Fossil Fuel Emissions May Cause Radiocarbon Dating to No Longer Work

First Posted: Jul 22, 2015 09:47 AM EDT

Fossil fuel emissions may actually complicate radiocarbon dating. Scientists have found that carbon released by burning fossil fuels is diluting radioactive carbon-14, which may make it impossible to distinguish new materials from artifacts that are hundreds of years old.

Radiocarbon measurements have uses that range from analyzing archaeological finds to detecting fraudulent works of art to find illegal ivory trading. Yet these uses could no longer be possible if carbon continues to enter our planet's atmosphere.

"If we reduced fossil fuel emissions, it would be good news for radiocarbon dating," said Heather Graven, one of the researchers, in a news release.

Carbon-14 is a rare, but naturally occurring radioactive type of carbon that decays over thousands of years. Radiocarbon dating, in particular, works by measuring 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. Fossil fuels, like coal and oil, are old enough that they contain no carbon-14. This means that when they enter the atmosphere, they flood it with non-radioactive carbon.

In radiocarbon dating terms, the effect that greenhouse gases have makes the atmosphere appear older. This is reflected in the tissues of plants taking in CO2 during photosynthesis, and their products such as cottons. In fact, at the rate fossil fuel emissions are going, by 2050 a new T-shirt would have the same radiocarbon date as a robe worn by William the Conqueror a thousand years earlier.

"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 Graven.

The findings are published in the journal Proceedings of the National Academy of Sciences.