Talk:Snowball Earth

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[edit] Good Article

I'd love to know how to re-improve this article to become a Good Article once more. What are the standards for being a Good Article? RaccoonFox • Talk • Stalk 22:40, 26 November 2006 (UTC)

See here. | Verisimilus T 10:56, 26 April 2007 (UTC)
One way to improve this article -- speaking as an editor -- would be to move the grammar a little toward the center of the Atlantic. I found at least six "whilsts" at the beginning of sentences. Too many. I changed them to "while" -- but the author is too dependent on the sentence form. Scott Adler 01:24, 9 July 2007 (UTC)

[edit] Hydrogen peroxide factor

New paper points out that sunlight-created hydrogen peroxide could have been a factor in the Snowball Earth environment. Geobiologists Solve "Catch-22 Problem" Concerning the Rise of Atmospheric Oxygen (SEWilco 05:33, 10 December 2006 (UTC))

Oops. Article is about an older snowball. Never mind. (SEWilco 16:17, 10 December 2006 (UTC))

[edit] Uncategorized & the geological period template

Someone put a "this is uncategorized" template in {{:Snowball Earth/Infobox}} instead of in Snowball Earth. I put it right. Anthony Appleyard 07:18, 11 December 2006 (UTC)

[edit] Vicious Cycle?

On the documentary on the Discovery Channel it said that a snowball earth would be a vicious cycle, as the ice reflects more heat back into space and further cools the earth. Shouldn't vicious cycle be added as a main introductory describer of snowball earth?--Exander 05:27, 15 December 2006 (UTC)

[edit] Opening Sentence

"The Snowball Earth hypothesis is a controversial hypothesis…"

I don’t think the wording in the opening sentence is very good; Repeating the word “hypothesis” seems like poor grammar. I propose we revise it to read simply:

"Snowball Earth is a controversial hypothesis…"

Since there’s some debate on the history page in the last two edits, I’d like to hear the reasons why anyone would object and see if there’d be a consensus on making the change.

--Robbins 18:49, 5 March 2007 (UTC)

I'd definitely agree with the change - the opening sentence should describe what the hypothesis is, and not start with why it's controversial. I think the opening sentence contains the seed of a good introduction, but is worded badly. I've changed it so it sounds better without actually adding anything. Feel free to reword it again if you can think of a better introduction. Routlej1 18:11, 3 April 2007 (UTC)

[edit] origins

i wrote a lot of new text in the origins section of the article replacing the sentence "The general hypothesis has been around for several decades." with a much more complete description of ideas concening low-latitude glacial deposits over the past 100 years.

I also added more information concerning Kirschvink and Hoffman's contributions and added citations where appropriate.

Nswanson 07:08, 7 March 2007 (UTC)


[edit] Recent evidence of warming cycles during this period

Someone should probably add info on the recent evidence of climatic cycles, indicating that the Earth was not much of a snowball during that period. — BRIAN0918 • 2007-03-23 14:43Z

[edit] Evidence section

I think this article has developed to a point now where we need to split the evidence section into "evidence for" and "evidence against" sections,, or perhaps add a "criticisms of snowball earth" section. I'd also like to see the new research into the weathering of sedimentary rocks from the period from Geology (vol. 35, p299) included. Any thoughts? Routlej1 18:23, 3 April 2007 (UTC)

Can someone add a ref to this paper which comes up with an alternative theory, called the "Zipper Rift"? Eyles N, Januszczak N. 2004. Zipper-rift': a tectonic model for Neoproterozoic glaciations during the breakup of Rodinia after 750 Ma EARTH-SCIENCE REVIEWS 65 (1-2): 1-73.

I've incorporated a brief description of the paper, which I'll expand; however it also contains a comprehensive history of the theory and further detail which could find a home in the article if anyone was willing to type it up! I'm able to provide access to anyone who can't view the PDF, just let me know your e-mail address. Verisimilus T 13:13, 29 May 2007 (UTC)

[edit] critiques of the hypothesis and the introduction

I agree that it would be good to have a section devoted to critiques of the hypothesis. I just made an edit where I created such a section. I moved the material the was in the introduction in which evidence against the hypothesis was presented to this new section. This section needs to be developed more and can include information about the recent research into chemical weathering that has been mentioned in the last two discussion posts.

In my opinion, it makes more sense to explain the actual hypothesis in the introduction than to spend the majority of the introduction explaining that the hypothesis is controversial. I made some edits in this regard.

