The continuing threat of nuclear war

The American poet Robert Frost famously mused on whether the world will end in fire or in ice. Nuclear weapons can deliver both. The fire is obvious: modern hydrogen bombs duplicate on the surface of the earth the enormous thermonuclear energies of the Sun, with catastrophic consequences. But it might be a nuclear cold that kills the planet. A nuclear war with as few as 100 hundred weapons exploded in urban cores could blanket the Earth in smoke, ushering in a years-long nuclear winter, with global droughts and massive crop failures. The nuclear age is now entering its seventh decade. For most of these years, citizens and officials lived with the constant fear that long-range bombers and ballistic missiles would bring instant, total destruction to the United States, the Soviet Union, many other nations, and, perhaps, the entire planet. Fifty years ago, Nevil Shute’s best-selling novel, On the Beach, portrayed the terror of survivors as they awaited the radioactive clouds drifting to Australia from a northern hemisphere nuclear war. There were then some 7000 nuclear weapons in the world, with the United States outnumbering the Soviet Union 10 to 1. By the 1980s, the nuclear danger had grown to grotesque proportions. When Jonathan Schell’s chilling book, The Fate of the Earth, was published in 1982, there were then almost 60,000 nuclear weapons stockpiled with a destructive force equal to roughly 20,000 megatons (20 billion tons) of TNT, or over 1 million times the power of the Hiroshima bomb. President Ronald Reagan’s ‘Star Wars’ anti-missile system was supposed to defeat a first-wave attack of some 5000 Soviet SS-18 and SS-19 missile warheads streaking over the North Pole. ‘These bombs’, Schell wrote, ‘were built as “weapons” for “war”, but their significance greatly transcends war and all its causes and outcomes. They grew out of history, yet they threaten to end history. They were made by men, yet they threaten to annihilate man’.

Influence of supernovae, gamma-ray bursts, solar flares, and cosmic rays on the terrestrial environment

Changes in the solar neighbourhood due to the motion of the sun in the Galaxy, solar evolution, and Galactic stellar evolution influence the terrestrial environment and expose life on the Earth to cosmic hazards. Such cosmic hazards include impact of near-Earth objects (NEOs), global climatic changes due to variations in solar activity and exposure of the Earth to very large fluxes of radiations and cosmic rays from Galactic supernova (SN) explosions and gamma-ray bursts (GRBs). Such cosmic hazards are of low probability, but their influence on the terrestrial environment and their catastrophic consequences, as evident from geological records, justify their detailed study, and the development of rational strategies, which may minimize their threat to life and to the survival of the human race on this planet. In this chapter I shall concentrate on threats to life from increased levels of radiation and cosmic ray (CR) flux that reach the atmosphere as a result of (1) changes in solar luminosity, (2) changes in the solar environment owing to the motion of the sun around the Galactic centre and in particular, owing to its passage through the spiral arms of the Galaxy, (3) the oscillatory displacement of the solar system perpendicular to the Galactic plane, (4) solar activity, (5) Galactic SN explosions, (6) GRBs, and (7) cosmic ray bursts (CRBs). The credibility of various cosmic threats will be tested by examining whether such events could have caused some of the major mass extinctions that took place on planet Earth and were documented relatively well in the geological records of the past 500 million years (Myr). A credible claim of a global threat to life from a change in global irradiation must first demonstrate that the anticipated change is larger than the periodical changes in irradiation caused by the motions of the Earth, to which terrestrial life has adjusted itself. Most of the energy of the sun is radiated in the visible range. The atmosphere is highly transparent to this visible light but is very opaque to almost all other bands of the electromagnetic spectrum except radio waves, whose production by the sun is rather small.

