Amiel Trust

Here are the two reading guides that I wrote in 2005-6 for the Barry Amiel and Norman Melburn Trust's Internet Archive, which you can find at http://banmarchive.org.uk/archive_index.htm

Dick Pountain/14 December 2005/12:19/Amiel Trust Contribution

GENETIC SCIENCE AND ITS POLITICAL IMPLICATIONS

We live in an era in which science and technology have achieved an unprecedented degree of influence over human societies. For those who subscribe to the view that most of human history can be explained as the struggle to dominate Nature by conquering disease and famine, it must appear that we are close to winning. But rather alarmingly, rather witnessing the triumph of reason, we’re in fact seeing a loss of faith in the beneficence of science by a very significant fraction of the population. On one side there’s been an unexpected revival of religious fundamentalism, which denies science's evolutionary explanation of the descent of Homo Sapiens, and on the other an identification of science as part of the enemy among sections of the political Left.

What became abundantly clear during the 20th century was that science and technology create problems as well as solving them – and that in some cases they may even create problems that they cannot solve. One of these problems is the application of science to warfare. At least part of the current distrust of science dates from the end of World War II with its revelation of the awful power of nuclear weapons. Of the Four Horsemen, War is the one that science has so far done the least to overcome and the most to exacerbate. Indeed there are those who would explain scientific progress as being principally driven by the needs of warfare, while others would reply that the problem lies in 'human nature', which contains an irrepressibly violent component, prone to abuse the power of science.

Now the science of genetics and its related technologies promise to open up even human nature itself to the possibility of modification. Genetic modification has of course been practiced by human beings for millennia, as the selective breeding of domesticated animals (and even to a lesser extent of ourselves via the closed marriage practices of aristocracies and sects). Even so, the mechanism by which living things pass on their characteristics to their offspring wasn't fully understood until the nineteenth century, when Charles Darwin [1] proposed his theory of evolution by natural selection, and then Gregor Mendel [2] uncovered the precise way in which these characteristics are transmitted. It remained for James Watson and Francis Crick [3] in 1953 to disclose the actual chemical structure of the human genetic substance, deoxyribonucleic acid or DNA, and the code by in it stores the information required to construct each creature's body and those of its children.

Briefly summarized chromosomes, the units of inheritance, consist of long chains of DNA organised into shorter sequences called 'genes', each of which encodes the recipe for making a particular kind of protein. The total set of genes in any creature is called its 'genome'. Proteins form much of the structure of all living creatures, and most importantly, they also manage the chemical reactions through which other, non-protein body constituents are built, like the bones of animals or the cellulose cell walls of plants. Watson and Crick's discovery lead directly to the possibility of so-called 'genetic engineering', in which molecular biologists replace a naturally-occurring gene in the genome of some creature with another deemed more desirable, for example to correct a defect that causes some genetically-transmitted disease in a human, or perhaps in a bacterium to make it produce a particular protein of commercial value as a drug. Genetic engineering has become possible thanks to modern biochemical techniques that enable scientists to read the sequence of long DNA chains, and also to synthesise artificial lengths of DNA of known sequence and splice them into natural genomes.

The crucial step toward the practical application of genetic engineering was the mapping of the whole human genome, which was completed in 2003 by a multinational consortium coordinated by the US National Institutes of Health and the UK’s Wellcome Trust. The Human Genome Project identified all of the 20,000-25,000 genes that make up human DNA, determined the three billion nucleotide base-pairs of which they are composed, and stored this information in a gigantic computer database, the analysis of which will continue for decades to come. However it must be stressed that identifying a gene sequence is not at all the same as identifying what the protein for which it codes actually does, which is what will be needed before all the miracles anticipated in the popular imagination could come true. The situation has been compared to asking someone to explain how to fly a Boeing 747 airliner, given only its parts-list.

Nature v Nurture

From the moment Darwin first published his 'Origin of Species' a debate raged between those who believe that heredity

determines almost all of human behaviour, and those who say that because Homo sapiens differs from the other animals in having created culture, that therefore social influences now predominate over those of heredity. This debate was quite explicitly political in its earliest stages. On the one side were those conservatives who believed that the fate of each individual was predestined by their genetic makeup, so that the poor were poor because of inferior genes, and some 'races' were genetically inferior to others. On the other side were those optimists, in the tradition of the Enlightenment, who believed that human nature was not a fixed thing, but could be reformed by reason and knowledge: most of the founders of the socialist movement adhered to this camp. The former position, often called Social Darwinism, is often associated with the British philosopher Herbert Spencer [4] (though in fact Spencer's thought was somewhat more complex than this suggests). Social Darwinism was invoked by conservatives from Victorian times up until the 1930s to justify an extreme form of laissez-faire capitalism in which welfare policies and regulation of markets were seen as futile attempts to interfere with the natural process of 'survival of the fittest'. Following World War II the optimists camp gained the upper hand, seeing human nature as something that could be reformed and elevated via education, and by alleviating the corrupting effects of poverty through welfare programs such as the British National Health Service.

