The papers in this volume aim to represent the most up-to-date research contributions on the observations, theoretical interpretations, and empirical and physical models of variations observed in solar and stellar irradiances, as well as on Sun-climate connections. Both theoretical studies and irradiance observations show that the energy output of the Sun and solar-type stars varies, changing on time scales related to the short-term surface manifestations of solar/stellar magnetic activity as well as long-term modulations driven by processes in the interiors of the stars. Papers presented in this book point out that at the Earth these variations influence the terrestrial climate, radiative environment and upper atmospheric chemistry.