Milankovitch cycles

[Pmt111500]

Digging into some several southern hemisphere glacial deposits, these scholars are among the troupe trying to reorganize the magnitudes and potential reasons of onsets and offsets of ice ages and at the same time question the famed Milankovitch cycles theory (a hypothesis, that was great when it was first done, but do the numbers add up, questions are rising) : http://phys.org/news/2015-03-global-ice-ages.html

As phys.org is again full of links pointing to the original article  ,
 I had to find it by using google, and get hit by the paywall.
http://geology.gsapubs.org/content/early/2015/03/19/G36477.1

for me, preferred story is still orbital, namely eccentricity, but so the happenstances in the SH matter more. Is this again a question of fallibility of human perception, 'if something as large as ice age happens, the reason and the evidence must be near humans'?? Anyway. One more to the pile of articles questioning quite hard the traditional explanation, we might be witnessing a coup in the glaciology department, to put it lively.

[Pmt111500]

Pointing again to the ScienceOfDoom-series on glacials, orbital theories of them, history of the study of the Pleistocene glaciations, etc. and among 'orbital tuning', a quite reasonable method until very recently. He also goes into the more modern adaptations of orbital theory later in the series. I thought this was very well done, almost too thorough to my taste. You'll find the various chapters at the end of the blog post: http://scienceofdoom.com/2013/10/06/ghosts-of-climates-past-part-two-lorenz/

[Martin Gisser]

Here we address a long-standing puzzle of ice-age climate called the "fly in the ointment of the Milankovitch theory." Using geomorphic mapping and 10Be surface-exposure dating, we show that five moraine belts were formed during maxima of the last ice age by the Pukaki glacier in New Zealand's Southern Alps. They afford ages of 41.76 ± 1.09 ka, 35.50 ± 1.26 ka, 27.17 ± 0.68 ka, 20.27 ± 0.60 ka, and 18.29 ± 0.49 ka. These five maxima spanned an entire precessional cycle in summer insolation intensity at the latitude of the Southern Alps. A similar mismatch between summer insolation and glacier extent also characterized the Chilean Lake District in the mid-latitudes of South America. Thus, in apparent contrast to northern ice sheets linked by Milankovitch to summer insolation at 65°N latitude, the behavior of southern mid-latitude glaciers was not tied to local summer insolation intensity. Instead, glacier extent between 41.76 ka and 18.29 ka, as well as during the last termination, was aligned with Southern Ocean surface temperature and with atmospheric carbon dioxide.

Indeed a fly, not an elephant.
1.1) The timespan investigated is way too short. It doesn't even span one period of precession (23ky). Plus, Milancovich is not just about precession. There's also tilt (41ky) and eccentricity (100ky).
1.2) The whole ice age thing is not totally deterministic: It seems a basic ingredient to ice age theory is stochastic resonance.
2) Alignment with Ocean temp and CO2 is just what is to be expected. Now, how do these align with Milancovich?

John Baez' Azimuth Project has a lot about Milankovitch and stochastic resonance, e.g. https://johncarlosbaez.wordpress.com/2014/05/10/the-stochastic-resonance-program-part-1/

[johnm33]

I'm not a fan of Milankovich cycles, nevertheless here's an interesting read
      abstract "Recent observations are used to crudely quantify and scale the direct heating of the global ocean surface by submarine volcanism. These suggest a current submarine magma budget that is substantially greater than the prevailing consensus. The current ocean heating effect is estimated at c. 0.7W/m2. Interglacial events are geologically sudden and predictably cyclical, overtly caused by the combined effect of Milankovitch cycles. Several possible causes for interglacial warmings arising from these cycles have been proposed, and rejected as inadequate. These are summarily reviewed. It is concluded, in the absence of other capable causes, and in particular given the evidence of continued ocean warming throughout the Dryas cooling events, that ice age interglacial events are probably caused by a sustained increase in the rate of submarine volcanic heating of the oceans. The primary cause of increasing emissions is suggested as the rising levels of solid gravitational tides caused by the combined orbital forcing of all three main Milankovitch cycles. These tides are at their largest during interglacial warmings. How the dominant climate control system of oceanic feedback responds to this internal perturbation change is also discussed. In particular how the upper equilibrium temperature of an interglacial period is imposed by this control. "