The rapid expansion of genetic science that followed Watson and Crick's 1953 revelation injected a more objective element into this debate. Through experiments, particularly those that involved studying pairs of identical and non-identical twins (identical twins share the same genes), it became possible to put an estimate on what portion of the behaviour of a person is due to their genetic make up and what to their upbringing, that is to social influences, and the answer rather conveniently turns out to be roughly 50:50. However it must be said that such attempts at quantitative measure miss the stupendous complexity of the actual interactions between genome and environment, which cannot be reduced to a pastry recipe of 8oz nature, 8oz nurture. Better is this summation by the philosopher George Santayana: "A materialistic interpretation of politics need therefore not be especially climatic or economic or Malthusian, but may take account of those important circumstances in letting loose or suppressing [my emphasis] the various instincts and powers of human nature. The initiative of individuals and the contagion of words and actions must not be excluded... The environment fosters and selects; the seed must contain the potentiality and direction of the life to be selected." In recent years Jared Diamond has published important studies that highlight the complex ways in which climate, geology, geography and biology interact with human psychology to determine the course of development of societies [5].

In the 1970s, coincident with a sharp turn to the Right in politics whose figureheads were Ronald Reagan and Margaret Thatcher, a new and more sophisticated form of Social Darwinism made its appearance. In 1975 Edward O. Wilson [6] published ‘Sociobiology: The New Synthesis’ and Richard Dawkins’ ‘The Selfish Gene’ [7] appeared the next year. Both these works suggest that a rigorous return to Darwinian first-principles would benefit the social sciences, and make strong claims for the influence of genetic makeup in all areas of human life. Dawkins title was intended as a metaphor – from the detached perspective of the geneticist the evolution of life on earth can be viewed as the activity of by a vast population of genes, which cause individual bodies to be built in order to propagate themselves and then 'selfishly' sacrifice the finite lives of these organisms (which include you and me) to ensure their own immortality. This is an interesting and valid scientific metaphor, but like all metaphors it risked being taken literally and many of Dawkins’ readers and followers have done just that, believing him to be saying that human nature is incorrigibly selfish. Neo-conservatives latched onto such ideas to stress that competition is the driving force behind the evolution not only of species but of societies too. A handful of left-wing geneticists, lead by the late Steven Jay Gould and Richard Lewontin [8] have cogently opposed such reductionist interpretations.

Evolutionary psychology is an outgrowth of socio-biology which holds that much of human behaviour can be explained genetically, as the way that genes program individuals to select the most appropriate mates. There's a great deal of truth in some of these findings, particularly those regarding the attitudes of men and women to monogamy and childrearing, but again the interactions between genetic and social factors in the real world are so complex that any simple formula is doomed to miss many other truths [9].

Just how complex this interaction is is suggested by recent discoveries and theories from the world of developmental neurobiology. Contrary to the belief of hard-core sociobiologists, the human brain is not in any simple and direct way the product of our genes. Considered as an information-processing organ, the brain is perhaps the most complex single entity in the universe, containing as it does around three billion neurons which can potentially connect to each other in ten-to-the-billionth-power (one followed by one billion noughts) different ways. Elementary calculations based on Information Theory indicate that the human genome is nowhere near large enough to encode the detailed structure of such an object, and that therefore the development of the brain must be not directly specified but rather guided by the execution of a much simpler set of rules within each growing individual. In a remarkable series of books between 1987

and 1989, Gerald Edelman [10] has suggested how this might happen, starting from his discovery of cell adhesion molecules or CAMs that enable neurons to organise their own connections. It appears that the brain develops by a process analogous to the evolution of species, but in which natural selection is replaced by neuronal selection under the pressure of sensory inputs: the brain’s structure as well as it content is moulded by the environment in which it grows up (if the distinction between content and structure can even be made). This implies for one thing that every human brain is structurally different from every other, and it also explains how we can so easily learn, say, English, German, Japanese or Urdu without their grammars needing to be encoded in our genes.

