Difference between radiometric carbon dating
The logical conclusion from this was that in order to obtain a modern radiocarbon reference standard, representing the radiocarbon activity of the 'present day', one could not very well use wood which grew in the 1900's since it was affected by this industrial effect.
Thus it was that 1890 wood was used as the modern radiocarbon standard, extrapolated for decay to 1950 AD.
Hans Suess (1955) discovered the industrial effect (also called after him) in the 1950's.
A number of researchers found that the activity they expected from material growing since 1890 AD was lower.
Radiocarbon samples which obtain their carbon from a different source (or reservoir) than atmospheric carbon may yield what is termed apparent ages.The effect has been suggested as providing dates in error for the eruption of Thera which has been linked to the demise of the Minoan civilisation in the Aegean.