Carbon 14 dating organic material
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.
In addition to spatial variations of the carbon-14 level, the question of temporal variation has received much study.
A 2 to 3 percent depression of the atmospheric radioactive-carbon level since 1900 was noted soon after Libby’s pioneering work, almost certainly the result of the dumping of huge volumes of carbon-14-free carbon dioxide into the air through smokestacks.
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.
The occurrence of natural radioactive carbon in the atmosphere provides a unique opportunity to date organic materials as old as roughly 60,000 years.
Unlike most isotopic dating methods, the conventional carbon-14 dating technique is not based on counting daughter isotopes.
Since Libby’s foundational studies, tens of thousands of carbon-14 measurements of natural materials have been made.
Expressed as a fraction of the contemporary level, they have been mathematically converted to ages through Improvements in measurement accuracy and the ever-mounting experience in applying carbon-14 dating have provided superior and more voluminous data with which to better answer Libby’s original questions.
And, if so, has today’s uniform level prevailed throughout the recent past?