Studies have revealed that the atmospheric radiocarbon level prior to 1000 it was about 8 percent above what it is today.
Of more recent date was the overcompensating effect of man-made carbon-14 injected into the atmosphere during nuclear bomb testing.
The result was a rise in the atmospheric carbon-14 level by more than 50 percent.
It is clear that carbon-14 dates lack the accuracy that traditional historians would like to have.
There may come a time when all radiocarbon ages rest on firmer knowledge of the sample’s original carbon-14 level than is now available.