More recently Antonio Damasio [11] has extended Edelman's insights to propose that human consciousness is intimately linked with, and indeed evolved out of, the system of emotions (which in primitive animals are simple fight/flight mechanisms). The implication is that every memory trace and thought automatically gets labelled with a moral value, and that pure reason is an evolutionarily late (possibly non-essential) development made possible by the acquisition of language. His schema lends support to the Freudian notion of an unconscious [12] and offers the beginnings of a biological explanation for the tenacity of humans' attachment to religion, myth, tribalism and other 'irrational' behaviours. It should also stand as a corrective to the extreme rationalism displayed by many advocates of science, although it does not sanction that anti-rational, anti-humanist, Counter-Enlightenment stance adopted by many postmodern critics.

The fact that we are genetically predisposed to make value judgements wouldn’t prove that our predatory and destructive behaviours are genetically unavoidable, because such urges are as likely as any other to determined by the interaction of nature with nurture. There’s excellent evidence – for example in the work of Frans de Waal [13] with his chimpanzees – that instincts for empathy and cooperation just as genetically determined as aggression. It's even possible that scientific rationality itself may amplify our worse nature, an argument developed by some moral philosophers on the responsible wing of the environmental movement: for example Mary Midgley [14] contends that scientific atomism is inappropriate outside of the 'hard' physical sciences and that its metaphorical application to the social sciences leads to a view of humans as isolated social atoms: "In the real world, as many biologists have pointed out, co-operation and competition go together as two sides of the same coin and, of the two, when things get at all complicated, co-operation must usually come first, because it makes other interactions possible."

Advances in genetic science have been of enormous assistance to anthropologists studying human origins: the discovery that we share 96% of our genome with the chimpanzee has passed into public knowledge and provides excellent confirmation of the correctness of Darwin's theory (though it's unlikely to convince those creationists and 'intelligent design' proponents who are currently gaining so much influence in the USA). The comparative study of gene sequences in modern humans provides a powerful new tool for studying human migration in the remote past, tracking the global distribution of particular DNA segments that include non-fatal genetic changes called 'founder mutations' [15] (sickle cell disease is one of these). The results confirm archaeological evidence for successive waves of diaspora radiating from Africa, but they have also added previously unknown connections such as that between the Celts and the Basques. There's growing evidence that the enormous expansion of relative brain-size that began in humans around two million years ago was associated with repeated and rapid climate fluctuations (not unlike the one causing so much anxiety today) [17]. In unpredictable environments the increased flexibility of behaviour conferred by a big brain more than compensated for the disadvantages (high nutritional demands, difficult birth, prolonged infant helplessness).

DNA comparison has also become an essential tool for identifying individual humans in the present day, and is widely used in forensic work: there are bound to be heated debates in future over whether or not one's DNA 'footprint' should be added to other bureaucratic markers of identity such as passports and ID cards.

Genetic Engineering

No subject has aroused more wrath in recent years than that of genetically-modified (GM) foodstuffs. It's seldom remarked just how effective the informal and spontaneous boycott of GM crops outside of the USA has been. However the subject is seldom discussed in a satisfactory way because it’s become a touchstone for deeper political attitudes toward science, progress, capitalism and nutrition. The best that can be said is that much of the opposition to GM foods is irrational, even superstitious, but that perhaps an equal part of the support for GM is motivated by dubious commercial agendas.

GM crops are plant species in which biologists have deliberately introduce a gene from a different species, to impart

discovered to prevent others from catching up [20]. Patents normally encourage competition by protecting an invention for a period but leaving others free to better it. However every gene is unique, so patenting one bestows a total monopoly. If gene therapy ever overcomes its current difficulties, such patents will become extremely valuable, but to the detriment of further research efforts.

Epigenetics

When Charles Darwin was thinking through the theory of natural selection, one of the obstacles he had to clear out of his way was the idea advanced by Jean Baptiste Lamarck that evolution proceeds by the inheritance of acquired characteristics. This notion is untrue, but still plausible enough to be rather hard to dispel: to reduce it to the absurd, we know that professional boxers' children are not generally born with broken noses and cauliflower ears. Anti-Lamarckism has become enshrined as the central dogma of molecular biology – which has served the science very well – that information only flows from DNA out into the world, never the other way around.

