Global warming is messing with the accuracy of radiocarbon dating

A new study suggests that climate change is having a profound effect on the way scientists calculate the date of old objects. 

Frank Franklin II/File/AP
A reconstructed Neanderthal skeleton, right, and a modern human version of a skeleton, left, on display at the Museum of Natural History in New York. Fossil fuel emissions could soon make it impossible for radiocarbon dating to distinguish new materials from artifacts that are hundreds of years old.

Fossil-fuel emissions are not only messing with our future, but they are also messing with our ability to accurately date the past.

A new study has found that fossil-fuel emissions could impact radiocarbon dating, which is a vital research technique used to determine the age of organic artifacts in fields like archaeology, geology, and ecology. 

An analysis by Heather Graven, a climate-physics researcher at Imperial College London, finds that emissions from fossil fuels are artificially raising the carbon age of the atmosphere, which makes objects today seem much older than they are when scrutinized by a radiocarbon dater.

“Combustion of fossil fuels is “diluting the fraction of atmospheric carbon dioxide containing radiocarbon,” Dr. Graven told Environmental Research Web. “This is making the atmosphere appear as though it has ‘aged,’ or lost radiocarbon by radioactive decay occurring over time.”

The way radiocarbon dating works is by measuring the amount of carbon-14 decay, or how much the fraction of carbon-14 versus non-radioactive carbon has changed in an object. The older an object is, the less C-14 there is to be detected. That indicates how long the object has been around.

Fossil fuels like coal and oil are so old that they contain no carbon-14. When their emissions mix with the modern atmosphere, they flood it with non-radioactive carbon.

This is not the first time in modern history that carbon-14 levels have changed. According to the press release of 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 preindustrial proportions.

Although the study states that the carbon-dating technique is in actual risk, scientists say that reducing fossil fuel emission levels is still an option. Graven said that at current rates of fossil fuel emissions, increases in non-radioactive carbon could start to impact carbon dating by 2020.

“If we reduce emissions rapidly we might stay around a carbon age of 100 years in the atmosphere, but if we strongly increase emissions we could get to an age of 1,000 years by 2050 and around 2,000 years by 2100,” Graven told the BBC. “If we reduced fossil fuel emissions, it would be good news for radiocarbon dating.”

A wide array of scientific disciplines and industries use radiocarbon analyses. For example, it is used in dating of archaeological specimens and in forensic identification of human and wildlife tissues, including traded ivory.

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