Verge of IceAge distinct possibility?

[mpaul]

To go through the motions:
* mankind has been living on a "temperature plateau" of 15k to 20k years
* these temp plateaus have been determined to arise about every 100k to 150k
years. Translate: paleo-historically, the earth is in it's ICE ages for
about 100k years, with relatively short periods of warmth.
* it is known that we live at the end of the warm temperature plateau ( I, PM,
remember conjecturing, when seeing the graphs, that it could be between zero to
3,000 years before heading into an Ice Age {which happen relatively
dramatically...how dramatically? no idea when the paleo-history is 100k year
stuff} )
and here is the kicker:
* the solar-geo-magnetic index (a.k.a. the Ap Index) graph just (December 09)
fell of the cliff. In 166 years of measuring, it has just dropped WAY below
where it has ever gone (despite sunspots increasing).
----
Theoretically (and I assume actual): low geomagnetism > high cosmic ray penetration > high cloud formation > lower global temps
---------
Short translation:
-- end of the plateau. Zero to 3,000 year (my conjecture, I confess)
timeframe for the next ICE AGE to come. Unlikely, right? Especially in the
total time frame of an ice age / plateau cycle being over 100,000 years.
- then KABOOM. The geo-magnetic index goes WAY down. By far the lowest
reading in 166 years. Put that in that zero to 3,000 year timeframe, and a
recognition of the reality of a distinct possibility of an impending, mankind
destroying ice age dawns on you.
Not saying likely. But distinct?

www.leif.org/research/Ap-Monthly-Averages-1844-Now.png

[jurinko]

The real ice age depends on Milankovitch cycles and it is nowhere near AFAIK. But repeat of medieval type solar minimum can happen within decade-two.

[sentient]

Must confess ignorance here. What is an AFAIK?

Are we near the cliff of the next ice age? Yes and no. Of the past 6 interglacials, 5 have lasted between 10-12k years. This one is about 11,500 years old now. Milankovitch wise, we are at an eccentricity minimum, just like MIS-11 was at the last eccentricity minimum, and that was that 6th interglacial. MIS-11 lasted about 30k years. It skipped a precessional beat and no one knows precisely why.

[boxman]

mpaul
I think sun only modulates the short term climate while milankovich cycles are responsible for the glacial and interglacial periods. The milankovich cycles are currently at the point where a ice age could hit at any point. Sun on the other hand is probably the main cause for things like the LIA and i guess another future LIA could be what finally brings the climate into the tipping point where a full ice age is imminent.

One thing is for sure.. This interglacial has already lasted longer than average and previous interglacials ended very suddenly with temps dropping drastically over just a few decades. But it is impossible to say if it will happen within the next 50 years or the next 1000 years. I personally think it will happen in less than thousand years but that is just my non scientific feeling based on what has happened in the past.

[sentient]

The period from the end of the penultimate glacial (known as Termination II or TII) through the Eemian (MIS-5e or MIS-5.5) has been the focus of my personal research for the past 2 years. I have accumulated hundreds of papers on the subject as this period is the best known since it is the most recent and therefore best preserved of all the Quaternary/Pleistocene climate changes.

I have attached a very interesting paper from 2005 which is worth a few moments of your precious time to read:

Attachments:

[boxman]

Jan 15, 2010 14:14:26 GMT sentient said:

Must confess ignorance here. What is an AFAIK?

AFAIK=As far as i know

[nautonnier]

Jan 15, 2010 16:44:04 GMT sentient said:

The period from the end of the penultimate glacial (known as Termination II or TII) through the Eemian (MIS-5e or MIS-5.5) has been the focus of my personal research for the past 2 years. I have accumulated hundreds of papers on the subject as this period is the best known since it is the most recent and therefore best preserved of all the Quaternary/Pleistocene climate changes.

I have attached a very interesting paper from 2005 which is worth a few moments of your precious time to read:

Thanks - that _is_ an interesting paper

One of the more salient ones is:

"We interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the North Atlantic drift, the ocean current that brings warm surface waters to the northern European region. The late Eemian aridity pulse occurred at a 658 N July insolation of 416Wm22, close to today’s value of 428Wm22 (ref. 9), and may therefore be relevant for the interpretation of present-day climate variability."

Then one looks at this:



And note the Gulf Stream apparently fading out where it would normally be seen northbound

I am glad I am currently in frosty Florida

[aj1983]

Jan 15, 2010 14:14:26 GMT sentient said:

Must confess ignorance here. What is an AFAIK?

Are we near the cliff of the next ice age? Yes and no. Of the past 6 interglacials, 5 have lasted between 10-12k years. This one is about 11,500 years old now. Milankovitch wise, we are at an eccentricity minimum, just like MIS-11 was at the last eccentricity minimum, and that was that 6th interglacial. MIS-11 lasted about 30k years. It skipped a precessional beat and no one knows precisely why.

That might because besides milankovic cycles, it is thought that the inertial period of major ice sheets also plays a significant role. Using both, my Ice and Climate dynamics teacher (Prof. Oerlemans) could show rather well which of the milankovic wobbles would lead (or had lead) to an ice age. He came to the conclusion that the coming minima are not deep enough to induce another ice age, and that this interglacial would last much longer than the previous ones (even without AGW).

