According to the simplest model of the earth’s radiative balance, global warming will occur with certainty as humankind increases its production and consumption of nonsolar energy. This prediction is revisited, using a broader model that allows the greenhouse effect to be considered. The new model predicts a global warming of where ε is the rate of surface energy release in units of the average incident solar radiation, and is the average temperature rise at the earth’s surface. Present values of these quantities, excluding geothermal sources, are and The model assigns a small number of optical parameters to the atmosphere and surface and qualifies the simple warming prediction: It is rigorous only if parameters other than ε are unchanged. The model is not complex and should serve as an aid to an elementary understanding of global warming.
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