Lamarckism made one disastrous comeback during the 20th century, when Joseph Stalin fell for the Lamarckian heresies of the agronomist Trofim Lysenko, and based Soviet agricultural policy around the possibility that wheat varieties could be improved via their growing environment rather than their genes, and hence grown in a different season. They could not, and Soviet agriculture was held back for many years.

In recent years though geneticists have discovered, or remembered, that there are mechanisms by which information from the external environment can appear to be 'written back' into the DNA, although these are not truly Lamarckian and they preserve the central dogma. These discoveries go by the collective name of 'epigenetics' [16]. Not all the genes in an organism's genome are expressed all the time, and there are some genes that act only to switch other genes on and off. These genetic switches operate through special proteins called histones that surround the DNA strands, and it now appears that histones can be affected by the cell's external environment (unlike the DNA sequence itself) and this may change the switch state of their associated gene – this switch state can then be passed from a mother to her baby via her chromosomes, to affect its metabolism throughout its life.

Indeed the very shape that any multi-cellular organism takes on at birth depends upon epigenetic effects: every cell in your body contains exactly the same set of genes, but some of them must become brain, some bone and some liver. Their epigenetic switches were flipped in the correct sequence while you were developing in the womb, to make the right tissue types at the right time. Unsurprisingly epigenetic effects are also deeply implicated in the formation of tumours (carcinogens can switch genes on and off). Much of the recent research on epigenetics has employed data from nutritional studies: a mother's diet may throw epigenetic switches on that are passed on to her baby and affect the child's own nutritional state, such as obesity or height, in later life. One such study found a correlation between Dutch mothers' impoverished diet during WWII and the size their children attained as adults. The implication for social policy should be obvious: epigenetics may offer biological support for what was already suspected by many progressive thinkers, namely that the deleterious effects of poor nutrition and work environment can be passed down the generations and turn class into caste. Regrettably though, the subject of epigenetics attracts more than its fair share of crankery from those who are overly keen to deny Darwin and refute genetic determinism – and it's often not easy to sort out what's real science from fringe opinion (hint: whenever you see the word 'holistic', run like the wind).

To conclude, genetic science has huge implications for future politics. Like most other branches of science it will create as many new problems as it solves, and the solutions to those additional problems will often need to be political, not scientific. Science can will us whether we can make our children smarter through gene replacement, and whether that will create dangerous side-effects, but only the body politic can decide whether we even want to allow people to do it. Politics must rule in the moral world and science in the world of matter – getting them the wrong way round, as King Canute demonstrated, doesn't really work.

REFERENCES

[1] Darwin, Charles: "On The Origin of Species by Means of Natural Selection" 1859; "The Descent of Man", 1871; "The Expression of the Emotions in Man and Animals", 1872.

[2] Mendel, Gregor: “Versuche über Pflanzenhybriden” (“Experiments with Plant Hybrids”), Transactions of Natural Science Society (Brunn, 1866).

[3] Watson, James: "Molecular Biology of the Gene", 1965.

[4] Spencer, Herbert: "Social Statics", 1851

[5] Diamond, Jared: "Guns, Germs and Steel" 1999; "Collapse: How Societies Choose to Fail or Survive" 2005.

[6] Wilson, Edward O.: "Sociobiology: The New Synthesis", Harvard University Press 1975

[7] Dawkins, Richard: "The Selfish Gene", Oxford University Press 1989.

[8] Gould, Stephen Jay "The Panda's Thumb: More Reflections in Natural History" 1980.

Lewontin, R.C. "Biology as Ideology: The Doctrine of DNA" 1998.

[9] Pinker, Steven: "How the Mind Works", 1998; “The Language Instinct”, 1994.

Angier, Natalie: "Woman: An Intimate Geography", 1999.

[10] Edelman, Gerald: "Bright Air, Brilliant Fire" 1992.

[11] Damasio, Antonio: "Looking for Spinoza", Vintage 2004.

[12] Phillips, Adam: "Darwin’s Worms", Faber and Faber 1999.

[13] de Waal, Frans: "Good Natured", Harvard 1996.

Trivers, R: “The evolution of reciprocal altruism”, Quarterly Review of Biology 46, 1971.

[14] Midgley, Mary: "Science and Poetry" 2001

[15] Drayna, Dennis: "Founder Mutations", in Scientific American October 2005

[16] Jablonka, Eva and Lamb, Marion: "Epigenetic Inheritance and Evolution, The Lamarckian Dimension", Oxford University Press, 1995

[17] Calvin, William H.: "A Brain for All Seasons: Human Evolution and Abrupt Climate Change", University of Chicago Press, 2002.

