Background: The Intergovernmental Panel on Climate Change concludes that anthropogenic greenhouse gases are extremely likely to have been the dominant cause of observed global warming. Depletion of the ozone layer by manufactured chlorofluorocarbon gases and volcanic eruptions, however, provides a much more detailed and precise explanation for changes in climate observed since the industrial revolution and throughout geologic history. Climate models currently calculate that infrared thermal energy absorbed by greenhouse gases is greater than ultraviolet thermal energy reaching earth when ozone is depleted, yet we all know we get hotter standing in ultraviolet sunlight than in infrared radiation welling up from earth at night.Objective: To understand the physics of how ozone depletion could be a better explanation for observed warming. Method: Recognizing that thermal energy is the oscillations of all the degrees of freedom of all the bonds holding matter together, that energy of each atomic oscillator is equal to the Planck constant times the frequency of each oscillation, and that this energy is an intensive physical property that is therefore not additive, we examine from first principles how thermal energy flows via electromagnetic radiation. Results: Radiant thermal energy is not a function of bandwidth as currently calculated. It is a function only of frequency of oscillation. The higher the frequency, the higher the temperature to which the absorbing body will be raised. Intensity and amount of radiation only determine the rate of warming. Conclusions: Ozone depletion provides a more precise explanation for observed global warming than greenhouse-warming theory.