From NOVA: “Fossil Fuels Are Destroying Our Ability to Study the Past”

PBS NOVA

NOVA

21 Jul 2015
Tim De Chant

It’s been used to date objects tens of thousands of years old, from fossil forests to the Dead Sea Scrolls, but in just a few decades, a tool that revolutionized archaeology could turn into little more than an artifact of a bygone era.

Radiocarbon dating may be the latest unintended victim of our burning of fossil fuels for energy. By 2020, carbon emissions will start to affect the technique, and by 2050, new organic material could be indistinguishable from artifacts from as far back as AD 1050, according to research by Heather Graven, a lecturer at Imperial College London.

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The Great Isaiah Scroll, one of the seven Dead Sea Scrolls, has been dated using the radiocarbon technique.

The technique relies on the fraction of radioactive carbon relative to total carbon. Shortly after World War II, Willard Libby discovered that, with knowledge of carbon-14’s predictable decay rate, he could accurately date objects that contained carbon by measuring the ratio of carbon-14 to all carbon in the sample. The less carbon-14 to total carbon, the older the artifact. Since only living plants and animals can incorporate new carbon-14, the technique became a reliable measure for historical artifacts. The problem is, as we’ve pumped more carbon dioxide into the atmosphere, we’ve unwittingly increased the total carbon side of the equation.

Here’s Matt McGrath, reporting for BBC News:

At current rates of emissions increase, according to the research, a new piece of clothing in 2050 would have the same carbon date as a robe worn by William the Conqueror 1,000 years earlier.

“It really depends on how much emissions increase or decrease over the next century, in terms of how strong this dilution effect gets,” said Dr Graven.

“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.”

Scientists have been anticipating the diminished accuracy of radiocarbon dating as we’ve continued to burn more fossil fuels, but they didn’t have a firm grasp of how quickly it could go south. In the worst case scenario, we would no longer be able date artifacts younger than 2,000 years old. Put another way, by the end of the century, a test of the Shroud of Turn wouldn’t be able to definitively distinguished the famous piece of linen from a forgery made today.

See the full article here.

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