Posts Tagged ‘Solar cycles’

Solar Cycle 24 passes maximum? Low sunspot numbers and climate cooling indicated for next two cycles

February 11, 2015

It is not completely certain but it does look like Solar Cycle 24 has just passed its maximum. The maximum was initially expected to be reached in late 2012 and gradually drifted to late 2013. Now it would seem that this may not have occurred till late 2014.  While the minima at the beginnings of SC 23 and 24 seem to have been c. 12 years apart, the maxima are closer to 14 years apart.

SC24 2015 January  From NASA Hathaway

SC24 2015 January From NASA Hathaway

The length of Solar Cycles is thought to be linked to the solar activity to be expected in the following 2 cycles. Periods much longer than the average of 11.2 years seem to lead to decreased subsequent activity, lower sunspot numbers and also lower global temperatures.

Solheim et al predicted lower sunspot activity and cooler times during SC 24. Now it would seem this will also be the prevailing paradigm through SC25 and perhaps even SC26. Another two decades of reduced sunspot activity and a global cooling carried by the ocean cycles would seem to be on the cards.

Abstract

Relations between the length of a sunspot cycle and the average temperature in the same and the next cycle are calculated for a number of meteorological stations in Norway and in the North Atlantic region. No significant trend is found between the length of a cycle and the average temperature in the same cycle, but a significant negative trend is found between the length of a cycle and the temperature in the next cycle. This provides a tool to predict an average temperature decrease of at least 1.0ºC from solar cycle 23 to solar cycle 24 for the stations and areas analyzed. We find for the Norwegian local stations investigated that 25–56% of the temperature increase the last 150 years may be attributed to the Sun. For 3 North Atlantic stations we get 63–72% solar contribution. This points to the Atlantic currents as reinforcing a solar signal.

They write:

The length of a solar cycle is determined as the time from the appearance of the first spot in a cycle at high solar latitude, to the disappearance of the last spot in the same cycle near the solar equator. However, before the last spot in a cycle disappears, the first spot in the next cycle appears at high latitude, and there is normally a two years overlap. The time of the minimum is defined as the central time of overlap between the two cycles (Waldmeier, 1939), and the length of a cycle can be measured between successive minima or maxima. A recent description of how the time of minimum is calculated is given by NGDC (2011): “When observations permit, a date selected as either a cycle minimum or maximum is based in part on an average of the times extremes are reached in the monthly mean sunspot number, in the smoothed monthly mean sunspot number, and in the monthly mean number of spot groups alone. Two more measures are used at time of sunspot minimum: the number of spotless days and the frequency of occurrence of old and new cycle spot groups.”

It was for a long time thought that the appearance of a solar cycle was a random event, which means that each cycle length and amplitude were independent of the previous. However, Dicke (1978) showed that an internal chronometer has to exist inside the Sun, which after a number of short cycles, reset the cycle length so the average length of 11.2 years is kept. Richards et al. (2009) analyzed the length of cycles 1610–2000 using median trace analyses of the cycle lengths and power spectrum analyses of the O–C residuals of the dates of sunspot maxima and minima. They identified a period of 188±38 years. They also found a correspondence between long cycles and minima of number of spots. Their study suggests that the length of sunspot cycles should increase gradually over the next ~75 years. accompanied by a gradual decrease in the number of sunspots.

An autocorrelation study by Solanki et al. (2002) showed that the length of a solar cycle is a good predictor for the maximum sunspot number in the next cycle, in the sense that short cycles predict high Rmax  and long cycles predict small Rmax. They explain this with the solar dynamo having a memory of the previous cycle’s length.

Assuming a relation between the sunspot number and global temperature, the secular periodic change of SCL may then correlate with the global temperature, and as long as we are on the ascending (or descending) branches of the 188 year period, we may predict a warmer (or cooler) climate.

It was also demonstrated (Friis-Christensen and Lassen, 1992, Hoyt and Schatten, 1993 and Lassen and Friis-Christensen, 1995) that the correlation between SCL and climate probably has been in operation for centuries. A statistical study of 69 tree rings sets, covering more than 594 years, and SCL demonstrated that wider tree-rings (better growth conditions) were associated with shorter sunspot cycles (Zhou and Butler, 1998).

Solar Cycle 24 will be the smallest sunspot cycle since 1906 (SC 14)

January 5, 2013

The January 2013 NASA forecast for the development of Solar Cycle 24 is out.

sc 24 prediction January 2013

SC 24 prediction Jan 2013 – Hathaway -NASA

The current prediction for Sunspot Cycle 24 gives a smoothed sunspot number maximum of about 69 in the Fall of 2013. The smoothed sunspot number has already reached 67 (in February 2012)due to the strong peak in late 2011 so the official maximum will be at least this high and this late. We are currently over four years into Cycle 24. The current predicted and observed size makes this the smallest sunspot cycle since Cycle 14 which had a maximum of 64.2 in February of 1906.

With sunspot activity at this low level the planet will cool. It remains to be seen whether this is the start of something like a Dalton Minimum (SC5 and 6) or even a Maunder Minimum. This cooling has begun and global temperatures peaked about 16 years ago and are now declining slightly while carbon dioxide concentration continues to increase. It is only a matter of time before the belief that carbon dioxide concentration (whether man-made or not) causes global warming will have to be completely discarded. But there is so much money now riding on this belief (and even though there is only conjecture and no direct evidence for this belief), that we will likely see a decade or more of rationalisation of reality before the belief is abandoned.

SC24 compared to SC5 in 2011 is shown below:

SC24 compared to SC5

NASA reduces forecast for Solar Cycle 24 again

January 19, 2011

In December NASA had reduced its forecasts for SC24 to a peak sunspot number of 64 being reached in June 2013. Now less than two months later, the latest forecast has been reduced again to a peak sunspot number of 59 to be reached in June / July 2013.

We find a starting time of May 2008 with minimum occurring in December 2008 and maximum of about 59 in June/July of 2013.

NASA SC24 forecast - January 2011: image NASA

At these levels the current Landscheidt minimum is comparable to SC5 and SC6 – the Dalton Minimum of 1790 to 1830 – where peak sunspot numbers were just over 50. (The earlier Maunder Minimum – 1645 to 1715- was before the modern period of sunspot number measurement and nominally was a period with no significant sunspots – presumably at sunspot numbers of less than 20 in today’s measurement values).

From my previous post:

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.

The development of the NASA predictions are in the table below:

NASA Forecasts for SC24

Date of

forecast

Expected date

of peak

Expected peak

sunspot number

March 2006 June 2010 168
October 2008 March 2012 137
January 2009 June 2012 104
January 2010 June 2013 90
December 2010 June 2013 64
January 2011 June / July 2013 59


Related:

https://ktwop.wordpress.com/2010/12/23/is-the-landscheidt-minimum-a-precursor-for-a-grand-minimum/

Solar Cycle 24 is unusually quiet but not unprecedented

December 29, 2010

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 (http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif)

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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