Roger K. Ulrich

A discussion of recent evidence for solar irradiance variability and climate

Abstract One of the over-arching questions, among others, to be addressed by studying Sun-Earth connections is: “Is the climate changing in a way we can understand and predict?” The Earths climate is the result of a complex and incompletely understood system of external inputs and interacting parts. Climate change can occur over a range of time scales, may be driven by natural variability, including solar variability, and/or anthropogenic causes and may be identified through the study of a variety of measurable parameters. Global climate change in response to human influences is one of the pressing threats facing science today. However, many of the external factors that govern our climate, including solar variability, cannot be adequately determined from existing operational observations. Since the Sun is the fundamental source of energy that sustains life on Earth, establishing its radiation environment, controls its temperature and atmospheric composition, the accurate knowledge of the solar radiation received by the Earth and understanding of its variability are critical for environmental science and climate studies. In this paper we point out the necessity of a new strategy, i.e., to study global solar properties, such as solar irradiance, solar shape, shape oscillations, and radius, to better understand the origin of solar-induced climate changes.