The Maunder Minimum: An Interlaboratory Comparison of Delta-14C from AD 1688 to AD 1710

Abstract

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 per mil for Ioffe compared to +/2.1 per mil for Tucson. There is also a calibration difference of 4.3 +/1.2 sigma per mil. Comparison of the same years measured in Seattle on wood from the Pacific Northwest shows an offset of 2.2 +/0.5 sigma per mil. 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.