Why Milankovitch Cycle Theory Is Like Astrology
Sometimes a hunch proves to be unworkable. The Milankovitch Cycle theory has too many complications. It’s time to give it up.
In the 1920s, Milutin Milankovitch, a Serbian astronomer, mathematician and popularizer of science, had a bright idea. Knowing that certain orbital cycles drift over time, he wondered if they could influence the earth’s climate. Though not the first to think about this, he set about calculating periods where sunlight would be more likely to hit the northern latitudes more directly, thinking that those areas would heat up. Other areas might receive sunlight at a more oblique angle, becoming cooler. The cycles might even generate an Ice Age!
Milankovitch’s idea sent astronomers on a planetary snipe hunt. Intrigued by the suggestion, they calculated changes in the earth’s eccentricity, its inclination, orbital obliquity, the drift of the apsides, and other factors. There are enough free parameters to find a host of coincidences. Like modern astrologers, they calculated cycles on the orders of tens to hundreds of thousands of years that might have left a mark in the strata of the earth. Milankovitch theory attracted a cult following, as geologists and planetary scientists, armed with visions of long age cycles resembling zodiacal signs, tried to associate various orbital cycles with geological evidence of climate variations. And like astrology, its predictions found some support – provided that epicycles could be added, and anomalies could be explained away. The allure of the notion led to visions that Milankovitch cycles could influence the course of evolution! Maybe it caused a climate change that forced apes out of the trees to become human beings!
Milankovitch-ology, Milankovism, Milank-astrology, or whatever we might call it, continues today. Occasional papers claim success tying orbital dynamics to the geological record. Scientists peruse oxygen ratios in ice cores drilled in the Antarctic or Greenland, seeing if they can find signatures of climate change tied to the Milankovitch cycles. Here are some recent samples:
Thank the moon for Earth’s lengthening day (Phys.org). The moon has been receding from the earth due to tidal forces, but this article ties it into Milankovitch cycles. The similarity to astrology is striking. Supposedly the movement of distant worlds affects the character of the planet.
Earth’s movement in space is influenced by the other astronomical bodies that exert force on it, like other planets and the moon. This helps determine variations in the Earth’s rotation around and wobble on its axis, and in the orbit the Earth traces around the sun.
These variations are collectively known as Milankovitch cycles and they determine where sunlight is distributed on Earth, which also means they determine Earth’s climate rhythms. Scientists like Meyers have observed this climate rhythm in the rock record, spanning hundreds of millions of years.
Well, hasn’t the earth been orbiting the sun for billions of years, according to secular astronomers?
But going back further, on the scale of billions of years, has proved challenging because typical geologic means, like radioisotope dating, do not provide the precision needed to identify the cycles. It’s also complicated by lack of knowledge of the history of the moon, and by what is known as solar system chaos, a theory posed by Parisian astronomer Jacques Laskar in 1989.
The solar system has many moving parts, including the other planets orbiting the sun. Small, initial variations in these moving parts can propagate into big changes millions of years later; this is solar system chaos, and trying to account for it can be like trying to trace the butterfly effect in reverse.
So already, we see the believers putting escape hatches in the theory. Anything that doesn’t fit the predictions of Milank-astrology can be explained away by chaos.
To be sure, certain orbital parameters can be measured accurately in the present. Geophysicists can monitor the shift of our polar axis, and can credibly state that, ‘All things being equal, if the drift continues uninterrupted, the pole will point at such-and-such a position in 26,000 years.’ Astrology itself, though, had very precise measurements of planetary positions, predicting where conjunctions would occur centuries or millennia in advance. Those measurements, however, did not justify the suppositions placed on them about human destiny. And scientists can only validate predictions made within their lifetime, not 26,000 years in the future. An even more difficult supposition to make is that a certain orbital parameter will cause an Ice Age.
Can the believers gain credibility by tying previous Ice Age(s) to orbital parameters? That’s what they try to do, linking measurements from ice cores to Milankovitch periods. They can measure ratios of oxygen isotopes in ice to periods when Milankovitch Cycles say that the earth should have been cooler. But this kind of corroboration requires auxiliary hypotheses. The oxygen ratios fluctuate on the assumption that foraminera, when their shells harden, preferentially pick up one isotope over another depending on temperature. It becomes even more complicated, however, when trying to correlate cores from different parts of the world. Theoretically, a Milankovitch ice age should affect the globe, but the signals are sometimes noisy, and don’t easily line up. It’s tempting for geologists to force this peak in one core to line up with another peak in another core. You can start seeing patterns in the noise that reflect more the mind of the researcher than the actual history of the earth.
In the case of this Phys.org article, the proximity of the moon, with its big influence on tides, could have swamped the influence of Milankovitch cycles on climate. The wizards of Milank-astrology boast of understanding, just like astrologers did to their clients, both kings and peasants:
With the approach, they could reliably assess from layers of rock in the geologic record variations in the direction of the axis of rotation of Earth and the shape of its orbit both in more recent time and in deep time, while also addressing uncertainty. They were also able to determine the length of day and the distance between the Earth and the moon.
“In the future, we want to expand the work into different intervals of geologic time,” says Malinverno.
The study complements two other recent studies that rely on the rock record and Milankovitch cycles to better understand Earth’s history and behavior.
Proterozoic Milankovitch cycles and the history of the solar system (PNAS). The paper on which this is based, in PNAS, boasts even more:
Periodic variations in Earth’s orbit and rotation axis occur over tens of thousands of years, producing rhythmic climate changes known as Milankovitch cycles. The geologic record of these climate cycles is a powerful tool for reconstructing geologic time, for understanding ancient climate change, and for evaluating the history of our solar system, but their reliability dramatically decreases beyond 50 Ma. Here, we extend the analysis of Milankovitch cycles into the deepest stretches of Earth history, billions of years ago, while simultaneously reconstructing the history of solar system characteristics, including the distance between the Earth and Moon. Our results improve the temporal resolution of ancient Earth processes and enhance our knowledge of the solar system in deep time.
Only careful reading of the paper shows how they reduce uncertainties in their ‘knowledge of the solar system in deep time.’ They use Milankovitch theory to validate Milankovitch theory!
At the core of this approach are three components: (i) the TimeOpt method (8), which explicitly considers timescale uncertainty, and utilizes multiple attributes of the astronomical signal to increase statistical reliability; (ii) the underlying astronomical theory, which links observed climatic precession and orbital eccentricity rhythms to fundamental frequencies of the solar system and Earth–Moon evolution (2, 4) (Table 1); and (iii) a Bayesian Markov Chain Monte Carlo approach that allows explicit exploration of the data and model space and uncertainties. The result is a robust methodology for astrochronology that is suitable for the Proterozoic, and greatly enhances the astronomical knowledge that we can obtain from younger strata (e.g., the early Cenozoic). We refer to this approach as TimeOptMCMC. We emphasize that although TimeOptMCMC provides a rigorous quantification of the uncertainties in astrochronologic results, the method does not by itself reduce these uncertainties. Ultimately, uncertainties in astrochronology can only be decreased by additional information provided by measured data.
OK. So where is the “additional information provided by measured data”? Call in Darwin; the wizard of the Stuff Happens Law. He supplies that.
Astronomical metronome of geological consequence (PNAS). In this commentary about a Milankovitch paper by Kent et al., “Empirical evidence for stability of the 405-kiloyear Jupiter–Venus eccentricity cycle over hundreds of millions of years,” Linda Hinnov reveals some of the confirmation bias that allows believers in Milank-astrology to pat themselves on the back. They simply look for the data that confirms what they expect, and discount the ones that don’t (see Card Stacking in the Baloney Detector).
