Evolution of the sun's spectral irradiance since the Maunder Minimum

Because of the dependence of the Sun's irradiance on solar activity reducti ons from contemporary levels are expected during the seventeenth century Ma under Minimum. New reconstructions of spectral irradiance are developed sin ce 1600 with absolute scales traceable to space-based observations. The lon g-term variations track the envelope of group sunspot numbers and have ampl itudes consistent with the range of Ca II brightness in Sun-like stars. Est imated increases since 1675 are 0.7%, 0.2% and 0.07% in broad ultraviolet, visible/near infrared and infrared spectral bands, with a total irradiance increase of 0.2%.