Is Orbital Inclination the Key to Understanding Climate Change?

[Mammo]

This of the 100 kyr Glacial Cycle:
eccentricity or orbital inclination?[/url] paper claims to solve 4 of the 6 problems with Milankovitch cycles Wikipedia Milankovitch cycles. I was very impressed, but presumably their suggested mechanism for climate change, namely extraterrestrial accretion of dust or meteoroids, has not been supported by recent findings. Is it not worth considering another possible mechanism, when the inclination cycle solves so much?

• 100,000-year problem
• 400,000-year problem (Stage 11 problem)
• Causality problem (Stage 5 problem)
• The unsplit peak problem

The existence of the 100 kyr cycle of orbital inclination does not seem to have been previously noticed by climatologists. It may have been missed for two reasons. Ever since Milankovitch, the implicit assumption has been that insolation is the driving force for climate cycles, and insolation is not directly affected by orbital inclination. In addition, the 100 kyr cycle is not evident until one transforms to the invariable plane, or to a plane close to it.

 

[Monique]

Here is the published version of the paper, your quoted text does not seem to appear in that article: http://www.pnas.org/content/94/16/8329.full.pdf
Also, the paper is from 1997, not 2005.

 

[Andre]

This is a typical example of good science, failed prediction.

So Richard Muller (yes the same one as Physics for future presidents) had this inclination cycle idea, the Earth entering a dust belt every 100,000 years in a possible inclination cycle of the Earth orbit, obscuring the sun a little and causing ice ages. He predicted that this would have left traces of that dust and associated ions in the ice core. So he carried out that research himself and found nothing. (Perhaps I look up that paper later), So he was basically refuting his own hypothesis. Therefore indeed inclination is not an important word and kudoos to Richard Muller for being a true great scientist, completing the scientific method, despite the result: Beautiful theories are often destroyed by ugly facts.

 

[Mammo]

Here is the published version of the paper, your quoted text does not seem to appear in that article: http://www.pnas.org/content/94/16/8329.full.pdf
Also, the paper is from 1997, not 2005.

My apologies Monique, the Wikipedia reference mentioned a retrieval date of 2005 - my mistake. The quote does exist on page 3, right hand column in the published version of the paper, although not exactly the same, so you are right in bringing that to my attention.

This is a typical example of good science, failed prediction.

I agree with this part.

So Richard Muller (yes the same one as Physics for future presidents) had this inclination cycle idea, the Earth entering a dust belt every 100,000 years in a possible inclination cycle of the Earth orbit, obscuring the sun a little and causing ice ages. He predicted that this would have left traces of that dust and associated ions in the ice core. So he carried out that research himself and found nothing. (Perhaps I look up that paper later), So he was basically refuting his own hypothesis. Therefore indeed inclination is not an important word and kudoos to Richard Muller for being a true great scientist, completing the scientific method, despite the result: Beautiful theories are often destroyed by ugly facts.

You've missed the point that I was making. I don't agree with his assumed mechanism of climate change through this inclination cycle, but think that it is possible that there is another one, as yet unthought of by the paleoclimate community. It is such a wonderful explanation for the many problems of the Milankovitch cycles that it deserves to be reconsidered, especially due to the apparent lack of progress in the 12 years since the hypothesis. I can think of an alternative, and so can you if you tried.
(BTW can anyone else find the evidence to link the inclination cycle with the timing of Heinrich events? It seems to have been missed by the authors.)

 

[wolram]

My apologies Monique, the Wikipedia reference mentioned a retrieval date of 2005 - my mistake. The quote does exist on page 3, right hand column in the published version of the paper, although not exactly the same, so you are right in bringing that to my attention.


I agree with this part.

You've missed the point that I was making. I don't agree with his assumed mechanism of climate change through this inclination cycle, but think that it is possible that there is another one, as yet unthought of by the paleoclimate community. It is such a wonderful explanation for the many problems of the Milankovitch cycles that it deserves to be reconsidered, especially due to the apparent lack of progress in the 12 years since the hypothesis. I can think of an alternative, and so can you if you tried.
(BTW can anyone else find the evidence to link the inclination cycle with the timing of Heinrich events? It seems to have been missed by the authors.)

What is your point Mammo?