[sentient]

aj,

Yes, I have read (and saved in my cybrary) many articles on the dynamics of eccentricity minima. The facts of the matter is that there do indeed seem to be tipping points, precisely what combination of thermohaline circulation, north atlantic deepwater formation, atlantic meriodinal overturning, solar magnetic dynamics, insolation at N65 degrees, orbital dynamics and even the weak forcing evident in the paleo proxy records due to GHGs all appear to have their adherents.

I suspect that often more than one variable might be involved, and at different times, the combination might be different.

At an eccentricity minima, obliquity and precession are also minimized due to the nearly circular orbital path of gaia about the sun. I have many papers detailing research into various aspects of the Eemian that state, alternatively, that the climate was at least as stable as the Holocene, and others that state the variability was far more severe than in the Holocene.

A cherry-pickers paradise supporting or denigrating variable after variable. A large part of the problem appears to be the locations where the research was done, the proxies used, and even who used them. Suffice it to say that in some locations and in some data sets evidence of stability and instability are to be found.

Even where MIS-5 sea levels are considered, the range seems to be anywhere from -8M to +70M with many workers seeming to find evidence supporting the +6 - +20 meter range.

It is one thing to ponder the degree of "noise" in the various positions of the various workers on a particular time slice, but beyond that lies the recognition of the enormous range of natural climate noise which constitutes the envelope in which one may attempt to see one's favorite "signal" within. Even on millenial scale events, such as the D-O oscillations, the century and decade scale noise dramatically eclipses any model prediction I have yet see in terms of both temperature or sea level excursions.

From a geologist that has read thousands of papers on this, and has some 4,000+ papers in digital form, the elevation of a laggard bit player, CO2, to forcing status is some of the best evidence I can point to confirming the hypothesis that the only known substitute for intelligence is indeed stupidity (or at best, ignorance).

[boxman]

Jan 15, 2010 18:53:07 GMT aj1983 said:

Jan 15, 2010 14:14:26 GMT sentient said:

Must confess ignorance here. What is an AFAIK?

Are we near the cliff of the next ice age? Yes and no. Of the past 6 interglacials, 5 have lasted between 10-12k years. This one is about 11,500 years old now. Milankovitch wise, we are at an eccentricity minimum, just like MIS-11 was at the last eccentricity minimum, and that was that 6th interglacial. MIS-11 lasted about 30k years. It skipped a precessional beat and no one knows precisely why.

That might because besides milankovic cycles, it is thought that the inertial period of major ice sheets also plays a significant role. Using both, my Ice and Climate dynamics teacher (Prof. Oerlemans) could show rather well which of the milankovic wobbles would lead (or had lead) to an ice age. He came to the conclusion that the coming minima are not deep enough to induce another ice age, and that this interglacial would last much longer than the previous ones (even without AGW).

I have also seen someone debunked that, claiming eccentricity and other milankovich cycles were similar to now and yet we still had a ice age. I am not sure how reliable this source is though, as it has been a while since i read about it.
One thing for sure though is that the average trend is down: earthintime.com/holocene.jpg

[Ratty]

Sentient, I have just changed the tag line on my emails to:

"Climate science is a cherry picker's paradise."

Hope you don't mind ....

[bxs]

At least once in Earth’s history, global warming ended quickly, and cientists have long wondered why. University of Oregon
Diamonds Linked to Quick Cooling Eons Ago
By KENNETH CHANG
Published: January 1, 2009


Scientists found microscopic diamonds in the black layer of rock at Murray Springs in Arizona.

Now researchers are reporting that the abrupt cooling — which took place about 12,900 years ago, just as the planet was emerging from an ice age — may have been caused by one or more meteors that slammed into North America. That could explain the extinction of mammoths, saber-tooth tigers and maybe even the first human inhabitants of the Americas, the scientists report in Friday’s issue of the journal Science.

The hypothesis has been regarded skeptically, but its advocates now report perhaps more convincing residue of impact: a thin layer of microscopic diamonds found in rocks across America and in Europe. “We’re up over 30 sites, as far west as offshore California, as far east as Germany,” said Allen West, a retired geology consultant who is one of the scientists working on the research.

The meteors would have been smaller than the six-mile-wide meteor that struck the Yucatán peninsula 65 million years ago and led to the mass extinctions of the dinosaurs. The killing effects of the hypothesized bombardment 12,900 years ago would have been more subtle.Climatologists believe that the direct cause of the 1,300-year cold spell, known as the Younger Dryas, was a sudden rush of fresh water from a giant lake in central Canada to the North Atlantic.

Usually a surface current of warm water flows northward in the Atlantic toward Greenland and Europe, then cools and sinks, returning south in the deep ocean. But the fresh water, which is less dense, blocked the sinking of the cold, salty water in the North Atlantic, disrupting the currents. That sudden change in plumbing has long been known, but what caused it has never been satisfactorily explained.

The authors of the paper in Science say it was meteors.

