Scientists have discovered a massive spike in radiocarbon levels 14,350 years ago by analyzing ancient tree-rings. The radiocarbon spike was caused by a solar storm — the biggest ever identified.

In the study, Postdoctoral Researcher and Professor at the University of Oulu, Finland utilized their newly developed chemistry–climate model called SOCOL:14C-Ex, specifically designed to reconstruct solar particle storms under ancient glacial climate conditions. The model confirmed that the detected solar event was approximately 18 percent stronger than the notorious AD 775 event — until now the strongest solar storm ever recorded in tree-ring archives.

“Compared to the largest event of the modern satellite era — the 2005 particle storm — the ancient 12,350 BCE event was over 500 times more intense, according to our estimates”, explains Dr. Golubenko.

Other large solar storms have occurred around 7,176 BCE, 5,259 BCE, 663 BCE and 994 AD. A few other events are still under investigation.

The new chronology used wood samples recovered from the Drouzet River in the French Alps. Here the river is cutting into ancient sediments, exposing fossil tree stumps dating back over 14,300 years ago.

Looking at the individual tree-ring allows researchers to reconstruct environmental and chemical changes for almost every year the tree lived. By stacking sections of different trees together, scientists can reconstruct a tree-ring record spanning many thousands of years.

Coronal mass ejections or flares are powerful outbursts of high-energy particles. When such a flare hits Earth, it can cause a solar storm. The particles coming from the sun collide with gases in Earth’s atmosphere, forming new isotopes like the radioactive beryllium-10 and carbon-14 (or radiocarbon). Trees absorb these isotope, creating an isotopic record with their tree-rings.

“The ancient event in 12,350 BCE is the only known extreme solar particle event outside of the Holocene epoch, the past 12,000 years of stable warm climate”, says Golubenko. This discovery is not only of great importance to better understand how frequent extreme solar flares are, but also improves the use of radiocarbon to date archeological and biological samples. “Our new model lifts the existing limitation to the Holocene and extends our ability to analyze radiocarbon data even for glacial climate conditions.”

“Miyake events (distinct spikes in past radiocarbon levels) allow us to pin down exact calendar years in floating archaeological chronologies”, adds Usoskin. Radiocarbon signals from such events have already enabled researchers to precisely date Viking settlements in Newfoundland and Neolithic communities in Greece.

The largest observed solar storm occurred in 1859 and is known as the Carrington Event. Polar lights were observed during daylight as far as the equator. At the time, long before mobile telecommunications and the widespread use of electronic devices, damage was fortunately quite limited.The solar storm recorded in the fossil trees was an estimated ten to hundred times more powerful.

Today the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center monitors solar activity and its impact on our infrastructure. Electronics with no electromagnetic shielding are still at a high risk of interference and jamming. A similar massive event happening today could be catastrophic for our technology-based society.

The study,"New SOCOL:14C-Ex model reveals that the Late-Glacial radiocarbon spike in 12350 BC was caused by the record-strong extreme solar storm," was published in the journal Earth and Planetary Science Letters.

Additional material and interviews provided by the University of Oslo.