind's influence on climate. Thus the carbon dioxide debate: industry spews, yearly, millions of tons of carbon dioxide into the atmosphere, and global concentrations are increasing at an alarming rate — 13 per cent since the advent of the industrial revolution, perhaps 25 per cent by the beginning of the next century. Deforestation further aggravates the effect, since this decreases the planet's ability to, cope with the extra load of carbon dioxide. Such changes are cause for worry, for they imply a disturbance of the balance of heat absorbed by the atmosphere and reradiated back into space: the net effect, it is often claimed, will be to turn our planet into a vast greenhouse. Whether warming is taking place is not clear — the effect is yet, at best, a small one; but no one seriously denies its possibility. Many uncertainties surround the problem; there is even difficulty in accounting for the carbon dioxide produced by industry, to within a factor of twro, or even three. I t has been pointed out, also, that other effects, such as increasing atmospheric dust, could cancel or reverse the greenhouse effect. Palaeoclimatic evidence from the deep-sea cores suggests that we are — or have been, until recently — sliding into a new ice age . . . The fact is that no one is sure of the long-term prognosis. At present, there are no answers; perhaps there can be none. One thing, however, is certain: we are perturbing a system whose stability we do not understand. Nevertheless, there are still those who talk of tampering with the weather and, indeed, of modifying the climate here and there, to suit their purposes. Some years ago it transpired that the Pentagon was interested in climatic problems. In the early 1970s there was talk of the USA manipulating the climate, spraying large snow-covered arctic areas with coal dust, inundating low-lying flatlands with seawater or changing the nature of the vegetation so as to alter the balance of heat absorbed from the sun and reradiated back into space. Doing this in the North American arctic, it was reasoned, might affect the climate in Russia or Siberia to their disadvantage. Such problems, one gathered, were already on the computers. One hasn't heard much about this in recent years. One trusts the computer's message was one of sterling uncertainty — sufficient to discourage even the brashest of our Strangeloves. One doesn't know though: their workings, too, are unpredictable.

Indeterminism on this scale, radical uncertainties concerning the long-term behaviour of our planet's oceans, atmosphere and rocks, impinge upon society's workings in a myriad ways. Debates on pollution, resource depletion, population explosion, economic growth, nuclear power, even the planning of scientific research are all, in some measure, affected thereby. Consider the future of nuclear power. The complexities of this issue are endless: economic, ecological, environmental, social, political, geological problems, and many others, are involved — all embroil one, willy-nilly, in unquantifiable and at times indeterministic phenomena. The pollution problems involved in a nuclear economy alone are staggering; one must be concerned, into the decades and centuries ahead, with the diffusion of radioactive carcinogens in the atmosphere, the oceans and the solid earth itself.

By the beginning of next century, a full-blown world nuclear economy would be disposing of yearly quantities of radioactive wastes equivalent to hundreds of thousands of tons of pure radium. The practicalities of such disposal confront us directly with our inability to make long-term predictions concerning the earth's seismicity, underground water flows, ocean currents, or even the climate itself. Yet proponents of nuclear power maintain they will guarantee confinement of high-level radioactive wastes in geological formations on land or in the ocean bed for hundreds of thousands or even millions of years. This is a case of scientific illiteracy: the concept of indeterminism, i t seems, has yet to percolate into industrial and technocratic circles.

Wrong turnings and technological errors

Civilization is faced today with conundrums for which technical solutions may or may not be possible, depending upon the degree of indeterminism one must concede to the phenomena. That indeterminism is present is indisputable; but when does i t significantly affect our power to act? In fairness to the technologists and technocrats whose work this is, efforts to face the problems raised by technology have not been lacking — a proliferation of risk-assessment schemes, pollution standards, industrial legislation, technology assessment committees, attest to this. Nevertheless, one suspects that awareness of indeterminism is only marginal. Expert pronouncements on a variety of matters, from stratospheric pollution to radioactive waste disposal, all too often suggest a strictly nineteenth century faith in the technological fix — i.e., adherence to the idea that, given money, time and New Ecologist No. 4 July/Aug 1978

application, definite answers to all such problems must be forthcoming. Perhaps this is not entirely surprising, in basic theory, pure science is usually well ahead of technology and engineering — particularly when the message is an unwelcome one. And the perception of indeterminism as a large-scale, macroscopic phenomenon is surely unwelcome to technologists, economists, politicians, engineers, generals, statesmen — to all of society's decision-makers.

Insofar as the final decades of the twentieth century are concerned, the message of this kind of scientific indeterminism is clear: a growing number of seemingly technical issues cannot be decided on technical merit alone. This implies, inevitably, the politicalization of technology and, to some extent, of science too. Issues which, not so long ago, would have been regarded as only technical, to be resolved exclusively by scientists or engineers, may now turn upon values, not numbers.

In recent years, technocracy has supplied a variety of proof for its inability to cope predictively with the consequences of its decisions. Leaving aside the unsuccessful gropings of economic theory, there have simply been too many technical catastrophes, too many wrong turnings — thalidomide, Soweso, DDT, industrial explosions, collapsing dams, worldwide pollution . . . the list is endless. The public, aware of vast threats lurking in the background, is worried and uncertain. Less innocent than in the past, it is no longer convinced by the stage entrances of learned men, brandishing diplomas and assuring us that all is well, because they understand the problem, even i f we do not. For every expert who tells us not to worry, you'll find one to contradict him, and the bewildered observer must ask himself how to find the truth. The sobering fact is that he won't get it from the experts — not, that is, solely from their expertise. Positions cannot be taken on purely technical grounds; logic takes us only so far: sooner or later, one must make a value judgment or an act of faith.

Indeterminism of principle, scientifically based uncertainty — this is a twentieth century insight. Appearing first on the atomic scale, in the microcosm, it has now spread to the everyday, macroscopic world of sense and engineering. Whilst science has endowed us with monstrous power, it is now, ironically, teaching us its restrictions, telling us that our abilities are circumscribed forever by uncertainties we do not control. Perhaps this will be our ultimate perception of the universe — a succession of insights each revealing the limitations of the ones that came before, a sort of philosophical Chinese box, enclosing ultimately some strange, and no doubt unexpected, pearl of wisdom.

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