Is The Milankovitch Hypothesis Really Based On Celestial Mechanics - Or Sea Floor Geology?

In 1976 three scientists (James Hays, John Imbrie,  Nicholas Shackleton)  published a seminal paper. In it they presented a deep sea "climate record"  which they claimed contained the same temporal cycles as three parameters shown in Fig. 1 below, from a recent paper appearing in Physics Today (May, p. 48) by Mark Maslin.  

Their technique basically entailed using deep sea sediment cores to extract marine micro-fossils, to then estimate past sea surface temperatures.  The claim then was made that this geological proxy climate record revealed the same temporal cycles manifested in the three orbital parameters: eccentricity, obliquity, and precession.  All this is to substantiate the so-called Milankovitch theory which asserts these three distinct cycles are applicable to Earth's orbital motion.

The eccentricity (a) describes the shape of Earth's orbit around the Sun,  said to vary from near circular (as it is now) to more elliptical, with a period of 96,000 years.  The obliquity (b) is the tilt of the Earth's axis of rotation with respect to the orbital plane, and oscillates with a period of 41,000 years. The precession (c) combines the spin of Earth's orbital axis and its orbital path over time, producing a 21,000 year cycle.

Let me now back up to say I do not regard this as a "theory" but rather a hypothesis.  A theory, as I (and most physicists) define it, refers to a hypothesis which actually has made predictions that have been verified.  To my knowledge no such predictions have been made by Milankovitch's acolytes.   To be consistent, one would also expect such predictions to come out of a pure model from celestial mechanics - not one dependent on sea floor topography or geology.  These are two distinct sciences after all. (Paleo-climatology, i.e. based  on marine mciro-fossils,  is also distinct from celestial mechanics.)

Start with its contention that the obliquity of the ecliptic (inclination of Earth to its orbital axis) varies from 21 to 24 degrees over a 41,000 period in a process called ‘nutation’. This is certainly a magnitude in excess of a half degree (1800”) on either side of its current 23.5 deg.

Astronomers-astrometrists recognize no such period or differential of axial tilt. The following is from the book, Astronomy- Principles and Practice by A.E. Roy and D. Clarke, 1978, Adam Hilger Books, p. 118:

“Because of the nutational wobble in the Earth’s axis of rotation, the obliquity of the ecliptic (KP in Fig. 10.32) varies about its mean value. The magnitude on either side is about 9.”2.”

For the benefit of non-astronomers, the magnitude cited (9.”2) isn’t even one hundredth of a degree! Indeed it is nearly a factor 4 LESS than a hundredth of a degree! (which translates to 36”- there are 3600” = 1 degree))

Going now to Eichhorn and Mueller’s standard text in astrometry and geodesy, 

 p. 69, “astronomic nutation’:

"The main term of astronomic nutation is produced by the non-coincidence of the Moon's orbit with the ecliptic in conjunction with the retrograde motion of the lunar nodes. This results in a periodic change in the obliquity of the ecliptic termed nutation in obliquity, denoted by d  e

The astronomic nutation, from now on called simply ‘nutation’ is not to be confused with the true nutation appearing as a force-free precession (Eulerian motion) of the Earth’s rotation axis about its principal moment of inertia axis, which is part of the polar motion

The first six terms of the expression for nutation in obliquity are:

(9.”2100 + 0.”00091t) cos W - (0.”0904 - 0.”0004t) cos 2W – (0.”0024 cos (2 w m + W) + 0.”0002 cos (2 w s  – W) + 0.”0002cos 2 ( w m  + W) + (0.”5522 – 0.”00029) cos 2W s  

Where t denotes the time interval measured from 1900 January 0.5 d ET in Julian centuries (1 JC = 36525 mean solar days), W is the longitude of the mean ascending node of the lunar orbit on the ecliptic measured from the mean equinox of date, w m  is the ‘argument’ of the point where the Moon is nearest the Earth (i.e. from the lunar perigee),  w s  is the mean longitude of the solar perigee measured from the mean equinox of date, and  W s  is the geometric mean longitude of the Sun measured from the mean equinox of date.

