Data source:

• 1976/01/05 to 2003/02/28 Physikalisch Meteorologisches Observatorium Davos, World Radiation Center
• 2003/03/01 to 2020/02/25 University of Colorado Solar Radiation & Climate Experiment. Data are matched using the 2003/03/01 to 2004/02/29 period.
  The above web page writes, "End of Operations (25 Feb. 2020): The SORCE instruments and spacecraft were powered off on 25 Feb. 2020, ending a very successful 17-year mission."
• 2018/01/11 to 2026/05/21: GES DISC SORCE and GES DISC data are matched using 2018/01/11 to 2020/02/25 period, by shifting GES DISC data by -0.86 W/m2.
• Solar forcing = irradiance change /4 x (1-earth's albedo) = 0.175 x irradiance change (albedo of the Earth = 0.30) The forcing is based on the mean of the irradiance for Jan 1, 1976 to Dec 31, 2019 (1361.09).

  Long-Term Sunspot Numbers

  

  Data source:WDC-SILSO, Royal Observatory of Belgium, Brussels Note from SILSO: Since July 1st 2015, the original Sunspot number data are replaced by a new entirely revised data series. On this occasion, the data are presented in a new array of files, containing additional values that were not present in the original series. For proper tracking of those changes, the present version is numbered 2.0. (Data are through December 2025, Last modified: 2026/01/04)