Why has the Holocene temperature cycle deviated from previous cycles?

[DarioC]

Reading a lot about climate change over the past few years has lead me to a question.

From looking at the available temperature charts for the past 450K years I have become curious about the lack of comment on the deviation for the last 12K years from previous periodic 124K year peak temperatures.

Previous 124K year cycles appear to average about 3 degrees Centigrade warmer at the peak than our present temperature. It appears from available charts, all in agreement, that about 12K ago the temperature rolled over at approximately the temperature we are experiencing now, never going near previous 124K peaks. That is to say there is a 10 to 12 K year "flat" spot that is in contrast with records of previous cycles which exhibit a rather sharp peak and then rapidly go into a stepped temperature drop.

I have been unable to find any reference to this seeming "anomaly," in climate discussions or literature.

Considering that the existence of modern civilization is due to the world not heading toward having a mile of ice over most of the presently temperate areas of the Earth that might be the situation had the cycle continued to a "normal" peak and flipped, one might expect the subject to get a little more attention.

Any experts here that care to comment, or can anyone give me ANY reference that addresses the subject.

 

[Evo]

Discussion of AGW and current climate change is not allowed due to the flame wars it causes, but as long as this stays strictly on the subject of the holocene, it is ok.

 

[cesiumfrog]

Previous 124K year cycles appear to average about 3 degrees Centigrade warmer at the peak than our present temperature. It appears from available charts, all in agreement, that about 12K ago the temperature rolled over at approximately the temperature we are experiencing now, never going near previous 124K peaks. That is to say there is a 10 to 12 K year "flat" spot that is in contrast with records of previous cycles which exhibit a rather sharp peak and then rapidly go into a stepped temperature drop.

Where is the evidence for this?
(In particular, when you describe the "flat spot" shape of this peak, do you have a graph that shows the shape of the peaks over the previous several hundred ky in the same level of detail as this last several ky?)

 

[DarioC]

Not interested in the GW discussion at all; just want to hear from maybe a pro who is familiar with the data such as the Vostok ice cores and is willing explain or discuss what it is that I am seeing. Or--refer me to an expert that might explain it to me, or even a book that covers the subject.

As a courtesy I will respond that the "flat" recent (10K year) line on a 450k year graph shows as a series of small variations of considerable width, whereas the previous 124 year peaks, on the same scale, show a single sharp point at maximum temperature.

I have no need to "prove" anything, the charts are all over the Internet, and they all show the same thing.

If I can edit this thing I will put a link to some of the charts here. I thought most of the people who hang out here would know what I was talking about.
DC

EDIT: How about that; looking for a link to Vostok and IPCC charts and found a discussion of this exact subject. I never ran across it before. Sorry, can't link as it is part of a GW article.
Later.
DC

 

[wvdirtboy]

The records you mention are probably regional records (e.g., EPICA) that are not necessarily representative of overall global temperatures. Extensive literature exists RE interglacial temperatures, so you may want to try different search words in someplace like Google Scholar.

 

[granpa]

I heard that the Sahara has cycled between desert and Savannah repeatedly over this time period.

 

[Evo]

I heard that the Sahara has cycled between desert and Savannah repeatedly over this time period.

Approximately every 21,000 years, from what I remember.

 

[granpa]

this is all I could find
http://en.wikipedia.org/wiki/Timeline_of_environmental_history
http://en.wikipedia.org/wiki/Younger_Dryas
http://en.wikipedia.org/wiki/4.2_kiloyear_event

 

[DarioC]

GP that last link is rather interesting, thanks.

The site I went too did mention what I am asking about at least. First time I have seen anything. Just a quick reference and nothing further.

I did watch a program on TV (PBS?) a while back, on the possible evidence of a massive atmospheric meteorite explosion taking out the fauna at about 12K back. That is the only thing I have seen referenced that might have changed the pattern. Sometimes a good hammer strike at the right time will change a sequence completely out of proportion to it's size. Although I see now that other researchers say they cannot find the particles that show this happened.

Thanks for all the replies, I am still looking.

DC

 

[Evo]

I did watch a program on TV (PBS?) a while back, on the possible evidence of a massive atmospheric meteorite explosion taking out the fauna at about 12K back.

Actually, that is disputed.

 

[DarioC]

...Although I see now that other researchers say they cannot find the particles that show this happened.

My last sentence in last post. Yep.

Sure would be nice to talk to a student/expert on historical temperatures for that time period.

Ah, well , the search goes on. Think I will continue to email Universities on the subject.

DC

 

[Xnn]

There are several Professionals moderating various topics at the RealClimate website: http://www.realclimate.org/ Probably more likely to get a response there than from emailing universities.

Concerning comparisons of our current interglacial and past interglacials; these are likely due to small differences in the various forcing factors. Notice that greenhouse gas levels were slightly higher 125,000 , 240,000 and 330,000 years ago than they were 12,000 years ago. This in turn allowed sea levels to rise more and forest to grow further north; both positive feedbacks. Unfortunately, discussions of our current climate (over the last 300 years ago or so) is not tolerated on this Physics Forum.

Richard Alley's 2 Mile Time Machine is a good book on past interglacial periods

https://www.amazon.com/dp/0691102961/?tag=pfamazon01-20as is the following paper about our current interglacial:

http://earth.geology.yale.edu/~avf5/teaching/Files_pdf/Ruddiman2003.pdf

 

[DarioC]

Xnn,
Thank you. Good paper and references. Appreciate it.
DC