At each site the scientists looked at, the diamond layer in the rocks correlates to the date of the hypothesized impact. Within the layer, the scientists report finding a multitude of diamond particles, all encased within carbon spheres. “We’ve yet to find a single diamond above it,” Dr. West said. “We’ve yet to find a single diamond below it.” Perhaps more telling, the scientists reported last month at a meeting of the American Geophysical Union in San Francisco, the carbon atoms inside some of the diamonds are lined up in a hexagonal crystal pattern instead of the usual cubic structure. The hexagonal diamonds, formed by extraordinary heat and pressure, have been found only at impact craters and within meteorites and cannot be formed in forest fires or volcanic eruptions, Dr. West said.

Last year the scientists presented other evidence of an impact, including elevated levels of the element iridium. At least some skeptics are not convinced. “The whole thing still does not make sense, and there are lots of contradictions,” said Christian Koeberl, a professor of geological sciences at the University of Vienna in Austria.

His chief reservation is that there is no crater. “A body of this size does not just blow up without a trace in the atmosphere,” Dr. Koeberl said. “Physics won’t have it.”

Proponents have suggested that the meteor hit an ice sheet a couple of miles thick or that there was a series of smaller objects that exploded in the air. But Dr. Koeberl said something hitting an ice sheet would still generate a hole in the ground underneath, and he questioned whether smaller impacts or air explosions would produce the shock waves needed to make diamonds. An impact should also have left remnants of melted rocks and shocked minerals, Dr. Koeberl said. But if true, the hypothesis could explain the disappearance of ice age mammals like mammoths and argue against the alternative idea that the animals were hunted to extinction by humans.

It might also help explain the disappearance of the Clovis people, a culture named after a distinctive arrow point discovered in a mammoth skeleton in Clovis, N.M., who are believed to have arrived in the Americas more than 13,000 years ago. Douglas J. Kennett, a University of Oregon archaeologist who is the lead author of the Science paper, said no Clovis points or bones of the extinct animals had been found above the diamond layer. “It seems those two things synchronously end,” he said.

Dr. Kennett said there also appeared to be a gap of several centuries between the disappearance of the Clovis and the resettlement by other people. Gary Huss, a scientist at the University of Hawaii, Manoa, who was one of the early reviewers of the paper in Science, said though the scientists had not proved their case, they had offered enough evidence that the idea warranted a closer look by others.

“They have a hypothesis that explains several things that hard to explain any other way,” Dr. Huss said. “Diamonds are less convincing by themselves, but they strengthen their case considerably.”
_____________________
NASA did the actual simulation with a railgun.

www.bing.com/videos/watch/video/who-killed-the-woolly-mammoth/26e3uvl6




www.nytimes.com/2009/01/02/science/02impact.html

[mpaul]

Pertaining to Milankovitch Cycles: I certainly defer to those more mathematically and astronomologically aware.
Acknowledging my ignorance, I'll nonetheless put my two bits in, expecting to be rebuked (probably for good reason).

Only 2 of the 4 aspects of the Milankovitch (or Milankovic) Cycle SEEM to me to be pertinent. And those 2 are very gradual processes, which don't line up to the approx 100,000 year timetable of ice ages...

* eccentricity: the elliptical "off center" aspect of earth's rotation around sun. VERY GRADUAL PROCESS. It seems to occur only as a cycle of about 400,000 years.

* axial tilt ("obliquity"): it seems to me (only a layman) that the total ice formation would not change, only shift (the cycle here is about 40,000 years)....seems net temp change would be ZERO

* Precession is the change in the direction of the Earth's axis of rotation relative to the fixed stars, with a period of roughly 26,000 years.......seems to layman me that the overall / net effect on temps on earth would be ZERO


* Apsidial precession: Planets orbiting the Sun follow elliptical (oval) orbits that rotate gradually over time (apsidal precession). Cycle about 23,000 years. Very gradual cycle.......DOES NOT CORRESPOND WITH THE SUDDEN TYPICAL GLOBAL TEMP DROPOFFS?

[boxman]

* axial tilt it seems to me (only a layman) that the total ice formation would not change, only shift (the cycle here is about 40,000 years)....seems net temp change would be ZERO

Sure it does.. It makes summers colder in the high latitude regions, which means that less ice/snow will melt during the shorter and less extreme summers. This will lead to albedo change which in turn will lead to more sunlight being reflected into space.

Also milder winters is believed to also lead to more precipitation as snow from what i have heard. So you will have more snow in winters and less snow melt during summers. And who knows what cooling at higher latitude regions will do to oceanic cycles and such. But i guess it depends alot on the combination and timing of all these cycles.

[sentient]

Here's a link on this board which may help those interested in learning more about MIS-11, when we were last at an eccentricity minimum.

solarcycle24com.proboards.com/index.cgi?board=globalwarming&action=display&thread=989

mpaul, the eccentricity cycle is rougly 100,000 years, however it too has cyclicity ranging 400kyrs from minima to maxima. We are at a minimum now, just like we were 400kyrs ago during MIS-11.

On ocean circulation back to the Eemian:



On forest stages for the past 350kyrs:

Attachments: