Catastrophes

The St Andrews Prize Lecture, Royal Institution, London - 2001-10-22

Sir Crispin Tickell was speaking as Chairman of the St Andrews Prize Trustees

The definition of catastrophe in the Collins dictionary is "sudden, extensive or notable disaster or misfortune": from the Greek to overturn. The history of the earth and of life on it is full of overturnings, many of them sudden; and tonight I shall focus on four such: those from beyond the earth; those from within the earth system; those affecting life in general; and those caused by the small animal species which is ourselves. I will then say something at the end about what, if anything, we can do to anticipate, prevent, mitigate or adapt ourselves to them.

The very notion of overturning has long been the subject of controversy. At the beginning of the 19th century the arguments crystallized. Different schools of thought lined up against each other, among them the Catastrophists versus the Uniformitarians. Embedded in the Judeo-Christian tradition is the notion that God interferes from time to time in the affairs of the Earth, and in particular those of humankind. If humans do not control the Earth's destiny, then God does. From this comes thinking about the Creation, the Flood, the Last Day, and divine punishment for human aberrations, manifest in disease, famine, earthquakes and other natural disasters.

As this range of ideas became discredited with the rise of science - time became immeasurably longer and the Earth immeasurably smaller in the scheme of things - so also was discredited the idea of catastrophes coming from outside the Earth. The Uniformitarians believed in slow and accumulating change as the norm. James Hutton wrote of "no vestige of a beginning, no prospect of an end". Charles Darwin saw evolution by natural selection as a process covering hundreds of millions of years.

But as so often in ferocious scientific arguments, both were right and both were wrong. There is an important concept to grasp throughout: change may be linear most of the time but at crucial moments it is non-linear, and goes in jumps as thresholds of tolerability are passed. The unanswerable question is how to identify the thresholds. We rarely know them until after the event. Such events fall squarely into chaos or complexity theory. We simply cannot forecast what will happen.

Particularly repellent is the notion of catastrophes from space. Whatever the natural or human-induced problems we face as we scurry around on its surface, the Earth is our only home. Perhaps this is why it has taken us so long to understand the realities. We all know how difficult it is to change ways of thinking. People went through agonies trying to reconcile the Bible with geology in the first half of the 19th century. To this day there are people who deny tectonic plate movement and the human contribution to climate change, and seek to explain impacts on the Earth or the Moon by any means other than what is now obvious.

From Beyond the Earth

What are the objects from space that hit the Earth from time to time? They range from the very big to the very small. They include meteorites, asteroids, planetesimals, and comets, many of them dating from the origins of the solar system.

The biggest of all was the object which hit the young Earth more than four billion years ago, and led to the creation of the Moon. Since then there has been an intermittent barrage. Only in the last quarter century have we come to understand the scale of the problem. A vivid illustration in July 1994 was the spectacle of the comet Shoemaker-Levy colliding with the planet Jupiter. As the comet entered Jupiter's gravitational field, it broke up into fragments, resulting in multiple impacts. One fragment alone created a fireball as big as the Earth. In 1997 many of us saw the comet Hale-Bopp as it travelled magnificently and harmlessly across our skies.

Fortunately for us the atmosphere of the Earth acts as a protective shield for most Near Earth Objects, which burn up or explode at high altitudes. By contrast the larger ones can hit the Earth with devastating effects. The main ones are blast waves, tsunamis (or huge ocean waves), injection of material into the atmosphere, and electro magnetic charges near the surface. Obviously such effects vary enormously, and depend on the composition of the object, and its speed and angle of entry. More than two thirds of the Earth's surface is ocean, and much of the rest is desert, uninhabited mountain and polar ice cap. Blast waves can be so intense that they are more important than the material behind them, and affect both land and sea. Tsunamis can be 70 metres or more in height, and are probably more destructive - and more frequent -than anything else. Changes in the atmosphere affect the temperature at the Earth's surface, and also the chemistry of the troposphere, with consequences for its carbon dioxide content and the protective ozone layer. Electro magnetic effects can be compared with those caused by the explosion of nuclear devices.