We can then examine the putative change in the eccentricity e, which is currently at 0.0167 but which Milankovitch adherents claim can reach e = 0.07. (Elongating the orbit so as to influence climatic factors, e.g. see this video demonstration:

But what would it take to change the shape of the Earth's current orbit, to the one proposed by Milankovitch supporters?  How much energy would be required?  We can use the equation for the total energy of the orbit, in terms of the eccentricity, e, and the dimension of orbit known as the semilatus rectum,  r o   (=   b ² /a)  and the other familiar parameters for Newtonian orbit computations, e.g.

The objective is to find the change in energy E, i.e. when e is altered from 0.0167 to 0.07.  This turns out to be approximately:

D E   »  1.9  x 10   ⁴² J


This is an enormous amount of energy input.  WHERE does it come from? HOW is it produced?  What is the time evolution - in energy increments- leading to the final more eccentric orbit?  The Milankovitch adherents who adopt the work of a Serbian civil engineer, provide no answers.  How can they when they are working from reconstructed sea floor geology  findings and not celestial mechanics per se?

Given the preceding we should acknowledge that  there are significant problems with that Serbian civil engineer's hypothesis that bid us to exercise much more caution, i.e. before adopting it without qualification.  Especially given its reversed engineered construction from geological data, to arrive at a celestial mechanics format requiring new orbital elements.   Or conferring the benediction of an origin in celestial mechanics, as opposed to geology. One major issue was raised in a paper by Daniel B. Karner and Richard A. Muller ² which pointed out a number of serious problems, inconsistencies associated with the Milankovitch hypothesis. 

Specifically the authors – after  assessing the  data from numerous sources (e.g. U-Th dating from the Devil’s Hole cave in Nevada) found that:

-         

       the Devil’s Hole data indicated a shift in d ¹⁸ O  to interglacial values and was “essentially complete by 135 ka but the Northern Hemisphere summer insolation hadn’t yet warmed to the point when it would have triggered anything extraordinary, let alone a glacial termination”  Adding: “We call this discrepancy the causality problem”

-         Most of the sea level rise took place prior to the expected insolation warming

The authors conclude (op. cit.):

“The standard Milankovitch insolation theory does not account for the termination of the Ice Ages.”

Adding that:

“We can conclude that models that attribute the terminations to large insolation peaks (or equivalently to peaks in the precession parameter)…are incompatible with the observations.”

Equally significant, perhaps, Richard A. Muller  has pointed out in a separate paper ³ that “the spectral shapes predicted by the Milankovitch theory do not match those in the spectrum and bispectrum of the data..”

In addition, Muller notes that the net forcing associated with clouds, i.e. about 30 W/m ²  is substantially greater than the rms variations in insolation.   This leads him to conclude:  “The changes in cloud cover could be more important than the changes in Milankovitch parameters.” 

Finally, Puetz et al⁴,  employed a “universal cycle model” – using a Universal Wave Series (UWS) with cycles in the kyr range -  to show that  orbital tuning limits independent and objective testing of an empirical hypothesis like that of Milankovitch. In effect, while Milankovitch offers a “seductively elegant solution to the problem of age-stratum mapping”, its template remains a trap for selection effects (and data bias) to enter. This results in a condition, as it pertains to the Milankovitch hypothesis,  whereby:

 ”Reporting bias occurs when articles mention favorable results from orbitally tuned records, which are supportive of the Milankovitch theory, while failing to mention unfavorable results from un-tuned versions of the same records.”

The reason is clear given that (ibid.): “Statistically significant positive results that support a desired outcome are more likely to be published in high impact journals.”

Thus, while one can certainly appreciate Prof. Maslin’s article, it is also worthwhile to be aware of the problems to do with the underlying hypothesis, most of which I suspect were engendered by the origins in sea floor geologic data.. 

