Earth's Tilt Increase Averted Ice Age?

[Mammo]

There is a lot of speculation about why the Earth has not entered into a new ice age, following on from the pattern of glacial cycles recorded in the polar ice cores. It is a possibility that the Earth's tilt towards the Sun actually increased in the recent past. I know this sounds slightly crazy, but it is a possibility. This would have the effect of increasing the summer temperatures of the high latitudes, which is a vital factor in determining whether there is snow accumulation which leads to glaciation. Here is an article which validates this idea:article.

 

[mgb_phys]

We aren't due another ice age just yet (at least not for another 15-20,000 years). Interglacials last around 30,000yrs and we only had the last one 11,000 years ago.
By another definition we are in an ice age, in that there is ice at the north pole which isn't usual taken over the history of the earth.

 

[Mammo]

We aren't due another ice age just yet (at least not for another 15-20,000 years). Interglacials last around 30,000yrs and we only had the last one 11,000 years ago.
By another definition we are in an ice age, in that there is ice at the north pole which isn't usual taken over the history of the earth.

Where do you get your information from?

The Encyclopedia Britannica (link) states:

Oxygen isotope records indicate that interglacial periods have typically lasted 10,000–15,000 years, and maximum glacial periods were of similar length.

Is this idea a valid explanation for global warming trends?

 

[mgb_phys]

http://www.up.ethz.ch/people/flueckiger/publications/epica04nat.pdf
The idea that 11,000 years between recent ice ages doesn't look good. Especially because we are 11,000 years form the last one and the ice is still retreating - although to be fair, ice ages might start a lot quicker than they end.

 

[Andre]

The obliquity is currently decreasing which according to the Milankovitch hypothesis makes the Earth more sensitive to glaciation.

As we have seen that isotopes and actual other Earth temperature geologic proxies and records do not match, and we have seen that the dominant 100,000 isotope cycle cannot be associated with Milankovitch cycles, it's probably somewhat different.

 

[Skyhunter]

Is this idea a valid explanation for global warming trends?

No. The Holocene thermal optimum peaked ~7000-8000 years ago. The long term trend has generally been one of cooling until recently.

http://www.globalwarmingart.com/wiki/Image:Holocene_Temperature_Variations_Rev_png

We are now in a new geologic epoch that is being termed the http://www.eoearth.org/article/Anthropocene"

The Anthropocene defines Earth's most recent geologic time period as being human-influenced, or anthropogenic, based on overwhelming global evidence that atmospheric, geologic, hydrologic, biospheric and other Earth system processes are now altered by humans. The word combines the root "anthropo", meaning "human" with the root "-cene", the standard suffix for "epoch" in geologic time. The Anthropocene is distinguished as a new period either after or within the "Holocene", the current epoch, which began approximately 10,000 years ago (about 8000 BC) with the end of the last glacial period.

The alteration of the chemical and thermal structure of the atmosphere by human activity is more than enough to offset the small insolation distribution shifts. Human activity will prevent another glaciation.

http://www.sciencedaily.com/releases/2008/12/081217190433.htm

"We're at a very favorable state right now for increased glaciation," says Kutzbach. "Nature is favoring it at this time in orbital cycles, and if humans weren't in the picture it would probably be happening today."

 

[Gokul43201]

Especially because we are 11,000 years form the last one and the ice is still retreating

Even if the onset and retreat of interglacials looked symmetric, doesn't this assume that orbital forcing far outweighs all anthropogenic forcings? What kind of impact on the length of the interglacial would a 30% contribution from greenhouse gas forcings have?

 

[Mike Davis]

"No. The Holocene thermal optimum peaked ~7000-8000 years ago. The long term trend has generally been one of cooling until recently."
That statement might not be accurate!

 

[Evo]

"No. The Holocene thermal optimum peaked ~7000-8000 years ago. The long term trend has generally been one of cooling until recently."
That statement might not be accurate!

Hi Mike, please use the "quote" button when replying to a post, not only does it separate your comment from the one you are responding to, it also serves as a link to the post you are quoting.