In geology, a reliable “metronome” in the geologic record with a sufficiently short repeat time would greatly enhance the resolving power of the geologic timescale. Astronomers recognized the potential importance of a dominant 405-ky cycle in Earth’s orbital eccentricity variation for supplying such a metronome (2, 3), leading geologists to turn to the stratigraphic record of astronomically forced paleoclimate change to search for this cycle. In fact, one of the first geological studies to describe 405-ky scale stratigraphic cycling was on the Triassic–Jurassic Newark Basin lacustrine strata recovered in the National Science Foundation-funded Newark Basin Coring Project, in which each of the prominent 60-m-thick McLaughlin cycles in the cored sequence was assigned a 412.885-ky periodicity based on a now-legacy analytical astronomical solution, BRE74/BER78 (6, 7). Since the 1990s, there have been dozens of reports for strong 405-ky scale cycles in stratigraphic sequences from around the world that appear to bear out this astronomical calculation (8). However, not one of these reports has presented incontrovertible support from independent geochronology that links specific 405-ky cycles, identified by their order of appearance relative to the present day, to those in the astronomical solution. Until now, this has included the Newark Basin, which, besides the flood basalts at the top of the core series, suffers from a lack of datable materials—for example, volcanic ashes—that could help establish a numerical timescale for the core series….
Kent et al. (1) demonstrate that assigning a 405-ky periodicity to the McLaughlin cycles is verified by high-precision geochronology….
Assuming that the Chinle dates approximate stratigraphic age, the results presented by Kent et al. (1) disentangle multiple issues concerning Triassic chronostratigraphy, the geologic timescale, paleoclimate, evolution, and Solar System behavior, and open new lines of inquiry.
What an amazing set of confirmations! Perhaps it can also advise you on what day to go shopping this week? What they’re not telling you is that some of the same assumptions about dating are used to bring the data sets into conformity: assumptions about long ages (“the geologic timescale”), evolution, and the ‘proper’ data sets that support the expected (or desired) conclusions. That doesn’t matter; it’s a good-enough horoscope, Hinnov says, so it’s time to party!
The independent confirmation of the 405-ky orbital eccentricity cycle in these ancient sedimentary deposits has been long-sought and will be enthusiastically welcomed by geologists. It represents an important “benchmark” in the rapidly expanding annals of cyclostratigraphy, the branch of stratigraphy dedicated to the study of astronomically forced climate change and the development of an astrochronology to support and refine the geologic timescale.
But if the ‘chrono’ is wrong in astrochronology, only ‘astrology’ remains. It’s similar to the lack of ‘bio’ in astrobiology.
Pacing of Paleozoic macroevolutionary rates by Milankovitch grand cycles (PNAS). The National Academy of Sciences seems to be on a Milank-astrology kick. This is the 3rd paper in recent months. This one tries to link the evolution of a certain microscopic planktonic animal to its horoscope in the skies. The authors are aware that not all scientists are true believers yet.
There has been long-standing debate about the relative roles of intrinsic biotic interactions vs. extrinsic environmental factors as drivers of biodiversity change. Here, we show that, relatively early in the history of complex life, Milankovitch “grand cycles” associated with astronomical rhythms explain between 9 and 16% of variation in species turnover probability (extinction probability plus speciation probability) in a major Early Paleozoic zooplankton group, the graptoloids. These grand cycles would have modulated climate variability, alternating times of relative stability in the environment with times of maximum volatility, which influenced oceanic circulation and structure and thus, phytoplankton populations at the base of the marine food web.
It’s a grand vision, that’s for sure. Skeptics may wonder about the other 91% to 84% of variation in species turnover that is not explained by Milank-astrology.
Ancient Greenland was much warmer than previously thought (Phys.org). This article from Northwestern University is a combination of surprise and dogma. The surprise is in geological and fossil evidence that Greenland in the past “was much warmer than thought.” The dogma is in re-affirmations of the climate consensus, and in blind acceptance of Milankovitch explanations for past warming: “Well-known changes in Earth’s orbit caused warming during the early Holocene and Last Interglacial periods.”