[18] Fukuyama, Francis: "Our Post-Human Future: Consequences of the Biotechnology Revolution", Picador 2003.

[19] Wilson, Edward O.: "Consilience: The unity of Knowledge", Vintage 1999; "The Future of Life" Vintage 2003.

GLOBAL WARMING

Global warming, which ought more accurately to be called ‘anthropogenic (ie. man-made) global warming’ to distinguish it from natural temperature trends – is one of the more serious threats that currently face the human race, along with epidemic viral disease and nuclear war. It is without doubt the most controversial of these threats though, and for several reasons. Firstly the science involved in predicting the effects of global warming is so difficult and the data so sparse, that until very recently climate scientists themselves have lacked agreement about its extent, or even its reality.

Secondly, many of the debates over global warming are dominated by partisan ideological positions rather than real science. If the phenomenon is real and its effects really will be catastrophic, then it represents a natural obstacle to any further expansion of our technology-based civilisation – similar to the population explosion and mass-starvation predicted by Malthus in the early 19th century (which proved to be a chimera, or at any rate was surmounted by new technologies). For this reason those who oppose any further growth – whether on conservationist, moral or anti-capitalist political grounds – are prone to exaggerate the evidence, while on the other side many economists, techno-optimists, free-market capitalists, and the oil industry seek to minimise or ignore it. Trying to steer a rational and prudent middle course is far from easy.

What is Global Warming?

Anthropogenic global warming means an alteration of the earth’s climate, in the direction of increased average global temperatures, due to the agricultural and industrial practices of Homo Sapiens – as opposed to any such warming that might or might not be occurring as part of various natural climate cycles. Hence the difficulty of the science: the Earth’s climate changes all the time anyway, according to many different cycles with different periods in the tens, hundreds, thousands and even millions of years, and which are all superimposed on one another. These changes are caused by factors like the eccentricity of the earth’s rotation on its own axis and of its orbit around the sun, by cyclic changes in the sun’s activity, and by the delayed, cumulative effect of these factors on slow-changing earthbound systems like the ice caps and ocean circulation.

Unravelling any warming trend from the ‘noise’ produced by these overlapped variations is extremely hard (see graph). Nevertheless there are experimental data that suggest there’s an accelerating warming trend over and above these ‘natural’ effects, and there are sound theoretical reasons for why it could be happening, namely the ‘Green House Effect’, so-called by analogy with the ordinary garden greenhouse.

For most of the year a greenhouse can maintain its inside hotter than its outside, even without any internal source of heat, thanks to a property of the glass in its windows which lets through infra-red (that is, heat) rays from the sun of different wavelengths with different ease. Short wavelength rays pass easily through the glass into the interior, where they are absorbed by the plants and soil – the warm plants re-radiate the heat at longer wavelengths which cannot easily pass through glass, and so they’re reflected back inside and raise the air temperature.

The earth’s atmosphere acts just like a greenhouse, by trapping infra-red radiation of longer wavelengths than those it receives from the sun, but in this case it’s certain gasses in the air, rather than glass, that cause the differential transmission. Life on earth would be impossible without some greenhouse effect – all solar radiation would be reflected or radiated back into space and our planet would resemble the moon, with temperatures of 126ºC (hot enough to boil water) on the daylight side and -175ºC on the night side. Our atmosphere and oceans moderate solar heating by many different mechanisms – reflecting some from clouds, trapping some via the greenhouse effect, storing some in ocean water – with the effect of evening out the daily fluctuations and maintaining the average temperature within the range at which life can flourish (roughly speaking between the freezing and boiling points of water).

It’s not oxygen and nitrogen, which make up most of the air, that cause the greenhouse effect but other gasses present in much smaller amounts – the so-called ‘greenhouse gasses’ – by far the most important of which are carbon dioxide (CO2) and methane (CH4).

These gases have the property, like glass, of absorbing long-wave infra-red rays more strongly than short-wave and so retain heat in the atmosphere. The levels of carbon dioxide and methane in the atmosphere therefore act as yet another factor that controls the surface temperature of the earth. Both the gasses are produced naturally: all animals exhale carbon dioxide as they metabolise food; plants alternately absorb carbon dioxide during the day and exhale it at night; animals also generate methane during digestion, and dead plants generate it when they rot. Now human activity now appears to be causing them to rise well beyond natural variation.