My primary gripe, then,  is there is no independent confirmation of the Milankovitch hypothesis from celestial mechanics proper. That is, where is the model, or even numerical simulation,  actually showing how the three orbital parameters evolve over time t to yield  the temporal cycles suggested by the  marine microfossil studies?  Granted Hays et al's paper is ingenious - even somewhat convincing - but when you strip away all the ersatz arguments it is still reverse engineered geology, from which the changing orbital elements must be indirectly  inferred.

Where is the direct connection to orbital parameter development in a celestial mechanics context?  In particular, leave out the geological data, where is the theory based on celestial mechanics showing how Earth's orbit changes its parameters to yield the temporal cycles claimed by Maslin, as well as Hays et al, and oh yes, Milankovitch.

References:

1. J.D. Hays, J. Imbrie, N.J. Shackleton, Science 194, 1121 (1976)

2.Daniel B. Karner, Richard A. Muller, A Causality Problem for Milankovitch, Science, 288, 2143 (2000)

3. Richard A. Muller, Limitations and Failures of the Milankovitch Theory, poster paper, American Geophysical Union Fall Meeting (2001)

4. Stephen J. Puetz, Andreas Prokoph, Glenn Borchardt, Evaluating Alternatives To The Milankovitch Theory, Journal of Statistical Planning and Inference, 170,  158 (2016)

High CO2 Levels Have Prevented New Ice Ages

According to new research published Wednesday in the  journal Nature  humans may have had a close escape from an imminent Ice Age as recently as the current geological epoch known as the Holocene. The tenet being that pre-industrial  modifications of the climate through agriculture, large  fires and deforestation might have barely avoided it

In the words of Hans Joachim Schellnhuber, one of the paper's three authors and founding director of the Potsdam Institute for Climate Impact Research:

"Humanity narrowly escaped a glacial inception in the middle of the Holocene, which was almost suppressing the formation of civilization,"

In addition, the study asserts that massive human greenhouse gas emissions since that time have probably "postponed" what might otherwise be another ice age "by at least 100,000 years."
The new research is based on the idea that there are two key factors that shape whether Earth goes into an ice age. There's one that humans can influence, as well as one they really can't.

The authors claim that the factor "out of our control" is Earth's "Milankovitch cycles", which  supposedly describe the erratic way in which the planet orbits the sun and spins on its axis over vast time periods. Earth's orbit grows slowly more and less elliptical, even as the angle of the planet's axial tilt and the wobble of the poles as the planet spins (much like what you see with a spinning top) also change slightly over thousands of years.

However, in an earlier blog post I noted there is no support from standard celestial mechanics for any such changes, e.g. in obliquity,

I wrote:  cf. http://brane-space.blogspot.com/2007/12/travails-of-milankovitch-hypothesis.html

'its contention that the obliquity of the ecliptic (inclination of Earth to its orbital axis) varies from 21 to 24 degrees over a 41,000 period .... is certainly a magnitude in excess of a half degree (1800”) on either side of its current 23.5 deg.

Astronomers-astrometrists recognize no such period or differential of axial tilt. The following is from the book, Astronomy- Principles and Practice by A.E. Roy and D. Clarke, 1978, Adam Hilger Books, p. 118:

“Because of the nutational wobble in the Earth’s axis of rotation, the obliquity of the ecliptic (KP in Fig. 10.32) varies about its mean value. The magnitude on either side is about 9.”2.”

For the benefit of non-astronomers, the magnitude cited (9.”2) isn’t even one hundredth of a degree"

The point is that until such time this conjecture is confirmed and integrated into celestial mechanics, it is really not a factor at all, especially one "out of our control".

Hence, the authors' claimed  "second factor that's in our control" is actually the only one:  how much carbon dioxide is in the atmosphere. We are able to turn this knob by how many forests we cut down and how many fossil fuels we burn, both processes that transfer carbon into the atmosphere.

Atmospheric carbon dioxide traps heat, causing an overall warming effect, and this will happen no matter where the planet is in its various orbital cycles. And if there's enough of it, it can counteract the tendency of these cycles to make and then unmake ice ages.

Using analysis of past planetary glaciations and a computer model of Earth that is able to predict their occurrence, the researchers found that carbon dioxide concentrations were only slightly too high to push us into glaciation a few thousand years ago.