Also, a response such as "That statement might not be accurate!" doesn't tell us anything. Please furnish information to substantiate why you believe this.

Thanks.

 

[Skyhunter]

Even if the onset and retreat of interglacials looked symmetric, doesn't this assume that orbital forcing far outweighs all anthropogenic forcings?

Not at all. There were no significant anthropogenic forcings until the Holocene. The orbital forcings themselves are very slight. Without the low frequency feedback from albedo changes and the carbon cycle there would be no interglacial periods. The dominant anthropogenic forcings are atmospheric emissions and albedo.

What kind of impact on the length of the interglacial would a 30% contribution from greenhouse gas forcings have?

Here is one perspective.

But shouldn’t Earth now, or at some point, be headed into the next ice age? No. Another ice age will not occur, unless humans go extinct. Orbital conditions now are, indeed, conducive (albeit weakly6) to initiation of ice sheet growth in the Northern Hemisphere But only a small amount of human-made GHGs are needed to overwhelm any natural tendency toward cooling. The long lifetime of human-made CO2 perturbations assures that no human generation that we can imagine will need to be concerned about global cooling. Even after fossil fuel use ceases and its effect is drained from the system an ice age could be averted by chlorofluorocarbons (CFCs) produced in a single CFC factory. It is a trivial task for humanity to avert an ice age.

http://www.columbia.edu/~jeh1/mailings/2008/20080910_Kingsnorth.pdf

 

[Skyhunter]

"No. The Holocene thermal optimum peaked ~7000-8000 years ago. The long term trend has generally been one of cooling until recently."
That statement might not be accurate!

You could be right.

The Holocene Climate Optimum was a warm period during roughly the interval 9,000 to 5,000 years B.P.. This event has also been known by many other names, including: Hypsithermal, Altithermal, Climatic Optimum, Holocene Optimum, Holocene Thermal Maximum, and Holocene Megathermal.

This warm period was followed by a gradual decline until about 2,000 years ago.

http://en.wikipedia.org/wiki/Holocene_climatic_optimum

 

[Gokul43201]

Not at all. There were no significant anthropogenic forcings until the Holocene.

But we are talking about today (and tomorrow), not before the Holocene. Couldn't current anthropogenic forcings affect the timing of the next glacial?

 

[Skyhunter]

But we are talking about today (and tomorrow), not before the Holocene. Couldn't current anthropogenic forcings affect the timing of the next glacial?

According to this article it already has.

http://www.sciencedaily.com/releases...1217190433.htm

 

[Mike Davis]

I see People using a trend in one cycle to claim a change in the current trend of a longer cycle. I would relate this to me claiming that I can use this morning to prove that the year has changed.

 

[Mammo]

The obliquity is currently decreasing which according to the Milankovitch hypothesis makes the Earth more sensitive to glaciation.

As we have seen that isotopes and actual other Earth temperature geologic proxies and records do not match, and we have seen that the dominant 100,000 isotope cycle cannot be associated with Milankovitch cycles, it's probably somewhat different.

The idea that I have is that in the last glacial cycle, a very large celestial body could have had a near-miss with the Earth. This could have significantly increased the Earth's tilt due to gravitational interaction. We are familiar with the Earth's tilt today, along with it's nutational cycle, and we assume that this is how it has always been. But it is not necessarily so. In the past the tilt could have been a lot less. There is no easy way to tell.

In another thread, we have discussed the possibility of a massive body near-miss being responsible for the unusually well preserved mammoth finds around 40,000 B.P. See post #30 in this thread link. This idea has the potential to solve a number of Earth Science problems. All it requires is a bit of lateral thinking.

Note that an increase in the Earth's tilt wouldn't increase the overall insolation reaching the Earth (i.e. it wouldn't cause global warming), but it would have the possibility of terminating the end of the pleistocene cycle of the ice ages. (article)

 

[Skyhunter]

I encourage you to explore your idea.

What first order evidence is there to support such a hypothesis?

If there was such an event there should be lots of supporting evidence.

