Human Activities And The Atmospheric Environment

Certain elements in the environment remain untamed, uncontrollable and imperfectly understood. Nowhere is this more evident than in the realm of weather and climate. Neither nineteenth nor twentieth century technology could prevent cyclones from devastating the shores of the Bay of Bengal, or hurricanes from laying waste the Caribbean. The Sahelian drought spread uncontrollably even as the first astronauts were landing on the moon. The developed nations, where society's dominance of the environment is furthest advanced, continue to suffer the depredation of tornadoes and blizzards as well as the effects of less spectacular weather events such as frost, drought, heatwaves and electrical storms, which even today are difficult to forecast. No one is immune.

It is scarcely surprising, therefore, that weather and climate are universal topics of interest at all levels of society. In most cases, concern centres on the impact of short-lived local weather events on individuals and their activities. It is very much one-sided, normally ignoring the potential that mankind has to alter its atmospheric environment. There is a growing appreciation, however, that the nature and extent of the climatological component in many current global issues is strongly influenced by human interference in the earth/atmosphere system. The evolution of this awareness has been traced by William Kellogg (1987) who points out that as long ago as the late nineteenth century, the first tentative links between fossil fuels, atmospheric carbon dioxide and world climate had been explored. The results failed to elicit much interest in the scientific community, however, and remained generally unknown to the public at large. Such a situation prevailed until the mid-1960s. From that time on the cumulative effects of a number of high-level national and international conferences, culminating in the Study of Critical Environmental Problems (SCEP) in 1970, produced a growing awareness of global environmental issues. The impact of human activities on regional and global climates was considered in the SCEP, and when it became clear that the issue was of sufficient magnitude to warrant further investigation, a follow-up conference was convened. It focused on inadvertent climate modification, and in 1971 produced a report entitled The Study of Man's Impact on Climate (SMIC). The report was recognized as an authoritative assessment of all aspects of human-induced climatic change, and it might even be considered as the final contribution to the 'critical mass' necessary to initiate the numerous and increasingly detailed studies which characterized the next two decades. The pace quickened in the late 1980s, with international conferences on various aspects of climate and the changing atmosphere being held in Montreal, Toronto, Hamburg, London and Geneva (see Chapter 8). A significant step forward was the creation in 1988 of the Intergovernmental Panel on Climate Change. Set up to evaluate global climate trends—particularly global warming—it provided major input for the discussions leading up to the signing of the convention on climate change at the United Nations Conference on Environment and Development in Rio de Janeiro in 1992.

One of the results of all that activity was the positive identification of human interference as a common element in many of the major problems of the atmospheric environment. The information gathered during the studies is quite variable in content and approach. It has been presented in highly technical scientific reports, as well as in simple, basic articles prepared for popular consumption. The latter are particularly important as a means of disseminating information to the wider audience which past experience suggests must be educated before progress can be made in dealing with environmental problems. Because of the time and space constraints and the marketing requirements of modern journalism, however, the issues are often treated with much less intellectual rigour than they deserve. In addition, the topics are often represented as being new or modern when, in fact, most have existed in the past. Drought, acid precipitation and the greenhouse effect all result from natural processes, and were part of the earth/atmosphere system even before the human species came on the scene. Their current status, however, is largely the result of human intervention, particularly over the last 200 years, and it is the growing appreciation of the impact of this intervention that has given the issues their present high profile. One topic that can be classified as new is nuclear winter. Unlike the others, which exist at present, and have developed gradually as the accumulated results of a variety of relatively minor inputs, nuclear winter remains in the future, with an impact that can only become reality following the major catastrophic inputs of nuclear war. For many in the mid-1980s it was seen as the ultimate intervention; the ultimate blow to environmental equilibrium. Despite this, nuclear winter is no longer considered a major environmental issue by most observers. Events such as the ending of the Cold War, the break-up of the USSR and the signing of a variety of arms control agreements have reduced the potential for inter-continental nuclear war, and as a result interest in nuclear winter has declined almost to zero.

