One of the essential prerequisites for the IPCC case for extended global warming is the claim that we face an extended Holocene because orbital geometry now is similar to the 400KY (Stage 11) interglacial which lasted for 28, 000 years.
Based on the paper by Berger and Loutre (2003) it is claimed that the extraordinarily long Stage 11 interglacial period resulted from the low orbital eccentricity at the time, and now we have similar eccentricity and should therefore expect an extended Holocene. (IPCC TS 6.4 1.5)
It is reported that “It is very unlikely that the earth would naturally enter another ice age for at least 30 000 years” (IPCC TS 6.2.4 “Robust Findings”)
This position is completely without merit.
An analysis of FIG 1. below shows the orbital forcing during the 400KY precedent compared to the present configuration and it can be seen that we are very close now to the tipping point like that which led Stage 11 into the following ice age.
FIG.1 QUINN, LEVINE, RAYMO ET AL ORBITAL GEOMETRY VS CLIMATE
(AA) Projection at present insolation, (BB) Projection of Glaciation, (X) Paillard
The position (X) shows the insolation maximum at 427KY which triggered the Stage 11deglaciation. (Paillard 1998) The following small dip in insolation was not sufficient to reverse the warming trend . “The Interglacial thus lasts an additional precessional cycle, yielding a total duration of 28 000 years.” (IPCC 6.4.1.5)
This is the so called precedent for an extended Holocene. This is the reason given by IPCC for the “Robust Finding” that it is very unlikely that the earth would enter another ice age for at least 30 000 years. But as shown in FIG.1 there is no such change in insolation now and Solar Forcing is in rapid decline.
Projecting present Solar forcing (insolation) (AA) back to the 400KY precedent we intercept at exactly 400KY which corresponds to the collapse of the Stage 11 interglacial climate as it enters the following ice age.
The collapse of the Stage 11 interglacial occurs when the insolation decline is similar to today.
From this analysis, based on the Solar Forcing from present global geometry which has been accepted as the external signal for climate, the contention that it is very unlikely the Earth would naturally enter another Ice Age for at least 30 000 years is unsafe.
There is good reason to expect the imminent termination of the interglacial because of the coincident action of 3 major cyclic processes.
1. Insolation in rapid decline similar to the 400KY precedent.
2. We are near the end of the nominal 100KY glaciation cycle.
3. The present interglacial is near the average age for termination.
We are also witnessing some major natural processes which occur at the end of each interglacial such as the slow down of the MOC and polar ice melt.
It is time to plan for the coming Ice Age.
Peter Harris
September 2007
Well I emailed Hollan last night and he says the 400kya bottom is 10 watts lower - so what do we do? I hear your comment about transition - I ahve not overlooked it.
Hollan has not reversed the time scale. A simple labelling error and corrected in his new information. In any case his data correlates with Laskar et al which it derives from. We are reading the graphs correctly. Do we have reason to doubt Laskar's calculations??
If there is a transition now - where is it?
All the previous cycles and wiggles are irrelevant - it's the formal calculation of insolation is THE issue. Do you have an alternative formal calculation. Who says it's out of phase?
10 watts is a mile out !
You'll have to get over your aversion to other information. Science doesn't stay on one source you know.
And now you ducking off to 780 kya where we do not have a Hollan number calculated.
As far as the current situation is concerned with temperature flattening etc internal variability is an easy explanation and can be even modelled. http://www.sciencemag.org/cgi/content/abstract/317/5839/796
And solar insolation is constant for last few decades.
I cannot accept glib statements like "the CO2 modelled is contentious" when your own modelling is contentious.
In any case what's your basis in physics for saying all this CO2 will do nothing ?
I have reopened this very interesting post topic above if you wish to continue. I assume this thread will go off page within hours.
Luke
Yet more references.?? I thought we had finished with Hollam.
