ABSTRACT The potential effects of five energy technologies on global, regional, and local climate were assessed. The energy technologies examined were coal combustion, light water nuclear reactors, satellite power systems, terrestrial photovoltaics, and fusion. The assessment focused on waste heat rejection, production of particulate aerosols, and emissions of carbon dioxide. The current state of climate modeling and long-range climate prediction introduces considerable uncertainty into the assessment, but it may be concluded that waste heat will not produce detectable changes in global climate until world energy use increases 100-fold, although minor effects on local weather may occur now; that primary particulate emissions from coal combustion constitute a small percentage of total atmospheric particulates; that carbon dioxide from coal combustion in the U.S. alone accounts for about 30% of the current increase in global atmospheric CO2, which may, by about 2050, increase world temperature 2-3°C, with pronounced effects on world climate; that rocket exhaust from numerous launches during construction of an SPS may affect the upper atmosphere, with uncertain consequences; and that much research in climatology is needed before potential effects can be quantitatively predicted with any confidence. Although climatic impact is an appropriate concern in formulating long-term energy policy, the level of uncertainty about it suggests that it is not currently useful as a decision criterion. 1 INTRODUCTION It is becoming increasingly evident that human activities have the potential for significantly perturbing the global as well as the local environment. Of particular importance is the extent to which human activities are inadvertently modifying the earth's climate. The worldwide population explosion has created increasing demands for the production of food, and as population pressures increase, the competition for finite food supplies could severely threaten world peace and stability. Relatively small global climatic changes can substantially alter patterns of agricultural production as well as affect the total amount of biological production. Therefore, it is apparent that the potential of human activities for changing the earth's climate is a global issue of enormous proportions. Man has the ability to change the earth's environment in several different ways. The increase in size and distribution of human populations
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