The Home of American Intellectual Conservatism — First Principles

October 16, 2018

On Climate Change
P. E. Hodgson - 02/13/09
trees blown in storm

From the current edition of Modern Age (50:4)

Part One: The Energy Crisis

Part Two: Nuclear Power and the Energy Crisis

When I first became interested in the applications of nuclear physics I was most concerned by the coming shortage of energy. Since then it has become clear that this is not the main problem. There is plenty of energy for the next few hundred years: enormous deposits of coal, substantial amounts of oil and natural gas, and the likelihood of increasing contributions from nuclear power.

The main concern is now the effects on the world’s climate from the pollution of the atmosphere from fossil fuel power stations. It will be many decades before fossil fuel power stations can be replaced by non-polluting sources such as nuclear and renewable energy, and all that time the pollution will increase. Detailed studies by the Intergovernmental Panel for Climate Change show that the amount of carbon dioxide in the atmosphere is inexorably increasing and the evidence for its effects on the climate is steadily becoming more convincing. In addition, the predicted rise in sea level will have catastrophic effects on low-lying countries.

It is now becoming clearer that the principal danger is not the effects of gradual changes in the climate but the possibility of rapid and irreversible changes. We tend to think of the earth and its climate as a reliable and generally stable system where the weather remains more or less the same when averaged over long periods. There is now increasing evidence that this may not be true, that there is a distinct possibility of large, unexpected, and irreversible changes that quite rapidly have catastrophic consequences.

The study of climate changes is fraught with serious difficulties. Since time immemorial the weather has fluctuated unpredictably, with cold and hot periods, heavy rainfall and droughts, hurricanes, and earthquakes. How can the changes due to man’s activities be distinguished from these natural changes? It is notoriously difficult to establish the presence of a new trend in a fluctuating quantity, and the difficulty is compounded when the fluctuations are on several different timescales, as is the case for climate. There are changes from year to year and ice ages on a much longer timescale. If a trend over a few decades is established, how do we know whether it is soon to be reversed by a major change acting on a longer timescale?

When definite evidence for climate change has been found, it is important to understand the underlying causes and to deduce what is likely to happen in the future. The earth’s seas and atmosphere form a highly complex system, and although much research has been done we still know very little compared with what there is to know. This is an area of highly speculative science, where hypotheses are made to explain a few observations and are then refuted by the discovery of new facts. Scientists group themselves into schools of thought and argue fiercely with scientists of other schools. An agreed consensus may arise one year and dissipate the next. There is only one thing on which all agree, namely that the more we know the more frightening are the prospects for the future of the world.

Even if we understand the forces determining the climate we still have the problem of deciding what to do about it. Even if we have decided on the optimum course of action, we then have the problem of persuading governments to do what has to be done.

This article is concerned with the evidence for climate change and the possibility of future catastrophic changes. The political problems will be discussed in the next article.

The Evidence for Climate Change

By climate we mean the sum of the many variables describing the condition of the atmosphere: the temperature and humidity of the air, the rainfall, the strength of the winds, and the clouds. All these are constantly changing, and we can take averages for a local region or for the whole earth. Climate is determined by many natural causes, and in addition there is evidence that it is affected by human actions. We cannot do anything about the natural causes, but if there is a causal link between human actions and climate change we may have reason to expect the present changes to continue, and furthermore, we will have a strong incentive to take action to mitigate their harmful effects.

