Even after nuclear weapon testing was banned, the bomb effect still remains.
According to literature, the excess carbon 14 produced during nuclear weapons testing has already decreased due in part to the global carbon exchange cycle.
The level of bomb carbon was about 100% above normal levels between 19.
The level of bomb carbon in the northern hemisphere reached a peak in 1963, and in the southern hemisphere around 1965.
Burning of large quantities of fossil fuels like coal, referred as the Suess effect, had significantly lowered the radiocarbon concentration of the atmospheric carbon reservoir.
In contrast, nuclear weapons testing in the 1950s and 1960s dramatically increased the level of carbon 14 in the atmosphere.
Nuclear weapons testing brought about a reaction that simulated atmospheric production of carbon 14 in unnatural quantities.
One assumption is that the global levels of carbon 14 (also called radiocarbon) in the atmosphere has not changed over time.
The phenomenon is often referred to as the bomb effect.
The bomb effect refers to the phenomenon that produced “artificial” radiocarbon in the atmosphere due to nuclear bombs.
Mixing and exchanges happen between the atmosphere and the biosphere until such time that equilibrium is established.
Radiocarbon dating rests heavily on this assumption such that other sources of carbon 14 had, at first, not been considered nor accounted for.