Radiocarbon dating is set to become more accurate than ever after an international team of scientists improved the technique for assessing the age of historical objects.
The team of researchers at the universities of Sheffield, Belfast, Bristol, Glasgow, Oxford, St Andrews and Historic England, plus international colleagues, used measurements of nearly 15,000 samples of objects dating back to 60,000 years ago as part of a seven-year project.
They used the measurements to create new international curves for radiocarbon calibration (IntCal), which are fundamental across the scientific spectrum for accurately dating artifacts and making predictions about the future. Radiocarbon dating is essential for fields such as archeology and geosciences to date everything from the oldest modern human bones to historical climate patterns.
Archaeologists can use this knowledge to restore historical monuments or study the decline of the Neanderthal, while geoscientists at the Intergovernmental Panel on Climate Change (IPCC) rely on the curves to find out what the climate was like in the past. was to better understand and prepare for future changes.
Professor Paula Reimer, of Queen’s University Belfast and head of the IntCal project, said: “Radiocarbon dating has revolutionized the field of archeology and environmental science. As we improve the calibration curve, we learn more about our history. The IntCal “Calibration curves are the key to help answer big questions about the environment and our place in it.”
The team of researchers has developed three curves depending on where the object to be dated was found. The new curves, to be published in Radiocarbon, are IntCal20 for the Northern Hemisphere, SHCal20 for the Southern Hemisphere, and Marine20 for the oceans of the world.
Dr Tim Heaton, from the University of Sheffield and lead author on the Marine20 curve, said: “This is a very exciting time to work in radiocarbon. Developments in the field have made it possible to really advance our understanding. I look forward to seeing what new insights into our past these recalculated radiocarbon timelines provide. ”
The previous calibration curves for radiocarbon developed in the past 50 years were highly dependent on measurements taken from pieces of wood covered from 10 to 20 years large enough to be tested for radiocarbon.
Advances in radiocarbon testing mean that the updated curves instead use small samples, such as tree rings that last just one year, which provide previously impossible precision and detail in the new calibration curves. In addition, improvements in the understanding of the carbon cycle have meant that the curves have now been extended to the limit of radiocarbon technology 55,000 years ago.
Radiocarbon dating has been the most widely used approach to dating for the last 55,000 years and supports archaeological and environmental science. It was first developed in 1949. It depends on two isotopes of carbon called stable 12C and radioactive 14C.
While a plant lives as an animal, it absorbs new carbon, which has the same ratio of these isotopes as the atmosphere at that time. But once an organism dies it stops absorbing new carbon, the stable 12C remains but the 14C decay at a known rate. By measuring the ratio of 14C to 12C left in an object, the date of its death can be estimated.
If the level of atmospheric 14C were constant, this would be easy. However, it has fluctuated greatly throughout history. To date organisms, scientists just need a reliable historical record of their variation to accurately transform 14C measurements at an exact age. The new IntCal curves provide this link.
The curves are made based on the collection of a large number of archives that store past radiocarbon, but can also be dated by another method. Such archives include tree rings dating to 14,000 years ago, stalagmites found in caves, corals from the sea, and cores drilled from lake and ocean sediments. In total, the new curves were based on nearly 15,000 measurements of radiocarbon taken from objects as old as 60,000 years.
Alex Bayliss, Head of Scientific Dating at Historic England, said: ‘Accurate and high precision with radiocarbon dating underpins the public’s enjoyment of the historic environment and enables better preservation and protection.
“The new curves have important international implications for archaeological methodology, and for practices in the preservation and understanding of wooden built heritage.”
Darcell Kaufman of the IPCC said: “The IntCal series of curves are critical for providing a perspective on past climate that is essential to our understanding of the climate system, and a baseline for modeling future changes.”
