Since the 1940s, scientists have used carbon dating to determine the age of fossils, identify vintages of wine and whiskey, and explore other organic artifacts like wood and ivory. The technique involves comparing the level of one kind of carbon atom—one that decays over time—with the level of another, more stable kind of carbon atom.
The approach was a sensation when it was introduced. The chemist who developed carbon dating, Willard Libby, won the Nobel Prize for his work. “Seldom has a single discovery in chemistry had such an impact on the thinking in so many fields of human endeavour,” one of Libby's colleagues wrote at the time, according to the Nobel Foundation.
Today, carbon dating is used so widely as to be taken for granted. Scientists across countless disciplines rely on it to date objects that are tens of thousands of years old.
That may soon change.
An analysis by Heather Graven, a climate-physics researcher at Imperial College London, finds that today's rate of fossil-fuel emissions is skewing the ratio of carbon that scientists use to determine an object's age. Combustion of fossil fuels is “diluting the fraction of atmospheric carbon dioxide containing radiocarbon,” 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.”
By 2050, Graven wrote in a paper published this month in the Proceedings of the National Academy of Sciences, the large amount of carbon dioxide in the atmosphere will make new organic material appear to be 1,000 years old based on today’s carbon-dating models. By the year 2100, the atmosphere will have a radiocarbon age of 2,000 years old.
The implications of this forecast are huge. If Graven's calculations are correct, carbon dating as we know it today will no longer be reliable by the year 2030. Which means scientists won’t be able to use carbon dating to distinguish between new materials and artifacts that are hundreds or thousands of years old. (Carbon dating is already limited in scope because older artifacts have to be dated using other methods. For instance, Lucy, the 3.2-million-year-old human ancestor, was dated by scientists who studied the volcanic flows and ashes in deposits where her bones were found.)
“Given current emissions trends, fossil fuel emission-driven artificial ‘aging’ of the atmosphere is likely to occur much faster and with a larger magnitude than previously expected,” Graven wrote. “This finding has strong and as yet unrecognized implications for many applications of radiocarbon in various fields, and it implies that radiocarbon dating may no longer provide definitive ages for samples up to 2,000 [years] old.”