Another thing this article needs is a good graphic. If anyone has some good ideas in this regard it would be a good addition to the page.

Nswanson 23:38, 16 April 2007 (UTC)


[edit] Clear Sky in Snowball Earth

I've discussed this with my grandfather, who is a scientist (now retired, but was with the University of Windsor for many many years). I asked him if the world's temperature were very low, as in this article (which I was able to show him), if the sky would be very clear and contain only a few clouds, compared to today's skies, which have many clouds. He said it was very well possible, if not probable, and pointed to the winter-time, when the skies are much clearer due to the cold temperatures. If that happens just locally, it then should be able to happen globally, if an ice age were to grip the entire planet. He explained that the reason wintertime has very few clouds was due to "radiation cooling".

My grandfather told me this is how radiation cooling works: "When there are no clouds, there is no "trapping" of the air and gasses on the surfaces to warm the Earth, much like an opposite of the Greenhouse Effect. Without clouds, heat cannot be retained, and the temperature drops accordingly."

I think that saying the sky would be very clear is not exactly dubious, as it occurs every year in the winter-time. What are your opinions, wikipedians? RingtailedFox • Talk • Stalk 17:53, 27 April 2007 (UTC)

Quite right. If all the liquid water on Earth is frozen - where will the evaporation required to form clouds come from? This is in fact a strong argument against total snowball Earth - it's very difficult to come up with a scenario where water - to become snow - is transported into the hearts of continents to build up the glaciers. Verisimilus T 21:37, 28 April 2007 (UTC)
That is not a strong argument. Although Antarctica is the driest continent on Earth (smallest annual precipitation of about 150 mm (5.9 inches) of equivalent water [1]), it has built up the largest ice sheet because it never melts [2]. A Snowball Earth would have an average tropical temperature equal to that of Antarctica today according to [3], being much colder at the poles. That same reference describes sublimation-condensation cycles which will still transport water vapor across the ice sheet. Only where water runoff exceeds precipitation will an ice sheet be absent. It is temperature, not precipitation, which determines whether the tropics, for example, will have an ice sheet. — Joe Kress 04:56, 29 April 2007 (UTC)
I think what my grandfather said could act as evidence for a Snowball Earth. As the temperature gets colder, less precipitation (rain, snow, sleet, hail, etc.) falls... RingtailedFox • Talk • Stalk 16:55, 6 May 2007 (UTC)
I'm not sure I follow your argument... Verisimilus T 17:55, 6 May 2007 (UTC)

My argument is that i don't think it's a dubious claim to assume the sky would be very clear during a global ice age. RingtailedFox • Talk • Stalk 19:22, 15 June 2007 (UTC)

I think its nonsense. To first order, clouds depend on relative not absolute humidity. If it gets colder the clouds might be a bit thinner but no less coverage. Think about it: is there a clear trend of more clouds at the equator to fewer at the poles? No. Oh, and water evaporates from ice (or snow) just as well as from water, once temperatures are taken into account William M. Connolley 20:52, 15 June 2007 (UTC)
On the other hand, the best seeing on Earth is in Antarctica. Dragons flight 21:03, 15 June 2007 (UTC)
Yeeeessss... but for a variety of reasons, not all cloud related. Its high; being cold there is very little moisture. There may well be clear-sky times in the interior, but that is largely due to the shape of Antarctica rather than the coldness William M. Connolley 21:06, 15 June 2007 (UTC)
It would be interesting to know if any literature had been published in this area. Verisimilus T 09:10, 17 June 2007 (UTC)
Not merely interesting, it also is necessary for WP:V. (SEWilco 14:04, 17 June 2007 (UTC))

[edit] Volcanic bombs

Thanks for your input guys.