It may be worth taking a look at some specific impacts of which we now have knowledge. First come the big hits of which the Chicxulub event of 65 million years ago is a good example; then the Tunguska event of 1908; then an event above Lake Tagish in the Yukon on 18 January last year; and finally the possible effects of cometary dust on the Earth's climate.

The Chicxulub event changed the history of life on Earth. An object with a diameter of 10 kilometres hit Yucatan at a shallow angle, digging out a crater traceable today with a diameter of around 180 kilometres. It threw up a cloud of vaporized and molten rock over north America. The consequent dust in the upper atmosphere darkened and drastically cooled the whole Earth, damaging the process of photosynthesis on the surface. When the dust settled, the temperature swung the other way. Water vapour and carbon dioxide in the atmosphere caused a runaway green house effect. It has been calculated that the surface temperature of the Earth could have risen by as much as 10oC for at least 500,000 years. It is no wonder that all living creatures were affected, and that a high proportion, including the dinosaur family, perished.

Extinctions of this magnitude are a disaster for some, but an opportunity for others. Indeed the rise of the mammals, with humans a very late arrival among them, would not have happened without Chicxulub. Fortunately major impacts are extremely rare. But they have occurred at very roughly 100 million year intervals throughout the history of the Earth, and could, at least in theory, happen at any time.

Let us now look at the Tunguska event of 1908. An object with a diameter of 60 metres broke up over Siberia, destroying some 2,000 square kilometres of forest. It lit up the night sky across most of the northern hemisphere, and in Belgium was likened to a great red glow after sunset as if from a huge distant fire. Had it struck St Petersburg or London, there would have been little left of either. Although the area was inhabited by very few people, a witness described the sky as being split in two, with the northern part covered with fire, then a great heat and a mighty crash. The devastation can still be detected today, almost a century later. Events of this kind are relatively frequent of the order of once every 250 years.

More frequent still are events of the kind that happened over Lake Tagish in the Yukon on 18 January last year. An object of around five metres in diameter exploded at an altitude of 25 kilometres, causing a long and bright fireball, a loud bang, a shower of fragments, and an electro magnetic pulse which caused a temporary loss of power transmission on the ground below. There were several witnesses. A curious effect was that many noticed smells, frequently described as sulphurous (although hot metal and rock were also mentioned) around the area of the shower. Analysis of the fragments has shown that they come from the asteroid belt between Mars and Jupiter, and derive from the early history of the solar system.

There is a fairly constant hail of small objects into the upper atmosphere, most unnoticed below. Examples of small impacts include the Mbale impact in August 1992, when a boy was hit by a stone after its deflection by a banana leaf. Then there was the so called Peeskill object which stove in the back of an old Chevrolet in upstate New York on 9 October 1992. The owner is said to have made a fortune out of it.

My last specific instance relates to the trails of dust left behind by comets though which the Earth passes from time to time. They are more serious than the fireworks displays (for example the Leonids next month) with which they are often associated. Such dust can provide the nuclei for ice crystals, sometimes known as diamond dust, to form at the top of the troposphere some 10 to 15 kilometres above the surface of the Earth. This has the effect of reflecting solar radiation back into space, and could, with other factors, help to trigger variations in the climate below.

We must also reckon with other much neglected influences on the Earth from space. We still know relatively little about them. Events outside our galaxy can generate bursts of immensely destructive radiation. The same can be said of supernova explosions nearer at hand. I add that without such explosions life as we know it could not exist. We are literally star dust. Then there are variations in radiation from the sun, our friendly neighbourhood hydrogen bomb. Finally there are the changing relationships in the Earth's orbit - variations in wobble, tilt and spin known as the Milankovitch effect - which profoundly affect the Earth's climate, and its current propensity to dip in and out of ice ages.

Together these factors point to one central conclusion which I shall return to many times. We and all living creatures live dangerously on Earth. It is only the shortness of our lives which shields us from understanding how vulnerable the Earth really is.

