Monday, November 19, 2012

SC 24

When in some very distant future the sun goes into nova, it will expand in size. Quite what will happen no one knows. One version of events is that the sun’s expansion will “push” the inner planets “out.” Another is that the sun will “engulf” all of the inner planets, out to the Earth’s orbit, so that we will be inside the sun. We have about 5 billion years to make our plans for escape.

All this, of course, is interesting, but what I would underline here is that we already have our being in the solar environment. As the third planet from the surface, we are quite close to this blazing giant with a mass a million times that of our little sphere of rock.

Back in 1963, at the time of President Kennedy’s assassination—and we do remember, if we’re old enough, what we were doing then—I was reading an article in a magazine suggesting that we were (believe it or not) on the edge of a new period of major global cooling. Yes. And that, in turn, got me interested in ice ages. And in turn then—in the solar cycle. It seemed to me that if the earth either heats or cools, the sun must be causing that change.

The sun has cycles of activity, the recurring solar cycle. It is measured by the appearance of sunspots. Their average number per month has been charted carefully since 1749 and they form peaks (lots of spots) and troughs (few or none). Each cycle is measured from trough to trough; cycles average about 11 years. Astronomers began to number them in the eighteenth century. The first sun cycle (SC 1) was the one extending from 1755 to 1766. We are now in SC 24. It began on January 4, 2008, when astronomers noted the appearance of a sunspot, high on the sun, with reversed polarity. Both are necessary to signal the change from cycle to cycle—appearance of a sunspot at high latitudes as well as magnetic reversal. Sunspots are magnetic fields and, like all magnets, have a N-S polarity. The spots of a cycle always have the same alignment. When a spot appears high on the sun with reversed polarity, S-N, that signals the start of a new cycle.

SC 24 is now beginning to peak. Above I show an image from NASA (link) of SC 23 and SC 24, the latter as far as it has gone. In an article that appeared in March 29 (link), NASA predicted that SC 24 will be “weak,” producing about 90 sunspots at its peak, the lowest observed since 1928. This follows SC 23 which had an unusually enduring and inactive trough. What this might mean is that the sun is going into a cooler period—and that, at least based on common-sense logic, should also mean that the Earth will echo that back. Is such speculation heterodox?

Well, let’s just see. Precise measurement of cycles began in 1749, but pretty good measurements go much farther back. And looking back, we see earlier periods of very low solar activity. The most pronounced of these was the Maunder Minimum, a seventy-year period extending from 1645 to 1715. That period was experienced on Earth, and has been referred to since, as the coldest period of the Little Ice Age, which began earlier. Another, later dip, which lasted 40 years, is known as the Dalton Minimum, 1790-1830. Significant global cooling took place then as well. These two minima are named after astronomers, Edward Maunder (1851-1928) and John Dalton (1766-1844). Measurement during the Maunder Minimum, as shown below in little red crosses, was not quite as systematic as it later became, but the extremely low activity of the sun was noted by a handful of expert astronomers at the time, and the Little Ice Age is well documented (see, for instance, The Little Ice Age: How Climate Made History, 1300-1850, by Brian M. Fagan). During the Dalton Minimum, lower-than-average temperatures were noted, and one observatory in Germany, Oberlach Station, observed a 2° C drop in temperature over a twenty-year period. Herewith a look at 400 years of sunspot observations from Wikipedia (link). The colored lines show the sun cycles; the black line is not identified in the source but may be carbon-14 measurements, an indirect indicator of sunspot activity. More on that on Ghulf Genes (link).

The modern scientific consensus rejects the idea that the solar cycle has a direct effect on global temperature. Climate is a massively complex phenomenon, not well understood even today. And the heat-production of the sun at its minimum (in the troughs) is only about 0.1 percent lower then its output at the maximum (in peaks). But then, of course, I wonder why we speak of the Little Ice Age—which had drastic consequences at least as recorded in Europe—and the cooling during the Dalton Minimum. Could the modern consensus have something to do with excessive caution in a day and age when Global Warming is a major socio-political issue? If the experienced global warming is due to what, in the chart above, is labeled the Modern Maximum, i.e., of solar activity, and may be followed by a lessening of solar heat production in due time (a “weak” SC 24 followed by others), let us hope that that period won’t last long either. Cooling periods are much worse for humanity than periodic warmings.

No comments:

Post a Comment