When politicians say that 98% of published scientists agree that man is the cause of global warming you may wonder who the other scientists are. It’s been known at least since the mid 1800s that the world was getting warmer; that came up talking about the president’s “Resolute” desk, and the assumption was that the cause was coal. The first scientist to present an alternate theory was James Croll, a scientist who learned algebra only at 22, and got to mix with high-level scientists as the janitor at the Anderson College in Glasgow. I think he is probably right, though he got some details wrong, in my opinion.

James Croll was born in 1821 to a poor farming family in Scotland. He had an intense interest in science, but no opportunity for higher schooling. Instead he worked on the farm and at various jobs that allowed him to read, but he lacked a mathematics background and had no one to discuss science with. To learn formal algebra, he sat in the back of a class of younger students. Things would have pretty well ended there but he got a job as janitor for the Anderson College (Scotland), and had access to the library. As janitor, he could read journals, he could talk to scientists, and he came up with a theory of climate change that got a lot of novel things right. His idea was that there were  regular ice ages and warming periods that would follow in cycles. In his view these were a product of the precession of the equinox and the fact that the earth’s orbit was not round, but elliptical, with an eccentricity of 1.7%. We are 3.4% closer to the sun on January 3 than we are on July 4, but the precise dates changes slowly because of precession of the earth’s axis, otherwise known as precession of the equinox.

Currently, at the spring equinox, the sun is in “the house of Pisces“. This is to say, that a person who looks at the stars all the night of the spring equinox will be able to see all of the constellations of the zodiac except for the stars that represent Pisces (two fish). But the earth’s axes turns slowly, about 1 days worth of turn every 70 years, one rotation every 25,770 years. Some 1800 years ago, the sun would have been in the house of Ares, and 300 years from now, we will be “in the age of Aquarius.” In case you wondered what the song, “age of Aquarius” was about, it’s about the precession of the equinox.

Our current spot in the precession, according to Croll is favorable to warmth. Because we are close to the sun on January 3, our northern summers are less-warm than they would be otherwise, but longer; in the southern hemisphere summers are warmer but shorter (southern winters are short because of conservation of angular momentum). The net result, according to Croll should be a loss of ice at both poles, and slow warming of the earth. Cooling occurs, according to Croll, when the earth’s axis tilt is 90° off the major axis of the orbit ellipse, 6300 years before or after today. Similar to this, a decrease in the tilt of the earth would cause an ice age (see here for why). Earth tilt varies over a 42,000 year cycle, and it is now in the middle of a decrease. Croll’s argument is that it takes a real summer to melt the ice at the poles; if you don’t have much of a tilt, or if the tilt is at the wrong time, ice builds making the earth more reflective, and thus a little colder and iceier each year; ice extends south of Paris and Boston. Eventually precession and tilt reverses the cooling, producing alternating warm periods and ice ages. We are currently in a warm period.

Global temperatures measured from the antarctic ice showing stable, cyclic chaos and self-similarity.

At the time Croll was coming up with this, it looked like numerology. Besides, most scientists doubted that ice ages happened in any regular pattern. We now know that ice ages do happen periodically and think that Croll must have been on to something. See figure; the earth’s temperature shows both a 42,000 year cycle and a 23,000 year cycle with ice ages coming every 100,000 years.

In the 1920s a Serbian Mathematician, geologist, astronomer, Milutin Milanković   proposed a new version of Croll’s theory that justified longer space between ice ages based on the beat frequency between a 23,000 year time for axis precession, and the 42,000 year time for axis tilt variation. Milanković used this revised precession time because the ellipse precesses, and thus the weather-related precession of the axis is 23,000 years instead of 25,770 years. The beat frequency is found as follows:

51,000 = 23,000 x 42,000 / (42000-23000).

As it happens neither Croll’s nor Milanković’s was accepted in their own lifetimes. Despite mounting evidence that there were regular ice ages, it was hard to believe that these small causes could produce such large effects. Then, in a 1976 study (Hayes, Imbrie, and Shackleton) demonstrated clear climate variations based on the mud composition from New York and Arizona. The variations followed all four of the Milankocitch cycles.

Southern hemisphere ice is growing, something that confounds CO2-centric experts

Further confirmation came from studying the antarctic ice, above. You can clearly see the 23,000 year cycle of precession, the 41,000 year cycle of tilt, the 51,000 year beat cycle, and also a 100,000 year cycle that appears to correspond to 100,000 year changes in the degree of elliptic-ness of the orbit. Our orbit goes from near circular to quite elliptic (6.8%) with a cycle time effectively of 100,000 years. It is currently 1.7% elliptic and decreasing fast. This, along with the decrease in earth tilt suggests that we are soon heading to an ice age. According to Croll, a highly eccentric orbit leads to warming because the minor access of the ellipse is reduced when the orbit is lengthened. We are now heading to a less-eccentric orbit; for more details go here; also for why the orbit changes and why there is precession.

We are currently near the end of a 7,000 year warm period. The one major thing that keeps maintaining this period seems to be that our precession is such that we are closest to the sun at nearly the winter solstice. In a few thousand years all the factors should point towards global cooling, and we should begin to see the glaciers advance. Already the antarctic ice is advancing year after year. We may come to appreciate the CO2 produced by cows and Chinese coal-burning as these may be all that hold off the coming ice age.

Robert Buxbaum, November 16, 2018.