Sami K. Solanki
Max-Planck-Institute for Aeronomy, D-37191 Katlenburg-Lindau, Germany
"Long-term changes in solar irradiance"
Measurements of solar irradiance with the necessary precision to reveal the sun's intrinsic variability started in 1978. These measurements have revealed dips in solar brightness due to the passage of sunspots across the solar disc on a solar rotation time scale and a remarkable increase of the solar irradiance at solar activity maximum. In order to uncover a possible connection between solar irradiance variations and climate it is necessary to extend the irradiance record to earlier times with the help of models.
A brief introduction to the results of the measurements and our current understanding of the variability they reveal is given, followed by an overview of the efforts to reconstruct irradiance or the underlying magnetic field at earlier times.