The improvements to these curves are based on new data gathered from tree rings, varves, coral, and other studies.Significant additions to the datasets used for INTCAL13 include non-varved marine foraminifera data, and U-Th dated speleothems.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was unclear for some time whether the wiggles were real or not, but they are now well-established.These were superseded by the INTCAL series of curves, beginning with INTCAL98, published in 1998, and updated in 2004, 2009, and, most recently, 2013.

These can be accessed online; they allow the user to enter a date range at one standard deviation confidence for the radiocarbon ages, select a calibration curve, and produce probabilistic output both as tabular data and in graphical form.

This output can be compared with the output of the intercept method in the graph above for the same radiocarbon date range.

For a set of samples with a known sequence and separation in time such as a sequence of tree rings, the samples' radiocarbon ages form a small subset of the calibration curve.

A normal distribution is shown at left; this is the input data, in radiocarbon years.

The central darker part of the normal curve is the range within one standard deviation of the mean; the lighter grey area shows the range within two standard deviations of the mean.

These can be accessed online; they allow the user to enter a date range at one standard deviation confidence for the radiocarbon ages, select a calibration curve, and produce probabilistic output both as tabular data and in graphical form.This output can be compared with the output of the intercept method in the graph above for the same radiocarbon date range.For a set of samples with a known sequence and separation in time such as a sequence of tree rings, the samples' radiocarbon ages form a small subset of the calibration curve.A normal distribution is shown at left; this is the input data, in radiocarbon years.The central darker part of the normal curve is the range within one standard deviation of the mean; the lighter grey area shows the range within two standard deviations of the mean.The output is along the bottom axis; it is a trimodal graph, with peaks at around 710 AD, 740 AD, and 760 AD.