At first I was a bit confused why this was a big deal given that Cosmogenic Radionuclide Dating[1] (which is based on cosmic rays) has been a thing for a while. But it turns out this uses an entirely different cosmogenic method based on atmospheric carbon (combined with Dendochronology from the tree rings). Very cool!
This is very cool. The article is worth a read, but the TL;DR is that a high cosmic ray event left a mark in a specific growth ring on trees, and so it is possible to 1) loosely date a piece of wood used in a building to within a few decades using carbon dating and then 2) precisely date when it was cut down by counting how far the marked growth ring is to the edge of the tree.
I remember a while back someone managed to build a many hundred year sequence of growth rings by analyzing all of the incremental construction in one town and aligning tree rings from one piece of wood with the same rings in newer or older pieces, using software not unlike reassembling DNA fragments, but with growth rings.
The maximum is not just many hundred years. The Hohenheimer Jahrringkalender based on pine trees of central Europe goes back 12,460 years and people are working on extending it backwards another 2,000 years.[1]
Such calendars are anchored in the present and require an unbroken backward chain of quality wood samples from the same region and the same tree species.
The advantage of the new method based on Miyake events is that such events are so rare that they can be used to determine an anchor point in the past, provided that external evidence for a piece of wood can be used to make plausible a time period for it in which there was only one such event whose date is known from external evidence, such as ice core drills.[2] From this single Miyake event tree ring one can then work one's way forwards and backwards to establish a tree ring chronology that does not need to be anchored in the present.
One can even imagine that in the future it might be possible to create such chronologies without a good time frame for a single Miyake event, if two Miyake events are found at a certain distance from each other in an otherwise unanchored tree ring chronology.
[2] Confirmed Miyake events took place in 7176 BCE, 5259 BCE, 660 BCE, 774 CE and 993 CE. Other candidates for Miyake events are 12,350 BCE, 5410 BCE, 1052 CE and 1279 CE. See: https://en.wikipedia.org/wiki/Miyake_event
I don't know about the rest of the world, but in the UK dendrochronology is widely used for dating wood structures. In England they have a database that can date (some) trees back basically to any time of human existence in England. In Ireland their data goes back before 5000 BCE.
Mick "the Dig" Worthington who was the resident excavation supervisor on Time Team, went on to become an dendrochronologist and has built a series of base chronologies for the East Coast of America stretching from Maine down to Georgia:
Interesting. This should also shed some light on the [Dispilio Tablet](https://en.m.wikipedia.org/wiki/Dispilio_Tablet) - which seems to feature some kind of archaic script (the oldest yet found, if the dating is correct) They have not yet published though.
Accuracy. Using carbon dating for things that long ago gives you only a rough idea. Counting tree rings is precise, but tree ring chronologies are relative, unless they can be continued to the present or anchored to an event with a known date. These researchers did the latter, using a global and well-dated Miyake event.
The innovation is to find traces of a global cosmic-ray event with which to connect the dating of objects in one local area, Greece, where the dendrochronological data is not continuous, with those in far away local areas, for example England/Ireland, where we have continuous dendrochronological data
There's an endless supply of organic, free range cosmic rays that rain down from the sky. They've been scientifically useful in many ways, not just this one.
TLDR: High cosmic ray events cause uptick in atmospheric carbon-14. This is deposited in yearly growth rings of trees and can be used as global alignment points for tree ring dating.
[1]: https://en.m.wikipedia.org/wiki/Surface_exposure_dating