From Within the Earth

This brings me to catastrophes - or overturnings - from within the Earth. The slow movement of the tectonic plates on its surface usually gives time for ecosystems and the species which compose them to move or adapt to change. But passing over thresholds can sometimes have dramatic effects on the behaviour of winds and ocean currents, and of course the living organisms adapted to them. Good examples are the effects of the collision of India with the Asian continent and subsequent rise of the Himalayas; and the joining of north and south America some four million years ago, which led to drastic changes in the direction of ocean currents.

Associated with tectonic plate movements are volcanoes and earthquakes. We are unused to major volcanic eruptions. The eruptions of the Siberian Traps some 250 million years ago, and the Deccan Traps 65 million years ago, both possibly associated with extra terrestrial impacts, changed the surface conditions of the planet. The eruption of Mount Toba in Indonesia some 75,000 years ago, which put enormous quantities of volcanic dust into the atmosphere, may have helped trigger a renewal of glacial conditions within the last ice age. By comparison the eruption of Tambora in 1815, which led to the famous "year without a summer", that of Krakatoa in 1883, that of Mount St Helens in 1980, and that of Mount Pinatubo in 1991, each with its specific global effects, were relatively minor. I claim to be the only ambassador who correctly predicted a drop in average world temperature of around half a degree Celsius following the eruption of El Chichon in Mexico in 1982.

Earthquakes are part of the same pattern. Mostly their effects, however destructive, are local. On average some 10,000 people a year are killed by them, usually by buildings falling in on them. But sometimes they can combine with tsunamis to cause much greater damage. Underwater landslides, such as that which brought a 2 or 3 metre wave into parts of eastern Scotland some 12,000 years ago, can be precipitated by Earth tremors. Recently there has been concern about the possibility that part of the Cumbre Vieja volcano in the Canaries might collapse into the sea, creating a tsunami with a height of up to 40 metres, which could hit the east coast of the United States.

Again we live dangerously.

Life in General

I come to the overturnings in the living world. Such overturnings can be disastrous for those ecosystems and species around at the time, but they are usually the opportunity for others. If the extinctions at the Permian/Triassic boundary 250 million years ago, and those of the Cretaceous/Tertiary boundary 65 million years ago, had not taken place, nothing like the world we know today, and the human species within it, could have existed. The history of living organisms, so far as we know it from the fossil evidence, shows a pattern of stability punctuated by relatively sudden departures of some species and arrivals of others. Stephen Jay Gould once described the process in a famous passage:

"Life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress. The divine tape player holds a million scenarios, each perfectly sensible. Little quirks at the outset, occurring for no particular reason, unleash cascades of consequences that make a particular future seem inevitable in retrospect. But the slightest early nudge contacts a different groove, and history veers into another plausible channel, diverging continually from its original pathway. The end results are so different, the initial perturbation so apparently trivial. If little penis worms ruled the sea, I have no confidence that Australopithecines would ever have walked erect on the savannas of Africa. And so, for ourselves, I think we can only exclaim, O brave - and improbable - new world, that has such people in it!"

Thus extinctions are an essential element in evolution. Few ecosystems or species last more than a few million years. But if extinctions happen all at once, they gravely impoverish life in all its interconnectedness. The time needed to recover can be millions of years. Thus mammals did not evolve to occupy all the niches left by the dinosaurs until the end of the Palaeocene epoch 10 million years later.

One point is worth adding, the product of recent and continuing research. To a considerable extent, and operating on Darwinian principles, organisms create and maintain the living environment most favourable to them. Thus they seek to offset and mitigate the consequences of catastrophes through complex systems of feedback. The Earth system behaves as a single, self regulating system, comprised of physical, chemical, biological and even human components.

Human Actions

This brings me to the role of our own little animal species, and our sometimes catastrophic influence on the condition, living and otherwise, of the Earth's surface. A periodical visitor from outer space would find more change in the preceding 200 years than in the preceding 2000, and more change in the last 20 years than in the last 200. The association between humans and their environment, including the micro-world in and around them, has changed at every stage of human evolution: from vegetarians to meat eaters, from hunter gatherers to farmers, and from country to city dwellers. But the most radical divide was the beginning of the industrial revolution in Britain some 250 years ago. Before then the effects of human activity were local, or at worse regional, rather than global. All the civilizations of the past cleared land for cultivation, introduced plants and animals from elsewhere, and caused a variety of changes. The southern and eastern coasts of the Mediterranean are a case in point. The soils have now become sand, the trees are often camel grass, animals of all kinds have disappeared, and the clouds sail overhead to drop their rain somewhere else.

