  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.
