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Reconstructions of sunspot group numbers since 1610, visualized with relative sunspot numbers from SILSO (Clette & Lefèvre, 2016; black continuous curve) and sunspot group numbers from Svalgaard & Schatten (2016; red broken curve). Two prolonged minima are evident here: the Maunder Minimum (1645–1715) and Dalton Minimum (1797–1827). Note that the solar activity during the Maunder Minimum is considered much lower in other studies (e.g., Vaquero et al., 2015; Usoskin et al., 2015).
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