DIMMING OF THE 17TH CENTURY SUN
- Heliophysics, Inc., Nahant, MA 01908 (United States)
- Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, N 0315 Oslo (Norway)
- Institute for Solar Physics, Royal Swedish Academy of Sciences, Alba Nova University Center, Stockholm (Sweden)
Reconstructions of total solar irradiance (TSI) rely mainly on linear relations between TSI variation and indices of facular area. When these are extrapolated to the prolonged 15th-17th century Spoerer and Maunder solar activity minima, the estimated solar dimming is insufficient to explain the mid-millennial climate cooling of the Little Ice Age. We draw attention here to evidence that the relation departs from linearity at the lowest activity levels. Imaging photometry and radiometry indicate an increased TSI contribution per unit area from small network faculae by a factor of 2-4 compared with larger faculae in and around active regions. Even partial removal of this more TSI-effective network at prolonged minima could enable climatically significant solar dimming, yet be consistent with the weakened but persistent 11 yr cycle observed in Be 10 during the Maunder Minimum. The mechanism we suggest would not alter previous findings that increased solar radiative forcing is insufficient to account for 20th century global warming.
- OSTI ID:
- 21562634
- Journal Information:
- Astrophysical Journal Letters, Vol. 733, Issue 2; Other Information: DOI: 10.1088/2041-8205/733/2/L38; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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