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Ed Stone

The Astronomical Theory Of Climate Change:

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And, now for something astronomical to discuss:

http://www.ncdc.noaa.gov/paleo/milankovitch.html

Maybe no Ice-Age for a few millennia? :mellow::D

Hi Pete,

This is just my thoughts without any 'googling' so should be treated as such ...

Ice ages, seem to be caused by a catastrophic switch - that is, it seems to get very warm over a reasonable amount of time, but then gets very cold very quickly. Some poepl call this tipping points, amongst other things. I know them as mathematical step functions.

Such functions are abound in nature; sometimes people see them as something abnormal, or special. They are everywhere - even a cursory study of population within an environment will yield a host of step functions that will take a lifetime to study.

Excessive warming, and the Vostok ice-core backs it up, suggests that something, with some relation to temperature, hits such a tipping point. There is rational evidence for this, too - there is a limit to radiation that can be absorbed by a black body, for instance - implying that the atmosphere probably won't go completely out of control - even though it might end up being uninhabitable for humans. Assuming of course the biosphere+atmosphere constitutes a black body (and for most numerical models it does)

Milankovitch cycles, to me, then, seem to coincide with something to do with temperature, but, perhaps, they are some very small part of the cause. Something else happened. I have no evidence of this claim, of course. A first look at solar irradiance coinciding with astronomical distances, say, yields very insignificant results.

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I haven't read it all yet, VP. But, I think I saw something somewhere about sudden rapid adjustments occurring after protracted periods of reduced/enhanced irradiance/seasonal variance??

Would such events constitute step functions??

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Would such events constitute step functions??

Yup. A dangerous place to live if we are near one, too. Stuff changes quickly under such conditions.

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Richard A Muller has an alternative theory also here

In a nutshell, the inclination of the earth's orbit to the "invariable plane of the solar system" reaches an extreme tilt every 100,000 years. Whereas the invariable plane is swept free of dust by the planets as they orbit, the remaining dust from the accretion disk that formed the solar system, is still mixed up on either side.

If you think of a fried egg sandwich with the sun as the yolk, and the planetary orbits as the white, and the bread as the remaining dust, you get the picture, I hope.

When the earth's orbital inclination is at an extreme, then twice a year, the earth will pass through the dust, and in fact drag dust around the orbit in its wake. There should be spectacular meteor showers, and the amount of solar radiation reaching the surface of the earth would diminish, because the finest dust would enter the upper atmosphere, dimming the sun. Dust acts as nuclei for condensation of the water in the cooling atmosphere and the earth enters a glaciation. Eventually the earth's orbital tilt clears the dust fields, and the dust clears from the atmosphere, but the earth is now in a glacial state and the high albedo, low water vapour levels due to low temperature, and low CO2 levels mean there is little greenhouse effect and the earth is in a glacial low temperature equilibrium state.

The assumption is then that Vulcanism, perhaps exacerbated by continents sinking due to additional weight of ice, increase the greenhouse gases by melting ice and release of carbon dioxide, until the ice caps retreat once more.

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Good link, Chris...Yet another piece of the puzzle?

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I have recently been involved in a discussion elsewhere, about the asymmetrical way the earth behaves over time because of the differences between what happens at the poles. Here is an example, Global Sea Ice (source: http://polynya.gsfc.nasa.gov/seaice_datasets.html, Arctic and Antarctic combined):

post-7302-1253799663441_thumb.png

Note the shape of the curve - it is not a sine wave - there is typically a sharp trough in early March, a small peak in late July, a small trough in late September and another small peak in early November, although the dates vary from year to year. A little investigation shows that the deep trough corresponds to the minimum for Antarctic ice extent, the little trough for the Northern ocean minimum.

The curve is the product of both polar quasi-sinusoidal ice-extent curves running at 180degrees out of phase.

This curve, or variations of it, crops up all over the place when you become aware of it - even superimposed over decadal trends, when looking at global datasets. It is the major part of the data that is filtered out of anomaly datasets. It occurs in Global SST measurements

2zgi8n7.png

(From Bob Tisdale), the cool southern summer Antarctic meltwater providing the deep trough in SSTs, before the southern ocean starts to warm up.

Global Ozone measurements

total_ozone_M.jpg

(from ESA), can anyone suggest why?

The pattern shows up in some even more surprising places.

Here is the variation in the Length of Day (i.e. the speed of rotation of Earth) since 1962.

post-7302-12538021853295_thumb.png (source IERS) .

A major component in the cause for LOD changes is the AAM, which again has a similar annual pattern.

Note the similar pattern over the year, but also notice that it is not in phase with the sea ice. However, is there a connection between the redistribution of sea ice and the Atmospheric angular momentum?

Not only the earth shows an asymmetric north-south pattern, so does the sun!

CosmicRayFlux.png

(From Leif Svalgaard).

The Cosmic ray counts are a proxy for the strength of the solar Magnetic field, the measurements on earth rectify (like a diode) the changing north-south polarity of the sun's magnetic field over the course of the Hale cycle. If you visualise the sharp peaks as troughs (southwards), and the flat peaks as peaks (northwards), I think you will see what I mean.

Finally, the curve is the similar to the light curve that is supposed to arise from eclipsing binary stars, with a big trough, a small peak, small trough and another small peak. Differential polar radiation (i.e. a dark south pole, bright north pole) for a star with a precessing axis could create this waveform.

If anyone can suggest other datasets which show this pattern, I will do some further analysis and see if there are any links between the seasonal variations.

If this is out of place, I would be happy for it to go somewhere else.

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