The luminosity of the sun governs the temperatures of the planets. Yet the solar forcing, or driving, of climate, primarily due to changes in solar radiation, has never been well documented. Recent satellite measurements have shown that solar radiation varies as a function of time and wavelength, a concept that has been hypothesized for the past two centuries and has recently become a major topic with all the attention paid to global warming. This book reviews the physics of the concept of solar forcing, from its beginnings in the early 1800's and apparent success in the 1870's, to its near...