"The Earth system would already be well on the way towards a new glacial state if the pre-industrial CO2 level had been merely 40 (parts per million) lower than it was during the late Holocene," the authors write. Indeed, they note that about 800,000 years ago, orbital alignments were similar, but carbon dioxide concentrations were around 240 parts per million, and glaciation did indeed occur.  But now, as concentrations push 400 ppm and are rising by 2 ppm/ yr. there is no chance at all of further Ice ages, period - unless our planet truly did suddenly tilt its axis by three degrees or more, or somehow alter its orbit to one with a longer semi-major axis.

Climate scientists from CU near Niwot Ridge, measuring snow depth.

Speaking of glaciers, alarming new findings from here in Colorado disclose that rock glaciers and other ice contaiing water -  west of Boulder - will soon vanish. The Arikaree Glacier, which feeds North Boulder Creek, had held steady from 1965 through 1997. This glacier, likely more than 1,000 years old — has been thinning by about 1 meter a year over the past 15 years and will disappear completely in 25 years, a team of scientists concluded.

The scientists, from CU - Boulder, scientists using ground-penetrating radar to learn that climate change is shrinking glaciers and other icy terrain in the Rocky Mountains — raising concerns about water supplies. In the words of hydrologist Mark Williams of the Institute of Arctic and Alpine Research, and lead author of the study and a principal investigator at CU's Niwot Ridge station:

"We can't get out of this. It is wired now, on the Colorado Front Range and in the Arctic. There's going to be less ability, on the water side, to address low flows in July and August .Glacier National Park is not going to have glaciers in another couple decades. People are going to be upset about that. We're in a loop we cannot get out of."

He added that a loss of sunlight reflectivity, as snow and ice disappear, will push temperatures even higher.

While idiot deniers continue their harangues against the "climate change and global warming hoax"  actual science has had the last word. In this case, the melting of glaciers and other ice in Colorado's mountains jibes with a worldwide trend that scientists and governments have linked to climate change. The shrinking of Earth's frozen "cryosphere" has been documented across Arctic sea ice, tundra and other areas that traditionally hold packed snow.

Janice and I observed these effects also, back in March, 2005, when we flew in a small plane round Mt. Denali, Alaska, e.g.














Before taking off, above, and one view from the cockpit of the plane on or approach  below

The original deal was that we were supposed to land on a glacier near the peak and be able to walk around and see Denali up close and personal. This was the package promised. However, after several swoops low over the area the pilot warned he wouldn't be able to fulfill it. His 27 years of experience and hawk eyes informed him the supporting snow and ice was much too treacherous to sustain even a small plane landing. Did we really want our "money's worth"? Uh no.  What we saw, however, was enough to show us that those who denied global warming were spouting bollocks and balderdash.

Alpine glaciers form when net snow accumulation leads to snow compressing and re-crystallizing into dense ice, which flows slowly to lower elevations, sculpting land. Over the past three decades, scientists measuring glaciers worldwide, using remote sensing and other methods, have documented shrinkage. We saw it in Alaska, as well as in Switzerland (Jugfrau region) when we were there in Sept. 2014, and compared it to photos of when we were there in August, 1978.

The work in Colorado focused on the size of the glacier, which had a maximum depth of 25 meters, shallower at the top and toes. Scientists also measured ice thickness in the Green Lakes Valley area below Niwot Ridge, which includes mounds of ice, dirt and rock that store water as well as subsurface ice and seasonally frozen lakes. They used radar, electrical devices and seismometers that send signals through subsurface ice.

The data continue to accumulate that the Earth's warming is real and having major consequences, and yet a sector of the populace remains firmly committed to the fiction that it's all part of "natural cycles".  Mostly done to try to escape species' responsibility and the sobering economic changes needed to at least make the coming climate onslaught more adaptable for humans,

We may have to "repent at leisure" thanks to attending too long to these naysayers.

Sandy: An Omen of Abrupt Climate Change?

