Unraveling long-term solar variability and its impact on space climate: The stars as suns project

It is well-known that solar variability influence s the near-Earth Space environment at short timesca les of days - an effect collectively termed as Space Weather. A less er known and more subtle influence of solar variabi lity at longer timescales is however just beginning to be appreciated. This l ong-term solar forcing, which is sometimes referred to as Space Climate, has important consequences for the formation and evolut ion of planetary atmospheres and the evolution of l ife and global climate on Earth. Understanding the Sun's variability and i ts heliospheric influence at such scales stretching from millennia to stellar evolutionary timescales is therefore of fundamental importance and a very promising area of future res earch. However, our understanding of this variability, which is in part connected to the evolution of the solar magnetic d ynamo, is limited by continuous sunspot observations, which exist only f rom the early 17th Century onwards. In this paper w e review the "Stars as Suns" project - in which we take a radically new ap proach to unraveling long-term solar variability th rough theoretical modeling and magnetic activity observations of Sun-like stars, which are at various evolutionary phase s relative to the Sun.