A new observational solar irradiance composite

Variations in the solar spectral irradiance (SSI) are an important driver of the chemistry, temperature, and dynamics of the Earth's atmosphere and ultimately the Earth's climate. To investigate the detailed response of the Earth's atmosphere to SSI variations, a reliable SSI data set is needed. We present an observational SSI composite data set that is based on 20 instruments and has been built by using probabilistic approach that takes into account the scale-dependent uncertainty of each available SSI observation. We compare the variability of this new composite with available SSI reconstructions and discuss the respective modeled responses in the Earth's atmosphere. As the composite is based on purely statistical means, we consider it as a valuable independent data set. Plain Language Summary The changing solar spectrum incident at Earth has important impact on the composition and dynamics of the Earth's atmosphere as well as the climate. In order to quantify the processes at play, it is crucial to have a reliable solar spectral irradiance data set, including the uncertainties, at hand. We present a new composite data set that includes observations from 20 different space instruments and is based on a probabilistic approach. This new composite is compared with available reconstructions, and its response in the Earth's atmosphere is discussed. We consider this new composite as a valuable independent data set.