Learning from the wood samples in ICS, TIRI, FIRI, VIRI and SIRI

Each of the laboratory inter-comparisons (from ICS onwards) has included wood samples, many of them dendrochronologically dated. In the early years, as a result of the majority of laboratories being radiometric, these samples were typically blocks of 20-40 rings, but more recently (SIRI), they have been single ring samples. The sample ages have spanned background through to modern. In some inter-comparisons, we have examined different wood pre-treatment effects, in others the focus has been on background samples. In this paper, we illustrate what we have learnt from these extensive inter-comparisons involving wood samples and how the results contribute to the global IntCal effort.