Centennial Total Solar Irradiance Variation

Total Solar Irradiance (TSI) quantifies the solar energy received by Earth and therefore is of direct relevance for a possible influence on climate change Earth. We analyse TSI space measurements from 1991 to 2021, we derive regression model that reproduces measured daily variations with Root Mean Square Error (RMSE) 0.17 W/m2. The uses MgII core wing ratio as facular brightening proxy Photometric Sunspot Index (PSI) measure sunspot darkening. reconstruct annual mean backwards 1700 based Number (SN), calibrated an RMSE 0.086 analysis 11 year running reconstruction confirms existence 105 Gleissberg cycle. level current grand minimum only about 0.15 W/m2 higher than in beginning 18th century.