My article shows that the assumption by the IPCC (and others) that we have will have an extended interglacial now because of the similarity with 400KY is incorrect for two reasons ie
1.we do not have an additional cycle such as position (X)now,
2.and Insolation now IS AT THE SAME LEVEL AS THE 400KY TRANSITION. (see AA)
It is also at the same level as the when transitions occurred at 120,190,240,and 330KY.
The data speaks for itself.
In the 2005 Hollam article you have forwarded now he is proposing the extended Holocene because insolation minimum now will be 10W above the 400KY min, but the 400KY transition happened AT THE SAME INSOLATION LEVEL AS TODAY Luke.
ALL of those transitions happened well before the insolation went to it's lowest level.They happened when insolation was close to the same level as today. (See intercepts AA)
Take a look at 780KY which is the next previous precedent for orbital conditions now and you will see that the transition ocurred at a very much higher level of insolation than now.
While insolation is a reliable template to predict the timing of transitions is not a linear relationship with climate. A small movement in insolation such as 780KY has produced a transition of similar magnitude to the lower insolation levels at 900 and 700KY. The muted departure at 400KY produced a transition of the same magnitude as any of the more recent glaciation derived from much less insolation.
I see that he has corrected the chart which was more than 10KY out of phase in your first post.
He has used the TAR model projections for CO2 radiative forcing which are now out of date and the modeling is contentious.
But there is no need to make a projection, my argument is based on current proven data which has been misinterpreted. It covers the reason why there is no case for an extended Holocene. It is based on the self evident corelation between the mathematics and the geology.
Hollam has also reversed the time scale . It is OK either way provided it is labeled.
Global temperature at present is not increasing it has flat lined since 1998 (despite increased CO2). Southern Hemisphere temp is declining. (HadCRUT3).A Southern hemisphere decline is expected to lead the transition.
The MOC is slowing (RAPID 2007)
We are past the 100KY glacial cycle, the interglacial is past due for termination and solar activity is due to wane by 2020.
More reasons to expect a transition soon.
OK I emailed Jan Hollan and his response tabled below is as I suspected:
As I see that the -400 ka glaciation is discussed, I've added a graph showing the relevant period in more detail, at the end of
http://amper.ped.muni.cz/gw/articles/
The bottom line is: we should not extrapolate past trends (like decline in summer insolation, or the shape of the past glaciation cycles). We should look at reliably computed past, current and future forcings instead. It's evident we have almost reached the near-future insolation minimum already.
Before the atmosphere returns to normal (thousands of years), we will be on the increasing part of the insolation curve again...
Peter - golly gee I have explicitly addressed your point.
The regularity of recent cycles is no guide and the 400 kya transition is an example of that.
Insolation has NOT declined over the last 30 years - so we're waiting .... I guess you're going to say "this is the turnover point" - but temperatures are high and the Artic is melting..
I do not have an exact fix on now but you don't have a modelled future insolation scenario either. All you're doing is extrapolating from past graphs.
Where are your future insolation calculations??
I am listening to you - but you have not got enough here for a case.
I'm on threshold of communicating with the authors and getting some real data. For example I'm not even sure where we are NOW in the fine detail of the insolation curves.
All you have to do to progress this debate is to get some formal calculations of the future insolation from eccentricity, obliquity an precession and where we are now.
Come on that's not a bad bit of indulgence from myself.
There is a need to make formal calculations - I thought you were an engineer. Eyeballing data is not enough. And if you seriously believe your case a bit more to nail is is worth it. Remember Hollan's model comes from Laskar et al.
Luke
Once again you have quoted from yet another paper and made no attempt to address my argument.
One more time:
1.Eccentricity now is similar to 400KY but insolation now is NOT affected by an additional cycle like (X) and that means we should NOT expect an extended Holocene.
2.Furthermore insolation now is in rapid decline like when the 400KY (and other) transition occurred therefore we should expect transition NOW.
We have also exceede the 100KY glaciation cycle and the Holocene has exceeded the average age for transition.
A number of papers refer to an expected 28000 year Holocene ALL based on this misinterpretation of the insolation then and now.
