Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.
Organisms capture a certain amount of carbon-14 from the atmosphere when they are alive.
By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.
Learn More The occurrence of contamination can be natural or artificial.
Natural contamination pertains to the introduction of contaminants to the sample by its surrounding material.
The recalibrated clock won’t force archaeologists to abandon old measurements wholesale, says Bronk Ramsey, but it could help to narrow the window of key events in human history.
“If you’re trying to look at archaeological sites at the order of 30,000 or 40,000 years ago, the ages may shift by only a few hundred years but that may be significant in putting them before or after changes in climate,” he says.For example, bone samples can be contaminated by the presence of limestone or organic acids in the soil (like humic or fulvic acids) where the bones were found.Another example of a natural contaminant is plant root penetration on wood, charcoal, or soil.Any carbon-containing material that affects the carbon 14 content of any given sample is therefore a contaminant.Important Note on Pretreatment – It is important to understand the pretreatments which are going to be applied to samples since they directly affect the final result.Artificial contamination refers to the introduction of contaminants by man during the collection, field conservation, or packaging of the samples.