Posted on 06/21/2012 10:11:38 AM PDT by Ernest_at_the_Beach
fyi
What is wrong with using standard Gregorian dates, or Hebrew years, or something that is NOT a relative measurement. /rant off
Thanks for posting this. I've always been interested in the Younger Dryas era and the following warming.
/johnny
Maybe someone comments at WUWT on the article.
Do you love the first graph that has wild temperature swings, and there is a teensy weensy blip with an arrow pointed at the present with a label “global warming”? Also, note that the temperature of the little ice age appears to be higher than our current temperature.
Still meditating.
Pet peeve. Sorry. I did like the article.
/johnny
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Andrew says:
Don-It’s true that events like the younger dryas do not appear to be orbitally forced, but good agreement has been shown between the rate of change of global ice volume and the near Arctic circle summer insolation. It is certainly clear that some “spikes” of rapid change exceed what would be expected from Milakovitch alone, but I wouldn’t be so quick to say that the Milankovitch theory of the glaciations is “dead” at all. The long term correlation is quite good. We just need to invoke other factors for some episodes that deviate from the right Milankovitch model.
This is all very fascinating to me.....more from the comments:
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Dennis Cox says:
The article states:
The climatic fluctuations before and after the Younger Dryas, as well as the fluctuations within it, and the duration of these changes are not consistent with a single event cause of the YD. Neither cosmic impact or volcanic eruptions could produce the abrupt, multiple climatic changes that occurred during the late Pleistocene.
In point of fact, since the given astronomical model for the Younger Dryas Impact Hypothesis is the progressive disintegration of the progenitor of the Taurids, as described in The Structure, and Evolution of the Taurid Complex by D.I. Steel et al. and proposed in W.M. Napier’s Paleolithic Extinctions and the Taurid Complex, it should be noted that the YDIH as written does not propose a single event at all.
The progenitor of the Taurid family of objects is thought to have entered the inner solar system, and a very short period elliptical orbit that crossed the orbits of all the planets of the inner solar system sometime between 20,000 and 30,000 YA. The astronomical data on the Taurids is as good as anything you can dig up with a shovel, and trowel. And that evidence indicates the 50 to 100 km wide Taurid Progenitor object immediately began to breakup as soon as it entered the inner solar system.
The the Earth’s passage though the debris from the progressive breakup of the Taurid Progenitor would have resulted in devastating impact showers, and storms of varying intensity twice a year for thousands of years, both before, and after, the start of the Younger Dryas.
The evidence so far is implying that the event at the start of the YD that produced a global impact layer comparable only to the Cretaceous/Tertiary boundary layer that marks the extinctions of the dinosaurs 65 million YA was only the worst of many annual cluster airburst events of varying intensity over a period that lasted for many millennia.
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Jim Clarke says:
What I find most interesting is that, according to the Greenland ice core (figure 1) Greenland has been about 3-5 degrees C warmer than it is now for most of the Holocene! All those gloom and doom studies about the rapidly melting Greenland ice sheet are maybe just picking up on the very beginning of a return to Holocene average!
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has no institution ever considered that there might be an irregular rotational hotspot in the earth’s core that gives more heat to the southern hemisphere during glaciations, and that it may be the cause of deglaciations? This is the case with some of Saturn’s moons Enceladus, where the southern tip is excessively warm, as a result of its core, and has more heat coming out of the southern cap, whilst the north is frozen. Geo-thermal events must have a considerable, if hitherto unstudied impact, particulary submarine.
Its one of climatology’s great weaknesses that the entire earth is not studied, and only the atmposphere
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You miss the big picture: when I looked at the first figure I recognised it looks like a diagram of an engine where somebody turned first time the key and it rumbled a couple of times before it died.
That’s the Younger Dryas break.
If you look at the Pleistocene 10Be levels in Figure 2 of the link I provided in my previous comment (Russian Journal of Earth Sciences) you see a rapid decline of 10Be (denoting increased solar activity) as it warms and then a very sudden and deep increase in 10Be production during the YD which would normally indicate a sudden and deep reduction in solar magnetic field activity. There is also, of course, another possible cause. To assume that 10Be production is a good proxy for solar magnetic activity one assumes that GCRs are constant. Maybe they aren’t. Maybe we are buffeted from time to time by “gusts” of dense cosmic rays or maybe sometimes pass through a “stream” of them where there are just more of them. The point is that it could be a combination of both things working at the same time. Maybe we get more GCRs hitting the atmosphere because the solar system is passing through an area with more GCRs and not because the sun changed. The GCRs are subject to being channeled by magnetic phenomena in the Galaxy.
