Measurements on same-age tree-ring samples from proximal Ural
Mountain trees by the Ioffe Institute research group and at the
University of Arizona demonstrate a variance corresponding to a standard
deviation of ±5.1 0 for Ioffe compared to ±2.1 0 for Tucson. There is
also a calibration difference of 4.3 ± 1.2
0. Comparison of the same
years measured in Seattle on wood from the Pacific Northwest shows an
offset of 2.2 ± 0.5 0. This is not a calibration error, but rather is
expected from the well-documented evidence for divergence and upwelling
of 14C-depleted
CO2 along the west coast of
North America.
[Radiocarbon Volume 41, Number 1, 1999]