If the world depends on fossil fuels for its energy needs over the next two centuries, the U.S. National Academy of Sciences/National Research Council report Energy and Climate foresees the possibility of a peak atmospheric concentration of carbon dioxide of between 4 and 8 times the preindustrial level as occurring in A.D. 2150 to 2200. Climatic models of the general circulation of the atmosphere predict a 2–3°C rise in average temperature of the atmosphere for each doubling of the carbon dioxide content. Thus, a mean value of about 6°C increase in average atmospheric temperature would be anticipated if the models prove to be accurate and if the growth scenario used in the report were to be realized.