The IntCal20 approach to radiocarbon calibration curve construction: a new methodology using Bayesian splines and errors-in-variables

Heaton, T.J., Blaauw, M., Blackwell, P.G., Bronk Ramsey, C., Reimer, P.J. and Scott, E.M. (2020) The IntCal20 approach to radiocarbon calibration curve construction: a new methodology using Bayesian splines and errors-in-variables. Radiocarbon, 62(4), pp. 821-863. (doi: 10.1017/RDC.2020.46)

Abstract

To create a reliable radiocarbon calibration curve, one needs not only high-quality data but also a robust statistical methodology. The unique aspects of much of the calibration data provide considerable modeling challenges and require a made-to-measure approach to curve construction that accurately represents and adapts to these individualities, bringing the data together into a single curve. For IntCal20, the statistical methodology has undergone a complete redesign, from the random walk used in IntCal04, IntCal09 and IntCal13, to an approach based upon Bayesian splines with errors-in-variables. The new spline approach is still fitted using Markov Chain Monte Carlo (MCMC) but offers considerable advantages over the previous random walk, including faster and more reliable curve construction together with greatly increased flexibility and detail in modeling choices. This paper describes the new methodology together with the tailored modifications required to integrate the various datasets. For an end-user, the key changes include the recognition and estimation of potential over-dispersion in 14C determinations, and its consequences on calibration which we address through the provision of predictive intervals on the curve; improvements to the modeling of rapid 14C excursions and reservoir ages/dead carbon fractions; and modifications made to, hopefully, ensure better mixing of the MCMC which consequently increase confidence in the estimated curve.

• Item Type: Articles
• Additional Information: T.J. Heaton is supported by Leverhulme Trust Fellowship RF-2019-140\9, “Improving the Measurement of Time Using Radiocarbon.”
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Scott, Professor Marian
• Authors: Heaton, T.J., Blaauw, M., Blackwell, P.G., Bronk Ramsey, C., Reimer, P.J., and Scott, E.M.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Statistics
• Journal Name: Radiocarbon
• Publisher: Cambridge University Press
• ISSN: 0033-8222
• ISSN (Online): 1945-5755
• Published Online: 12 August 2020
• Copyright Holders: Copyright © 2020 Arizona Board of Regents on behalf of the University of Arizona
• First Published: First published in Radiocarbon 62(4):821-863
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher