"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.
“Thus it is necessary to pay [special] attention when using such old carbon data for palaeoclimatic or archaeological interpretations," they added.
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.
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.
Since 1947, scientists have reckoned the ages of many old objects by measuring the amounts of radioactive carbon they contain.
New research shows, however, that some estimates based on carbon may have erred by thousands of years.
Other corrections must be made to account for the proportion of throughout the biosphere (reservoir effects).
Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.
Their work was detailed in a paper in the latest issue of the journal .
For over 50 years, scientists and researchers have relied on carbon dating to find the exact age of organic matter.
The technique hinges on carbon-14, a radioactive isotope of the element that, unlike other more stable forms of carbon, decays away at a steady rate.