Variations of radiocarbon in tree rings: Southern Hemisphere offset preliminary results

The Queen's University of Belfast, Northern Ireland and University of Waikato, Hamilton, New Zealand radiocarbon laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus patrea) and cedar (Libocedrus bidwillii) from Great Britain and New Zealand, respectively. The results show a real atmospheric offset of 3.4 +/- 0.6 parts per thousand (27.2 +/- 4.7 C-14 yr) between the two locations for the interval AD 1725 to AD 1885, with the Southern Hemisphere being depleted in C-14. This result is less than the value currently used to correct Southern Hemisphere calibrations, possibly indicating a gradient in Delta(14)C within the Southern Hemisphere.