Influence of Solar Activity Cycles on Earth's Climate

In order to determine the influence of mankind on climate change it is important to understand the natural causes of climate variability. A natural effect that has been hard to understand physically is an apparent link between climate and solar activity. From historical and geological records there are strong indications that the sun has played an important role in the past climate of the Earth, but the physical mechanism is currently unknown. Whatever mechanism caused those earlier changes would most likely also be operating today and may have been active throughout the history of our planet. There have been several attempts to explain the link between solar activity and climate from variations in the sun’s radiative output. These have tended to rely on simulations involving Global Climate Models (GCM), which are limited by our current understanding of the fundamental physics. In the following contribution, an outline of the current candidate mechanisms involving solar activity will be presented together with a description of the ESA funded project to study the Influence of Solar Activity cycles on Earth’s Climate (ISAC)