Challenges and opportunities for the construction of the next IntCal and SHCal radiocarbon calibration curves

Radiocarbon (14C) provides the most frequently used approach to dating the last 55 000 years. However, owing to fluctuations in past levels of 14C, all radiocarbon dating requires calibration to convert the 14C measurement obtained from a sample into a calendar age. This is achieved by comparing the sample's 14C determination against a suitable calibration curve constructed from 14C measurements of reference samples that have known, or independently estimated, calendar age. The internationally agreed standards for these 14C calibration curves are provided by the IntCal working group, which ensures comparability between derived chronologies. The IntCal curves are periodically updated as significant new reference 14C datasets and Earth system insights become available. Since the last IntCal update in 2020, we have seen a substantial increase in the volume of reference 14C datasets available for use in calibration curve construction, in particular, measurements of annual growth rings in trees that represent individual calendar years. The rapid increase in reference 14C datasets provides exciting new opportunities for the radiocarbon community, but also presents challenges to ensure that 14C calibration remains reliable and accurate for all users. In this paper, we present some of these challenges and opportunities, and discuss some of the ideas under consideration for the next set of IntCal curve updates, which are planned to be released within the next year. This article is part of the Theo Murphy meeting issue 'Radiocarbon and cosmic radiation events'.