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The most conspicuous climatic aberration of the past two millennia was the temperature decline and glacial advance of the A.D. 1550 to 1900 period. This temperature decline has been correlated with an interval of lower solar activity and there is evidence from both the post-Pleistocene glacial record and from oxygen-18 analysis that such an interval han recurred at cyclic periods of around 2400 to 2600 years.
J. R. Bray (Fri,) studied this question.