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I think the sentence in the 'variations in solar energy output' section should be changed... "rising temperatures produce more water vapour, water vapour is a greenhouse gas (much weaker than CO2, but there will eventually be vastly more water vapour), the temperature rises, more water vapour is produced, etc." This seems to imply that water vapor is only responsible for a small part of the greenhouse effect, and it also says that their will be vastly more water vapor, when in fact their already is in relation to CO2
Semantics are important, but shouldn't we adress the blatant vandalism found in the overview?
'A minor series of glaciations occurred from 460 to 430 million years ago. Two more extensive glaciations were from 350 million years before present to 250 million, and from 4 million years ago to about 10,000 years ago (the Pleistocene period).'
Isn't there general agreement that we're still in a "series of gaciation" - that is, an Ice Age? Glaciations have come and gone regularly for the last 4 million years, and we're in between two now. As long as we're talking about "series of glaciations", I think the "to about 10k years ago" is misleading.
HERES THE LINK [1]
( William M. Connolley 20:01, 20 Jan 2004 (UTC)) SEW added some stuff, including: "Han-Shou Liu[2] and others[3] have pointed out that changes in obliquity seem to be relevant", which are:
and
The first of these appears to be about "Orbital Noise of the Earth Causes Intensity Fluctuation in the Geomagnetic Field" and doesn't seem to have any relevance to climate/ice age.
( William M. Connolley 19:19, 1 Feb 2004 (UTC)) From what I'm reading above, Liu seems to think there is a problem with the 100 kyr ecc cycle causing ice ages. Thats OK, because everyone knows that: the forcing is too weak. People invoke various geophysical explanations for this, e.g. response times for ice sheets. Jus to be clear: I've no objections to the article talking about Liu's work, but your one-sentence bit just didn't make sense to me.
The second contains useful stuff but some nonsense ("Muller and MacDonald theorize that this narrow peak in this and other data implies an astronomical origin" is true but misleading, implying they originated the idea; "They further suggest that this narrow peak has been missed due to the spectral analysis methods used" is nonsense; the peak in question is the commonplace 100 kyr peak).
I think the Rial (the pretty colour pic) work *supports* the Milank stuff and opposes Muller etc.
"However, Milankovic cycles predict an extremely cold period 400 thousand years ago which seems to have not happened." needs a ref.
"Milankovic patterns also have two peaks near 100 thousand years but not at 100 thousand years." - not sure this is v important - peaks in spectral space don't nec correspond in real time.
Following the lack of reply to the above comments, the offending para is removed to here, and a v brief summary left behind ( William M. Connolley 19:45, 25 Jan 2004 (UTC)).
However, Milankovic cycles predict an extremely cold period 400 thousand years ago which seems to have not happened. Milankovic patterns also have two peaks near 100 thousand years but not at 100 thousand years. Richard A. Muller and Gordon J. MacDonald have pointed out that those calculations are for a two-dimensional orbit of Earth but the orbital inclination in the three-dimensional orbit has a 100 thousand year peak. Earth's movements through and out of the plane of the ecliptic of all planets match the temperature patterns of the past 1 million years. He suggests this might be due to an interstellar dust cloud or increased collisions in the Themis and Koronis asteroid families causing their dust band to increase. The sudden change 1 million years ago from 41 thousand year cycles to 100 thousand cycles is not explained by unchanging two-dimensional Milankovic cycles but is explained by a cause which is affected by the inclination cycle. Han-Shou Liu [2] and others [3] have pointed out that changes in obliquity seem to be relevant.
How does this look? ( SEWilco 18:47, 2 Feb 2004 (UTC)) Again? ( SEWilco 10:07, 4 Feb 2004 (UTC))
However, Milankovic cycles have periods of 95, 125, and 400 thousand years [4]. Difficulties with Milankovic predictions include that the 400 kyr cycle is not detectable in most records, the major climate cycle has a sharp 100 thousand year peak (instead of 95 and 125 kyr), and some orbital changes which were expected to end an ice age actually took place after the ice age had already ended. Richard A. Muller [5], Gordon J. MacDonald [6], and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100 thousand year cycle of orbital inclination. Earth's movements through and out of the plane of the ecliptic of all planets match the temperature patterns of the past 1 million years. Being in the plane of Jupiter's orbit seems to have the greatest effect. Suspected causes include solar radiation or atmospheric effects due to an interstellar dust cloud or a dust band in our solar system. The change 1 million years ago, during the Middle Pleistocene Revolution, from 41 thousand year cycles to 100 thousand cycles is not explained by unchanging two-dimensional Milankovic cycles but is explained by a cause which is related to the orbital inclination cycle, such as increased collisions in the Themis and Koronis asteroid families. J.A. Rial [7] replies with more details for traditional explanations.