Public policy towards catastrophe

The Indian Ocean tsunami of December 2004 focused attention on a type of disaster to which policymakers pay too little attention – a disaster that has a very low or unknown probability of occurring, but that if it does occur creates enormous losses. The flooding of New Orleans in the late summer of 2005 was a comparable event, although the probability of the event was known to be high; the Corps of Engineers estimated its annual probability as 0.33% (Schleifstein and McQuaid, 2002), which implies a cumulative probability of almost 10% over a thirty-year span. The particular significance of the New Orleans flood for catastrophic-risk analysis lies in showing that an event can inflict enormous loss even if the death toll is small – approximately 1/250 of the death toll from the tsunami. Great as that toll was, together with the physical and emotional suffering of survivors, and property damage, even greater losses could be inflicted by other disasters of low (but not negligible) or unknown probability. The asteroid that exploded above Siberia in 1908 with the force of a hydrogen bomb might have killed millions of people had it exploded above a major city. Yet that asteroid was only about 200 feet in diameter, and a much larger one (among the thousands of dangerously large asteroids in orbits that intersect the earth’s orbit) could strike the earth and cause the total extinction of the human race through a combination of shock waves, fire, tsunamis, and blockage of sunlight, wherever it struck. Another catastrophic risk is that of abrupt global warming, discussed later in this chapter. Oddly, with the exception of global warming (and hence the New Orleans flood, to which global warming may have contributed, along with manmade destruction of wetlands and barrier islands that formerly provided some protection for New Orleans against hurricane winds), none of the catastrophes mentioned above, including the tsunami, is generally considered an ‘environmental’ catastrophe. This is odd, since, for example, abrupt catastrophic global change would be a likely consequence of a major asteroid strike.

Evolution theory and the future of humanity

No field of science has cast more light on both the past and the future of our species than evolutionary biology. Recently, the pace of new discoveries about how we have evolved has increased (Culotta and Pennisi, 2005). It is now clear that we are less unique than we used to think. Genetic and palaeontological evidence is now accumulating that hominids with a high level of intelligence, tool-making ability, and probably communication skills have evolved independently more than once. They evolved in Africa (our own ancestors), in Europe (the ancestors of the Neanderthals) and in Southeast Asia (the remarkable ‘hobbits’, who may be miniaturized and highly acculturated Homo erectus). It is also becoming clear that the genes that contribute to the characteristics of our species can be found and that the histories of these genes can be understood. Comparisons of entire genomes have shown that genes involved in brain function have evolved more quickly in hominids than in more distantly related primates. The genetic differences among human groups can now be investigated. Characters that we tend to think of as extremely important markers enabling us to distinguish among different human groups now turn out to be understandable at the genetic level, and their genetic history can be traced. Recently a single allelic difference between Europeans and Africans has been found (Lamason et al., 2005). This functional allelic difference accounts for about a third of the differences in skin pigmentation in these groups. Skin colour differences, in spite of the great importance they have assumed in human societies, are the result of natural selection acting on a small number of genes that are likely to have no effects beyond their influence on skin colour itself. How do these and other recent findings from fields ranging from palaeontology to molecular biology fit into present-day evolution theory, and what light do they cast on how our species is likely to evolve in the future? I will introduce this question by examining briefly how evolutionary change takes place.

Long-term astrophysical processes

As we take a longer-term view of our future, a host of astrophysical processes are waiting to unfold as the Earth, the Sun, the Galaxy, and the Universe grow increasingly older. The basic astronomical parameters that describe our universe have now been measured with compelling precision. Recent observations of the cosmic microwave background radiation show that the spatial geometry of our universe is flat (Spergel et al., 2003). Independent measurements of the red-shift versus distance relation using Type Ia supernovae indicate that the universe is accelerating and apparently contains a substantial component of dark vacuum energy (Garnavich et al., 1998; Perlmutter et al., 1999; Riess et al., 1998). This newly consolidated cosmological model represents an important milestone in our understanding of the cosmos. With the cosmological parameters relatively well known, the future evolution of our universe can now be predicted with some degree of confidence (Adams and Laughlin, 1997). Our best astronomical data imply that our universe will expand forever or at least live long enough for a diverse collection of astronomical events to play themselves out. Other chapters in this book have discussed some sources of cosmic intervention that can affect life on our planet, including asteroid and comet impacts (Chapter 11, this volume) and nearby supernova explosions with their accompanying gamma-rays (Chapter 12, this volume). In the longerterm future, the chances of these types of catastrophic events will increase. In addition, taking an even longer-term view, we find that even more fantastic events could happen in our cosmological future. This chapter outlines some of the astrophysical events that can affect life, on our planet and perhaps elsewhere, over extremely long time scales, including those that vastly exceed the current age of the universe. These projections are based on our current understanding of astronomy and the laws of physics, which offer a firm and developing framework for understanding the future of the physical universe (this topic is sometimes called Physical Eschatology – see the review of ćirković, 2003). Notice that as we delve deeper into the future, the uncertainties of our projections must necessarily grow.

Artificial Intelligence as a positive and negative factor in global risk

By far the greatest danger of Artificial Intelligence (AI) is that people conclude too early that they understand it. Of course, this problem is not limited to the field of AI. Jacques Monod wrote: ‘A curious aspect of the theory of evolution is that everybody thinks he understands it’ (Monod, 1974). The problem seems to be unusually acute in Artificial Intelligence. The field of AI has a reputation for making huge promises and then failing to deliver on them. Most observers conclude that AI is hard, as indeed it is. But the embarrassment does not stem from the difficulty. It is difficult to build a star from hydrogen, but the field of stellar astronomy does not have a terrible reputation for promising to build stars and then failing. The critical inference is not that AI is hard, but that, for some reason, it is very easy for people to think they know far more about AI than they actually do. It may be tempting to ignore Artificial Intelligence because, of all the global risks discussed in this book, AI is probably hardest to discuss. We cannot consult actuarial statistics to assign small annual probabilities of catastrophe, as with asteroid strikes. We cannot use calculations from a precise, precisely confirmed model to rule out events or place infinitesimal upper bounds on their probability, as with proposed physics disasters. But this makes AI catastrophes more worrisome, not less. The effect of many cognitive biases has been found to increase with time pressure, cognitive busyness, or sparse information. Which is to say that the more difficult the analytic challenge, the more important it is to avoid or reduce bias. Therefore I strongly recommend reading my other chapter (Chapter 5) in this book before continuing with this chapter. When something is universal enough in our everyday lives, we take it for granted to the point of forgetting it exists. Imagine a complex biological adaptation with ten necessary parts. If each of the ten genes is independently at 50% frequency in the gene pool – each gene possessed by only half the organisms in that species – then, on average, only 1 in 1024 organisms will possess the full, functioning adaptation.

Catastrophe, social collapse, and human extinction

The main reason to be careful when you walk up a flight of stairs is not that you might slip and have to retrace one step, but rather that the first slip might cause a second slip, and so on until you fall dozens of steps and break your neck. Similarly, we are concerned about the sorts of catastrophes explored in this book not only because of their terrible direct effects, but also because they may induce an even more damaging collapse of our economic and social systems. In this chapter, I consider the nature of societies, the nature of social collapse, and the distribution of disasters that might induce social collapse, and possible strategies for limiting the extent and harm of such collapse. Before we can understand how societies collapse, we must first understand how societies exist and grow. Humans are far more numerous, capable, and rich than were our distant ancestors. How is this possible? One answer is that today we have more of most kinds of ‘capital’, but by itself this answer tells us little; after all, ‘capital’ is just anything that helps us to produce or achieve more. We can understand better by considering the various types of capital we have. First, we have natural capital, such as soil to farm, ores to mine, trees to cut, water to drink, animals to domesticate, and so on. Second, we have physical capital, such as cleared land to farm, irrigation ditches to move water, buildings to live in, tools to use, machines to run, and so on. Third, we have human capital, such as healthy hands to work with, skills we have honed with practice, useful techniques we have discovered, and abstract principles that help us think. Fourth, we have social capital, that is, ways in which groups of people have found to coordinate their activities. For example, households organize who does what chores, firms organize which employees do which tasks, networks of firms organize to supply inputs to each other, cities and nations organize to put different activities in different locations, culture organizes our expectations about the ways we treat each other, law organizes our coalitions to settle small disputes, and governments coordinate our largest disputes.

The totalitarian threat

During the twentieth century, many nations – including Russia, Germany, and China – lived under extraordinarily brutal and oppressive governments. Over 100 million civilians died at the hands of these governments, but only a small fraction of their brutality and oppression was necessary to retain power. The main function of the brutality and oppression, rather, was to radically change human behaviour, to transform normal human beings with their selfish concerns into willing servants of their rulers. The goals and methods of these governments were so extreme that they were often described – by friend and foe alike – as ‘total’ or ‘totalitarian’ (Gregor, 2000). The connection between totalitarian goals and totalitarian methods is straightforward. People do not want to radically change their behaviour. To make them change requires credible threats of harsh punishment – and the main way to make such threats credible is to carry them out on a massive scale. Furthermore, even if people believe your threats, some will resist anyway or seem likely to foment resistance later on. Indeed, some are simply unable to change. An aristocrat cannot choose to have proletarian origins, or a Jew to be an Aryan. To handle these recalcitrant problems requires special prisons to isolate dangerous elements, or mass murder to eliminate them. Totalitarian regimes have many structural characteristics in common. Richard Pipes gives a standard inventory: ‘[A]n official all-embracing ideology; a single party of the elect headed by a “leader” and dominating the state; police terror; the ruling party’s control of the means of communication and the armed forces; central command of the economy’. All of these naturally flow from the goal of remaking human nature. The official ideology is the rationale for radical change. It must be ‘all-embracing’ – that is, suppress competing ideologies and values – to prevent people from being side-tracked by conflicting goals. The leader is necessary to create and interpret the official ideology, and control of the means of communication to disseminate it. The party is comprised of the ‘early-adopters’ – the people who claim to have ‘seen the light’ and want to make it a reality.

