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Radiocarbon dating (or simply carbon dating) is a radiometric dating technique that uses the decay of carbon-14 (14C) to estimate the age of organic materials, such as wood and leather, up to about 58,000 to 62,000 years Before Present (BP, present defined as CE 1950).

Carbon dating was presented to the world by Willard Libby in 1949, for which he was awarded the Nobel Prize in Chemistry. The Earth’s atmosphere contains various isotopes of carbon, roughly in constant proportions.

The half-life of 14C (the time it takes for half of a given amount of 14C to decay) is about 5,730 years, so its concentration in the atmosphere might be expected to reduce over thousands of years.

The straight line at 45° indicates a 1:1 transformation of the radiocarbon age into an uncalibrated calendar date.Calibration curve for the radiocarbon dating scale. The calibration method also assumes that the temporal variation in 14C level is global, such that a small number of samples from a specific year are sufficient for calibration. Significantly, in the ill-behaved regions of the calibration curve, increasing the precision of the measurements does not have a significant effect on increasing the accuracy of the dates. Marine Effect This effect is not uniform – the average effect is about 440 years, but there are local deviations of several hundred years for areas that are geographically close to each other.The carbon exchange between atmospheric CO2 and carbonate at the ocean surface is also subject to fractionation. Reservoir Effects Libby’s original exchange reservoir hypothesis assumed that the exchange reservoir is constant all over the world, but it has since been discovered that there are several causes of variation in the 14C/12C ratio across the reservoir. Marine Effect The CO2 in the atmosphere transfers to the ocean by dissolving in the surface water as carbonate and bicarbonate ions; at the same time the carbonate ions in the water are returning to the air as CO2.This exchange process brings14C from the atmosphere into the surface waters of the ocean, but the 14C thus introduced takes a long time to percolate through the entire volume of the ocean. Hard Water Effect If the carbon in freshwater is partly acquired from aged carbon, such as rocks, then the result will be a reduction in the 14C/12C ratio in the water. Volcanoes Volcanic eruptions eject large amounts of carbon into the air.These include the main stable isotope (12C) and an unstable isotope (14C).