So while we do know that solar magnetic activity can modulate GCRs reaching Earth, to assume that is the ONLY thing that chances those numbers might be a bit naive. Maybe we are bombarded from time to time with what amounts to shock waves or gusts of these particles. Maybe we find ourselves in streams of them. But one things does seem clear: for most of the Pleistocene the 10Be production was much higher than it has been during the Holocene. Why? I guess we will find out “shortly”.
The YD can be looked at as a cool interval or two successive warm intervals, the first short, the second long (the Holocene). The 2 warm periods of different length paradigm makes more sense. Just before the YD were deep glacial conditions and the YD was just a drop back to current glacial “normality” after an abortive jump to interglacial conditions. The first spike was an abortive interglacial, the second a “successful” one.
Indeed, if we remind ourselves that these very short abortive interglacial spikes occurred regularly throughout the glacial period, then the YD cool interval disappears as an anomaly, it is just an abortive interglacial spike that just happened to occur shortly before the “successful” interglacial rize which – unlike the abortive spikes – held on stably to the interglacial attractor rather than falling away from it.
Further, if we consider glacial and interglacial being alternate attractors in a nonlinear/nonequilibrium climate system, then abortive interglacial spikes and the less frequent interglacial rises which “stick” are an expected and normal behaviour.
Thus the YD is not in any way a “problem” except a problem of imagination and paradigm of the observer. The need for every upward or downward wiggle of earths climate history to have some discreet and unique external forcing comes from ignorance of quasi-chaotic systems and a deficient paradigm. It is even slightly absurd to imagine the climate system to be so passive.
Earth’s climate can change BY ITSELF.
OK it might be entrained in a simple or complex way by external periodic forcing, but it is not slavishly forced. Hunting for the magic celestial rhythm is futile.
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“Both 14C and 10Be production rates in the upper atmosphere changed during the YD. 14C and 10Be are isotopes produced by collision of incoming radiation with atoms in the upper atmosphere. The change in their production rates means that the Younger Dryas was associated with changes in the amount of radiation entering the Earth’s atmosphere, leading to the intriguing possibility that the YD was caused by solar fluctuations.”
At about this time there was a magnetic reveral (the Gothenberg). Changes in the magnetic field of the Earth could have changed the amount of radiation entering the Earth’s atmosphere.
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Michael g. Wallace says:
Nice article. In response to some other comments, I don’t see how anyone can claim to see a correlation between Milankovitch and past glacial oscillations. There are many intervals of time over the past several 100K glacial cycles where orbital forcing is the opposite of the global temperature trend. It’s no surprise that Principal Component Analyses applied to Milankovitch don’t match up with PCA applied to O18. I have seen a paper by Roe which shows a better match of these, but only when some nonlinear cause and effect assumptions are applied. When you invoke nonlinear causation, you can prove anything.
Also amusing how people don’t seem to worry about squaring Milankovitch with pre Quaternary climate patterns, going back hundreds of millions of years, where no ice ages have been identified. Orbital cycling likely persisted throughout that period, but for some reason that no scientist has been able to explain, or has bothered to try to explain, Milankovitch impacts were apparently nil.
I think the description of the sudden warming period (over decades) should by itself ‘kill’ any claims that current warming and sea level rise rates are unprecendented. And that should ‘kill’ any certainty about anthropogenic catastrophic climate change. But for some reason it won’t.
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Dennis Cox says:
The absence of a time lag between the N and S Hemispheres glacial fluctuations precludes an ocean cause and is not consistent with the North Atlantic Deep Ocean Water hypothesis for the cause of the Younger Dryas, nor with a cosmic impact or volcanic origin.
Hmmm,
On the contrary, I’m thinkin’ that an event that produced a global impact layer is perfectly consistent with “The absence of a time lag between the N and S Hemispheres glacial fluctuations”. So while that absence of a time lag between the two hemispheres is not consistent with the Deep Ocean Water hypothesis, it is consistent with a cosmic event of sufficient magnitude that it simultaneously emplaced high energy blast-effected materials into a global stratigraphic layer.
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Just for fun:
New Evidence Supports Cosmic Impact Theory
http://www.archaeorama.com/archaeology/cosmic-impact-theory/ P>
Rather revealing study in comparisons of warming and cooling cycle intensities.
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