Mysterious radiation burst recorded in tree rings

Just over 1,200 years ago, the planet was hit by an extremely intense burst of high-energy radiation of unknown cause, scientists studying tree-ring data have found.

The radiation burst, which seems to have hit between AD 774 and AD 775, was detected by looking at the amounts of the radioactive isotope carbon-14 in tree rings that formed during the AD 775 growing season in the Northern Hemisphere. The increase in ¹⁴C levels is so clear that the scientists, led by Fusa Miyake, a cosmic-ray physicist from Nagoya University in Japan, conclude that the atmospheric level of ¹⁴C must have jumped by 1.2% over the course of no longer than a year, about 20 times more than the normal rate of variation...

The only known events that can produce a ¹⁴C spike are floods of γ-rays from supernova explosions or proton storms from giant solar flares. But neither seems likely, Miyake says, because each should have been large enough to have had other effects that would have been observed at the time.

A massive supernova, for example, should have been bright enough to produce a 'new' star visible even in the daytime, as was the case for two known supernovae in AD 1006 and AD 1054. Such an explosion would have needed to be brighter than either of these, Miyake says, because those events were not large enough to leave traces in the ¹⁴C record.

It is possible, he says, that the proposed event might have occurred in the far southern skies, where astronomers of the era wouldn't have seen it. But still, he says, if it did happen, today's X-ray and radio astronomers should have found signs of a "tremendously bright" remnant of the explosion.

Is carbon-14 used for dating ?

Yes

If so, would such bursts cause skewing in results?

Yes. The Theory behind carbon-14 dating relies on a constant rate of upper atmosphere ¹⁴C generation, based on a constant flux of solar protons converting nitrogen-14 to carbon-14.

The Practice attempts to compensate for variations in proton flux by ¹⁴C dating samples of know ages and making a table of ¹⁴C dates Vs calendar dates.

This is further complicated by plants having species specific varying rates of ¹⁴C uptake.

The upshot?

Carbon-14 data provides a fairly accurate estimate of age, providing the sample isn't so old that all the ¹⁴C has decayed.

How does the existence of additional carbon-14 affect dating? Do objects absorb new amounts from the burst? Do objects with carbon-14 convert slower if atmosphere contains more carbon-14?

Wondering about the process.

I get the estimating is pretty accurate, but wonder about the variables. Do these known and unknown variables have a significant +- range that causes dating to be within decades/centuries etc as we go further back in time without less corresponding data points? Could local conditions have significantly different rates than the assumed average?

Or are these fluctuations minor compared to the totals?

Not sure why but I would guess that such bursts might have larger affect when recent that if long ago.

Yes. More carbon-14 in the atmosphere means more CO₂ with carbon-14, that means that plants and anything that eats them absorb more carbon-14 and therefore have a higher level ¹⁴C and "look" younger.

The generally accepted error is ±50 years, with the known date corrections.

There are local variations and species to species variation (grasses absorb ¹⁴C at a different rate than broad leaves, for example)

I would also guess that the older the sample the larger the error, but don't know if a recent burst would have a larger effect.

I decided to do some research on Charlemagne and volcanoes, and the history of the period.

732 Arab defeat at Tours by Charles Martel
742 Charlemagne born in Aachen
753 Pepin the Short, his father, defeats Lombards bothering the pope.
754 Pepin the Short crowned by the pope
768 Pepin dies leaving Charlemagne and brother Carlman in charge
At some point Carlman died and Charlemagne engaged in various conquests
774 our target year — Charlemagne responds to the Pope who is under attack by neighbors. He is subsequently crowned by pope and becomes Holy Roman Emperor
814 Charlemagne dies

Then I looked at volcanoes to see if their was any influence there. Source - Encyclopedia of Volcanoes, Editor Haraldur Sigurdsson. These were listed for Japan as no other data goes back that far except in Europe which had no major volcanic events then. Some time ago I had read that there were over 30 famines in the 100 years following the death of Charlemagne which explained why the Carolingian renaissance faded away. Some of these famines lasted several years.
There were only 3 significant volcanoes (VEI-4 or more) for the period around the 774 event except ones in 751, 764, and 800. For the period during the 100 years after the death of Charlemagne in 814, we have 838, 874, 885, 886, 887, and 915, clearly a busier 100 years.

I would conclude that the 774 event was not caused by volcanoes, but the 100 year famine might have been influence to some extent. Another cause was wheat and rye spoilage cased by introduction of the barberry bush, and it’s rust, used in Arab cuisine, and wheat rust. Colder weather caused by increased volcanic cooling could have interected with these crop pests.

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