On the variability of total solar irradiance
  Knowing the variability of total solar irradiance (TSI) at the top of the atmosphere is crucial for specifying solar influence to climate variability. Satellite measured TSI data are available only for the last 32 years. But there is an opportunity to estimate approximate daily TSI values on the basis of the observed variability of solar activity. A common approach is based using data for Wolf sunspot numbers. Series of daily data from the DAVOS based TSI starting from 1978 have been compared with daily values of Wolf numbers and with the corresponding estimates for daily summary sunspot area. Our goal is to use established correlations to hindcast earlier TSI values. The available solar activity data enabled us to reproduce rough TSI estimates back to the 1870's. 
Jaan Pelt, Olavi K\"arner
astro-ph.SR