American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 343824 bytes)

GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L15714, doi:10.1029/2005GL023621, 2005

A review of the solar cycle length estimates

R. E. Benestad

Meteorological Institute, Oslo, Norway


Abstract

New estimates of the solar cycle length are calculated from an up-to-date monthly sunspot record using a novel but mathematically rigorous method involving multiple regression, Fourier approximation, and analytical expressions for the first derivative based on calculus techniques. The sensitivity of the estimates to smoothing are examined and the analysis is used to identify possible systematic changes in the sun. The solar cycle length analysis indicates a pronounced change in the sun around 1900, before which the estimates fluctuate strongly and after which the estimates show little variability. There have been speculations about an association between the solar cycle length and Earth's climate, however, the solar cycle length analysis does not follow Earth's global mean surface temperature. A further comparison with the monthly sunspot number, cosmic galactic rays and 10.7 cm absolute radio flux since 1950 gives no indication of a systematic trend in the level of solar activity that can explain the most recent global warming.

Received 25 May 2005; accepted 22 July 2005; published 13 August 2005.

Index Terms: 1694 Global Change: Instruments and techniques; 1650 Global Change: Solar variability (7537); 1616 Global Change: Climate variability (1635, 3305, 3309, 4215, 4513).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 343824 bytes)

Citation: Benestad, R. E. (2005), A review of the solar cycle length estimates, Geophys. Res. Lett., 32, L15714, doi:10.1029/2005GL023621.