An inter-laboratory comparison of radiocarbon measurements in tree rings

Results from a collaborative study designed by the Glasgow 14C laboratory to assess experimental variability in radiocarbon dating are presented. A series of eight replicate samples from one tree were dated independently by 20 14C laboratories. While the results are in general agreement they reveal the existence of systematic bias and unexplained variability. Thus as a general guideline for users of 14C dates, quoted errors, particularly those derived solely on the basis of the counting procedure, should be multiplied by a factor of between 2 and 3. (author)