IT FLICKERS

And then there is something else. The solar constant, the energy arriving at the terrestrial orbit per second per square meter (due to the atmosphere it is somewhat larger than the 1 kW/m^2 that we usually use to gauge Lovinsian pipe dreams) is not really constant: the sun flickers. In a cycle of roughly 70 years, the sun probably "dims" and "flares" slightly; when it dims, the sunspot cycles attain lower maxima.

This was good news for Dr John Eddy of the National Center for Atmospheric Research in Boulder, Colo., who had found impressive correlations between decades of low (or high) sunspot maxima, and cold (or warm) periods, such as the "Little Ice Age" of the late late 17^th century, coinciding with a virtual absence of sunspot maxima between 1645 and 1715. (This, incidentally, includes the Great Winter of 1683-84, vividly described in Blackmore's Lorna Doone.)

Eddy also looked at tree rings, but not at their width; he looked at their radioactivity.