Earth's core, climate, and magnetic field

Abstract

H.H. Lamb (Climate, Present, Past and Future, vol. 2., Methuen Co., N.Y., 1977) postulated convincingly that there is a tight correlation between variations in the earth's climate and solar exposure (as represented by mean surface temperature 8). Given constant radiation and surface, solar exposure is a function of the length of day, and thus it has been tempting to correlate, as well, mechanisms that could cause or be the result of changes in the earth's rotation rate. Such mechanisms have been reviewed by Lambeck (The Earth's Variable Rotation, Geophysical Causes and Consequences, Cambridge University Press, London, 1980).Lambeck examined the variations in terms of fluid mechanical coupling between the earth's fluid core and the mantle but deduced that the electromagnetic coupling process between core and mantle probably plays the most dominant role in affecting the spin rate. The factors, climate (9), length of day, variation in the earth's rotation rate, and variations in the geomagnetic field, have been recently correlated by a group of French geophysicists (V. Courtillot et al., Nature, 297, 386, 1982) to form the basis of what is described as an ‘attractive causal chain’ to forecast future climatic variations. The predictive correlations are not subject to circular reasoning as to which—climate variations or variations within the core—was the ultimate cause. Courtillot et al. note a lag in time between core changes and climate changes—in terms of 0—of 15–25 years to predict the climate.