Since 1750 – roughly the start of the Industrial Revolution – atmospheric concentrations of carbon dioxide and methane have increased by 31% and 149%, to levels higher than at any time during the last 650,000 years. The cause is largely the burning of so-called ‘fossil’ fuels, and de-forestation. Plants remove carbon dioxide from the atmosphere, using it to build their own tissues with the aid of sunlight (photosynthesis). When we cut down a living tree and burn it, we merely return to the atmosphere the carbon that it had absorbed during its lifetime, so it doesn’t in itself change the long-term carbon dioxide level. However the earth’s crust contains vast quantities of buried, fossilised plant material deposited millions of years ago, in form of coal and oil. When we dig these up and burn them, we do add net carbon dioxide to the atmosphere because the carbon they contain had been removed from circulation. Also, that tree we just cut down is no longer alive to absorb any of the resulting carbon dioxide.

Recently it has been suggested that another effect is at work, namely the production of excess methane by human agricultural activities, including the digestion of vegetation by ruminants like cows and sheep (over 90% of the mammals alive today are domesticated ones) and the rotting of vegetation in flooded fields, for example during rice cultivation. If this is so, anthropogenic global warming actually started with the invention of agriculture rather than the invention of heavy industry, and if confirmed this would make the task of combating global warming even more intractable, since it would imply a return to hunter-gathering!

The biggest difficulty in establishing the reality of anthropogenic global warming is that the earth’s temperature varies naturally on a roughly 100,000 year cycle which caused the series of Ice Ages (see graph above). We live during an ‘interglacial’, that is a period between Ice Ages – it appears that the evolutionary transition from earlier Homo species to modern Homo sapiens occurred during the last Ice Age – but we don’t know how long this interglacial will last. Hence we can’t be sure whether we’re still on an upswing or on the downslope to the next Ice Age: in other words, whether the climate is naturally warming or cooling. This allows global warming sceptics to argue that the warming we see is real, but natural rather than man-made. To complicate the issue further still, US palaeoclimatologist William Ruddiman [3] has argued that human influence on the climate actually began 8000 years ago with the discovery of agriculture, rather than with the 18th century Industrial Revolution. He contends that this influence in fact prevented carbon dioxide (and later methane) levels from falling as rapidly as they would otherwise have done, and that we would otherwise be entering (perhaps would already have entered) the next Ice Age. In other words, even if we could do something to stop global warming, maybe we shouldn’t!

The Arguments and the Evidence

The major questions that need to be answered before anthropogenic global warming can be

definitely stated to be real and measures agreed to combat it are the following:

1) Is the climate really changing beyond the range of natural variation?

2) If so, is human industrial and agricultural activity responsible for these changes?

3) How large are the climate changes likely to become in future?

4) How will such climate changes affect human welfare?

5) What measures are possible that might mitigate climate change?

6) Can major political and economic policy changes be justified on the currently available evidence?

The Evidence

Evidence for climate change can only be obtained by attempting to reconstruct past climates – no direct information is available, of course, prior to the invention of writing and human historical records. Such reconstructions can be made on the strength of indirect evidence. Past climate can be inferred from the growth rate of plants, the diversity of plant and insect species, and the isotopic composition of water, air and plant materials, which can in turn be inferred by inspection of certain biological and chemical indicators that can be found in many places.

Sources of such evidence are found in fossils; ice cores drilled out of the polar caps; sediment samples from lake beds; marks left in the geological record by sea level changes; by counting tree rings (dendrochronology); from the geological evidence left by retreating glaciers; and for the last few thousand years, from human historical records, including cave paintings and grave depths as well as written descriptions. Many of these studies employ powerful dating techniques that depend on the constant decay rate of naturally-occurring radioactive isotopes like carbon-14 (the famous ‘radio-carbon dating’), potassium-argon and rubidium-strontium.

Results to date – published by The Intergovernmental Panel on Climate Change in a 2001 report – suggest that there is a real, if modest, warming going on. Average temperatures have increased over both land and sea by between 0.4 and 0.8ºC over the last century, and are predicted to rise further by 1 to 5ºC over the coming century, while temperatures in the lower troposphere have been increasing by between 0.12 and 0.22ºC per decade since 1979. However there’s still some uncertainty over what proportion of these rises is due to human activity, over the accuracy of the underlying climate models, and over the accuracy of estimated future carbon dioxide emissions.