 

[Xnn]

Milankovitch is the popular name, but he is long gone and I don’t think he ever had a computer to work with. Here is some of what Peter Huybers has very recently published on the subject:

http://www.people.fas.harvard.edu/~phuybers/Doc/HuybersTziperman_Paleoceanography2008.pdf

If a colder climate is prescribed, or in the absence of basal motion, ice sheets tend to be larger and undergo greater precession period variability, in keeping with proxy observations of late Pleistocene glaciation.

and

Finally, the cooler climate also permits ice sheets to reach farther equatorward, and while this would normally be associated with a warmer climate, the insolation at lower latitudes is more sensitive to variations in precession.

Remember, Milankovitch was primarily focused on insolation at 65 degrees North, where obliquity rules. But many ice sheets were much closer to the equator, where precession is more important. And it is not just maximum intensity, but integrated solar insolation that ice sheets respond to.

In North America, land at about 45N was at one time under a mile or 2 of ice, so it makes sense, that while insolation at 65 degree north may initiate glaciations, what happens between 40 to 60 N is also very important. And of course, there is always the problem of how and when greenhouse gases like CO2 and CH4 respond. How else could an ice sheet become established at sea level at 45N?

 

[Xnn]

Some more gems from Peter Huybers:

http://www.people.fas.harvard.edu/~phuybers/Doc/HuybersTziperman_Paleoceanography2008.pdf

Annual ablation is expected to be a function of both the solar radiation intensity (related to Earth’s distance from the sun) and the duration of the ablation season (related to Earth’s angular velocity). These two influences are both taken into account by integrating insolation intensity over the time variable duration of the summer, a quantity referred to as the summer energy. In this case, summer is defined as the period during which daily average insolation intensity exceeds a specified threshold. The summer energy is generally insensitive to precession because, for example, just when perihelion occurs at summer solstice, summertime is shortest. That is, Kepler’s second law dictates that duration and intensity counterbalance one another.

and

The latitude-threshold space in which an ice sheet’s ablation zone exists helps determine the ratio of obliquity to precession period variability. When ablation occurs at thresholds below _350 W/m2 and at latitudes above 60_N, glaciers are expected to be most sensitive to changes in Earth’s obliquity. Moving the ablation zone equatorward or requiring a higher ablation threshold would increase the precession period variability.

and

Numerous studies have used numerical models to explore glacial variability, but for such a model to address the summer-energy hypothesis requires the representation of both the full seasonal cycle and the secular variations in precession, obliquity, and eccentricity, thus spanning 5 orders of magnitude in timescales. We are aware of only four previous studies which include the full seasonal cycles and attempt to simulate 40-Ka glacial cycles.

Oh, and by the way, obliquity if the top secret code word for inclination.

 

[Andre]

Some more gems from Peter Huybers:

http://www.people.fas.harvard.edu/~phuybers/Doc/HuybersTziperman_Paleoceanography2008.pdf

The abstract starts with:

Although the origins of the 40,000-year glacial cycles during the early Pleistocene are readily attributed to changes in Earth’s obliquity (also having a 40,000-year period), the lack of ice-volume variability at precession periods (20,000 years) is difficult to reconcile with most parameterizations of the insolation forcing.

What ice volume? Aren't we talking about isotope variations in benthic foraminifera stacks? It is supposed to represent ice volume, but that's an untested hypothesis which appears to be in serious trouble once we attempt to test it with real life data, both in volume and in dating.

So the study appears to be based on a hypothesis, which is facing falsification. Better sort out the fundamentals first before finding oneselfs on the wrong track.

Oh, and by the way, obliquity if the top secret code word for inclination.

not sure if I understand this unless "if" is a typo for "is". Indeed a higher inclination angle also affect obliquity but the essence of Mullers hypothesis was that Earth would enter a hypothetical dust band of some cosmic dust when at a higher inclination.

 

[Mammo]

What is your point Mammo?

There is another possible mechanism - the ocean tides. Not only is there insolation to consider but also gravity. There is a report which links the millennial cycle with the lunar tides, http://pangea.stanford.edu/research/Oceans/GES205/1800yrTidalCycleForcingAbruptClimateChange.pdf . Extending the same idea to the 100 ka cycle seems a likely possibility to me, which would solve 4 of the 6 problems with Milankovitch cycles. It would be very unprofessional to dismiss this exciting new line of enquiry.

 

[Xnn]

The abstract starts with:
What ice volume? Aren't we talking about isotope variations in benthic foraminifera stacks? It is supposed to represent ice volume, but that's an untested hypothesis...QUOTE]

Good point.

