Solar Irradiance Variability and Climate

TL;DR

This paper reviews how solar irradiance variability influences climate, discussing observed variations, their spectral dependence, and potential mechanisms, highlighting current understanding and open questions in the field.

Contribution

It provides a comprehensive overview of solar irradiance variability's impact on climate, emphasizing spectral and secular variations and identifying key open research questions.

Findings

Solar brightness varies across all observed time scales.

Spectral dependence of solar variations influences climate response.

Open questions remain about the magnitude of secular variations.

Abstract

The brightness of the Sun varies on all time scales on which it has been observed, and there is increasing evidence that it has an influence on climate. The amplitudes of such variations depend on the wavelength and possibly on the time scale. Although many aspects of this variability are well established, the exact magnitude of secular variations (going beyond a solar cycle) and the spectral dependence of variations are under discussion. The main drivers of solar variability are thought to be magnetic features at the solar surface. The climate reponse can be, on a global scale, largely accounted for by simple energetic considerations, but understanding the regional climate effects is more difficult. Promising mechanisms for such a driving have been identified, including through the influence of UV irradiance on the stratosphere and dynamical coupling to the surface. Here we provide an overview of the current state of our knowledge, as well as of the main open questions.