Present concerns may be seen to some extent as the most recent elements in a continuum. In the 1960s and early 1970s, the main environmental issues were those associated with pollution in its various forms. Pollution is the contamination of the components of the earth/

atmosphere system, to such an extent that normal environmental processes are adversely affected. Contamination is not always serious, however. The environment has a considerable capacity for ridding itself of pollutants, and problems only begin to arise when the input of contaminants exceeds the ability of the environment to deal with them. In modern times, this situation has become common as a result of the tremendous amount of waste generated by human activities and deposited in the environment. In the 1960s and 1970s, the most pressing popular concerns were often local in origin, dealing with such problems as urban air pollution or reduced water quality in rivers and lakes, although consideration was given to the environment as a whole in the academic and scientific community (e.g. Detwyler 1971). Along with increased concern there was also increased understanding of the environment, brought about by the development of educational programmes at all levels, from elementary school to university, and by judicious use of the media by environmental groups such as the Sierra Club, Friends of the Earth, Pollution Probe and Greenpeace. The high level at which public interest in environmental affairs was sustained during the years when improvement was marginal is in no small measure attributable to these groups.

Public pressure forced the political and industrial establishment to reassess its position on environmental quality. Oil companies, the forest products industry and even automobile manufacturers began to express concern for pollution abatement and the conservation of resources. Similar topics began to appear on political platforms, particularly in North America, and although this increased interest was regarded with suspicion, and viewed as a public relations exercise in some quarters, legislation was gradually introduced to alleviate some of the problems. By the early 1970s some degree of control seemed to be emerging. While this may have helped to reduce anxiety over environmental concerns, progress was slow, and some observers attribute the decline in interest in all things environmental at about this time to disenchantment rather than recognition that the problems were being solved (Bach 1972).

Whatever the reason, the level of concern had peaked by then, and when the oil crisis struck in 1973, energy quickly replaced environmental issues in the minds of the politicians, academics and the public at large. In the first half of the 1990s, the energy situation is perceived as less critical, the dire predictions of the economists and energy futurists have not come to pass, and the waning of interest in energy topics has been matched by a resurgence of environmental concern, particularly for problems involving the atmosphere. The new issues are global in scale and, at first sight, may appear different from those of earlier years; in fact, they share the same roots. Current topics such as acid rain and global warming are linked to the sulphurous urban smogs of two or three decades ago by society's continuing dependence on fossil fuels to meet its seemingly insatiable demand for more energy. Population pressures on land of limited carrying capacity contribute to famine and desertification much as they did in the past. The depletion of the ozone layer, associated with modern chemical and industrial technology, might be considered as only the most recent result of mankind's continual, and seemingly inherent, desire to improve its lot—all the while acting in ignorance of the environmental consequences.

Many of the problems currently of concern have causes which can be traced to ignorance of the workings of the atmosphere. This is particularly true when the impact of air pollution on climate is considered. Almost all human activities produce waste products, and some of these are introduced into the atmosphere. This presented no great problem when populations were small, and technological levels were low, for the atmosphere includes mechanisms designed to keep such emissions in check. For every process adding material to the atmosphere, there is another which works to remove or reduce the excess, either by neutralizing it or by returning it to the earth's surface. Gases, for example, may be absorbed by vegetation, neutralized by oxidation or dissolved in water and precipitated.

Particulate matter falls out of the atmosphere as a result of gravity or is washed out by precipitation. These processes have removed extraneous gases and aerosols from the atmosphere, usually quite effectively, for millions of years.

Ongoing physical and biological activities— such as volcanic eruptions, soil erosion and the combustion or decay of vegetable matter—ensure that the cleansing process is never complete, and that, in itself, is a natural part of the system. There are indications, for example, that a minimum level of extraneous material is essential for the working of such atmospheric processes as condensation and precipitation. Thus, a completely clean atmosphere may not be desirable (Barry and Chorley 1992). Desirable or not, it is unlikely to be achieved, given the present rates of gaseous and particulate emissions.

In the past, the main pollutants were natural in origin, and sources such as the oceans, volcanoes, plants and decaying organic material continue to provide about 90 per cent of the total global aerosol content (Bach 1979). Events, such as the eruption of Mount Pinatubo, indicate the continued capability of nature to provide massive volumes of pollutants, but anthropogenic sources are now paramount in many areas. Human activities provide pollutants in such amounts, and with such continuity, that the atmospheric cleansing processes have been all but overwhelmed, and a full recovery may not be possible, even after large-scale attempts to reduce emission levels.

