The Maunder Minimum: A reappraisal

Abstract

A number of papers have questioned the reality of the Maunder Minimum of solar activity (A.D. 1645–1715). A recent study by Xu and Jiang (1982) of newly-discovered Chinese provincial records listing 21 naked-eye sunspot sightings in the 17th century is a case in point, as is Landsberg's (1980) report of 52 sunspots found in ‘unexploited’ German diary sources. We demonstrate that neither claim is cause to alter Eddy's (1976) quantitative description of the Maunder Minimum. The new Chinese data add at most three possible sunspots to the 600–1000 that were previously known in the Maunder Minimum years; moreover, the number of 17th century naked-eye reports drops after 1640 in the same manner as do known telescopic reports. The historical sunspots found by Landsberg are almost entirely duplicates of spots included in prior analyses, based on earlier studies of the same well-known sources. The principal evidence for secular solar variability is the precision record of tree-ring radioacarbon compiled in 1980 by Stuiver and his colleagues that establishes an unequivocal drop in solar activity during the Maunder Minimum and on three prior occasions in the current millennium.