2 ANTHROPOGENIC IMPACTS ON CLIMATE 2.1 WASTE HEAT Almost every human activity results in the dissipation of heat. The release of heat to the atmosphere directly affects its temperature and thus the local climate. Rejection of heat to the lower atmosphere can also result in a change of atmospheric stability, which directly affects precipitation and cloud formation. As population growth continues, man’s energy needs will increase, as will the amount of heat released to the environment. This increased anthropogenic heat rejection may play a role in shaping the future climate of the earth. It is appropriate to look at the climatic effects of waste heat on three different geographic scales. The release of a large amount of heat at one or a few major sources could produce local perturbations (withing a few kilometers of the source) in climate. Extremely large heat releases from several closely grouped sources or moderate heat release over a larger region, such as from a metropolitan area, can affect the climate on a regional scale (out to about 50 km). The impact of all of the heat released by man can be examined in terms of its possible contribution to changes in global climate. The severity of waste heat impacts varies considerably, depending on the geographic scale of interest. 2.1.1 Sources of Waste Heat Although man’s release of heat to the environment is generally referred to as waste heat, it is important to note that all anthropogenic heat dissipated to the atmosphere will contribute to potential climatic change. An example is a coal-fired electrical generating plant with a conversion efficiency of about 34%. Of the energy input to the plant, approximately two- thirds will be released on the premises as waste heat and one-third will be converted into useful energy. However, almost all of this useful energy, in the form of electricity, will eventually be dissipated to the atmosphere in the form of waste heat from homes, industries, and other locations. Therefore, it is the total energy input to the system that is important in assessing the impact on the global climate. Waste heat should be considered as all heat released to the atmosphere that would not be there as a result of natural sources such as the solar radiation balance or volcanic activity.
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