In the shortest-wavelength parts of the electromagnetic spectrum, the Sun is a strongly variable star, but these radiations are absorbed in the Earth's atmosphere and cannot be studied from the ground. Recently, precision measurements of the Sun's properties, including its total brightness and brightness as a function of wavelength, have been made by many spacecraft. Among others are the Solar and Heliospheric Observatory (a collaboration between the National Aeronautics and Space Administration [NASA] and the European Space Agency), NASA's Solar Radiation and Climate Experiment, the Solar Dynamics Observatory, and a new French mission, Picard, named after the 17th century French astronomer Jean Picard, who was the first to measure the Sun's diameter and its variations with a high degree of precision. Along with measuring the Sun's magnetic properties, these missions are studying the reasons for the Sun's brightness variations and their effects on the Earth's atmosphere and climate. This symposium will discuss new knowledge about the effects of solar magnetic activity on the Sun's radiation across the spectrum and what is known about the links between solar variability and fluctuations in Earth's weather and climate.