Have you looked into the geomagnetic record? Is there evidence of a major shift in the geomagnetic field? tidal disruptions would also be evident, and the moon's orbit would also likely be altered.

Personally I think that most of climate history is explained by the interactions of the major forcings. The NH record is dominated by temperature spikes known as http://www2.ocean.washington.edu/oc540/lec01-31/"

I suspect that these events are dominated by ocean circulation. As one area cools another warms. Regional ice sheets begin to disintegrate until the rate of fresh melt water once again speeds up the THC.

 

[Andre]

The idea that I have is that in the last glacial cycle, a very large celestial body could have had a near-miss with the Earth. This could have significantly increased the Earth's tilt due to gravitational interaction. We are familiar with the Earth's tilt today, along with it's nutational cycle, and we assume that this is how it has always been. But it is not necessarily so. In the past the tilt could have been a lot less. There is no easy way to tell.

In another thread, we have discussed the possibility of a massive body near-miss being responsible for the unusually well preserved mammoth finds around 40,000 B.P. See post #30 in this thread link. This idea has the potential to solve a number of Earth Science problems. All it requires is a bit of lateral thinking.

Note that an increase in the Earth's tilt wouldn't increase the overall insolation reaching the Earth (i.e. it wouldn't cause global warming), but it would have the possibility of terminating the end of the pleistocene cycle of the ice ages. (article)

In my lateral thinking, the close passing of a hypothetical large body would do a lot of other things before changing the obliquity of the spin axis. It's gravity would exert unusual forces on Earth with two main effects, both an unpredictable assymetric tide change, which could be generating massive floods and a major exchange of energy disrupting the orbit around the sun, which would be causing a noticeable shift in yearly day count and eccentricity.

Do we see that?

 

[Mike Davis]

The magnetic field has "flipped" more than just once. The globe appears to be following/experienceing a cause and effect group of cycles for some time and other than speculation there is insuffecient evidence to suppport a major shift in that pattern recently. (within the last 100k years)

 

[Mammo]

No-one is talking about magnetic pole reversals. This is something completely different.

 

[Evo]

Mammo, we do not allow overly speculative posts without any serious scientific backup, such as published peer reviewed papers.

 

[Mammo]

There is a paper which relates to a major event around 40,000 B.P by Rick Firestone et al. I know that his 12.9ka comet airburst theory is shakey, but that doesn't necessarily mean that this idea isn't right. Major Event paper 2001.

In Fig. 2, the sharp drop in 14C activity before 41,000 yr B.P. suggests that global radiocarbon increased by about 45 percent at that time and by about 20 percent at 33,000 and 12,000 yr B.P The results are remarkably consistent with Vogel's comparison of 14C and U-Th dates of a stalagmite that indicates global radiocarbon increased about 75 percent from 30,000 to 40,000 yr B.P. and about 30 percent around 18,000 yr B.P.

 

[Andre]

There is a paper which relates to a major event around 40,000 B.P by Rick Firestone et al. I know that his 12.9ka comet airburst theory is shakey, but that doesn't necessarily mean that this idea isn't right. Major Event paper 2001.

Around 41-42,000 year ago the Earth magnetic field collapsed, known as the Lachamps paleo magnetic excursion and that may have repeated 33,000 years ago with the Mono Lake excursion (debated). The result could be an increase of cosmic radiogenic 14C production. Paleo Magnetic excursion are rather common in the current Brunhes chron, so the production of 14C can be explained with more down to Earth means. No need for extra terrestrial events.

 

[Mammo]

The radionuclide measurements, for example, confirm that the earth’s magnetic field weakened about 40,000 years ago to around 10% of its current strength. However, just before a reversal of polarity could occur, it returned to its old state.

Excellent Reference for Geomagnetic Understanding. This was a major event!

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TJN-41MHFHC-3N&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=df3e12623ce30306efcf950fc40aa3a1. This article states:

A pure physical model for the simulation of cosmic ray particle interactions with the Earth’s atmosphere was used to investigate the effects of a changing geomagnetic field on the production rates of cosmogenic nuclides.. Comparison with remnant magnetism records from marine sediment cores shows excellent agreement. This validates the use of cosmogenic nuclides in ice cores to reconstruct geomagnetic field variations.

