  The total solar irradiance (TSI) varies on timescales of minute to centuries.
On short timescales it varies due to the superposition of intensity
fluctuations produced by turbulent convection and acoustic oscillations. On
longer scale times, it changes due to photospheric magnetic activity, mainly
because of the facular brightenings and dimmings caused by sunspots. While
modern TSI variations have been monitored from space since 1970s, TSI
variations over much longer periods can only be estimated using either
historical observations of magnetic features, possibly supported by flux
transport models, or from the measurements of the cosmogenic isotope (e.g.,
\textsuperscript{14}C or \textsuperscript{10}Be) concentrations in tree rings
and ice cores. The reconstruction of the TSI in the last few centuries,
particularly in the 17th/18th centuries during the Maunder minimum, is of
primary importance for studying climatic effects. To separate the temporal
components of the irradiance variations, specifically the magnetic cycle from
secular variability, we decomposed the signals associated with historical
observations of magnetic features and the solar modulation potential $\Phi$ by
applying an Empirical Mode Decomposition algorithm. Thus, the reconstruction is
empirical and does not require any feature contrast or field transport model.
The assessed difference between the mean value during the Maunder minimum and
the present value is $\simeq2.5 Wm^{-2}$. Moreover it shows, in the first half
of the last century, a growth of $\simeq 1.5 W m^{-2}$ which stops around the
middle of the century to remain constant for the next 50 years, apart from the
modulation due to the solar cycle.
