By Frank Bosse and Prof. Fritz Vahrenholt
(Translated and edited by P Gosselin)
Also last month the sun was relatively inactive. The observed sunspot number (SSN) was 44.7, which was just 64% of what is the average for the previously observed 23 cycles.
The average cycle has a duration of 11 years. The current cycle number 24 is depicted by the red curve in the following chart:
Figure 1: The current solar cycle 24 is shown in red. The mean of the previous 23 cycles is shown by the blue curve. The black curve depicts solar cycle 5, which had a similar behavior as the current cycle 25.
What stands out is that the last 18 months of activity of the current cycle has been consistently weaker than during the same period of solar cycle 5, which ushered in the Dalton-Minimum in 1795.
So what can we say about the upcoming solar cycle 25, which is expected to begin around 2020? Next month we will take another look at the solar polar field because its strength is a leading indicator for what the sun has in store for us. Up to now everything looks like the situation we saw in the early 19th century.The comparison of the individual cycles with respect to their sunspot deviation from the mean after 94 months into the cycle follows:
Figure 2: The accumulated monthly sunspot totals for each cycle and their respective deviation from the mean (blue curve in Figure 1), 94 months into the cycle. Only 2 cycles were less active than the current cycle: cycles no. 5 and 6 – some 200 years ago! The second half of the 20th century was the most active phase with respect to amplitude and duration.
Beginning with solar cycle 18 in the year 1944 until the mid 1990s (SC22) there were 4 strong cycles. The peak was SC 19, which ended in 1964. SC 21 was the third strongest cycle and 1986. The strong cycles ceased in 2005, and one is not expected with strong certainty until 2033.
Note from NTZ: Yesterday Kenneth Richard posted on 18 very recent papers showing a strong correlation between solar activity and global temperature over the past centuries. Many accept that periods of low solar activity lead to periods of global cool-offs. But some experts caution that the effects from the series of the powerful solar cycles of the late 20th century will not be offset by the single weak cycle we are currently experiencing.