Intensity of the Earth''s magnetic field over the last 10 000 years

Analyses of over 600 archaeomagnetic data compiled by Burlatskaya and Nachasova (1977) illustrate that our knowledge of the intensity of the Earth's magnetic field is much poorer than generally believed. The data exhibit high scatter and the distribution of sampling localities is extremely limited. Rock magnetic and experimental contributions to the scatter are probably significant, although it is impossible to determine uniquely the sources of scatter without a substantial increase in the data base and without making additional assumptions about the past magnetic field behaviour. Nevertheless, when averaged in 1000 year intervals, the archaeomagnetic intensity data for the past 5000 years can be simply, but non-uniquely, interpreted in terms of a change in the intensity of the dipole field. This interpretation is broadly consistent with independent evidence from radiocarbon data. Because of inconsistencies in radiocarbon data prior to 8000 years B.P. and because of inadequacies in the archaeomagnetic data, the previously alleged sinusoidal variation of the dipole field intensity with a period of 8000–9000 years should be regarded as highly tentative.