Just a quick question; are you sure bombs are always so easy to distinguish? How would you distinguish them from, say, an erratic of volcanic origin? Could sediments formed in a caldera potentially be ejected as bombs? Verisimilus T 22:25, 28 April 2007 (UTC)

Out of context, a single erratic of volcanic origin, recognizable from its chemistry, could fool 'em. In a survey, it would immediately drop out as an anomaly. Not worth mentioning unless there is an article on erratica of volcanic origin, aside from pumice.--Wetman 23:00, 28 April 2007 (UTC)
Fair enough Verisimilus T 23:14, 28 April 2007 (UTC)

[edit] End of the frozen period

Shouldn't the effects of methane be mentioned in this section? 14:34, 29 April 2007 User:Verisimilus

[edit] Removal of content branching

I feel your re-write and removal of content branching, whilst more concise, doesn't give sufficient mention to the non-glacial mechanisms of production; it also forces the non-specialist to redirect to another page to follow the flow of the article... I'd advocate re-incorporation of maybe a couple of lines for each sediment type? 14:34, 29 April 2007 User:Verisimilus

  • In Snowball_Earth#Glacial deposits at low latitudes I have put short explanations. The trouble is, that if a page has a link to another page, all too often a short explanation accompanying the link gradually enlarges into a long essay cluttering the page and content-forking with the page that the link points to. Anthony Appleyard 16:27, 29 April 2007 (UTC)

[edit] removal of "causes of snowball earth" section?

the causes of snowball earth section does not contain much in the way of new information and simply reiterates what it is laid out in the initiating snowball earth subsection. in my view, this section should be removed thereby simplifying the article and reducing repitition. 03:22, 2 May 2007 "Nswanson"

[edit] First foot note

I think it is unfortunate that the first footnote directs readers towards a non-digital resource "A succinct expression in layman's terms can be found in Tjeerd van Andel's New Views on an Old Planet: A History of Global Change (Cambridge University Press) (1985, second edition 1994)."

What the introduction should ideally be is a "succinct expression in layman's terms." If it is not that currently it should be improved and this footnote removed.

Nswanson 22:11, 2 May 2007 (UTC)

[edit] "History" section

At the moment, the history section doesn't read very fluidly. I've removed a couple of completely non-informative sections; most of the information could be more usefully included in the article where it has context. I'm not sure that the history of the concept is of sufficient interest to merit inclusion in the article at all. Perhaps one coherent paragraph could cover the progression of ideas - but as far as I can tell, nothing's *really* changed - there has just been a steady influx of new evidence (which is mentioned in the text). Verisimilus T 16:54, 4 May 2007 (UTC)

[edit] comment on history section

I think that in many ways the history section is of interest. The development of a scientific hypothesis is quite interesting both in terms of the history of science and to people who ponder the philosophy of science and are interested in how ideas progress.

I think the section should be retained. I also think that if we keep the section, the subsections about work in the 1990s is very important as that is when the current hypothesis as it stands developed. Before that there were pieces of a puzzle that were not brought together. I disagree with the assertion that since 1969 the only thing that has been added is evidence. There has been lots of original thinking that has pieced together how such an event could be feasible in the Earth system. —The preceding unsigned comment was added by Nswanson (talk • contribs) 19:29, 4 May 2007 (UTC).

I'm still not convinced that there's a strong progression of the concept, or even that the argument has swung to a large degree from one side to the other. I still feel that the evidence and thoughts have reflected an expansion, rather than significant modification, of the theory; no paper has been published that appears to conclusively disprove the Snowball Earth hypothesis (except perhaps Reiu's last month, to which there's been no time to allow a come-back), nor vice versa.
I suppose the challenge is on your shoulders to coin an interesting and compelling section that brings out the progression of the idea and the fitting together of the pieces, rather than (as before) a brief description of a few books and papers without any comment as to their significance. I'd also prefer to see the section without any subheadings, as these break the flow of the text substantially. Hope you agree! Verisimilus T 11:55, 5 May 2007 (UTC)

[edit] sed structures under open water reference?

does anyone know about the papers that discuss the following statement:

"In contrast, some features which only form in below open water have also been discovered from a similar time."

Nswanson T , 6 May 2007

Not looked for papers regarding it yet, imagine I will sometime soon. I found the assertion on snowballearth.org which presents a very pro-snowball case, so presumed that they'd not put in such a striking anti-snowball hypothesis without it being founded in truth! Verisimilus T 16:04, 5 May 2007 (UTC)
Update: Try this: Halverson, G.P.; Maloof, A.C., Hoffman, P.F. (2004). "The Marinoan glaciation(Neoproterozoic) in northeast Svalbard". Basin Research 16 (3): 297-324. 
Verisimilus T 16:10, 5 May 2007 (UTC)

[edit] Relevance of Inertial interchange true polar wander

Whilst I personally consider it a bit of a crackpot theory, IITPW is relevant in that it provides an alternative mechanism for glacial sediments to reach the equator. Hence I'd question its removal. The section could certainly be shortened though, as I don't feel it merits much attention. —The preceding unsigned comment was added by Verisimilus (talk • contribs) 16:02, 5 May 2007 (UTC).

