Fossil fuel emissions interfering with radiocarbon dating, scientists say

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Researchers have suggested that increase fossil fuel emissions may eventually make it impossible for scientists to use radiocarbon dating techniques to distinguish between old artefacts that are genuinely hundreds of years old and new materials.

Researchers reveal in a paper published in the journal PNAS, that fossil fuel emissions are diluting radioactive carbon-14 and artificially raising the radiocarbon ‘age’ of the atmosphere. Researchers claim through their new study that some of the applications that use radiocarbon dating will be affected over the course of next few decades and the effect will be depended on the amount of emissions.

Some of the applications of radiocarbon dating include analysing archaeological finds, detecting fraudulent works of art, detection of illegal ivory trading, regeneration of brain cells in neurological patients among others.

Carbon-14 is a rare, but naturally occurring, radioactive type of carbon that decays over thousands of years. The way radiocarbon dating works is that it measures how much the fraction of carbon-14 versus non-radioactive carbon in an object has changed and therefore how long the object has been around.

In case of fossil fuels like coal and oil, there is no carbon-14 because of their age. When these fossil fuels are burnt, their emissions mix with the modern atmosphere and flood it with non-radioactive carbon. The direct effect of this is that it makes the atmosphere appear older and this in turn is reflected in the tissues of plants taking in CO2 during photosynthesis, and their products such as cottons.

Researchers say that if the current rate of fossil fuel emissions continue, by 2050 a new T-shirt would have the same radiocarbon date as a robe worn by William the Conqueror a thousand years earlier. If fossil fuel emissions were rapidly curbed, the new t-shirt would only have the same radiocarbon age as something 100 years old, according to the study.

The fraction of carbon-14 in the atmosphere decreased after the Industrial Revolution with the rise of fossil fuel combustion. But in the 1950s and 60s, nuclear weapons testing caused a sharp increase. Since then atmospheric observations show the levels have been dropping, and are now close to the pre-industrial proportions.

The new study indicates that by 2020, the fraction of carbon-14 could drop to such an extent that radiocarbon dating will start to be affected.

“We can see from atmospheric observations that radiocarbon levels are steadily decreasing. How low they go depends on changes in our fossil fuel emissions,” said Dr Heather Graven from the Department of Physics and the Grantham Institute – Climate Change and Environment at Imperial College London.