A strange accumulation of radiation in ancient trees dating back to the Early Middle Ages

Just over 1,200 years ago, the planet was hit by an extremely intense burst of high-energy radiation of unknown cause, scientists studying tree-ring data have found.

Cryptomeria japonica, also known as Japanese Cedar. ¹⁴C measurements in annual rings of Japanese cedar trees from AD 750 to AD 820 demonstrated a rapid increase of about 12‰ in the ¹⁴C content from AD 774 to 775, which is about 20 times larger than the change attributed to ordinary solar modulation. Image credit: Corrie Barklimore, Forbes, Australia