A Warning from Trees: Miyake Events

14,300 years ago, a pine forest in France bore witness to an event that has never been experienced in modern times: a bombardment of solar particles so fierce that it would likely knock out all communications satellites and fry power grids across the globe if it were to happen today. While we often point to the Carrington Event of 1859, (that knocked out all telegraph communications around the world), as a worst-case scenario, for solar storms, the 774-75 AD storm was at least 10 times stronger.

“It would be a catastrophe,” says Edouard Bard, a climatologist at the Collège de France in Paris, who led a new study that discovered the ancient event.

Bard and his colleagues made their finding by analyzing tree rings in a buried forest, exposed at the edge of riverbeds in the French Alps. The signs they uncovered point to what’s called a “Miyake Event” named after Fusa Miyake, a physics doctoral student at Nagoya University in Japan, who made the discovery in 2012 while studying rings in the stump of a 1900-year-old Japanese cedar. One ring, in particular, drew her attention. Grown in the year 774–75 AD, it contained a 12% jump in radioactive carbon-14 (14C), about 20 times greater than ordinary fluctuations from cosmic radiation. Other teams confirmed the spike in wood from Germany, Russia, the United States, Finland, and New Zealand. Whatever happened, trees all over the world experienced it.

Most researchers think it was an extraordinary solar storm, but it’s not clear that all Miyake Events are caused by the sun because supernova explosions and gamma-ray bursts also produce carbon-14 spikes. However, evidence leans towards solar storms.