The Sun provides virtually all the principal energy input to the Earth’s climate system and solar variability is a significant external climate forcing. For instance, the sun irregularly expels large amounts of energetic particles into the interplanetary space and towards Earth which can be observed as so-called solar proton events (SPE), which can potentially cause major damages to satellites and can even disrupt sensitive electronic systems at ground level. While direct observations of the sun’s activity via sunspots only cover the last about 400 years, cosmogenic radionuclides such as 14C, 10Be, and 36Cl stored in tree-rings and ice cores serve as solar activity proxies extending back thousands of years.
Here we present several annually resolved records of atmospheric 14C covering different time periods. The new data is analyzed by using a carbon cycle box model to reconstruct past solar activity and shows the presence of the 11-year solar cycle. Additionally several extreme solar energetic particle events could be found. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records (via 10Be or 36Cl) and provide critical information on the previous occurrence of extreme solar events which threaten modern infrastructure.