Solar activity and climate – part 2


In a recent post we looked at the average daily sunspot numbers, finding that far from the claimed decades-long decline of solar strength, averages were high from 1933-2008 followed by a sharp decline in the recently-ended solar cycle 24.

This time the focus moves to another metric from the same source, Wikipedia’s List of solar cycles.

After the main table of data they introduce another one, stating:
The following table is instead divided into (unofficial) cycles starting and ending with a maximum, to give a better feel for the number of spotless days associated with each minimum.

For this short exercise the ‘Spotless days’ column of data will be split into two groups of six, comparing the overall average of each from the list.

Group 1 (‘Start(maximum)’ data from 1878-1928 inclusive):
Solar cycle 11-12 1870-08 1028 spotless days
Solar cycle 12-13 1883-12 736
Solar cycle 13-14 1894-01 934
Solar cycle 14-15 1906-02 1023
Solar cycle 15-16 1917-08 534
Solar cycle 16-17 1928-04 568

Sum of spotless days: 4823
Average per cycle: 803.8

Group 2 (‘Start(maximum)’ data from 1937-1989 inclusive):
Solar cycle 17-18 1937-04 269 spotless days
Solar cycle 18-19 1947-05 446
Solar cycle 19-20 1958-03 227
Solar cycle 20-21 1968-11 272
Solar cycle 21-22 1979-12 273
Solar cycle 22-23 1989-10 309

Sum of spotless days: 1796
Average per cycle: 299.3

Few would dispute that more global warming occurred in the more recent group 2 than the earlier group 1. The spotless day averages reflect this, with group 2 being a lot less than half of the group 1 number.

Turning to the latest figures:
Solar cycle 23-24 2001-11 817 spotless days
Solar cycle 24-25 2014-04 808 (Jan 27 2021)

Now the ‘virtual’ pendulum is swinging back the other way again, towards much higher numbers of spotless days.

We await to see what, if any, effect this may have on global temperatures if the trend continues for a significant length of time.

via Tallbloke’s Talkshop

January 28, 2021 at 08:42AM

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