Some Implications Using the Group Sunspot Number Reconstruction

Abstract

The Wolf or Zürich sunspot number Rz, (values available from 1700 onwards) is considered the primary descriptor of solar activity for the past 100 years or more. Recently, another, more accurate time series, called the Group sunspot number, R _G, has become available. Comparison of the indices suggests that Rzmay be grossly overestimated in the early sunspot records. In this paper, some results based previously on Rzare reexamined using R _G. Conclusions based on data from about 1850 to the present remain the same. For the 18th century, however, small differences are seen. For estimates of solar irradiance in the Maunder Minimum (1645–1715), because both Rzand R _Gwere near zero then and are almost comparable today, irradiance estimates remain about the same, whether Rzor R _Gis used to calculate them. However, the evolutions of Rzand R _Gfrom their near zero value in the Maunder Minimum to their present similar value, are different, with Rzincreasing more rapidly than R _Gfrom 1700 to 1790. While the temperature of the Earth has increased almost monotonically for the past few centuries, the relationship of both Rzand R _Gwith the temperature trend is not especially great.