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William McClenney's comment

Quote:The thing I love about these discussions is the sort of presumption that if it were not for the “anthropogenic climate disturbance” things would just keep rolling on climatewise, presumably forever.
It’s as if no one is aware, and therefore does not consider, that as best we can tell, the Holocene is 11,719 years old this year based on the end of the Younger Dryas.

As Wallace Broecker tells us:

“In order to estimate how long it will be before the present period of interglacial warmth comes to an end, we first have to estimate how long previous periods of extreme warmth lasted. Our best indicator is 180 records in benthic foraminifera. In these records, the periods of extreme warmth appear to be roughly one half of a precession cycle (i.e., “‘ 11,000 yr) in duration.”
“However, the duration of these intervals of peak warmth were not likely to have been exactly 11,000 yr. Take, e.g. the duration of the present warm period. Depending on one’s definition as to when it started, it has already lasted somewhere between 17,000 calendar years and 11,500 calendar years. The 17,000-year estimate would place the onset just after Heinrich event # 1, when a rapid retreat of the ice sheets commenced. If, instead, the onset is pegged at the beginning of the Bolling warm interval, then its current duration would be about 14,500 calendar years. Finally, if the Younger Dryas cold punctuation is assumed to lie within the glacial period, then the current duration would be about 11,500 calendar years. But, regardless of the choice among these definitions, the present interglacial has already lasted at least one half of an insolation cycle.”

The precession cycle varies between 19-23kyrs and we are at the 23kyr point now, making 11,500 half. Of the 8 interglacials since the Mid Pleistocene Transition only 1 has lasted longer than about half a precession cycle (MIS-11). MIS-11 had two precession based insolation peaks separated by near glacial conditions in between, so not exactly an ideally extended interglacial.

The problem here is that very few of us are even cognizant of exactly when we live, about 219 years longer than half the current precession cycle length. And that makes the discussion about anthropogenic global warming very interesting indeed.One might be tempted to conclude that we are presently living in the Anthropocene extension of Holocene interglacial warmth.
All who want to end the Anthropocene say “aye”.
And this is where it gets ugly:

“The possible explanation as to why we are still in an interglacial relates to the early anthropogenic hypothesis of Ruddiman (2003, 2005). According to that hypothesis, the anomalous increase of CO2 and CH4 concentrations in the atmosphere as observed in mid- to late Holocene ice-cores results from anthropogenic deforestation and rice irrigation, which started in the early Neolithic at 8000 and 5000 yr BP, respectively. Ruddiman proposes that these early human greenhouse gas emissions prevented the inception of an overdue glacial that otherwise would have already started.”
conclude Muller and Pross (2007)

“We will illustrate our case with reference to a debate currently taking place in the circle of Quaternary climate scientists. The climate history of the past few million years is characterised by repeated transitions between `cold’ (glacial) and `warm’ (interglacial) climates. The first modern men were hunting mammoth during the last glacial era. This era culminated around 20,000 years ago [3] and then declined rapidly. By 9,000 years ago climate was close to the modern one. The current interglacial, called the Holocene, should now be coming to an end, when compared to previous interglacials, yet clearly it is not. The debate is about when to expect the next glacial inception, setting aside human activities, which may well have perturbed natural cycles.”

Crucifix, M. and J. Rougier, 2009, On the use of simple dynamical systems for climate predictions: A Bayesian prediction of the next glacial inception, Published in Eur. Phys. J. Spec. Topics, 174, 11-31 (2009)

Bringing this discussion up to date, Ganopolski et al (2016):

“The situation is completely different for a CO2 concentration of 240 p.p.m., which is close to that observed at the end of MIS19. In this case all four model versions simulate rapid ice growth several thousands of years before the present and large ice sheets exist already at the present time (Extended Data Fig. 1). This means that 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 p.p.m. lower than it was during the late Holocene, which is consistent with previous results.”

Paywalled here:
Fascinating isn’t it? Just think about it, all it took to delay glacial inception was a measly 40ppm! So, I ask query the readership once again:

All who want to end the Anthropocene say “aye”.
Because if warmists are absolutely correct about the heathen devil gas CO2, then they might be dead wrong about what to do about it.
It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.

–William O. Douglas, U.S. Supreme Court Justice, 1952

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