Such a causal link has been proposed. Extensive measurements have shown that the concentrations of carbon dioxide, methane, and some other gases in the atmosphere are steadily increasing. In the 1780s the level of atmospheric carbon dioxide was about 280 parts per million (ppm), as it had been for the last six thousand years. Industrialisation increased the level to 315 ppm by the 1930s, 330 ppm by the mid-1970s, and 360 ppm by the mid-1990s. In the last ten years the level has risen by a further 20 ppm. By the middle of the present century it could rise to 500 ppm. The annual increase of carbon dioxide is now 0.4 percent, that of methane 1.2 percent, of nitrous oxide 0.3 percent, of the chlorofluorocarbons 6 percent, and of ozone about 0.25 percent. In the European Union, fossil fuels are the main source: oil 50 percent, natural gas 20 percent and coal 28 percent. Of this, electricity generation accounts for 37 percent, transport 28 percent, industry 16 percent, households 14 percent, and the service sector for 5 percent. These are established facts, and in addition there is a strong correlation between carbon dioxide concentrations and temperature changes. It is then suggested that these increased concentrations are responsible for global warming and that global warming is responsible for other climate changes and predicted effects such as a worldwide rise in the sea level. The evidence for anthropogenic climate change has increased in recent years, and its reality is now generally accepted.

The connection between the increase in carbon dioxide and global warming is known as the greenhouse effect. The carbon dioxide in the atmosphere acts like the glass in the greenhouse; it lets the heat of the sun reach the earth, and some of this heat is emitted with a different wavelength that is stopped by the carbon dioxide. The heat that is trapped in this way warms the earth so that the average temperature is 14 C. Without the greenhouse gases it would be –18 C (or –64 F).

There is impressive evidence for the reality of climate change during the last few decades. Some of this has been described in a book by Sir Ghillean Prance, former Director of the Royal Botanic Gardens in Kew, London. [1] He recalls that there were devastating floods in Mozambique and Venezuela and quite serious ones in England. In other countries there has been drought that in the Midwest of the United States in 1988–9 caused losses estimated at $39 billion. Hurricane Mitch killed ten thousand people in Central America. The average temperatures are rising in many countries: of the five warmest years ever recorded in the United Kingdom, four have been in the last decade. The heatwave in 2003 killed about 20,000 people in Italy and 15,000 in France as the temperatures topped 40 degrees celsius during the day and 30 degrees celsius at night. Crops failed, forests burned, and rivers reached an all-time low. It was almost certainly the direct result of global warming. On a longer timescale, one result of these increasing temperatures is that in some regions the growing season for plants is increasing, with earlier development in spring, and autumn events being delayed. Birds and animals are also affected, and some species, unable to cope with the climate change, have become extinct.

There are however many examples of climate change occurring long before large amounts of carbon dioxide were emitted into the atmosphere by human beings. Some communities that have flourished for centuries have been destroyed by climate change. One example is the Anasazi who lived in Colorado and were finally forced by major droughts in 1130–1180 and 1275–1299 to abandon their cities and to move away to areas with a climate that allowed them to continue their way of life. Greenland, as its name implies, was at one time a fertile land and supported a colony of Vikings until colder weather forced them to move elsewhere.

Other changes have not been quite so catastrophic. The same cold spell around the fourteenth century caused parts of the Baltic Sea to freeze, and also the river Thames. In the 1930s the reduction in rainfall on the Great Plains in the USA, followed by winds that removed the topsoil and created a dustbowl, forced farmers to pack up and move away. In other parts of the world weather patterns are subject to violent changes. The normally regular monsoons in India, for example, can sometimes fail, causing catastrophic famines. The warm ocean current called El Niño can have disastrous effects on the eastern Pacific shores. It is now known to be part of a vast global water circulation, and satellite observations and computer modeling now enable some predictions of its effects to be made. [2] Thus for example severe floods and storms were predicted to occur in California in 1997–1998. During autumn and over Christmas the weather was fine, but in January and February hurricane-force winds battered San Francisco, floods rose, and mudslides swept houses away. Floodwaters submerged the freeway to Los Angeles and swept away the Southern Pacific railroad bridge. Fourteen years earlier another El Niño caused floods and landslides that caused a billion dollars worth of damage. In other tropical regions, the 1997–1998 El Niño caused over $10 billion in damage. There were severe droughts in Australia and Southeast Asia, vast forest fires in Indonesia and Mexico, and famine in Brazil.

