Guest post by David Archibald

Predicting the amplitude of Solar Cycle 24 was a big business. Jan Janssens provides the most complete table of Solar Cycle 24 predictions at: http://users.telenet.be/j.janssens/SC24.html

Prediction activity for Solar Cycle 24 seemed to have peaked in 2007. In year before, Dr David Hathaway of NASA made the first general estimate of Solar Cycle 25 amplitude:

http://science.nasa.gov/science-news/science-at-nasa/2006/10may_longrange/

Based on the slowing of the Sun’s “Great Conveyor Belt”, he predicted that

“The slowdown we see now means that Solar Cycle 25, peaking around the year 2022, could be one of the weakest in centuries.” He is very likely to have got the year wrong in that Solar Cycle 25 is unlikely to start until 2025.

In this paper: http://www.probeinternational.org/Livingston-penn-2010.pdf,

Livingston and Penn provided the first hard estimate of Solar Cycle 25 amplitude based on a physical model. That estimate is 7, which would make it the smallest solar cycle for over 300 years.

This is figure 2 from their paper:

Livingston and Penn have been tracking the decline in sunspot magnetic field, predicting that sunspots will disappear when the umbral magnetic field strength falls below 1,500 gauss, as per this figure from their 2010 paper:

Dr Svalgaard has updated of the progression of that decline on his research page at:

http://www.leif.org/research/Livingston%20and%20Penn.png

With data updated to year end 2011, the line of best fit on Dr Svalgaard’s figure of Umbral Magnetic Field now intersects the 1,500 guass sunspot cutoff in 2030:

Using the Livingston and Penn Solar Cycle 25 amplitude estimate, this is what the solar cycle record is projected to look like:

And, yes, that means the end of the Modern Warm Period.

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Further reading:

NASA Long Range Solar Forecast – Solar Cycle 25 peaking around 2022 could be one of the weakest in centuries.

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