( William M. Connolley 18:24, 4 Feb 2004 (UTC)) OK, we're getting a bit bogged down in detail here. Instead of nit-picking yours, let me try mine again. But first, a couple of principles...
With that in mind, I propose:
The "traditional" Milankovitch explanation struggles to explain the dominance of the 100 kyr cycle over the last 1 Myr. Richard A. Muller and Gordon J. MacDonald [2] [3] [4] and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100 thousand year cycle of orbital inclination. They proposed that these variations in orbital inclination lead to variations in insolation, as the earth moves in and out of dust clouds. Although this is a different mechanism to the traditional view, the "predicted" periods over the last 400 kyr are nearly the same. The Muller and MacDonald theory, in turn, has been challenged by Rial [5].
(No room for Liu, because... I don't understand what he is saying).
We also seem to be in some uncertainty as to what the ice age periodicities are, and when. So a list of, last 1 Myr: 100 kyr; 1.5-2.5 Myr: 41 kyr; or whatever; would be useful. Hmm, actually, thats in the article, but the break is set at 0.8 Myr. This should be ref'd.
Meanwhile, I've re-arraned the paras in the Causes section to roughly chronological: ie first ice ages first, and ending with most recent, Milank. This stuff is a touch nusatisfactory at the moment as I think that 9without a good idea in your head already) you are likely to get confused by the article as to which causes fit which periods.
All of these dates assume an old earth, just as many pages assume evolution and take it as fact. I think we should get both sides of the issue. That's why I put the young earth stuff in there. Please consider it. - SamE 21:21, 3 May 2004 (UTC)
If you want to put together a page entitled something like "ice cores interpreted from a young earth perspective" then feel free. That would be OK. But I very much doubt it can be done.
The debate really belongs on the young earth pages, where it is occurring as we speak... (though of course as DJC commented on the talk pages, wiki is not a debating society).
The IPCC http://www.grida.no/climate/ipcc_tar/wg1/fig2-22.htm [8] indicate that there has been a major interglacial period every 100ky, including one at 400ky. Is this an error?
http://www.museum.state.il.us/exhibits/ice_ages/insolation_graph.html [9] shows particularly strong 400 ky cyclicity and as much as a 25% difference in insolation during one precession cycle during the more high-amplitude 100ky cycles. I would think 25% less solar energy might make a difference.
http://amper.ped.muni.cz/gw/articles/html.format/orb_forc.html [10] shows a similar pattern, though he assumes a different solar constant and therefore gets somewhat higher average fluxes, but the amplitude af the variations is on the order of 25%.
This article just got moved from "ice age" to "Ice Age" and I don't think that's quite right. The article itself uses lower-case throughout. Furthermore this article is discussing ice ages in general, not a specific ice age which might have the proper name "Ice Age" (as the most recent glacial period is often called). I thought I'd bring it up here first, though, since I'm no expert. Bryan 04:20, 26 Aug 2004 (UTC)
I proposed the change a couple weeks ago, and there has been no comment on it, so regarded it as consensus. The talk on that got moved to talk at Ice Age (movie) if you want to see it. Capitalization is not the primary issue. The problem was that people looking for information on continental glaciation first got referred to a B movie about it. In this way the "main event" got the primary page. Pollinator 11:35, Aug 26, 2004 (UTC)
The end of the paragraph defining ice ages and glacial ages is very confusing. You have used ice age in two differnt ways and then you try and clarify the issues by defining glacial in terms of ice ages. I'm still not quite sure what you meant so i can't fix it. Logicnazi 05:18, 21 Dec 2004 (UTC)
The current naming conventions for glaciations and interglacials are a bit of a mess. This is more the fault of the international glaciological community that it is ours. Even so, we have lots of red links for the varying names and some duplicate entries under different regional names. From an archaeological perspective it would make more sense to give each region's name for the same glaciation its own article, each one explicitly linked with its analogues. This would permit better discussion of the relevant cultures and any other local phenomena. From a geologist's or biologist's standpoint and in the name of simplicity though it may be better to merge each name into one article as has been done in Wisconsin glaciation with lots of redirects set up. Any thoughts? adamsan 12:06, 30 Dec 2004 (UTC)
"Since the earth has significant continental glaciation in the Arctic and Antarctic, we currently are in a glacial minimum of a glaciation" doesn't quite make sense to me.
I am reverting the edits by 131.172.4.45. The user gives no citations and the stated science appears to be wrong. Veizer et al.'s strontium isotope measurements do not support a long-term relationship between continental erosion and CO2 changes. The Sr measurements suggests that the Himilayan orogeny has been uniquely profound during the Phanerozoic in it's ability to increase continental erosion (and so might contribute to recent declines in CO2), but previous mountain building events have either been too extented in time or too randomly distributed through time to significantly perturb the continental erosion budget. And as far as I know, the weak perturbations that do occur during most of the record haven't been strongly tied to CO2 changes.