The weather cycles in Peru and Bolivia are quite regular, unless they are interrupted by El Niño, which is unpredictably variable. Mostly the result is torrential rainstorms, warmer seas, and changes in fish populations. Occasionally however an El Niño event causes significant changes to the climate and brings ruin to fishermen and farmers. Thus in 1925 the sea temperature off northern Peru rose over six degrees in ten days. Millions of seabirds perished as the anchovies on which they fed moved to cooler nutrient-rich waters. Cloudbursts turned dry ravines into raging torrents and the city of Trujillo received 396 mm of rain instead of the normal 1.7 mm. Farmlands and irrigation systems were destroyed by a sea of mud, and hundreds of people starved. Many other examples could be given of the devastating effects of El Niño.

It is conjectured that El Niño events played an important role in the decline and fall of ancient civilizations when they were already seriously stressed by other economic and political factors. Particular examples are the Maya civilization in Yucatan and the Moche civilization in Peru. In these cases, the devastation caused by El Niño was the final event that caused the once-flourishing societies to collapse.

The rapid changes in climate associated with El Niño events took place long before the temperature increase associated with global warming and still continue. They are not yet fully understood and make it more difficult to ascribe climate changes to anthropogenic emissions.

Another source of global warming is the variation in the brightness of the sun, already observed over several centuries. The sunlight intensity fell by 4 to 6 percent from the 1950s to the 1980s. Now it is rising again and there has been a 4 percent rise since 1990; it is estimated that this could account for a rise in temperature of 0.4 C by 2100. There are also daily variations of around 0.2 percent, and these could produce significant changes in the climate. In addition, there is a correlation between the temperature and the length of the sunspot cycle. The physical basis for this is suggested by another correlation, namely that between the cosmic ray intensity and the low cloud cover. The miniature Ice Age in the later part of the seventeenth century is known as the Maunder Minimum, which is correlated with the sunspot minimum between 1645 and 1715. The sunspot cycle is a measure of the solar activity, and this in turn affects the cosmic ray intensity. The cosmic rays produce ions in the atmosphere, and these can form condensation nuclei for clouds, which have a strong influence on the earth’s temperature. Detailed studies suggest that solar effects may be responsible for 30 to 57 percent of the observed global warming. Since this varies with the sunspot cycle, it sometimes reinforces and sometimes weakens the effects of global warming. Some fluctuations have been observed and these could be due to varying amounts of aerosols in the atmosphere. [3]

There is evidence that the mini Ice Age in the seventeenth century and the medieval warm period are part of a cycle that occurs over a period of about 1500 years. Supporting evidence is provided by the bands of rock in cores from the Northern Atlantic. These rocks came from Northern Canada, and must have been carried to where they were found by glaciers, indicating periods of cooling and warming. More evidence came from Greenland ice cores which revealed a series of temperature changes, again with a period of about 1500 years. There were also large increases in the dust particles in sediments off the coast of West Africa suggesting dust storms inland, also with the same period. It has been suggested that this cycle is ultimately due to periodic changes in the sun. The resulting changes in solar radiation changes the temperature and this may be detected by changes in the ratios of cosmogenic isotopes in ice cores. All this shows the extreme sensitivity of the climate to very small changes in the intensity of the solar radiation. The same must also be the case for man-made changes in the atmosphere. [4]

A recent study [5] has shown greatly increased frequencies for the more devastating hurricanes like Katrina, which struck New Orleans and the surrounding states in 2005. This increase has been attributed by some scientists to the rising temperatures of the oceans due to global warming. If this is the case, some regions of the earth will be liable to more devastating hurricanes in the future. The cost of the damage due to the hurricane Katrina has been estimated to be around $100 billion.

On a much longer timescale, the mathematician Milutan Milankovitch identified cold and warm periods alternating every 100,000 years, with smaller cycles every 41,000 and 10,000 years. These cycles are attributed to perturbations of the sun’s orbit by the moon that cause the precession of the equinoxes and by other small effects due to the planets and are confirmed by world-wide measurements of glaciers, coral reefs, peat bogs, and polar ice caps.