With the industrial revolution, all began to change. I suspect that the present generation - ours - is the first in which the magnitude of the effects on the Earth as a whole has become manifest.

In July of this year scientists involved in the four great global research programmes met at Amsterdam, and adopted a Declaration on Global Change, signed by almost a thousand people. In it they said that changes brought about by human activities had

"...the potential to switch the Earth's system to alternative modes of operation that may prove irreversible and less hospitable to humans and other life. The probability of human-driven abrupt change in Earth's environment has yet to be quantified but is not negligible."

What are these changes? They fall into five main categories, all inter-linked. First there has been a giddy making increase in human numbers, rising from around one billion at the time of Thomas Malthus (who first drew attention to the relationship between population and resources) at the end of the 18th century, to two billion in 1930 and now over six billion. The world population is increasing by over eighty million people each year. More than half our species now lives in cities, which are themselves like organisms drawing in resources and emitting wastes. In short we are spreading like dandelions, or any other species on a bonanza. Indeed it has been suggested that human multiplication is a case of malignant maladaption in which a species, like infected tissue in an organism, multiplies out of control, affecting everything else.

All this has profoundly affected the condition of the land surface. More people need more space and more resources. Soil degradation is currently estimated to affect some 10% of the world's current agriculture area. Although more and more land, whatever its quality, is used for human purposes, increase in food supplies has not kept pace with increase in population. Today many of the problems are of distribution. But even countries generating food surpluses can see limits ahead. Application of bio-technology, itself with some dubious aspects, can never hope to meet likely shortfalls. In the meantime industrial contamination of various kinds has greatly increased. To run our complex societies, we need copious amounts of energy, at present overwhelmingly derived from dwindling resources of fossil fuels laid down hundreds of millions of years ago. We also have to deal with the mounting problems of waste disposal, including the toxic products of industry.

Next there has been increasing pollution of water, both salt and fresh. No resource is in greater demand than fresh water. At present such demand doubles every twenty-one years and seems to be accelerating. Yet supply in a world of over six billion people is the same as at the time of the Roman Empire in a world of 200,000 to 300,000 people.

Then there have been changes in the chemistry of the atmosphere. Acidification from industry has affected wide areas downwind. Depletion of the protective atmospheric ozone layer permitting more ultra-violet radiation to reach the surface of the Earth with so far unmeasured effects on organisms unadapted to it. Greenhouse gases are increasing at a rate which could change average world temperature, with big resulting variations in climate and local weather as well as sea levels. According to the estimates of the Intergovernmental Panel on Climate Change, we could be altering the global climate at rates far greater than would have occurred naturally in the last ten thousand years with unforeseeable consequences. Carbon levels in the atmosphere are now the highest in the last 160,000 years, and rising fast.

Lastly humans are causing extinction of other organisms at many times the normal rate. Indeed the rate of extinction is reminiscent of the dinosaur extinction of 65 million years ago. The rising damage to the natural services on which we, like all species depend, is immeasurable. There is no conceivable substitute for such services. At present there is a creeping impoverishment of the biosphere. According to the Living Planet Index put forward by the World Wide Fund for Nature (WWF) in 2000, the state of the Earth's natural ecosystems has declined by about a third in the last thirty years, while the ecological pressure of humanity has increased by about a half during the same period.

Environmental change rarely proceeds in curves. As with most other things, it goes in steps and thresholds. Due perhaps to our lack of imagination, we tend to believe that what we know the current diversity of life and the climate around us will only change within narrow limits; and that if nature is allowed to take its course, things will revert to where they were. Unfortunately history gives no foundation for this belief. As was well said in the Amsterdam Declaration

"the nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change are unprecedented. currently operating in a no-analogue state."

