The future of the past: A robust framework for the upgrade and development of the international radiocarbon calibration/comparison curves

许多考古学和地球科学的研究人员通过放射性碳测年从他们工作的保存矿床中获得植物或动物遗骸的时间尺度。然而，放射性碳测年与日历测年并不相同，必须根据植物或动物生存时大气中放射性碳含量的变化进行校正。这种将放射性碳年代转换为日历年龄的方法，称为校准，并不是一种简单的校正。放射性碳年代测定的校准只能通过与合适的校准曲线进行比较来完成。这些曲线是基于已知日历年龄的样品（如树木年轮）中放射性碳的测量，或者在不太严格的意义上，基于其他类型的样品，其中可以使用独立的测年方法。对于在海洋中生长的样品，如贝壳和珊瑚，需要单独的校准曲线来解释海水循环的变化，这可能会从海洋深处带来“旧”水（水库效应）。校准曲线已定期完善，以提供更好的日历年龄估计。2004年，IntCal工作组利用放射性碳测年的树木年轮和独立测年的海洋样本构建了新的校准曲线，其中树木年轮可追溯到距今12，400年前，海洋样本可追溯到距今26，000年前。这些曲线不是简单地对数据进行平均，而是使用统计工具（模型）构建的，这些工具允许所用样本的日历年龄以及放射性碳年代的不确定性。当时超过26，000年前的数据并不一致，因此没有提供曲线，但估计数据集与潜在的真实曲线有多大差异。在过去的几年里，大量的研究已经从各种记录中产生放射性碳数据集。这些数据集中的许多数据现在都相当一致，因此应该可以提供估计日历年龄的曲线，可以追溯到55，000年前。此外，新的树木年轮记录也在不断出现，这将提高校准曲线的精确度。统计方法也在迅速发展，因此我们在2004年对模型所做的一些简化假设将不再必要。该项目将与IntCal工作组合作，开发一个易于维护的校准质量放射性碳数据库，用于定期更新校准曲线。统计学的进步将使我们能够改进以前的模型，以进一步完善校准曲线。对精心挑选的珊瑚进行测量将有助于确定需要对海洋样本进行哪些校正，以用于校准曲线。通过改进放射性碳校准，该项目将提高对考古学和重建过去环境的许多研究中事件的顺序和时间的理解。

Many researchers in archaeology and the geosciences obtain timescales for their projects by radiocarbon dating plant or animal remains from the preserved deposits with which they work. Radiocarbon dates are not the same as calendar dates, however, and have to be corrected for variations in the radiocarbon content of the atmosphere at the time that the plant or animal lived. This conversion of radiocarbon dates to calendar ages, known as calibration, is not a straightforward correction. Calibration of radiocarbon dates can only be done by comparison to a suitable calibration curve. Such curves are based on measurements of radiocarbon in samples of known calendar age such as tree-rings, or in a less strict sense, on other types of samples where an independent method of dating can be used. For samples which grew in the ocean, such as shells and corals, a separate calibration curve is needed to account for changes in ocean water circulation which may bring up 'old' water from the ocean depths (the reservoir effect). The calibration curves have been refined periodically to provide better estimates of the calendar ages. In 2004, the IntCal Working Group constructed new calibration curves from radiocarbon dated tree-rings back to 12,400 years before present and from independently dated ocean samples, using an estimated correction for the reservoir effect, back to 26,000 years before present. Rather than simply averaging the data, these curves were constructed with statistical tools (models) that allowed for the uncertainty in the calendar ages of the samples used as well as the radiocarbon dates. At that time data beyond 26,000 years before present did not agree so no curve was provided but an estimate of how far the data sets differed from the underlying true curve was given. In the last few years a lot of research has gone into producing radiocarbon datasets from a variety of records. Many of these datasets are now in fairly good agreement so it should be possible to provide curves for estimating calendar ages back to 55,000 years before present. In addition new tree-ring records are becoming available which will improve the precision of the calibration curve. Statistical methods have also been rapidly advancing and so some of the simplifying assumptions that we made about the models in 2004 will no longer be necessary. Working in collaboration with the IntCal Working Group, this project will develop an easily maintainable database of calibration quality radiocarbon data to be used to produce updates to the calibration curves on a regular basis. Advances in statistics will allow us to improve on the previous models to further refine the calibration curves. Measurements of carefully selected coral will help determine what corrections are needed for ocean samples to be used in calibration curves. By improving radiocarbon calibration this project will improve the understanding of the sequence and timing of events in numerous studies in archaeology and in the reconstruction of past environments.