There are thus many ways the climate can be changed in addition to the effects of the greenhouse gases. Careful scientific analysis is therefore needed before their contribution can be established. Many scientists worldwide are making detailed calculations using increasingly sophisticated models of the atmosphere. This is obviously a very complicated task. What, for example, do we mean by the temperature of the atmosphere? We can measure the temperature at a particular place and height, but this needs to be done over the whole surface of the earth and for heights up to several miles. The best we can do is to establish a grid of points and measure the temperatures at these points as a function of the time. Even a coarse grid contains millions of points and the calculations are very time-consuming even on a fast modern computer. The more accurate we want our calculations to be the longer they will take. In addition, the results may be very sensitive to the initial conditions; this is called the butterfly effect. The main uncertainty at present seems to be the effects of water vapour, which are greater than those of all the other gases combined. These are sensitively affected by changes in the cloud cover, which in turn changes the amount of solar energy absorbed or reflected.

The results of such calculations are published periodically by the Intergovernmental Panel on Climate Change, consisting of about two thousand of the world’s leading climate scientists, under the chairmanship of Sir John Houghton. [6] With many qualifications, the conclusion of their assessment is that there is good evidence that world temperature is increasing, and it is predicted that the average temperature will rise by about four degrees centigrade by the year 2100. In the same period the sea level will rise by about 60 cm, or by 40 cm if the carbon dioxide emissions are controlled. Such rises will eliminate many islands such as the Maldives in the Indian Ocean and will inundate much of Bangladesh and some of Holland. Already the sea level has risen by 0.1 to 0.2 cm per year during the twentieth century.

The connection between the rise in temperature and the rise in sea level has been attributed to the melting of the polar ice caps. However, the ice immediately around the North Pole and in the ice shelves around Antarctica is floating, and so when it melts, it has very little effect on the sea level, as Archimedes knew very well. There may however be some small effects due to differences in salinity between the ice and the sea. There are other effects of melting ice in Antarctica that are discussed below.

Another uncertainty is the effects of soot on global warming. This soot comes from the incomplete burning of coal, biomass, and diesel, and also from forest fires, domestic heating, and factories. It has been said to “mask” global warming and also that it “generates” global warming. It has been called “a cooling agent” and also “the biggest cause of global warming after carbon dioxide.” What seems to happen is that the soot shields the earth from the sun’s rays, thus making it cooler. It also absorbs some of the heat and re-radiates it into the surrounding air. Thus soot heats the air and cools the ground. Some scientists think that soot is the third most important contributor to global warming, after carbon dioxide and methane.

Catastrophic Events

In some respects the earth is a self-regulating mechanism so that any change initiates secondary changes that restore it to its original state. This idea has been developed by James Lovelock into the concept called Gaia (the Mother Earth). [7] The mechanism works for small changes, but he recognises that there may be changes that irrevocably flip it into another state. We are familiar with such changes, as for example when a bridge collapses under a particularly heavy load. If this happens to the climate, the results could be devastating for large numbers of people.

One way this could happen is if even a small change initiates a series of events that reinforce the original change; this is called positive feedback. It is a runaway process that continues until the system is destroyed. Some of these processes are already happening to our climate, and others are serious possibilities.

One example is the melting of the polar icecaps, which is already having devastating effects on people living in the Arctic. In several places their traditional method of hunting seals is no longer possible because the ice has melted. As the ice melts the albedo, a measure of the fraction of sunlight that is reflected, falls rapidly from 0.8—0.9 to less than 0.1 The result is that more sunlight is absorbed, melting more ice in a continuing feedback effect. This is one of the main reasons why the Arctic ice is melting so rapidly, thus providing a sensitive indicator of global warming. Some computer models indicate that by 2080 the Arctic will be ice-free in summer, making it impossible for the polar bears to survive.

