They look for carbon 14 isotope spikes in ancient tree rings, and compare to beryllium 10 and chlorine 36 in ice cores
We've developed a fairly decent record of events back to 14,000 years ago
Look up 'Miyake events'
We've developed a fairly decent record of events back to 14,000 years ago
Look up 'Miyake events'
This keeps getting more interesting!
> Six diverse historical occurrences, from archaeological sites to natural disasters, have thus been dated to a specific year, using Miyake events as benchmarks and counting tree rings. For example, wooden houses in the Viking site at L'Anse aux Meadows in Newfoundland were dated by finding the 993 CE Miyake event and then counting tree rings, which showed that the wood is from a tree felled in 1021 CE.[
> At present, five significant events are known (7176 BCE, 5259 BCE, 660 BCE, 774 CE, 993 CE)
Seems like the Carrington event wasn't strong enough to be considered a Miyake event.