Exactly how are ice volumes known?
Is there just one accepted method?
If it is isotopic variation in benthic foraminifera stacks, then what is the uncertaininty?
Naturally, I'd expect that uncertainity to propogate over time.
That is there is more uncertainity the further back in time we look.
So, we are fooling ourselves if we put much confidence into particular ancient measures and timings.

If there is more than 1 method, then how do they compare?

I can imagine that a rough approximation could be made as far as the height of ice over particular areas during the last glacial maximum by measuring the amount of rebound. But that has got to have lots of sources of errors and assumptions too.

What exactly do isotopic variations in benthic foraminifera stack mean?

Thanks!

 

[Mammo]

The abstract starts with:
What ice volume? Aren't we talking about isotope variations in benthic foraminifera stacks? It is supposed to represent ice volume, but that's an untested hypothesis...QUOTE]

Good point.

Exactly how are ice volumes known?
Is there just one accepted method?
If it is isotopic variation in benthic foraminifera stacks, then what is the uncertaininty?
Naturally, I'd expect that uncertainity to propogate over time.
That is there is more uncertainity the further back in time we look.
So, we are fooling ourselves if we put much confidence into particular ancient measures and timings.

If there is more than 1 method, then how do they compare?

I can imagine that a rough approximation could be made as far as the height of ice over particular areas during the last glacial maximum by measuring the amount of rebound. But that has got to have lots of sources of errors and assumptions too.

What exactly do isotopic variations in benthic foraminifera stack mean?

Thanks!

Wouldn't this line of discussion be more suitable in Andre's thread 'The ice age and the ice volume problem'?

 

[Andre]

Wouldn't this line of disussion be more suitable in Andre's thread 'The ice age and the ice volume problem'?

Yes I added an addemdum to that thread and the links there should explain what it is all about.

 

[Mammo]

There is another possible mechanism - the ocean tides. Not only is there insolation to consider but also gravity. There is a report which links the millennial cycle with the lunar tides, http://pangea.stanford.edu/research/Oceans/GES205/1800yrTidalCycleForcingAbruptClimateChange.pdf . Extending the same idea to the 100 ka cycle seems a likely possibility to me, which would solve 4 of the 6 problems with Milankovitch cycles. It would be very unprofessional to dismiss this exciting new line of enquiry.

Is it not reasonable to suggest that the ocean tides could increase the Gulf Stream enough to enter the Arctic Basin? This movie of the advance and retreat of the Arctic sea ice shows the magnitude of influence that the warm Gulf Stream has today. Orbital inclination on the 100-kyr cycle could explain the increase in glaciation intensity following the mid-Pleistocene transition. The increase in intensity of the Gulf Stream could completely melt the Arctic ice, and so activate a climate trigger. Remember, it is also the snow accumulation rate which dictates the advance and retreat of the ice sheets. I propose that the advance of the Gulf Stream into the Arctic Basin could alter weather patterns, bringing more precipitation to the northern latitudes. A tidal explanation for the ice ages is nothing to be scared of. It has the potential to now solve 5 of the 6 problems associated with Milankovitch cycles. The only one left to explain is the cause of the mid-Pleistocene transition. I have a reasonable suggestion for this to, if anyone is interested.

The inclination of the Earth's orbit would determine the latitude at which the force of the ocean tides is applied. A higher inclination would mean a more northerly influence of the tides, allowing the Gulf Stream to encircle the Arctic Basin. This would be a tipping point, dependent on the lunar and solar tides.

 

[peterjfharris]

Mammo if your out there can you provied a reference or more details about your idea that changes in the Earth orbital inclination (about the invariable plane) cause changes in the geological impact zone of Moon induced tides possibly leading to redirection of the MOC ?
if true this would fit with the evidence from ice analysis that the transitions are triggered in the NH.
Peter

 

[Evo]

Mammo if your out there can you provied a reference or more details about your idea that changes in the Earth orbital inclination (about the invariable plane) cause changes in the geological impact zone of Moon induced tides possibly leading to redirection of the MOC ?
if true this would fit with the evidence from ice analysis that the transitions are triggered in the NH.
Peter

You are talking to a member that was banned. He's not here anymore.

 

[peterjfharris]

Thanks, so I suppose his proposal is nonesense?
Peter

 

[Evo]

Thanks, so I suppose his proposal is nonesense?
Peter

I haven't read it, the thread has been dead for a year.