Satellite observations have shown that the perennial Arctic sea ice covers about seventeen billion acres. This area varies from year to year, but in recent years the overall trend has been strongly downward, particularly in the Beaufort and Chukchi seas and also to a lesser extent in the Siberian and Laptev seas. The shrinkage now amounts to about 250 million acres.

Another example is the melting of the permafrost, a thick layer of frozen soil in the Arctic. This contains moss and lichen that has accumulated for thousands of years and frozen before it could rot. The dry weather has caused widespread forest fires in Alaska, and the temperature of the permafrost has risen by two or three degrees. It has been predicted that most of the top three metres of permafrost across the Arctic will melt during the present century. As the thawed vegetation finally rots, it will release ten of billion tonnes of carbon dioxide if there is oxygen present, and the far more damaging gas methane if it is not. This methane will increase the rate of global warming still further, melting the permafrost by a positive feedback loop.

Antarctica occupies 13.2 million, about 1.3 times the area of Europe, and the ice cap is up to 4 km. thick. No less than 90 percent of the world’s ice is in Antarctica, and if this were all to melt the world sea level would rise by 70 to 90 meters. However the ice in central Antarctica is at a temperature from–40 to–60 degrees and so is unaffected by a rise in temperature of a few degrees. The same applies to central Greenland which occupies an area about one-sixth of Antarctica. The ice shelves surrounding Antarctica are somewhat warmer, but are floating like the Arctic ice and so melting them has little effect on the sea level. However the sea level is affected by warmer coastal glaciers flowing into the sea from the ice caps of Antarctica, Greenland, and Northern Canada. The glaciers are very thick, and the pressure on the ice where it rides over the ground is enough to liquefy it, and this makes it easier for it to slide down into the sea. An additional effect has been suggested: when the surface of the ice melts, lakes are formed and this water flows down through cracks in the ice until it reaches the bedrock. There it spreads and reduces the friction between the ice and the bedrock, further increasing the rate of travel of the ice towards the sea. When this happens it causes the sea level to rise, but by an amount that is difficult to estimate. There is increasing evidence that the ice shelves are breaking up, and this reduces the pressure on the glaciers so that their rate of flow increases.

The possibility of another type of irreversible change is provided by the Gulf Stream, which warms northwestern Europe. Without it, the climate would be like that of Labrador, at the same latitude on the western Atlantic. At present the Gulf Stream brings warm water from the tropics toward Europe by what is called the thermohaline circulation. This is due to the freezing of the Arctic water, which causes the salt water to drain out of the ice. This salty water is heavier than fresh water and so it sinks, thus drawing warmer water northwards from the tropics. As this water cools it becomes denser and also sinks, thus attracting more warm water. If the oceans are heated by global warming and more freshwater enters the polar seas it could slow and even stop the Gulf Stream. This could cause the temperature to fall by six to eight degrees celsius and so it would then be frozen for much of the year, and London would become like Siberia.

Further evidence of major climate changes is provided by the melting of glaciers in the tropics. In many countries in the Andes and the Himalayas, the Arctic, Alaska, and East Africa, studies of ice cores and the glaciers themselves provide massive evidence of permanent changes. Isotopic analyses of the ice cores show the evolution of climate from the start of the El Niños about 5,500 years ago, the drought that terminated the Moche empire, and the current effects of global warming. The glaciers began to form in South America about 25,000 years ago and were followed by glaciers in other tropical countries. The growth of the glaciers depends on the latitude, and this is linked with the slow precession of the earth’s axis. During this period the latitude at which the sun was directly overhead moved steadily from the Tropic of Cancer to the Tropic of Capricorn. It might seem strange that glacier formation takes place predominantly when the temperature is highest, but this is because maximum sunshine brings maximum rainfall and at the altitudes where glaciers form the temperature is always low enough to freeze the rain, forming glaciers. The melting of glaciers right across the tropics is quite unprecedented and seems to be an irreversible effect of global warming.

