Total Solar Irradiance Modelling during cycle 23

During solar cycle 23, which is now close to its end, the variations of the Total Solar Irradiance were determined by 3 composites time series: the RMIB, ACRIM and PMOD composites. An independent analysis of the different composites is performed through an empirical proxy model fit. The RMIB composite is fitted with 0.96 correlation and RMS error of 0.15 W m-2 reaching therefore the limit of individual instruments stabilities. Both the measurements and the model indicate that for the current cycle the minimum irradiance level has not been reached yet. Therefore we use the model to extrapolate measurements up to 2008 when the minimum irradiance level is expected. If we assume that there will be no changes in the solar irradiance from 2006 to 2008 that are not captured by the regression model, it can be predicted that there will be no variation of the solar minimum irradiance level during cycle 23 with an uncertainty of ± 0.14 W m-2.