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.
Plants which grow in the vicinity of active volcanic fumeroles will yield a radiocarbon age which is too old. (1980) measured the radioactivity of modern plants growing near hot springs heated by volcanic rocks in western Germany and demonstrated a deficiency in radiocarbon of up to 1500 years through comparison with modern atmospheric radiocarbon levels.Similarly, this effect has been noted for plants in the bay of Palaea Kameni near the prehistoric site of Akrotiri, which was buried by the eruption of the Thera volcano over 3500 years ago (see Weninger, 1989).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.In the northern hemisphere the amount of artificial carbon in the atmosphere reached a peak in 1963 (in the southern hemisphere around 1965) at about 100% above normal levels.
Since that time the amount has declined owing to exchange and dispersal of C14 into the Earth's carbon cycle system.
The effect of this has been to almost double the amount of C14 activity in terrestrial carbon bearing materials (Taylor, 1987).
De Vries (1958) was the first person to identify this 'Atom Bomb' effect.
The volcanic effect has a limited distance however. (1980) found that at 200 m away from the source, plants yielded an age in agreement with that expected.
They suggested that the influence of depleted CO2 declined rapidly with increasing distance from the source.
In this page, we consider natural reservoir variations and variations brought about by human interaction].