In addition, we have reanalyzed the radiocarbon and U age dates from our earlier radiocarbon calibration work using new pretreatment and analytical techniques and state-of-the-art instrumentation at higher precision; we report these new results in this WEB site and in Fairbanks et al., (2005). A raw radiocarbon date is a measurement of how much radiocarbon is left in an organic object, from which we calculate how long ago the object died.You can get an idea of the relationship between C14 and age at the Carbon Dating calculator page. 1950 was chosen for no particular reason other than to honour the publication of the first radiocarbon dates calculated in December 1949 (Taylor, 19).
A calibrated date is rarely a single year; it is more usually expressed as a range of years together with a probability in order to indicate the mathematical likelihood that the date falls within that range.
Over the past decade we have witnessed a remarkable development and proliferation of accelerator mass spectrometers; these instruments have reduced the counting time by a factor of 100 and reduced the sample size by a factor of 1000 compared to the classic B-counting systems.
It is estimated that nearly 90% of all measurements made at the more than 50 active accelerator mass spectrometry laboratories are radiocarbon dates.
This dramatic increase in the number of radiocarbon dates is driving the demand for a radiocarbon calibration program that spans the entire radiocarbon timescale from the present to 55,000 years BP.
Extension of the C record beyond the 0 to 11,900 year long tree ring record is well underway, being measured in many different archives, and undoubtedly an enormous amount of scientific knowledge will stem from these studies.