Again we live dangerously.

The Consequences

It would be tedious to enumerate the consequences of this combination of factors for human society. Most are pretty obvious. The pressure points of human proliferation, land degradation, water shortages, climate change with sea level rise, and damage to the biosphere as a whole cannot be seen in isolation. They suggest a dysfunctional world of ever increasing risks to the wellbeing of our society. Such risks include greater possibilities for conflict over resources, with use of dangerously destructive weapons with all the possibilities of terrorism, wider division between rich and sophisticated and poor and disadvantaged, larger flows of refugees both within and between countries, evolution of new and the return of old diseases, extinction of key ecosystems, and social and economic breakdown of a kind that can already be seen in parts of Africa.

Two quotations make the point better than I can. The first comes from the historian John Reader

"...in the brief space of time that civilization has been a feature of human existence, it has not demonstrated any tendency to produce a well regulated steady state whereby people are well fed and secure, generation after generation. Civilization is distinguished more by its erratic cyclesÉ Time and time again it has risen dramatically from the field of human endeavour, then collapsed and fallen. Human ingenuity drives the process. Inventions provide the initial impetus, intellect supplies methods of application and solutions to problems that arise as the system swells and grows, but in every instance so far, the uncontrolled growth of civilization has ultimately thrown up more problems than human intellect can solve."

The second quotation comes from a book by the authors of The Limits to Growth. This book on the twentieth anniversary of its predecessor is entitled Beyond the Limits. Building on their 1972 models, the authors - Donella Meadows, Dennis Meadows and Jorgen Randers - show that the world economy tends to overshoot capacity because of expanding population and continuing economic growth. To sustain this growth people draw down resources below certain thresholds at which the whole economy behaves differently. This is because of the step like - non linear - character of change: in jumps not curves. The authors wrote that

"In most [of our computer] runs... the world system does not run out of land or food or resources or pollution capacity, it runs out of the ability to cope."

Conclusions

All this gloomy stuff. It may not be the apocalypse, but it is certainly a powerful combination of overturnings. Even so there is a great deal we can do, if we have a mind to it, about almost all the categories of catastrophe I have described. There is a deep contrast between optimism about our understanding of the issues, and pessimism about our will to cope with them. Change normally comes about as a result of leadership from above, pressure from below, and the occasional catastrophe to concentrate the mind and provide the spur to action.

Let us look first at the kind of catastrophe which looks furthest from human control: impacts from outer space.

Last year I was a member of a Government Task Force to look into the risks for such impacts, and to make recommendations for policy. In my work I was guided by an interesting report entitled Response to the Potential Threat of a Near-Earth Object Impact published in 1995 by the American Institute of Aeronautics and Astronautics: It contained the following passage:

"If some day an asteroid does strike the Earth, killing not only the human race but millions of other species as well, and we could have prevented it but did not because of indecision, unbalanced priorities, imprecise risk definition and incomplete planning, then it would be the greatest abdication in all of human history not to use our gift of rational intellect and conscience to shepherd our own survival, and that of all life on Earth."

What then can we do? Let us suppose that with the help of a greatly improved telescope network, we could with reasonable accuracy predict the next range of extra terrestrial events. The range would of course be wide. We would have to reckon not only with the size and composition of an incoming object, but also with the possibility that it might enter into ever diminishing orbit round the Earth before colliding with it. Our response would fall into two categories.

The first would comprise conventional measures of civil defence. Depending on the length of notice and the size and composition of the incoming object, people could move out of target areas to relatively safer areas elsewhere. Such countries as Britain and Japan would be particularly vulnerable to tsunamis arising from oceanic impacts. Both have suffered from tsunamis in the long past. A big problem would be how to feed a displaced population. A big hit could lead to a darkened Earth which could affect growing seasons for food the world over.

The second is the more exotic prospect of planetary defence, either through destruction or through deflection of incoming objects. This is not a fantasy of such films as Deep Impact or Armageddon. Destruction of an object by high yield nuclear devices might be technically feasible, but would carry enormous risks of its own. Incomplete destruction of an object could subject the Earth to multiple impacts from pieces of the original body. We saw for ourselves what happened to Jupiter when Shoemaker-Levy broke into 21 pieces with 21 impacts.

