Rapid increase in cosmogenic 14C in AD 775 measured in New Zealand kauri trees indicates short-lived increase in 14C production spanning both hemispheres.

In 2012, Miyake et al. reported a sudden and strong increase of the atmospheric radiocarbon ( 14 C) content in Japanese cedar trees of 1.2% between AD 774 and 775. While their findings were quickly confirmed by a German oak chronology for the Northern Hemisphere (NH), the question remained if the effect was seen in both hemispheres. Here we present the first annually resolved Southern Hemisphere (SH) 14 C record spanning the interval AD 760–787, using New Zealand kauri ( Agathis australis ) chronology wood. An almost identical distinct increase compared to Northern Hemisphere data was observed, suggesting a cosmic event with globally uniform impact as a potential cause for the increase. Deploying a carbon cycle box model a worldwide averaged net 14 C production of 2.2 × 10 8 C 14 atoms cm − 2 was estimated, which is 3.7 times higher than the average annual 14 C production. The immediate appearance of the event in tree rings on both hemispheres suggests a short duration event of significantly less than 1 yr. [ABSTRACT FROM AUTHOR]