Arguments for the reality of global warming

Recent rises atmospheric greenhouse gas levels are greater than any seen for several hundred thousands of years… The reconstructed historical temperature record shows a rise of 0.4-0.8ºC in the last 100 years… Current conditions are warmer than would be expected from the graph of the past 1000 years… Natural variability or solar fluctuations cannot explain these changes… Climate models can only reproduce this warming trend if they include the human production of greenhouse gasses… There is now a scientific consensus behind all of these assertions.

Arguments against the reality of global warming

Earth's climate has been at various times colder and warmer than today, and such changes can be adequately explained without involving human greenhouse gas emissions… Volcanic activity accounts for 97% of the CO2 in the atmosphere, and the net contribution of human-produced CO2 is less than 1%...

Climate models cannot predict the future climate until they can accurately predict solar and volcanic activity: global temperatures are directly tied to sunspot activity on an 11-year cycle… The IPCC has drawn too firm conclusions from uncertain scientific evidence, due to inadequate climate models… The whole issue has become so politicised that some climate scientists who disagree with the consensus may be afraid to publish for fear of losing funding… Concern about global warming resembles the panic about a new Ice Age in the 1970s, is equally misplaced and alarmist.

Given the uncertainty of the data it’s not surprising that neither side has yet conceded defeat, and it’s terribly difficult for lay persons to judge the evidence effectively. It would be fair to say though that a majority of climate scientists have quite recently swung around to believing in global warming, thanks to analyses of ice-core data collected in the late 1990s coming on stream.

What might Happen?

The consequences of global warming are as difficult to predict accurately as its existence is to prove. Processes that are certainly happening at the moment include the melting of both Artic and Antarctic polar ice caps, and a weakening of the warm ocean current – known to oceanographers as the North Atlantic Conveyor, or more popularly the Gulf Stream – which transports warm water from the Caribbean and keeps the climate of Northern Europe warmer than that of Canada, which is at a similar latitude.

The water released by melting ice caps will certainly raise average sea levels, though predictions of how much and how fast still vary enormously. The present official estimate by the IPCC predicts a rise of just under 1 meter by the year 2100, but the panel also warns that this is based on current rates of melting: if the rate increases over that period it may cause irreversible changes in the earth's glacial system that will raise the sea level by many meters over the longer term. Many of the world’s cities are for obvious historical reasons located on coasts and estuaries and even quite small rises in sea level could flood many densely-populated areas, rendering them uninhabitable and destroying their agricultural value, so causing mass starvation and creating massive movements of refugees. Around 200 million people are vulnerable, especially in Egypt, low-lying Pacific islands, the Philippines, Bangladesh, China, India, Vietnam, Thailand, and Indonesia. A sea level rise of more than 4 metres would inundate almost every coastal city in the world, causing serious disruption to trade and manufacture.

A complete switching off of the Gulf Stream, which has happened before in geological times (for example during the great Ice Ages) could make Britain and Northern Europe as cold as Newfoundland. Indeed it’s a grim climatological irony that the phenomenon labelled ‘warming’ may in fact bring cold, dry weather – disastrous to agriculture – to many parts of the world, particularly the interiors of large continental landmasses [1]. Other effects of decreased ocean circulation might include increased severity of typhoons and hurricanes, prolonged droughts and failure of the Monsoons, all of which would have desperate economic consequences.

These are the more moderate catastrophe predictions. The ultimate worst case scenario – fit for a sci-fi blockbuster – would be a runaway heating effect that transforms the earth’s climate so completely that it obliterates all life and turns the planet into something resembling Venus.

Disturbingly, there is a scientifically plausible (which is not to say probable) mechanism for such an event, which depends on the fact that in addition to the fossil fuels we burn, there are enormous quantities of carbon stored under the earth and in solid ice crystals that chemists call ‘methane clathrates’, formed when methane dissolves in cold water. If the ice melts, these clathrates release methane gas like bubbles released from champagne. Vast deposits of methane clathrates exist on the sea-bed in the deepest parts of the oceans, and more a few metres below the ground in the permafrost soils of the Arctic tundras (where they were formed by vegetation rotting in swamps). Were global temperatures to rise to a point where the permafrost melts, or the deep ocean warms sufficiently, all this methane could be released and lead to a runaway greenhouse effect. Some geologists believe that the earth has experienced these sudden heatings due to clathrate decomposition in the past (for example the Permian-Triassic extinctions and the Paleocene-Eocene Thermal Maximum). Unlike the slow rise of sea levels, such an event could happen quite quickly once some temperature ‘tipping point’ was exceeded, making it effectively impossible to predict like the timings of earthquakes or volcanic eruptions. The consensus at present is that it is extremely unlikely.

