Carbon dating tree ring calibration
It was unclear for some time whether the wiggles were real or not, but they are now well-established.These were superseded by the INTCAL series of curves, beginning with INTCAL98, published in 1998, and updated in 2004, 2009, and, most recently, 2013.In the example CALIB output shown at left, the input data is 1270 BP, with a standard deviation of 10 radiocarbon years.The curve selected is the northern hemisphere INTCAL13 curve, part of which is shown in the output; the vertical width of the curve corresponds to the width of the standard error in the calibration curve at that point.This output can be compared with the output of the intercept method in the graph above for the same radiocarbon date range.
Deriving a calendar year range by means of intercepts does not take this into account.
Where the curve varies significantly both up and down, a single radiocarbon date range may produce two or more separate calendar year ranges.
Example t, in red on the graph, shows this situation: a radiocarbon age range of about 1260 BP to 1280 BP converts to three separate ranges between about 1190 BP and 1260 BP.
A third possibility is that the curve is flat for some range of calendar dates; in this case, illustrated by t The method of deriving a calendar year range described above depends solely on the position of the intercepts on the graph.
These are taken to be the boundaries of the 68% confidence range, or one standard deviation.