I would also question its removal for similar reasons. However, the section may well need some rewriting and simplification to make its relevance clearer. --Zamphuor 16:12, 5 May 2007 (UTC)


First of all, the interval of the true polar wander event proposed by Krischvink et al. is from 535 to 505 million years ago during the early Cambrian. This time period is not associated with either of the two major Neoproterozoic glacials: Sturtian (~740 Ma) or Marinoan (~635 Ma). I think it is a common phenomena to further compress time in our minds as we proceed further back in Earth history but this is a large seperation in time. Secondly, the evidence for low-latitude glaciation is from paleomagnetic data within the glacial deposits themselves. It does work to say that the sediments were deposited at high latitudes, and then moved to lower latitudes as the paleomagnetic evidence tells us that they were deposited at those low-latitudes.--Nswanson 5 May 2007 (UTC)
I reinstated the section, in an abridged form, before reading your comments. However, the paper does investigate Marinoan deposits - I imagine the use of a 600Ma date results from with the large uncertainties in the dating of sediments that existed in 1997. And I think that the conclusion is easily extrapolated back from the period through which the data exist. It's certainly been used in such a fashion by the anti-snowball crowd.Verisimilus T 17:09, 5 May 2007 (UTC)

[edit] Lede

Ringtailedfox, I hope you don't mind me removing the section you reinstated into the lede, but it didn't seem to add any new information to that section. The lede's already quite long and direct repetition within it is best avoided.

[edit] POV?

I'm not convinced a POV header is appropriate. What exactly (or roughly) is wrong, anyway? William M. Connolley 17:52, 24 May 2007 (UTC)

Sorry, on second reading I agree it's not necessary; someone else had left the article with a confused view and in that mindset I convinced myself that there were POV issues, it's in fact probably not that bad...

[edit] Counter-arguments to the criticism, part 1

Firstly, it is argued that carbonate rocks would not had formed in the oceans since they where as acid as the rain water which dissolved the minerals. However, the minerals may not have been deposited immediately as they reached the oceans. They may well have deposited as photosynthetic micro-organisms gradually consumed the carbon dioxide in the oceans making them less acid. Consequently, cap carbonates are not necessary a problem.

2007-05-26 Lena Synnerholm, Märsta, Sweden.

I think the argument is that acid rain would have dissolved terrestrial limestone. However, as I understand it, the formation of calcium carbonate in oceans is, counterintuitively, a PRODUCER of CO2 - the equation is as follows
Ca2+ + 2HCO3- → CaCO3 + CO2
The only major way of drawing down carbon is via the formation of organic matter (which may be what you're getting at) - but what happened to the dissolved calcium ions? Verisimilus T 15:32, 26 May 2007 (UTC)
The “problem” is not the drawing of carbon out of the air but the formation of limestone on top of the glacial deposits. Carbon dioxide is easily solvable in water resulting in acid rain. This acid rain dissolved some calcium-rich minerals which were moved to the seas. However, the seas where as acid as the rain meaning that the minerals could not have been deposited immediately. The deposition can not had taken place until photosynthetic micro-organisms had consumed so much of the carbon dioxide in the seas that it made them enough basic to not dissolve the minerals.
2007-06-01 Lena Synnerholm, Märsta, Sweden.
That's a good way of looking at it. Thanks for that explanation! Verisimilus T 16:19, 1 June 2007 (UTC)

[edit] Counter-arguments to the criticism, part 2

Secondly, it has been suggested that the tilt of the Earth’s axis might be responsible for low latitude glaciation since it would have made the average temperature at the Equator lower than that at the poles. This is not possible since due to the seasons brought about by such a high tilt. At the Equator the solstices would have been freezing cold but the equinoxes would have been as hot as today. Worse, an axial tilt of 54° or more was not possible due to the Moon’s tidal forces. In fact, it is the tidal forces from the Moon that prevent the tilt of the axis from varying to much today! 750 – 630 million years ago the Moon was closer making the tidal forces even stronger. In short, this hypothesis does not work.

2007-05-26 Lena Synnerholm, Märsta, Sweden.

