The Gleissberg Cycle of Solar Activity: Part 2

Sunspot Groups and the Gleissberg Cycle

In Part 1, sunspot numbers observed from 1750 to 2015 were used to display both the 11-year cycle and the century-long Gleissberg Cycle.

Here I plot the group sunspot numbers from 1610 to 2015 to include the Maunder Minimum, a period when few sunspots were observed, named after Mr. and Mrs. Maunder, a husband and wife team. (Edward Walter Maunder and Annie Scott Dill Maunder studied but did not observe the period now called the Maunder Minimum.)

GN anomaly

As before, the data source is WDC-SILSO, Royal Observatory of Belgium, Brussels. The data is version 2, the new series. The mean value of 3.78 has been subtracted from each data point in order to show the anomalies (departures from the mean (average). The plot shows the anomalies, not the absolute values.

The Maunder Minimum is the period during the 16th century when few observations exceeded the mean. The Dalton Minimum is a similar period of shorter duration from the end of the 18th to early 19th century. Not so obvious is a period centered around 1910 when sunspots were less numerous than usual.

Cumulative Group Anomalies

I accumulated the data series by adding the second value to the first value to get the value for the second data point. To get the third data point, I added the third value to the second data point. The new series will increase as the Group Number increases and will decline as the Group Number declines.

The graphic displays a metric for CUMULATIVE number of sunspot groups.

Cumulative GN

From the start date, the cumulative total increases and then declines until the Maunder Minimum. The cumulative value then rises during the 18th century and then declines until the Dalton Minimum, rises during the first half of the 19th century and then declines until around 1940 and then rises until the end of the 20th century.

I do not see a centennial-scale cycle here. The first cycle seems closer to 200 years, which would make it a Suess cycle (or de Vries cycle). Which is why I think of the Gleissberg and Suess/de Vries Cycle as pseudo-cycles.

The lack of regularity can mean either that the phenomenon is chaotic (like turbulence) or that other factors are operating, such as changes in gravity acting upon the Sun caused by the orbital motions of the planets.

[Ann Maunder noted the apparent association of sunspot appearances with the motions of the inner planets.]

I interpret the long sunspot cycles as indications of increases and decreases of the amount of energy entering the oceans and the ice caps of the Earth. The reason is that the atmosphere and uppermost few meters (yards) of land can store very little energy. I mention “ice” because when ice melts it absorbs a lot of energy as latent heat. So during the upward swing of the Gleissberg Cycle I expect an increase in solar energy entering the oceans in the tropics and melting ice at or near the poles.

The controversial aspect is the claim that changes in solar activity have a significant impact on the climate of the Earth. This question I leave until later in the series.

The model presented here shows a proxy (substitute) for solar activity. There are other proxies for solar activity that can be used alone or as “predictors” for sunspots. These I will discuss in Part 3 of this series.

First I ask the question, “Are counts of sunspot groups consistent with counts of sunspot numbers?” The reason I ask this question is that Group Number (GN) and the Sunspot Number (SSN) are two related but different proxies for solar activity.