Air pollution was one of the elements which elicited a high level of concern during the heyday of the environmental movement in the late 1960s and early 1970s. It was mainly an urban problem at that time, most common in large cities which had high seasonal heating requirements, were heavily industrialized, had large volumes of vehicular traffic or experienced combinations of all three. Even then, however, existing air pollution control ordinances were beginning to have an effect on the problem. In Pittsburgh, the introduction of smokeless fuel, and the establishment of emission controls on the iron and steel industry, brought a steady reduction in air pollution between 1945 and 1965 (Thackrey 1971). Similar improvements were achieved in London, England, where sunshine levels in the city centre increased significantly following the Clean Air Act of 1956 (Jenkins 1969). The replacement of coal by natural gas as the main heating fuel on the Canadian Prairies, in the 1950s and 1960s, allowed urban sunshine totals to increase there also (Catchpole and Milton 1976). Success was achieved mainly by reducing the atmospheric aerosol content. Little was done to reduce the gaseous component of pollution, except in California, where, in 1952, gaseous emissions from the state's millions of cars were scientifically proven to be the main source of photochemical smog (Leighton 1966). Prevention of pollution was far from complete, but the obvious improvements in visibility and sunshine totals, coupled with the publicity which accompanied the introduction of new air quality and emission controls in the 1970s, caused the level of concern over urban air pollution to decline markedly by the end of the decade.

The relationship between pollution and weather or climate is a complex one. Sometimes climatic conditions will influence the nature and extent of a pollution episode, while at other times the linkages are reversed, allowing the pollutants to instigate or magnify variations in climate. The problem of acid rain illustrates quite well the impact of atmospheric processes on the operation and distribution of a particular group of pollutants, whereas the issues of increased atmospheric turbidity and the depletion of the ozone layer illustrate the other relationship, in which pollutants cause sufficient change in the atmosphere to initiate climatic change.

The full complexity of the earth/atmosphere system is only now beginning to be appreciated, but in recent years, knowledge of the impact of human social and technological development on the atmospheric environment has grown quite dramatically. Government sponsored studies on such topics as the greenhouse effect and acid rain, along with reports by respected scientists and academics on nuclear winter and the depletion of the ozone layer, have become available. Although often quite technical, they have contained material of sufficient general interest that it could be abstracted and disseminated widely by the media. Other issues have been developed at the popular level from the outset. The interest in African drought, for example was to a large extent an emotional response to television coverage of events in Ethiopia and the success of the Live Aid concerts of 1985, although excellent academic studies of the problem have been carried out (Bryson and Murray 1977; Glantz 1977).

As more information becomes available on these global environmental issues, it is clear that the present problems have existed undetected for some time. It is also clear that the activities which produced them were entered into with the best of intentions—to improve the quality of human life—and society might even be seen as suffering from its own success. That, of course, does nothing to reduce the seriousness of the problems, but it indicates the need for extreme caution when initiating schemes which promise major advantages. The linkages in the earth/ atmosphere system are such that even local or regional changes can be amplified until their impact is felt system-wide and in the modern world schemes which might conceivably alter the environment, whether immediately or ultimately, cannot be entered into lightly. Unfortunately, even in the present era of high technology, predicting the eventual reaction of the environment to a specific input is seldom possible, and changes already initiated may well be expanding and intensifying undetected to provide the makings of some future problem.

The global environmental topics to be considered in the following chapters are those which currently enjoy a high profile. They include global warming and ozone depletion—presently the leading recipients of research funding—

together with acid rain and atmospheric turbidity, which now receive less attention than they did 5-10 years ago, but remain significant environmental issues. In keeping with its recently reduced status, nuclear winter is incorporated in the section on atmospheric turbidity, where it is considered as an example of the consequences of macro-scale air pollution. In contrast to these modern, high-tech problems, there is drought, a problem which has plagued mankind for centuries, causing millions of deaths and large scale environmental degradation, yet remains essentially unsolved. It deserves consideration in its own right, but as a well-established, recurring problem, it also provides a useful contrast with those of more recent origin.

Since society experiences the impact of these elements or induces change in them by way of the atmosphere, an understanding of the workings of that medium is important also. Although many processes are involved, in any discussion of global environmental issues questions of the composition of the atmosphere, its general circulation and its role in the global energy budget appear with some regularity. These topics will therefore be considered as a necessary introduction to the issues.

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