I agree. I've yet to meet anybody who's not convinced it's barmy. Verisimilus T 15:32, 26 May 2007 (UTC)
What do you mean with “barmy”? I don't have English as my mother tongue so I wrote this with some help from a dictionary.
2007-06-01 Lena Synnerholm, Märsta, Sweden.
Sorry. Barmy means "very unlikely to be true"

[edit] Counter-arguments to the criticism, part 3

Thirdly, no forces inside the system of the Earth can change it’s rotation drastically. Any outside force that could change it would kill all life on Earth because the energy required would vaporise the oceans and melt the crust. There would not even be geologic record of the event! However, the poles may just seem to wander because the tectonic plate around it moves. This “alternative explanation” would require a location to move from a polar climate to a tropical climate in less than three million years. Today the fastest tectonic plate is India which moves 17 centimetres (6½ inches) a year or 170 kilometres (106 miles) in a million years. With that speed it would take 28 million years to get from a polar climate to a tropical assuming present-day wideness of the temperate belt. Of cause, if global climate is warming up during the time it would take shorter and if it was cooling it would take longer. But the order of magnitude would still be the same. Is there any scientific reason to think that continental drift was so much faster 750 – 630 million years ago?

2007-05-26 Lena Synnerholm, Märsta, Sweden.

Apparent Polar wander due to tectonic motion is very different from the true polar wonder which the hypothesis invokes.
And there are several proponents for a faster rate of continental drift. I don't think their argument quite holds together - most of them are produced to explain an effect, rather because we'd expect it despite the evidence, which must make one suspicious. However, it is true that plate motion seems to occur in phases of fast motion separated by quiet periods, and that time frame was probably one of transition between two mega-continental arrangements. Verisimilus T 15:32, 26 May 2007 (UTC)
In fact I tried to debunk both versions. The first mean sudden changes in the position of the Earth’s geographic poles. (At least sudden on a geologic time-scale.) What mechanism could cause such changes? The other would require tectonic plates to move one order of magnitude (ten times) faster than today’s fastest speeds. Sure, the speed of continental drift varies much between plates and times. But it does not seem to have varied nearly that much in the past 400 million years. I can imagine that the tectonic plates moved much faster two billion years ago but not 750 – 630 million years ago. Remember, the Earth had already reached more than 80% of its present age.
2007-06-01 Lena Synnerholm, Märsta, Sweden.
Uniformitarianism doesn't always hold - things don't have to happen at a constant rate. But I do find drift that rapid hard to stomach. Verisimilus T 16:19, 1 June 2007 (UTC)

I still wonder what mechanisme is propsed for sudernly change the positions the geographic poles.

2007-06-05 Lena Synnerholm, Märsta, Sweden.

[edit] Counter-arguments to the criticism, part 4

Fourthly, some people claim that the Earth’s magnetic field was not roughly dipolar as today. But is such a different magnetic field credible? The Earth had already reached about 85% of its present age. Has the Earth’s core really changed that much in less than a fifth its age? I am sceptic to that claim.

2007-05-26 Lena Synnerholm, Märsta, Sweden.

This is an interesting point. The argument goes as follows: The Earth has been losing heat via radiation since its formation. the gradual cooling of the core is a constant process that has happened at a steady (or at least easily defined) rate as long as it's been there. However, the planform of convective cell which is stable is a function of the properties of the core, which themselves depend upon their temperature. Thus after cooling below a certain critical temperature, the convection (which produces the magnetic field) would switch from a four-plume system to a dipole, as today. The unpredictability of magnetic reversals throughout the Phanerozoic does add weight to a core in uncomfortable equilibrium. So whilst the jury is firmly out, I wouldn't be surprised if there did turn out to be some credence to this theory. But of course, I must commend your scepticism... never believe anything you read, especially on Wikipedia! Verisimilus T 15:32, 26 May 2007 (UTC)

[edit] Counter-arguments to the criticism, part 5

Personally I think a “Slushball Earth” is more credible than the original Snowball Earth hypothesis. It have turned out that all continents where not at the Equator. Which is not so strange since the time-span when “Snowball” scenarios have been proposed is 120 million years. With the real configuration of the continents climate models failed to acquire complete ice cover. Instead average temperature at equatorial sea level was above 0°C (32°F) allowing for at least partly open water. This more or less ice-free belt most have been crossed by landmass: otherwise ocean currents would have levelled out global climate making runaway glaciation impossible. Anyway, this “Slushball Earth” would have had very little ice-free land. As such it would explain the geological features quite well.

2007-05-26 Lena Synnerholm, Märsta, Sweden.

