Several factors make the city warmer than the country. Direct energy input from home heating units, industry, and air conditioning helps raise the annual mean temperature and minimum winter temperature. Buildings naturally shelter the city so that wind speeds are lower, and the turbulent transfer of energy from the city to moving weather systems may decline. The increased cloudiness over cities, together with the effect of buildings and pavements on the amount of solar heat retained, further accentuates the direct input into the atmosphere.

The increased rain and snowfall in cities are probably also caused by a variety of factors. The heat of the city in effect causes a “thermal mountain" in which the surrounding air is pushed up vertically over the city to colder levels, aiding the precipitation process. In addition, industry, home heating units, and automobiles all produce particulate materials. These small particles act as nuclei around which water vapor condenses to form drops. Or if the temperatures are cold enough, certain particles can act as nuclei for ice crystals. R. H. Frederick of ESSA supports the theory that particle pollution plays a role in precipitation. He decribes a systematic tendency for cold season precipitation at 22 urban Weather Bureau stations in the eastern United States to average several percent greater on weekdays than on weekends. If substantiated in further studies on other urban areas, this finding goes far in explaining the differences in rainfall between the cities and the country.

The most dramatic cases of the relation of industrial pollution and weather are found in regions where the pollutants are concentrated in valleys. The emission of water vapor condensation nuclei from the stack of a single wood pulp mill in Pennsylvania causes fog forma

tion which sometimes fills a valley several miles wide and 20 miles long and spills into adjacent valleys. Peter Hobbs at the University of Washington has shown that certain Washington State pulp and paper mills are prolific sources of cloud condensation nuclei and that clouds often form downwind of the mills. Hobbs argues that regions of abundant artificial condensation nuclei show an annual precipitation in the last 20 years 30 percent greater than the previous 30 years, although part of this increase is probably due to a natural change in climate. Furthermore, University of Washington researchers have found ice nuclei more abundant by as much as an order of magnitude over urban Seattle than over stations removed from industrial activity. These observations, taken along with those of Frederick, clearly show the potential influence of man-introduced particulate matter on the weather in industrial regions.

CONCLUSIONS

Examination of how man can change climate on a large scale leads to these conclusions:

• The chemical composition of the earth's atmosphere has been altered by man in a measurable way. Some of these changes, which have been mostly inadvertent, have only recently been recognized.

• The magnitude of these atmospheric changes is enough to alter the earth's surface temperature slightly. Carbon dioxide added to the atmosphere from burning fuels is sufficient to lift the average temperature by several tenths of a degree Fahrenheit. Other factors, however, have caused world temperature to drop slightly in the last 30 years.

• These changes in the atmosphere cannot be regarded as local. Heat input escaping from a city into the atmosphere changes the climate of that city. The combined effects of many cities may eventually alter regional and global climates.

• Enough is known about the physical environment to establish the fact that inadvertent modification is occurring. But not enough is yet known to predict all the consequences of atmospheric changes confidently.

Despite its importance, research on inadvertent climate modification has been neglected. Only about 1 percent of Federal Government research monies for weather modification go to programs investigating man's inadvertent modification.

WHAT NEEDS TO BE DONE

The following suggestions should be considered for dealing with long-term problems of climate alteration:

1. Worldwide recognition should be given to the long-term significance of manmade atmospheric alterations.

2. Worldwide ground monitoring of turbidity, carbon dioxide content, and water vapor distribution in the atmosphere should be done with particular attention to oceanic areas. Ground-based observations should be supplemented by airborne monitoring of the number, density, size, and composition of particulate matter in the atmosphere. Such programs are an essential first step to establish pollution baselines.

3. Satellite monitoring of global cloud cover, atmospheric heat balance, and surface albedo should be accelerated. Particular attention should center on effects of altering the thermal balance through changes in albedo, carbon dioxide, and particulate matter.

4. Research on models of the thermal and dynamical processes within the atmosphere and the boundary between the atmosphere and the solid earth and oceans need emphasis.

Solid Wastes

OLID WASTES etch a trail of visible blight that leaves few corners of the country

same scenes repeat-refuse in the streets, litter on beaches and along roadsides, abandoned autos on isolated curbsides and in weeded vacant lots, rusty refrigerators and stoves in backyards, thousands of dumps scarring the landscape. And the less visible aspects of the problemsolid wastes in the ocean, contamination of ground water, and wasted resources are just as critical. America's well-known penchant for convenience has come face-to-face with major environmental problems.

Proper management of solid wastes is a key to upgrading environmental quality. Stricter enforcement of air quality standards has focused attention on burning dumps and inefficient incinerators, many of them operated by municipal governments. Water quality research is beginning to probe the effects of dumps and landfills on the purity of ground water.

Public appreciation of the magnitude of the economic and social costs of solid waste is building and a concept of solid waste management is evolving. It assumes that man can devise a social-technological system that will wisely control the quantity and characteristics of wastes, efficiently collect those that must be removed, creatively recycle those that can be reused, and properly dispose of those that have no further use.

The growing technology and affluence of American society have laid a heavy burden on solid waste facilities. Refuse collected in urban areas of the Nation has increased from 2.75 pounds per person per day in 1920 to 5 pounds in 1970. It is expected to reach 8 pounds by 1980. This spiraling volume of solid waste has a changing character. The trend toward packaged goods in disposable containers has put more paper, plastics, glass, and metals instead of organic matter into the refuse. And technology of solid waste collection and disposal has not kept pace with this change.

There has been little attempt to tie the production of consumer goods together with the disposability of those parts that end as waste. Disposal costs are not included in the price paid by the consumer; rather they are borne by society in general. With few exceptions manufacturers do not accept responsibility for the costs of getting rid of products that have been sold and served their purpose.

Solid waste collection in most municipalities is inadequate and antiquated, partly because over the years it has endured more than its share of public neglect. Refuse collection jobs are low status and low paying, and injury statistics show that only logging is a more hazardous occupation. Sanitation workers have been striking with increasing frequency, and heaps of reeking wastes have been left for days on curbsides in our largest cities. This has dramatized the human factors in the business of refuse collection. It has pointed up the close correlation between the working conditions of trash collectors and the public health menace of inadequate collection and disposal.

Disposal facilities are equally inadequate and antiquated. The Bureau of Solid Waste Management of the Department of Health, Education, and Welfare estimates that 94 percent of existing land disposal operations and 75 percent of incinerator facilities are substandard.