"The radiocarbon dating technique may significantly underestimate the age of sediment for samples older than 30,000 years,” said the authors of the report from the Chinese Academy of Sciences and Germany’s Leibniz Institute for Applied Geophysics.
Since the 1960s, scientists have started accounting for the variations by calibrating the clock against the known ages of tree rings.
As scientists who study earth’s (relatively) modern history rely on this measurement tool to place their findings in the correct time period, the discovery that it is unreliable could put some in a quandary.
For instance, remnants of organic matter formerly held up as solid evidence of the most recent, large-scale global warming event some 40,000 years ago may actually date back far earlier to a previous ice age.
Prior to that, they had to depend on more rudimentary and imprecise methods, such as counting the number of rings on a cross-section of tree trunk.
This all changed in the 1940s when US chemist Willard Libby discovered that carbon-14, a radioactive isotope, could be used to date organic compounds.