That's a very interesting set of statements and I don't think you'd have difficulty finding people who believe the exact opposite to many of them. However, I'm personally led to agree with the gist of what you're saying. Are you able to find references for each of those facts? I'd be interested to peruse them. My suspicions would be that the continental reconstruction would have huge error bars - a lot of very different but equally credible reconstructions have been released - and that all models should be trusted with a respectful air of disbelief, especially for something as complex as the climate (just look at the IPCC report for an idea of how imprecise these things can be...) I do like your idea of circumequatorial currents averaging temperature, though. But wouldn't this serve only to redistribute temperature latitudinally, rather than north and south, in the same way as the circum-Antarctic "washing machine" current allows the buildup of ice on Antarctica by separating it from North-South circulation cells? Besides, in such a world, it does seem probable that thermohaline circulation would grind to a halt, and surface currents alone can only provide a limited amount of thermal redistribution.
I've probably made a few glaring scientific errors somewhere in my arguments so please feel free to quash them! And as it seems you have a fair grasp of the issues involved, please let me encourage you to contribute to this article! Just make sure any facts you add can be attributed to a reliable reference.
Thanks, Verisimilus T 15:32, 26 May 2007 (UTC)
If any of this could be presented as a report on published scientific material, rather than as a personal essay, it could find a place in the article. --Wetman 15:19, 26 May 2007 (UTC)

I am not a geologist just an ordinary sceptic who consider the idea of a Snowball Earth interesting. Reconstructions of the position of the continents are quite accurate for the time since Pangea begun to break up. If you go further back in time the reconstructions becomes more and more uncertain. For the time in question (750 – 630 million years ago) there is considerable uncertainties. But you can make many simulations based on different reconstructions. I think only reconstructions based on the presumption of a dipolar magnetic field should be used since others would need to many assumptions. About the souces to the ocean current argument they are in Swedish and as such probably not suitable for the English version of Wikipedia. What do you think?

2007-06-01 Lena Synnerholm, Märsta, Sweden.

I don't know of anybody who has attempted to construct a reconstruction with a non-dipolar field. As you say, it would probably be almost impossible to do with any useful degree of accuracy!
However, the Swedish sources are certainly permitted in English Wikipedia. My suggestion would be to translate any snippets you are using to support arguments on the talk page so that the non-Swede can access the facts behind the article. But I'd strongly encourage you to add to the article if you feel you can; if not I'll gladly try to incorporate any facts you can provide!
Thanks for your interest in the article, Verisimilus T 16:19, 1 June 2007 (UTC)

At a second though the sources are probably not good enough. What I do know is that free ocean circulation near the Equator would level out climate across the latitudes. On the other hand free circulation near a pole would make that pole colder. That is why the South Pole become ice-covered tens of millions of years before the North Pole. About the “ocean currents preventing runaway glaciation” argument the source I have is ambiguous. So I don’t think I should add to the article myself.

2007-06-22 Lena Synnerholm, Märsta, Sweden.

[edit] Article structure

Having expanded the article slightly today, I'm having doubts that its structure is ideal. Would it make sense to group each example of evidence for snowball Earth together with its counter-arguments, so people don't have to retain all the information until coming to the "coutner-evidence" section? An "alternative hypotheses" section could be created to house the parts that couldn't be rehomed in this way.

Further, the lede is very long, and could use some trimming!

Verisimilus T 13:37, 29 May 2007 (UTC)

[edit] General reader

As a general reader, I have no idea whatever as to what the following means: "The beginning of a Snowball Earth event could be facilitated by an equatorial continental distribution, which allows rapid, unchecked weathering of continental rocks, absorbing vast quantities of carbon dioxide from the atmosphere." Cutler 13:02, 3 July 2007 (UTC)

I've rewritten the second paragraph of the article with the aim of making it more accessible to non-scientists. I also added mention of the fact that a runaway cooling effect could be initiated by mechanisms other than loss of greenhouse gasses, such as changes in solar output or Earth's orbit. It seems to me that we cannot discount these possibilities when dealing with the distant past, although removal of carbon dioxide may be the most likely possibility.0nullbinary0 (talk) 03:01, 25 April 2008 (UTC)

[edit] Update

Thought I'd flag up a recent paper detailing the potential role of methane in the recovery from the glaciation. DOI:10.1038/nature06961 Smith609 Talk 13:28, 29 May 2008 (UTC)