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air pollution alters weather

Dr Eric Aynsley a research chemical engineer at Illinois Institute of-Technology Research Institute, Chicago.

It is evident that Man's pollution of his own environment is increasing with world population, increased industrialization, urbanization and bad farming practices. Plumes of pollution emanating from the eastern United States can often be observed hundreds of miles out over the Atlantic. Similar air pollution zones are associated with Britain, Europe and the western coast of the United States. This atmospheric dustiness acts like an umbrella and Shields the Earth from the Sun's radiation. Excessive dustiness can also initiate cloud formation, which both alters precipitation patterns and further reduces solar radiation.

Cloud coverage, especially at lower altitudes, is the most effective method of cutting off the Sun's rays and reducing the Earth's surface temperature. Global average cloud cover averages around 31 per cent. It is estimated that an increase of only five per cent in coverage of lower clouds would reduce surface temperatures sufficiently that a return to ice—age conditions could become a reality.

A slight reduction in the Earth's temperature has already been recorded in the last decade, and the Northern Atlantic ice coverage last year was the most extensive for 60 years. On the global scale Dr R.A. Bryson, a climatologist at the University of Wisconsin, suggests that pollution may even be responsible for the observed weakening of the trade winds and westerlies over the last decade.

Increase of atmospheric dustiness or turbidity has only recently been substantiated and. If it continues unchecked can have devastating consequences. Measurements at the Moana Loa Observatory in Hawaii, which is remote from any local sources of air pollution, indicate a long—term increase in turbidity or atmospheric dustiness. Mr R.A. McCormick and Mr J.H. Ludwig in Cincinnati have shown increases in recent years of turbidity over Washington, DC of 57 per cent and over Switzerland the increase was 88 per cent and Dr V J. Schaefer and his co—workers at the State University of New York have documented many examples of large increases in atmospheric particulates of the order of tenfold during the last five years.

"welcome sulphur dioxide hello carbon monoxide the air, the air is everywhere"

An excess of dust produces small droplets under condensing conditions which grow from further condensation and coalescence and ultimately fall as precipitation.

An example of increased precipitation from air pollution appears to exist at La Porte, Indiana, some 30 miles downwind from the smoky steel works of Gary and South Chicago. During the 14 years up to 1965 La Porte had 31 per cent more rain, 38 per cent more thunderstorms and 245 per cent more days with hail than nearby communities. In fact, rainfall at La Porte increases in harmony with steel production rates at Gary!

Excessive dustiness in the atmosphere can also reduce rainfall under certain conditions. Reduction in rainfall has occurred in the sugar producing area in Queensland, Australia. During the cane-harvesting season the common practice is to burn off the cane leaf before cutting and harvesting. This results in fires over extensive areas and large palls of smoke. The fine smoke particles have modified the cloud formation and hindered the rainfall process. A reduction of up to 25 per cent in the rainfall has occurred downwind of these areas, but there is no such effect in neighbouring areas unaffected by the smoke plume.

The ubiquitous automobile has a great potential to cause inadvertent weather modifications. The major offenders are components of the exhaust, which become highly reactive under intense sunlight, producing the well known brown smog. The lead additives in petrol combine in the car exhaust and atmosphere with the small numbers of iodine molecules present and provide excellent particles for ice crystal formation. Dr Schaefer has observed extensive ice crystal plumes in the winter around a number of large American cities.

An example of local climate modification by water vapour is Edmonton in Canada, which has more low—temperature fogs than neighbouring areas. During cold winter spells the air cannot absorb all the moisture produced from the additional natural gas burnt for space heating. Thus extended periods of fog or ice crystal fogs are experienced.

The vapour trails associated with high—flying aircraft are well known. What is not generally known is that aircraft inject carbon dioxide, water vapour and considerable quantities of fine particles into the rarified upper atmosphere. It is estimated that the high wispy cirrus clouds formed from jet contrails have already increased cloud coverage between North America and Europe by five to ten per cent. These hazards of artificial clouds will be greatly increased as supersonic transport aircraft become a commercial reality. Dr Bryson estimates that cirrus clouds could well attain 100 per cent coverage in these operational regions.

Man's knowledge of his ability to inadvertently modify his climate is still at best fragmentary. Insufficient is known about the long—term build—up of air pollutants the effects and their inter—relationships. A point of no return may be reached when air pollutant levels cause the climate to 'be modified to such a degree that a major irreversible global weather modification may follow. It is essential that mankind faces up to this problem to save his own atmospheric environment. Although detailed studies of air pollution and interrelated, weather effects are necessary, the primary solution requires a continuing effort aimed at control and ultimate abatement of air pollution sources. Only then will a future of clear blue skies be assured.