Was the Recent Solar Cycle Minimum Unique?
Joan Feynman [joan.feynman@jpl.nasa.gov], Jet Propulsion Laboratory, California
Institute of Technology, Pasadena
It is shown that the recent unusual behavior of the Sun was not confined to the 2008-2009
sunspot-cycle minimum but began at least 10 to 30 years earlier. Also the behavior observed
during this minimum reconfirms the validity of using cosmic ray intensity, geomagnetic
variations and auroral observations as proxies for solar output change. A ~2,000 year history
of the Sun reconstructed using these proxies suggests that the solar behavior during this
recent minimum was far from unique. For example, the Maunder and Spoerer Minima could
be identified by high cosmic ray intensities and the lack of low latitude aurora. In addition, a
clear ~90 year periodic variation in cycle amplitude (Gleissberg cycle) existed for at least a
millennium (450 AD to 1450 AD) and comparison between deep solar minima early in the
19th and 20th centuries and the 2008-2009 minimum suggest that the recent minimum was
part of an ongoing series of Gleissberg cycles.
It is widely believed that the increasing solar activity during the first half of the 20th
century contributed to global warming. At that time both increasing CO2 and solar activity
increased the Earths’ surface temperatures making it difficult to distinguish between the two
effects. However, in this last decade the Sun has decreased its output while the CO2 has
increased presenting us with a wonderful opportunity to distinguish the two climate drivers.