May 25, 2020 | David F. Coppedge

Guesswork in Carbon Dating Exposed

It’s the best-known radiometric dating technique for recent events, but it relies on numerous shaky input measures.

Radiocarbon dating is the “archaeological workhorse” of dating techniques but is the horse overworked? In her article in Nature May 19, Nicola Jones puts the best hoof forward on this widely-trusted dating technique, but also exposes numerous assumptions and educated guesses that go into the method. Radiocarbon dating is getting a “major reboot,” she says, and the consequences will change history: “A long-anticipated recalibration of radiocarbon dating could shift the age of some prehistoric samples hundreds of years.”

Radiocarbon dating — a key tool used for determining the age of prehistoric samples — is about to get a major update. For the first time in seven years, the technique is due to be recalibrated using a slew of new data from around the world. The result could have implications for the estimated ages of many finds — such as Siberia’s oldest modern human fossils, which according to the latest calibrations are 1,000 years younger than previously thought.

People who hear about radiocarbon dates may be unaware that the method needs “recalibration” every once in awhile. Every time the C14 calibration changes, so do the dates that archaeologists, paleontologists and evolutionists thought they knew. The date revisions become more extreme the farther back scientists look. Dates for prehistoric events, which cannot be reconciled with written records, become all the more sketchy.

The work combines thousands of data points from tree rings, lake and ocean sediments, corals and stalagmites, among other features, and extends the time frame for radiocarbon dating back to 55,000 years ago — 5,000 years further than the last calibration update in 2013.

What kinds of factors go into recalibration? Jones mentions several. Each category of data adds to the assumptions that must be included in the final calibration curve.

  • Tree rings: correlating rings between trees can include errors
  • Lake and ocean sediments: this assumes that scientists fully understand cyclic deposits
  • Corals: do scientists fully understand the growth rates of coral reefs?
  • Stalagmites: if the drip rate changes, or the mineral concentrations change, what then?
  • Nuclear tests: the post-WWII atomic bomb tests radically altered the amount of C14, and required an adjustment
  • Pollution: ditto for the burning of fossil fuels, which has not been uniform
  • Wobbles: “and there are non-anthropogenic wobbles going much further back”
  • Magnetic field reversals: these change the C14 concentration, but the reversals must be dated, too
  • Oceans: “The oceans also suck up carbon — a little more so in the Southern Hemisphere, where there is more ocean — and circulate it for centuries, further complicating things.”

Clearly, the early calibration curves by Willard Libby in the 1950s ignored some these factors. The dates obtained in the early days of radiocarbon dating contained substantial errors from unknowns he did not consider. How confident are physicists today about their knowledge of “unknown unknowns” that could revise the curves yet again, perhaps substantially?

Although the recalibration mostly results in subtle changes, even tiny tweaks can make a huge difference for archaeologists and paleo-ecologists aiming to pin events to a small window of time. A new calibration curve “is of key importance” for understanding prehistory, says Tom Higham, archaeological chronologist and director of the Oxford Radiocarbon Accelerator Unit, UK.

Hezekiah’s Tunnel brought water into the city walls. Photo by David Coppedge.

Dates back a few thousand years can be fairly confident, when they can be correlated with written records and agreed-on dates, such as the date King Hezekiah dug the water tunnel in Jerusalem around 750 BC. But how confident can scientists be about things that were never witnessed by humans, from before any eyewitness accounts existed? Consider some other possible sources of error in prehistoric events that were not mentioned Jones’ article:

  • Cosmic ray showers, from supernovas or fast radio bursts
  • Changes to atmospheric or oceanic circulation patterns
  • Magnetic field anomalies (see example at Fox News Science)
  • Meteor impacts
  • Extensive wildfires
  • Solar flares
  • Volcanic eruptions in land or under the sea
  • Human error counting tree rings
  • Unknowns affecting C14 production
  • Unknowns affecting the decay rate

Radiocarbon, in theory, can only provide estimates up to about 100,000 years max. Anything that old would require counting individual C14 atoms in the sample, because the decay half-life of 5,730 years would eliminate every C14 atom by around that time. Obviously the technique becomes very imprecise the older one goes.

Even dating historical events cannot provide certainty: “the calibration curve wiggles around a lot,” one expert says. Regarding the date for the eruption of Santorini, which occurred sometime around 1600 BC, Jones writes:

So the two groups still disagree, says Reimer, but less so, and with more complications. “Some of them are still arguing,” says Reimer. “There’s no hard answer.

If that is the case for eyewitness events less than 4,000 years ago, how much more uncertain are events that were not witnessed that the method says are tens of thousands of years old? Indirect methods that factor into the radiocarbon calibration curve must be calibrated, too. Assumptions and unknowns accumulate, contributing to the total error. So when paleoanthropologists agree on a date for a certain skull at 55,000 years old, do they really “know” that for sure, or is their confidence a sociological effect among experts bluffing to convince themselves that they know?

All dating methods involve unproveable assumptions. When assumptions calibrate assumptions, one cannot arrive at certainty. The problem of “unknown unknowns” is particularly troublesome. Secular geologists and paleontologists repudiate the Biblical record of Genesis, for instance, but what if the global Flood radically altered the C14 in the atmosphere? It could lead to highly inflated dates for anything before 4,000 to 5,000 years ago. This is a complication that creationists have written about, but is rejected by secular moyboys. It implies that secular dating is not only a function of unknowns, but also of selective religious and political biases.

These are matters that truth seekers should consider before accepting an expert’s word for a bluffing claim that ‘such-and-such a Neanderthal skull is 68,798 years old, plus or minus 15 minutes, as shown by radiocarbon dating and uranium-lead dating of stalactites in the cave where it was found.’ Don’t be a sucker. Ask questions.

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