It would appear that Chinese loess deposits aren't as good as ice cores for determining Earth's geomagnetic past history.

 

[Andre]

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TJN-41MHFHC-3N&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=df3e12623ce30306efcf950fc40aa3a1. This article states:

.. Comparison with remnant magnetism records from marine sediment cores shows excellent agreement. This validates the use of cosmogenic nuclides in ice cores to reconstruct geomagnetic field variations.

It would appear that Chinese loess deposits aren't as good as ice cores for determining Earth's geomagnetic past history.

What whould warant such a contrary conclusion?

Anyway, the Laschamps event was big, but so was Blake and many other paleomagnetic excursions. Lachamps was not unique.

source Guyodo and Valet 1999

However Paleomagnetic excursions were just as common in the later part of the previous Matuyama chron http://www.agu.org/pubs/crossref/2002/2001JB000491.shtml

Magnetic excursions (defined here by virtual geomagnetic polar latitudes crossing the virtual geomagnetic equator) are observed at 932, 1048, 1115, 1190–1215 (Cobb Mountain Subchron), 1255, 1472–1480, 1567–1575 (Gilsa Subchron), and 1977 ka.

See that there is nothing unusual at 40 ka

Notice that a semi ~100,000 years cycle seems to be kicking in 1.1 Ma which is also sort of visible in the Guyodo graph for the Brunhes chron. It's not synchronous with the Maritieme isotope stages, but could there be a connection anyhow? Provided that this also also started about one million year ago.

.

 

[Mammo]

See that there is nothing unusual at 40 ka.

The Earth's magnetic field suddenly dropped to 10% of it's current strength! This is absolutey amazing. Just because geomagnetic excursions have happened a few other times in the last 800,000 years doesn't detract from it's significance! It should also be noted that this an area which is still very poorly understood and that there may be a number of reasons for the Earth's geomagnetic excursions and reversals.

 

[Andre]

The Earth's magnetic field suddenly dropped to 10% ls.

that's the idea of ALL the Paleo Magnet Excursions. There is nothing significantly different with the Laschamps event, compared to the others.

 

[Mammo]

Can you not concede that the sudden drop to 10% of the Earth's magnetic field around 40,000 B.P is an indication of a major event? It is the fact that it so recent in our history which makes it so significant!

 

[Andre]

Can you not concede that the sudden drop to 10% of the Earth's magnetic field around 40,000 B.P is an indication of a major event? It is the fact that it so recent in our history which makes it so significant!

But it is not unique. Happened 14 times more to the 10-20% range. Perhaps click a link sometimes and study.

again: http://www.geo.uu.nl/~forth/publications/Related_pubs/Gubbins99.pdf

It doesn't allow copy paste so you really have to actually open it.

And there is nothing in the paleobotanic and paleotologic proxies and records that go with the excursions

 

[Mammo]

I've read the paper with interest, and it does nothing to disuade me from the idea of a 'massive body close encounter' major event around 41ka. This idea can not only explain the end of the Pleistocene and the 'Mammoth Mummies', but also has the potential to solve the 'Causality Problem for Milankovitch'. If the orbit and obliquity(tilt) of the Earth were different before the event, then the timings of earlier Milankovitch cycle forcings will need adjusting. Causality Problem For Milanovitch paper.

 

[Mammo]

But it is not unique. Happened 14 times more to the 10-20% range.

There is something unique about this excursion. Please look at the graph in the http://209.85.229.132/search?q=cach...storf+(2003).+timing&hl=en&ct=clnk&cd=5&gl=uk (click on html at the top for the graph version). It clearly shows that at around 41ka there was also a period of rapid global warming, similar to a D-O event, but out of phase with the 1,470 year cycle. This is first class evidence, which the author appears to have missed.

It also suggests that the mechanism of the 41ka excursion could be closely linked to the mechanism of the 1,470 year cycle.