Ancient observations link changes in Sun's brightness and Earth's climate

Abstract

From the frequencies of sunspot and aurora sightings, abundance of carbon‐14 in the rings of long‐lived trees, and beryllium‐10 in the annual ice layers of polar ice cores, we have reconstructed the history of a variable Sun. In the last 1,800 years, the Sun has gone through nine cycles of changes in brightness. While these long‐term variations account for less than 1%of the total irradiance, there is clear evidence that they affect the Earth's climate.