Catastrophic nuclear terrorism: a preventable peril

One can conceive of at least three potentially catastrophic events involving the energy of the atom: a nuclear accident in which massive quantities of radiation inadvertently are released into the environment including inadvertent nuclear missile launches; nuclear war among nation-states; and nuclear violence inflicted by non-state actors. This chapter focuses on the last of these threats – the dangers posed by nuclear terrorism, a phenomenon that lies at the nexus between what are widely considered to be two of the primary security threats of the modern era. Non-state actors have essentially four mechanisms by which they can exploit civilian and military nuclear assets intentionally to serve their terrorist1 goals: • the dispersal of radioactive material by conventional explosives or other means; • attacks against or sabotage of nuclear facilities, in particular nuclear power plants and fuel storage sites, causing the release of radioactivity; • the theft, purchase, or receipt of fissile material leading to the fabrication and detonation of a crude nuclear explosive, usually referred to as an improvised nuclear device (IND); and • the theft, purchase, or receipt and detonation of an intact nuclear weapon. All of these nuclear threats are real; all merit the attention of the international community; and all require the expenditure of significant resources to reduce their likelihood and potential impact. The threats, however, are different and vary widely in their probability of occurrence, in consequences for human and financial loss, and in the ease with which intervention might reduce destructive outcomes (for a detailed analysis, see Ferguson and Potter, 2005). Nuclear terrorism experts generally agree that the nuclear terror scenarios withthehighestconsequences–thoseinvolvingnuclearexplosives–aretheleast likely to occur because they are the most difficult to accomplish. Conversely, the scenarios with the least damaging consequences – those involving the release of radioactivity but no nuclear explosion – are the most likely to occur because they are the easiest to carry out. Constructing and detonating an IND, for example, is far more challenging than building and setting off a radiological dispersal device (RDD), because the former weapon is far more complex technologically and because the necessary materials are far more difficult to obtain.

Climate change and global risk

Climate change is among the most talked about and investigated global risks. No other environmental issue receives quite as much attention in the popular press, even though the impacts of pandemics and asteroid strikes, for instance, may be much more severe. Since the first Intergovernmental Panel on Climate Change (IPCC) report in 1990, significant progress has been made in terms of (1) establishing the reality of anthropogenic climate change and (2) understanding enough about the scale of the problem to establish that it warrants a public policy response. However, considerable scientific uncertainty remains. In particular scientists have been unable to narrow the range of the uncertainty in the global mean temperature response to a doubling of carbon dioxide from pre-industrial levels, although we do have a better understanding of why this is the case. Advances in science have, in some ways, made us more uncertain, or at least aware of the uncertainties generated by previously unexamined processes. To a considerable extent these new processes, as well as familiar processes that will be stressed in new ways by the speed of twentyfirst century climate change, underpin recent heightened concerns about the possibility of catastrophic climate change. Discussion of ‘tipping points’ in the Earth system (for instance Kemp, 2005; Lenton, 2007) has raised awareness of the possibility that climate change might be considerably worse than we have previously thought, and that some of the worst impacts might be triggered well before they come to pass, essentially suggesting the alarming image of the current generation having lit the very long, slow-burning fuse on a climate bomb that will cause great devastation to future generations. Possible mechanisms through which such catastrophes could play out have been developed by scientists in the last 15 years, as a natural output of increased scientific interest in Earth system science and, in particular, further investigation of the deep history of climate. Although scientific discussion of such possibilities has usually been characteristically guarded and responsible, the same probably cannot be said for the public debate around such notions.