Comparison to the 1976 paperThis paper is in large part a repackaging of the 1976 paper in many ways. In my opinion, each has their merits, but as a general overview this one seemed to be a little better presented. I won’t re hash the points made from the first paper that were already summarized. Basically, he starts again with a historical look at E. Walter Maunder’s and Gustav Spoerer’s look into the Maunder Minimum.
He then discusses the ability of the astronomers in those days to view and record sunspots. He more or less gives the same story on the evidence already discussed: the record of naked eye sunspots, the record of aurorae observations, the descriptions from full solar eclipses, sunspot counts recorded, and the like. Another clue that Eddy discusses that was not found in “The Maunder Minimum” is his work with Dorothy Trotter and Peter Gilman on reconstructing the sun’s rotation patterns in the 17th century. Currently, the sun rotates once every 27 days at the equator as viewed from earth – the actual rotation is around 25 days – the difference is due to the earth’s revolution around the sun in order to see something in the same relative spot, and increases as you move closer to the poles. This “differential rotation” lends itself to the theory of a dynamo effect that gives rise to sunspot activity through the interaction of deep seated magnetic fields in the sun and its surface.
A change in the rotation of the sun would change this interaction. By use of two old books: Rosa Ursina by Christoph Scheiner in 1630 and Selenographia by Johannes Hevelius in 1647, solar rotation could be estimated. Each book presented daily drawings of the sun nearly continuously for two years. Scheiner’s drawings were in 1625 and 1626. This book demonstrated a rotation similar to today.
Hevelius’ drawings from 1642 1644 show a significant change. The equatorial rotation sped up by a full day. The poles sped up slightly, but not in proportion to the equatorial change. Eddy questions whether or not a change in the sun that provides a faster rotation is the perpetrator of the Maunder Minimum. What About Now?Eddy suggests that there has been continuous increases in solar activity since the Maunder Minimum, and even anomalously so.
He bases this not only on the low anomaly of C 14 in modern times, but in the other observations of aurora, sunspot counts, the well defined corona. But he does have a large caveat with the Carbon 14 measure that I only briefly alluded to in the other summary. The “Suess Effect” which says that to the extent that fossil fuel production introduces isotopes other than Carbon 14 into the atmosphere, it dilutes the C 14 concentration. So, Eddy cautions about using the C 14 as a measure for solar activity, but based on the observations, it does appear that some portion of the current negative anomaly is due to solar activity, and we are in a period of anomalously high activity. The Climate ConnectionPossibly the most relevant point to come out of the new paper is Eddy’s ability to connect historical long term climate conditions to the solar activity, or lack thereof.
We have records of advancing glaciers and colder climate during the Maunder Minimum, but that could have been coincidental. But now with the radiocarbon dating extending back thousands of years, and multiple periods of C 14 anomalies, more investigation could be done. There are historical records where climate conditions of different periods are recorded, as well as the ability to determine and date the extent of glaciation in those different time periods. Comparing these records produced an undeniable pattern, that Eddy describes as “a key in a lock. ” Every extended decrease in solar activity matches a period of glacial advance, while every extended increase in activity matches a period of glacial retreat. As records allow, the long term temperatures match perfectly as well, as does winter severity indexes.