Bring in the Skeptics
Not everybody falls for Milankovich theory. Even its supporters recognize that there has been “long-standing debate” about it. Of all places, Wikipedia, usually a reliably pro-evolution and pro-materialist source when it comes to anything about long ages and Darwin, lists five problems with it:
- The 100,000 year problem: Milankovitch’s expected 41,000 year cycle doesn’t match the predicted 100,000 year cycle for ice ages. Various attempts to reconcile the discordant cycles have been made, but “Some have argued that the length of the climate record is insufficient to establish a statistically significant relationship between climate and eccentricity variations.”
- The transition problem: Some believers discern a 41,000-year period followed by a 100,000-year period. How did the cycles transition from one mode to the other?
- The unsplit peak problem: Peaks in the climate data don’t always match predictions from eccentricity cycles.
- The Stage 5 problem: A particular peak in the deep-sea core data said to be at 130,000 years falls 10,000 years earlier than Milankovitch Theory predicts. How can the effect precede the cause?
- The causation-exceeds-effects problem: The effects observed in geological records appear more extreme than what small variations in orbital factors predict: “the variation in Earth’s climate is much more extreme than the variation in the intensity of solar radiation calculated as the Earth’s orbit evolves.”
Dusty Rainfall Records Reveal New Understanding of Climate (University of Arizona). This study turns Milankovitch theory upside down. The press release explains:
Ancient rainfall records stretching 550,000 years into the past may upend scientists’ understanding of what controls the Asian summer monsoon and other aspects of the Earth’s long-term climate, reports a University of Arizona-led international team of researchers in the May 25 issue of the journal Science.
The standard explanation of the Earth’s regular shifts from ice ages to warm periods was developed by Milutin Milankovitch in the 1920s. He suggested the oscillations of the planet’s orbit over tens of thousands of years control the climate by varying the amount of heat from the sun falling above the Arctic Circle in the summer.
“Here’s where we turn Milankovitch on its head,” said first author J. Warren Beck, a UA research scientist in physics and in geosciences. “We suggest that, through the monsoons, low-latitude climate may have as much effect on high-latitude climate as the reverse.”
Closing a Loophole in the Refutation of a Key Argument for Milankovitch Climate Forcing (Jake Hebert, Creation Research Society Quarterly [CRSQ] 54:2, Fall 2017). Biblical creationists, naturally, disagree with Milankovitch theory because they don’t accept the long ages. But their critique, often at PhD level, cannot be ignored on that basis. In this recent issue of CSRQ, Dr. Jake Hebert of ICR documents severe discrepancies between data from orbital mechanics and from core samples. He also shows how an important “Pacemaker” paper from 1976 by Shackleton et al., touted as a strong vindication of Milankovitch theory, was subsequently found to rely on erroneous data that undermine its whole premise. “When all these changes are taken into account, the Pacemaker analysis provides no convincing support for the currently-accepted version of the Milankovitch hypothesis,” Hebert says. “In fact, agreement with Milankovitch expectations is worse than the previously published new results obtained using the reconstructed data sets.”
We can add that it’s not clear how tiny changes in sunlight within the habitable zone are capable of producing huge swings in climate on all parts of the globe (see problem #5 from Wikipedia, above). Certainly those variations are not going to cause Darwinian evolution! “It’s getting colder this winter. Somebody send me a mutation that will change my exterior, my diet, my metabolism, brain and my behavior. Whoops! Wrong mutation! I’m dead!” Imagine that the rare, beneficial mutation comes. “Sudden warm spell! I’m dead!” Wouldn’t it be easier for the animal to just migrate? The environment cannot cause anything to grow an eye, a wing, or a new body plan. Only intelligent design can pre-program a system for adaptability (ICR).
Secular philosophers could have fun picking apart Milankovitch theory. Throughout the text, we have sprinkled comparisons to astrology: self-fulfilling prophecies, tweaking of anomalies to get congruence, cherry-picking data, and extrapolation of effects beyond the capabilities of a cause. Kuhnians could point to the Milankovitch guild as a social group engaged in puzzle solving about the paradigm, not in questioning the paradigm itself.
This is not just harmless fun and games among that social group. As the shamans of our culture, scientists influence the thinking of impressionable adults and children, leading them down the primrose path to imagine that the positions of the planets determine their origin and their destiny.