More promising are the possibilities of deflection through modification of the object's orbit. The amount of modification required is inversely proportional to the time available before impact. So early warning would be vital. Methods considered include detonation of nuclear or chemical devices close to the body to change its orbit. But such devices would have to be used with care. There is a danger that they could deliver a huge amount of energy with very little momentum, whereas to deflect a massive object effectively, it is momentum that is needed: a steady gentle push, not an explosive jolt. This could be achieved by irradiation of the near side surface of the object which might give it the little shove required.

Other possible methods include the mounting of sails on the object to harness the Sun's radiation pressure to push it from its course. Another would be the use of mass drivers whose source of power would again be the Sun. In order to make the system work a number of major engineering problems would have to be solved, but with adequate warning time this should not be impossible. Let us remember the astonishing feat of the Americans in putting a satellite around the asteroid Eros, and then landing it there.

We are more used to catastrophes within the Earth system. There the remedies are less exotic. It is well within our capabilities to improve prediction and take measures to mitigate catastrophes. Anything on a larger scale would require international effort and administrative skills which are at present lacking. Obviously human ability to cope would depend on the resilience and good health of society in general. A world riven by war and degradation could easily be overwhelmed. Much would depend on the abilities of individual governments to manage at least within the areas of their responsibility.

Human damage to the current life system of the planet is not inevitable. Most of the solutions to the problems we have caused are well known. Take human population increase. The overall rate is still rising, but in several parts of the world it is levelling off. The main factors are improvement in the status of women, better provision for old age, wider availability of contraceptive devices, lower child mortality, and better education, especially for girls and young women.

Take degradation of land and water. We know how to look after them both if we try. We do not have to exhaust top soils, watch them erode into the sea, rely upon artificial aids to nature, eliminate the forests with their natural wealth of species, or poison the waters, fresh and salt. Take the atmosphere. We do not have to punch holes in the protective ozone layer. We do not have to rely on systems of energy generation which will affect climate and weather in such a fashion that change, even for the better, might put an overcrowded world at risk. Take the way in which we conduct most scientific enquiry. We do not have to break down issues into water tight compartments, and so miss the dynamics of the life system as a comprehensive whole.

In short we have to learn to think differently. Our ability to respond to the overturnings of life depend on two main factors : our knowledge of the behaviour of ecosystems, at present sadly lacking, and our own value system. We can certainly improve our knowledge, and devote more resources to it. But change in a value system that gives primacy to market forces, exploitation of resources and ever rising living standards will be uncommonly difficult. At present we seem to want to attach monetary value to almost everything. Of course some rule-of-thumb method of assessing and comparing values would indeed be useful, not least in giving comfort to economists and more plausibility to their models. But somehow we have to bring in the factor of environmental costs. As has been well said, markets are superb at setting prices but incapable of recognizing costs.

Definition of costs requires a new approach towards economics and, towards measuring things, and this has to be brought back into pricing. In addition to the traditional costs of research, process, production and so on, prices should reflect the costs involved in replacing a resource or substituting for it; and the costs of the associated environmental problems. Humans are not mere producers or consumers.

What are we then? There is at least one thing we can say for ourselves. We are the only animal species which could conceivably hope to do anything about the problems I have discussed. Our long term prospects for survival cannot be assured. I sometimes wonder how long it would take for the Earth to recover from the human impact. If we were to disappear, how soon would our cities fall apart, soils regenerate, the animals and plants we have favoured find a more normal place in the natural environment, the waters and seas become clearer, the chemistry of the air return to what it was before we polluted it? Life itself, from the top of the atmosphere to the bottom of the seas, and even below that, is so robust that the human experience could become no more than an episode.

Above all let us remember how small and vulnerable we humans are. We are like microbes on the surface of an apple, on an insignificant tree, in an insignificant orchard, among billions of other orchards stretching over horizons beyond our sight or even our imagining.