Solar Cycle 24 is unusually quiet but not unprecedented

NASA has made a new reduced forecast for the peak sunspot number and the time of occurrence of the peak of Solar Cycle 24. The peak number has been reduced from 90 to 64 and the time of the peak is unchanged at June 2013.

I have superimposed the development of the forecast peak and time of the peak on the base forecast. This is not any criticism of the forecast. It only emphasises that the forecasts are about something which is not very well understood. So far the forecast development is only in the direction of reducing sunspot numbers and delays in the time of attaining the peak. As the peak actually approaches the forecasts should stabilise but there is still some room for further reduction. It is not inconceivable that the SC24 will not peak till early 2014 and will only achieve peak sunspot numbers around 55. Solar cycle 24 could well have a length of 150+ months instead of the nominal 132 months.


SC24 forecast development superimposed on NASA forecast (

That SC24 represents a very quiet sun and that taken together with SC23 this Landscheidt minimum represents a behaviour similar to the period leading up to the Dalton minimum is quite clear insofar as sunspot number is concerned. But the length of Solar Cycle 23 and its extended quiet period also has precedence.

Further similarities to SC4 and 5 were reported in

Agee, Ernest M., Emily Cornett, Kandace Gleason, 2010: An Extended Solar Cycle 23 with Deep Minimum Transition to Cycle 24: Assessments and Climatic Ramifications. J. Climate, 23, 6110–6114.
doi: 10.1175/2010JCLI3831.1

The extended length of solar cycle 23 and the associated deep quiet period (QP) between cycles 23 and 24 have been examined using the international sunspot record from 1755 to 2010. This study has also introduced a QP definition based on a (beginning and ending) mean monthly threshold value of less than 10 for the sunspot number. Features addressed are the length and intensity of cycle 23, the length of the QP and the associated number of spotless days, and the respective relationships between cycle intensity, length, and QP. The length of cycle 23 (153 months) is second only to cycle 4 (164 months), with an average of 132.5 months for the 11-yr cycle. The length of the QP between cycles 23 and 24 ranks eighth, extending from October 2005 through November 2009 (but subject to continued weakness in cycle 24). The number of spotless days achieved within this QP was 751 (and for all days within the transition from cycle 23 to cycle24, a record number of 801 spotless days had been observed through May 2010). Shortcomings of solar-convection-model predictions of sunspot activity and intensity are also noted, including the failure in the initial predictions of cycle-24 onset.

It would not be too surprising if SC24 only reached levels which were  lower than the Dalton minimum and perhaps even approaching the lows of the Maunder minimum.


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2 Responses to “Solar Cycle 24 is unusually quiet but not unprecedented”

  1. NASA reduces forecast for Solar Cycle 24 again « The k2p blog Says:

    […] December NASA had reduced its forecasts for SC24 to a peak sunspot number of 64 being reached in June 2013. Now less […]

  2. mike mckinley Says:

    is that a downward trend suggesting little ice age out 22 or 44 years.

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