Prof. Klaus Jacob of the Earth Institute at Columbia University, appearing on Chris Hayes’ UP' Saturday morning, projected that the receded shoreline of New Jersey visible today after Superstorm Sandy will become the norm by 2100 – due to rising sea levels. Either coastal cities will have to construct massive barriers or dykes such as we see in the Netherlands, or watch coastal cities inundated. His Sept. 10, 2009 prediction of a storm with surge 1’ higher than Irene was described as “prescient” by Hayes. That was:

“If the surge had been just that much higher, subway tunnels would have flooded, segments of the Franklin Delano Roosevelt Drive and roads along the Hudson River would have turned into rivers and sections of the commuter rail system would have become impassable or bereft of power….”


Reading Jacob’s words as projected on the screen conveyed an eerie feeling that we now have ‘passed through the looking glass’ and may be staring precipitous or abrupt climate change in the face – muting any further denier bilge or protests.


But what is the scientific basis?


According to Prof. Harunur Rashid, the co-Editor of an AGU (American Geophysical Union) monograph entitled 'Abrupt Climate Change: Mechanisms, Patterns and Impacts', the "defining moment for abrupt climate change research" occurred in 1993 when Willi Dansgaard and colleagues published oxygen isotope records for Greenland ice core samples that showed the air temperature swingin back and forth - meaning oscillating warming and cooling periods with time intervals as short as 1,000 years. Such temperature swings have subsequently become known as Dansgaard-Oeschger oscillations.

Though these "D-O oscillations' were first noted in Greenland ice cores, they were later observed in North Atlantic marine sediment samples. Subsequent studies disclosed abrupt climate events to be essentially ubiquitious - emerging anyplace on Earth that was subjected to sufficient study, analysis, including: Antarctica, the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and on land with records captured in cave mineral deposits.

Before the D-O oscillations discovery, the general belief - grounded in paleo- oceanographic research - was that the climate was governed by the so-called "Milankovitch cycles" or forced events related to the relative positions of the Sun and Earth (e.g. the semi-major axis of Earth is believed to alter some small %) as well as the tilt of the Earth's axis which is believed to vary from 21 to 24 degrees over an approximately 41,000 year period.


The cycles are presumed to be driven by the eccentricity or the progressive alteration of orbital elements in the Earth's orbit combined with alterations in Earth's axial tilt. As Rashid has noted in an interview for EOS - the journal of the AGU (Vol. 93, No. 32, Aug. 7, 2012, p. 310):


"At the time these cycles were considered abrupt climate change but we now know that is not accurate.".


Indeed, in a blog - one of the first on Brane Space some five years ago (Dec. 5, 2007), I basically dismissed the entire notion of Milankovitch forcings Therein I showed the hypothesis actually arose in the geological rsearch community (the name comes from a Serbian engineer with an avocation of astronomy) and not the celestial mechanics - astronomy research community.


The point is, Milankovitch cycles can't explain abrupt or rapid climate change, nor do they conform to a workable hypothesis unless actual evidence for change in the orbital elements is determined from celestial mechanics principles, not deep ocean finds or conjectures based on what is really circumstantial geological evidence. In any case, as I noted, these cycles can only account for temperature differences on the order of 1-2 F whereas differences of 7-10 have been observed.


The primary mechanism for abrupt climate change? According to Rashid (op. cit.):

"If you polled climatologists, probably 99% of them would agree that the interaction between freshwater in the North Atlantic and the Atlantic Meriodonal Overturning Circulation (AMOC) is the biggest driver of abrupt climate change."


The critical tipping point for inundating cities on the east coast? Likely when enough atmospheric CO2 is added such that the concentrations induce even more Arctic sea ice melting - to which massive fresh water runoff is added (from the repeatedly freezing and thawing northern continents such as Siberia, northern Canada.) These, according to Rashid, can disturb the AMOC with the result that the temperature balance is upset between the northern and southern hemispheres.

It is then possible that the predictions made by Klaus Jacob will come to pass. More research needs to be done, but for sure 'Sandy' and its aftermath is a heads up. As Prof. Jacobs noted, we need to either invest in protecting our cities and coastlands now....or reap the whirlwind later.