Most of the world's energy is produced from stocks of carbon and carbon flow is one of the most critical global issues of all, the production and consumption of energy and the associated undesirable environmental effects, from smog, acid rain and oil spills to Chernobyl and global warming. Energy, like minerals, is talked of in terms of being a 'primary resource' but it is altogether distinctive, although both are clearly related. Some important energy resources, such as coal, oil and uranium, are themselves minerals; and the extraction and processing of minerals requires energy, in a suitable form, to drive digging and crushing machinery and to modify chemical structure, as in the process of smelting ores to produce useful metals.

The international debate on global warming and the need to limit the emission of harmful 'greenhouse gases', notably carbon dioxide, particularly from the burning of fossil fuels like coal and oil, is the focus for discussion in the next chapter.

To arrive at any meaningful assessment of 'choice' or 'practicable policy alternatives' requires consideration of a number of interrelated issues: the relationship between stocks and demand — the production of power from a variety of energy sources and global patterns of consumption; the balance between renewable and non-renewable energy resources; changing patterns of use in the more developed world and increasing energy requirements in the less developed world; energy efficiency, resource conservation and the exploration of new energy paths for the world to follow. To help us along the way we shall be looking at energy policies in Denmark, a country that has adopted a progressive approach in cateringfor its energy needs. However, first we should take a broad view of the global energy picture.

Britain's industrial revolution was based upon ready access to coal, which soon became equally important world-wide, as it still is. In the USA at the end of the nineteenth century, oil also became vital, supporting the development of the automobile, soon to become a world issue in its own right. In the mid-twentieth century the use of natural gas as a cleaner domestic and industrial fuel increased throughout the developed world. Current perceptions of the amounts of these fuels now available give an instant image of powerful economic and political influences at work at the end of the twentieth century'.

'Proved reserves' refers only to those resources judged to be extractable 'under existing economic and operating conditions' and not to the amounts that might be ultimately available. So the concept of reserves depends on the state of exploration and extraction technology, and on world prices, which in turn depend on the main operators in the energy industries.

Their influence was no better demonstrated than in the oil crisis of 1973, when the Middle East-dominated cartel OPEC (Organisation of Petroleum Exporting Countries) ensured that restricting supplies became a highly profitable venture. There is still a continuing overwhelming dominance of that region in terms of supplies of oil, which is a major factor of political instability. Iraq's invasion of Kuwait in 1990 and the subsequent Gulf War in 1991 were potent and horrifying reminders of the measures that some nations, for differing reasons, are prepared to take to 'safeguard' essential supplies of a basic resource. In the event, estimates of proven reserves will have to be revised following the fires that burned out of control throughout Kuwait. The environmental costs of that episode have been truly enormous.

In 1988 it was estimated that at current extraction rates oil supplies would last for 42 years, if averaged over the whole world, ranging from five years for the United Kingdom and 10 for North America to over 100 years for several Middle Eastern states. For natural gas the estimates were scarcely more encouraging, with an average world 'life expectancy' of 55 years, ranging from over 100 years for the Middle East to only 13 years for the UK and North America. The fossil fuel with the longest life span is coal, the original industrial fuel. Its world- wide distribution is more even than either oil or natural gas and at current consumption rates it could be at least the twenty- third century, and probably beyond, before known supplies are used up.

Allowing for the fact that all such projections should be viewed circumspectly, these figures nevertheless highlight one very significant part of the energy problem, the continuing dependence on fossil fuels by the majority of countries, whether less or more developed, and the reluctance of coal- rich countries to see any constraints placed upon the burning of coal, one of the principal contributors to the greenhouse effect. North America, the USSR and China are all richly endowed with coal reserves.

The total consumption of primary energy for the non- communist world 1970—1989. Excluded from these data are biomass fuels — wood, animal wastes - essential to the fuel requirements of many less developed nations (they are not traded and therefore do not appear in commercial statistics) and other forms of renewable energy too small to register on this diagram. Biomass fuels are believed to provide 10-15 per cent of the world's primary energy needs, which gives some indication of the pressure on forest resources of indigenous peoples.

The key point is that carbon stocks have been used and continues to be used in most parts of the world in an unsustainable manner, with demand being distributed quite unequally. About 25 per cent of the world's people consume over 75 per cent of the world's primary energy. Yet, even within the more developed world, energy is being consumed at variable rates, from about 4-5 kilowatts per capita in Europe and Japan through to about 10 kW per capita in the United States. Consumption is less than 1 kW per head in many less developed countries, but from the developing world demand is increasing all the time, partly as a factor of population growth, but more specifically related to an urgent desire to industrialise. If the growing world population follows the development path of industrialised countries, the pressure on existing energy resources will be overwhelming.