About three billion people, half the people on the earth, depend on the monsoon rains to grow their food. There have been several failures in the monsoon rains in the last two centuries, and the resulting droughts and food shortages have killed tens of millions of people. The reasons for this variability are not entirely clear, but a connection with the El Nino current seems very likely. Famines in India occur during large fluctuations in the Pacific climate. A study of the strength of the monsoons over ten thousand years based on the amount of plankton in marine sediments showed that that weak summer monsoons are correlated with colder periods in the North Atlantic whereas strong monsoons occur when the Northern Atlantic seas are warm. It is not clear just why these effects occur or how they interact with each other. The effects may prove to be benign or catastrophic.

Can These Changes Be Stopped and Reversed?

Whatever we do, the amount of carbon dioxide in the atmosphere will inevitably increase. The danger of catastrophic climate change can be mitigated, however, if resolute action is taken to reduce carbon dioxide emissions. The first essential step is to replace fossil fuels power stations with sources that emit nothing or only minuscule amounts. Already, several countries have substantially reduced their emissions by building nuclear power stations. Thus France (80 percent nuclear) has halved their emissions, Japan (35 percent nuclear) by 20 percent, and the USA (20 percent nuclear) by 6 percent.

Several international conferences have been held to encourage nations to promise reduction. At the Kyoto Conference in 1997 Britain promised to reduce emissions by 20 percent by 2020. Already there has been a reduction by 6 percent due to the improved efficiency of nuclear power stations. As most of these are scheduled to close in the next few years, emissions are bound to rise. Both Britain and the USA have no hope of reaching these very modest targets.

The importance of the atmospheric half-life of greenhouse gases in the atmosphere is seldom recognised. Carbon dioxide lasts about a hundred years, whereas methane is mostly used up in a decade. A molecule of methane causes a hundred times as much global warming as one of carbon dioxide so methane is much more important in the few years after emission. Averaged over a longer period, the effect of carbon dioxide increases, so that over a hundred years the ratio of effectiveness falls to about ten. It is therefore of great importance to reduce methane emissions as soon as possible, although this was not recognized by the targets set at Kyoto. The reduction of methane emission from landfill sites, gas pipelines, coal mines, and many other sources would have an important effect in reducing global warming on the short term. Soot lasts only a few days in the atmosphere but has a large effect on global warming and so its emission should also be reduced.

During the next forty years about two thousand fossil fuel power stations must be replaced. This can be done in several ways. One is to build 4000 windmills occupying 500 square km each week. Or we can cover ten square km of desert with solar panels each week. Perhaps we can find more Severn estuaries and build barrages costing £9 billion every five weeks. Or finally, we can build fifty new nuclear power stations each year. This figure may be compared with the 43 that were built in 1983, the peak year for nuclear construction. This is the choice faced by world governments.

The next article will be devoted to an account of how governments have reacted to the world-wide threat to their very existence.


  1. Sir Ghillian Prance, The Earth under Threat: A Christian Perspective (Wild Goose Publications: St Andrew’s Press, 1996).
  2. Brian Fagan, Floods, Famines and Emperors; El Niño and the Fate of Civilisations (New York: Basic Books, 1999). Brian Fagan, The Long Summer: How Climate Changed Civilisations.
  3. Bjørn Lomborg, The Skeptical Environmentalist (Cambridge: Cambridge University Press, 2004).
  4. Fred Pearce, The Last Generation (London: Eden Project Books, 2006).
  5. Richard A. Ker, “Is Katrina a Harbinger of still more Powerful Hurricanes?” Science 309.1807. 2005. P. J. Webster, G. J. Holland, J. A. Curry, and H-R Chang, “Changes in tropical cyclone number, duration and intensity in a warming environment,” Science 309.1844. 2005.
  6. John Houghton, Global Warming: The Complete Briefing (Oxford: Lion Publishing, 1994).
  7. James Lovelock, Gaia: A New Look at Life on Earth. 1979–2003. James Lovelock, The Ages of Gaia: A Biography of our Living Earth.
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