Throughout recorded history the fluctuations of the weather have played a major part in human life. Times of feast and times of famine have repeatedly occurred. The biblical story of Joseph's dream, accurately foretelling that 7 good years would be followed by 7 years of famine and describing the action that was taken to store the surplus from the good years to meet the shortages of the bad years appears to be the first recorded example of a periodic variation in the weather over a number of years, but it also shows the huge benefit that can accrue from the accurate predictions of such regular meteorological changes and their impact on harvests, and explains why the possibility of regular fluctuations in the weather has fascinated weather watchers for so long.

There may also be a more fundamental reason for searching for such orderly behaviour in the weather. Because so much of our lives is governed by the rhythms of the seasons, it is natural to look for the same sort of order in the longer term, more chaotic behaviour of the physical world around us.