Some fun stats with Sunspots and how the current activity stacks up against recent history
Posted by The Diatribe Guy on October 2, 2008
For a change of pace, I thought I’d take a look at the sunspot numbers, which can be found here and just take a look at how current averages in the index stack up historically against what has been recorded in the past.
Before I start, a couple comments…
First, here is a nice link for those who like to check out a picture of the sun online. I’ve included the current image here.
In addition, I want to point out a post at Watts Up With That? that shows the number of days the sun has been blank so far this year compared to the previous year counts. In summary, this is the most number of blank days since 1954 already, and if current trends continue for another three months we will easily pass up 1954.
OK, so I won’t cover that ground, thanks to Watts. But I took a look at a series of averages, and found some interesting little tidbits that I thought I’d share. Since people like charts, I’ll throw up a few. These aren’t rocket science, and I don’t claim that they are anything new that we haven’t seen before. But it adds a nice context to the post.
The first graph is a plot of the raw observed sunspots since records have been kept. For a more detailed look on the history behind the numbers, check out my posts summarizing a couple papers by John A. Eddy, found here and here.
I wanted to get some kind of a read on how the overall average sunspot numbers are trending in our lifetimes, and because of the cyclical nature this can be done by averaging. One note on the averaging, though… once you get up to multi-year averaging, since the cycles vary in length, you may retain the trough/peak points in the cycle in some areas of the chart, and lose them in other areas. One reason I wanted to collapse the chart in this way was because shorter cycles may increase the overall average sunspots over a period of a number of years. If that is occurring, we’d see an upward trend during those periods.
The following charts represent a 12-month averaging of the sunspot counts, a 5-year averaging of the counts, and a 12-year averaging. You can see how it transforms from a cyclical chart to a chart exhibiting more trend-like behavior.
I’m not making any particular claims on correlation with temperature at this point, but there is clearly an upward trend in the sunspot counts in modern times, averaged over a number of years. This trend, however, has lapsed over the last few years, as can be seen on the far right of the 12-year chart.
So, we’ve now got a prolonged minimum occurring. The chart at Watts shows that spotless day counts are high relative to recent history. How do other measures compare to the historical data?
Glad you asked… I’ve run some averages – nothing fancy – and taken a look at the historical averages. Here is what I’ve found:
*September 2008 sunspot value = 1.1. After 2 months at 0.5, and a value of 0.9 in October 2007, the next previous count at least this low is the 1.1 that occurred in June 1986.
Now, things get interesting…
*2-month average = 0.8: The previous 2-month average was 0.5, but prior to that the last time we’ve had a 2-month average this low was the period ending June 1954.
*3-month average = 0.7: This is the lowest three-month average since the period ending October 1913.
*6-month average = 1.8: The lowest 6-month average since the period ending December 1913.
*12-month average = 3.2: The lowest 12-month average since the period ending March 1934.
*2-year average = 6.7: The lowest since the period ending April 1924.
*3-year average = 10.2: The lowest since the period ending July 1935.
*4-year average = 15.9: The lowest since the period ending December 1935.
*5-year average = 22.0: The lowest since the period ending July 1936.
*6-year average = 30.2: The lowest since the period ending February 1937.
*7-year average = 41.9. It is finally at this point where we see this average reached in recent prior cycles, and isn’t an extraordinarily low value.
So, no matter how you look at it, for any stretch from 2-months to 6 years, we are in territory unseen since mid 1954 at the latest, and in some cases dating back nearly a century. Fun times.
Another item I took a gander at was the number of months that pass from minimum to maximum, and vice-versa, as well as the entire cycle (min to min, max to max). For the purposes of my review, I considered the minimum and maximum, to be the month in which the 12-month average reached its lowest and highest value, respectively. I doubt the convention used to select the peaks and troughs would matter much in the final result, but I didn’t test other averages.
I’m thinking about looking at these values to see if there seems to be a correlation with temperature. The reason I think this matters is due to a couple things. First, as the 144-month average graph shows, when cycles are shorter, the overall average activity of the sun over time is elevated. Obviously, magnitude matters, but so does the compression of the cycle in driving up averages over longer periods of time. Also, in my head I’m just thinking there has to be some limiting value to the effect of more sunspots on temperature. The theory as I understand it says that a quiet sun allows more cosmic rays into our atmosphere, inducing cloud cover, which in turn cools the planet. Sunspots disrupt the cosmic rays, and thus leaves our atmosphere more open to solar heating. At what point is there enough disruption to essentially eliminate, for all practical purposes, the cosmic ray effect? I don’t know the answer, I’m just musing. But if there is such a point, then higher magnitudes of sunspots wouldn’t necessarily drive temperature, so there will be an imperfect correlation. However, compressing the cycles in conjunction with higher activity should lead to noticeable warming, just as longer periods of low activity should lead to cooling. Shorter cycles with low amplitude and longer cycles with high amplitude will have some intermediate impact, if there is correlation to both measures.
I haven’t gone through that statistical exercise yet, but I will contemplate it. In the meantime, I have gone through and looked at the lengths of the cycles and semi-cycles.
Currently, we are at a point that is 96 months since the last maximum. The current minimum hasn’t yet been established, so this may increase. The last time this happened was at the minimum established in March 1879 (97) (per my definition of minimum). We are currently at a point of 143 months since the last minimum, and counting. The last time this occurred was with the minimum established December 1913 (144).
This is an interesting time.