There is no need to puzzle about the future data posted by Hollan.
By now you should be able to see for yourself what I have explained above. That insolation decline now should cause the transition as it has each cycle before.
Just look at now VS 400KY insolation along (AA)which shows the 400KY transition when insolation is the same as now and is in similar decline.
The data speaks for itself.
You are right when you say that if we are doing glaciation it needs to happen soon and that is the point .
Peter – have pondered your points long and hard and now have eye strain from peering at tiny squiggly lines 🙂
Your graph in the lead post here unfortunately does not have a simulated insolation into the future (from modelled eccentricity, obliquity and precession parameters).
So you are relying on series behaviour.of the last few cycles – not a good guide with 3 intercating periodic phenomena - eccentricity, obliquity and precession.
So for me it comes down to the insolation at 400 kya. So if we are going glaciation it need to happen it needs to happen soon.
If we get through the next few thousand years Hollan projects a growth to a moderate warmer period (small bump over 30,000 years hence).
Solar insolation has been pretty steady for the last 30 years. Greenhouse gases are much high 390 ppm and will get higher.
If you want to go on historical precedents I’m afraid I’m going to introduce YET ANOTHER paper which suggest the 400,000 kya transition had an interglacial stage much greater than the last cycle.
So if we want to further this discussion we need to really focus in on the 400 kya insolation, CO2 forcing and current conditions. Very hard peering at Hollan’s graph to see exactly where we are now in the decline sequence – need higher resolution data.
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Nature 429, 623-628 (10 June 2004) | doi:10.1038/nature02599; Received 27 February 2004; Accepted 22 April 2004
Eight glacial cycles from an Antarctic ice core
The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years.
For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long—28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.
Not just one paper to show Hollan had mislabelled his graph. That was only reason. Will consider your comments later - on the run just now.
Luke,
The work by Laskar is in close agreement with Quinn et al 1991 . I have used Quinn et al and the insolation computed by Levine, which is similar to the 400KY excursions shown by Hollan.
Once again you are throwing up even more papers . Are you afraid to address the nub of my argument? It is VERY VERY simple.
Now that you have discovered Hollan's 400KY and that the scales are in the same direction we have made some progress. Now please address the argument. Look at my yellow line(Insolation by Levine).
Working forward from 400KY we see that there is a transition to glaciation at 400, 330,240,190(split peak),and 120 approx.and EACH AND EVERY TRANSITION correlates with a decline in insolation.The transitions are 80 to 100KY apart.
Note that there is a transition at 400KY despite that the insolation is muted.
Note that the insolation is muted now but less muted than at 400KY.
Note that insolation now is in rapid decline as it was for the transitions in 400KY and at 330, 240,190 and 120KY.(see AA)AND IT IS OVER 100KY SINCE THE LAST TRANSITION.
THAT is why I say that we are near the tipping point to glaciation.
References by Berger and the IPCC to an extended interglacial based on the 400KY precedent are wrong. We do not have "an additional precessional cycle" see (X) now and they have ignored the transition which happened with the decline from muted insolation at 400KY.
I covered that on Sept 28th at 9.27AM please read it again.
Berger and the IPCC have incorrectly applied the 400KY insolation pattern to time now. They got it WRONG as you can see from the position X and the intercepts AA.
There is no case here for an extended Holocene.
Importantly there is no reason here to expect an extended global warming.
Well Peter you are correct about "ka" but without being tedious I was going on the original Laskar paper see page 526 here http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1993A%26A...270..522L&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf
You will note Laskar Fig 5 talks about the "last" million years. A negative scale. If you compare the negative side of the Hollan graph - the shape is an exact match for the Laskar et al graph.
Plus Hollan's interpretation does not make sense if one accepts the label as Ka instead of K yrs.
e.g. his comment about 130,000 years and 620,000 years.
The watts m2 are different from the Laskar paper but I think that's because Hollan has used a different solar constant.