Can Global Warming be Prevented?

If global warming is largely caused by human greenhouse gas emissions, the only plausible strategies for mitigating its effects are measures that reduce greenhouse gas emissions or else remove greenhouse gas from the atmosphere. Suggested countermeasures fall into four main categories:

1) Abandoning carbon-based fossil fuels in favour of alternative energy sources, such as nuclear power or ‘renewables’.

2) Energy conservation measures to reduce overall use of fossil fuels

3) Removal of carbon dioxide from the atmosphere by hugely increasing the earth’s plant cover, for example by massive reforestation.

4) Artificial carbon ‘sequestration’, for example by liquefying carbon dioxide and pumping it into deep disused oil-wells.

The most significant political initiative to combat global warming so far is the 1997 Kyoto Protocol, an amendment to the United Nations Framework Convention on Climate Change (UNFCCC) [10]. All countries that ratify this protocol commit themselves to reducing their emissions of carbon dioxide and five other greenhouse gases, and a market-based system of permit is set up that enables countries that fail to reduce emissions to trade ‘permits to emit’ with those who bettered their quota. More than 150 countries have so far ratified the Protocol, but notable non-signers include the USA and Australia, both of which claim that the economic costs are too high for the benefit.

There are also political and technical obstacles to each of the types of solution listed above:

1) Popular fear of nuclear power remains enormous, and the spent fuel disposal problem unresolved; few energy economists believe renewables can ever provide more than a small fraction of current needs. There is as yet no practical alternative fuel with sufficient portability and energy-density to sustain jet aeroplanes or even automobiles, and few promising candidates (hydrogen is one of those few).

2) Western consumer lifestyles require so much energy that there will be enormous political resistance to austerity measures – especially in transport, where the car and plane have become vital

signifiers of personal autonomy to affluent Westerners. We now know how to build houses that require virtually no heating, but they cost far more than traditional designs and replacing the whole world’s housing stock is unimaginable.

3) Many of the world’s soils are already badly degraded, agricultural land is in desperately short supply in many places [2]. Resistance to non-productive planting would be enormous, and its funding problematic.

4) Even if the massive costs and technical problems could be overcome, such stores would represent a risk like that of the methane clathrates, in the event that containment didn’t work.

All these objections though seem like nitpicking when compared to the real problem, which is that the Industrial Revolution is nowhere near complete yet. The phenomena we generally label as ‘globalisation’ and ‘outsourcing’ in fact represent the continuing spread of that industrialisation which started in 18th century Britain to the remaining parts of the world, most particularly to China, India and Indonesia. All of these nations want to achieve the levels of affluence that we have in Europe and the USA, and no amount of environmental pleading is likely to deflect them from this aim. And their unprecedentedly rapid industrialisation is almost totally dependent on increasing fossil fuel usage. It seems increasingly probable that they will not be able achieve their goal, but it will be shortages of oil, water, soil and possibly food that will stop them, not any amount of moral pressure from Westerners who are themselves loathe to give up their cars, fridges, and air-conditioners. Far the most likely scenario must be that industrialisation is forced into reverse gear by a slow, involuntary and painful series of famines, floods, droughts, wars over natural resources, financial collapses and mass migrations. Such a reversal may not involve a complete return to pre-industrial ways, but it might reduce the world’s population and living standards substantially.

If we have difficulty accepting this stark reality, that’s because we suffer a hangover from 20th century positivism. Almost all the great thinkers of the 19th and 20th centuries believed that technological advance would only continue, and that it was leading to a convergence on some kind of superior social organisation. To be sure they disagreed profoundly about what that organisation would be – from the techno-religion of August Comte, through Herbert Spencer’s laissez-faire capitalism to the egalitarian communism of Karl Marx. (Most of our current thinkers, from neo-cons to anti-globalizers, still cling to some derivative of one or other of those models). What none of them could imagine, because the facts were not then known, is that technological advance might eventually prove self-limiting due to processes like anthropogenic global warming. We are after all another animal species, subject like others to population pressures generated by the environment, and our belief that we could control every aspect of nature is being shown to be hubristic. Perhaps Malthus was right in principle (though wrong in details and timing) and the planet really does set a limit to the number of us it is prepared to support.