The unequal energy habits of different nations are highlighted by the dominance of the United States in the use of oil, gas and coal. In 1988 oil accounted for some 38 per cent of US commercial energy consumption, with oil imports amounting to over 40 million dollars' worth, approximately equivalent to one-third of the nation's trade deficit. The US transportation system alone consumes enough oil to provide for all Japan's energy needs. The sheer scale of energy consumption in the United States indicates that the US could have a major impact on global carbon emissions by developing more efficient cost- effective technologies. But is this likely to happen and if so, when?

The international community faces a daunting challenge in attempting to set targets for the reduction of global emissions from the continuing use of fossil fuels, let alone enforcing them. But where should the principal responsibilities rest for tackling the major problems? Is it feasible to shift dependence from non-renewable to renewable sources, and whilst this is being achieved to stretch existing energy supplies through energy efficient technologies, without exhausting those supplies and without having further recourse to the controversial and potentially hazardous generation of nuclear power? That is a tall order indeed, more especially for less developed countries that are heavily dependent upon 'dirty' and inefficient technology.

The OOA proposals were based upon an integrated energy and environment analysis, the objective of which was to increase the potential choices available in providing reliable and continuing sources of energy on a sustainable basis. The Alternative Energy Plan emphasises two basic principles:

1 Energy conservation to reduce total energy demand.

2 Renewable sources of energy increasingly to replace the conventional sources, but only in tandem with policies for conservation.

Supporters of the Alternative Energy Plan are convinced that it is and point to a series of technological developments and current projects that underline both the efficiency and conservation arguments and the requirements to shift progressively to the use of renewables. In terms of new technology, it is being widely demonstrated that significant energy savings can be made by investing in low energy domestic appliances, like refrigerators which use one-quarter of the electricity of conventional models and fluorescent lighting. Although the initial cost is higher, they are still cost effective because of the huge potential for energy conservation.

All of this requires a long-term commitment on the part of government and industry, but nevertheless these are the kinds of technical change that, followed through in detail, could lead to the projected reductions in total energy demand contained in the alternative plan. Relying on technological innovation is only part of the equation, however. Most European countries are active in promoting ways of meeting demand from renewable sources. Two in particular are worthy of note. Both are based upon traditional ideas, but make use of the latest technology: the production of methane gas and wind power.

Experimental projects are already well in hand to produce methane from wastes, either on intensive livestock farms and capped landfill sites for domestic wastes, using an 'anaerobic digester'. The methane is then used as a fuel for a local power and heating system. This type of solution is well suited to local, decentralised systems of power generation and is a good example of using biomass as an energy source, applicable equally to wood through the Industrial Revolution and at an ever more rapid rate in the twentieth century

What will be the effect of the rise in greenhouse gas concentrations on temperatures and on climatic patterns? This ceases to be a matter of evidence and requires the use of scientific models (see the box on page 139). Most analyses have focused on the likely effects of a doubling of carbon dioxide levels above the pre-industrial level. The estimates fall into the range 3-6 °C with 4 °C the most probable figure. Such a rise would take global temperatures well above any level which has occurred in the last few million years. How soon might it occur?

To put a time-scale on this change, it is necessary to predict the likely change in emissions of carbon dioxide and the other greenhouse gases. That takes us out of the realm of science and into economic forecasting —an even more difficult enterprise. It is clear that the main contributor is carbon dioxide released from the burning of fossil fuels, but growing problems are carbon dioxide released by deforestation, methane from agriculture and natural gas leaks, nitrous oxide in vehicle exhausts and CFCs. The growth in emissions has been spectacular: world energy use quadrupled between 1950 and 1984 and carbon dioxide emissions tripled in the same period. The future prospect is for even more rapid growth unless action is taken. The link between emissions and atmospheric concentrations is mysterious: about half the carbon dioxide emitted disappears from the atmosphere but scientists cannot at present identify where it goes. Without this fortunate accident, the predictions would be even more alarming. As it is, the worst case estimate (in other words, the fastest likely rate of emissions) would double carbon dioxide by 2040, the most probable case would delay doubling until the end of the century. Only the most optimistic assumptions about control of emissions yield any hope that the doubling can be prevented. However, that takes us on to the question of political response and there remains a crucial step in understanding the problem - the effect of a rising temperature on other things, notably on sea level, the frequency of extreme events and on ecosystems.