Further, the CO2 declines during the Carboniferous are a biological effect (the result of the evolutionary invention of lignin bearing plants and excess carbon burial) not a geological effect. It is called the Carboniferous because so much carbon ended up in the rocks after all.
Also, while I don't know what qualifies as "extensive" mountain building, there was significant mountain builing in the Rocky Mountain range and Eastern Alps during the Paleogene, which doesn't fit the notion of "absense" of mountain building.
Dragons flight 14:22, Mar 18, 2005 (UTC)
Can anybody justify the use of TOCright on an eight item table of contents? This template has only survived deletion on the grounds that it is used sparingly and it really doesn't seem to me to improve the layout of this article at all. Joe D (t) 8 July 2005 23:52 (UTC)
"During the last few million years there have been many glacial periods, occurring at 40–100,000 year frequencies..."
If this statement is meant to say 40,000 to 100,000 years between glacial periods, this is not the way to write it -- it's too open to confusion, and omitting extra zeroes is not important enough to risk complete misunderstanding. Common sense tells me it's ridiculous to think they can happen every 40 years. DavidH 00:36, July 28, 2005 (UTC)–
Just wondering, why do we have a special section on glaciation in North America, but not for any other continent? Perhaps knowledgeable folks could add sections for each other continent. This would be a bit of a feather in Wikipedia's cap, since most other resources seem to include a bit about North America and a little about Europe, but very little about South America, Asia, Australia, or Africa. -- Securiger 09:10, 17 February 2006 (UTC)
03-28-2006
I had a dream last night. I don't recall it's parameters. But I was suddenly jolted out of bed at 3 a.m. with a thought that just has to be written down and sent to a few people for their perusal.
Once or twice (or more) in the earth's history a huge rock fell on the earth which devastated life forms at the time. Many species went extinct. This theory has a very solid scientific foundation and is understood by geologists and planetary sciences as THE explanation for the end of the dinosaurs.
My theory of the Ice Ages also involves a very large meteor. But it didn't hit the earth. It actually hit the earth's moon. The massive explosion as the meteor plowed into the moon (this probably happened several times over the millennia) ejected many, many tons of dust and debris into near earth orbit. The dust cloud encapsulated the earth. Direct sunlight was cut off by a huge percentage by the dust cloud that encased the earth. Temperatures plunged. Ice Ages resulted. Over thousands of years the dust and debris were swept up by the moon or simply fell to earth and temperatures moderated.
To test this new theory I suggest that geologists analyze the dust and debris of the period for similarities with the "moon rocks" that NASA recovered . Some large chunks must have been transferred here from an explosion that large.
24.56.162.170 16:23, 31 March 2006 (UTC)
luokehao 17:25, 21 December 2006 (UTC)
I was under the impression that one of the contending theories for ice age causes was related to a cyclic interaction between atmospheric conditions and ocean currents. My understanding was to this effect: the warming of the atmosphere (via heightened carbon dioxide levels or methane, etc.--not sure how this part is explained; possibly by geological activity?) leads to the melting of polar freshwater ice, which in turn disturbs the currents of the saltwater oceans (which are responsible for the distribution of temperate and warm air currents), causing a calming of the oceans and consummate cooling of the atmosphere, thereby lowering the overall temperature and inducing the freezing of an ice age. Is this not a widely held hypothesis, or should it receive mention in the article? --5-23-06
http://www.livescience.com/forcesofnature/050330_earth_tilt.html
As far as I can tell, the theory explained at the above link isn't mentioned here. In fact, I don't see any mention of the idea that the 100,000-yr "cycle" is actually just a mixture of 80,000- and 120,000-yr periods (is it really true?). I don't know the subject very well, so maybe I misunderstand, or maybe the stuff in the above article is unworthy of mention. But if so, I would like to know. Thanks. Xezlec 03:27, 10 June 2006 (UTC)
What does "the forcing" mean? HMAccount 22:32, 25 June 2006 (UTC)
Copyrighted text from [11] was removed from the article. Conscious 17:11, 15 July 2006 (UTC)
Since Milankovitch cycles are inadequate to explain an ice age, there must be additional contributing cause. The following, which I believe is consistant with observations, describes how conditions can be brought about by which Milankovitch could then cause the climate to toggle to the opposite climate trend. The strong effect of the incident angle of light on the reflectance of water does not appear to be widely considered in ice age study.
During the current interglacial period, sea level has risen about 120 meters and water area increased accordingly covering the continental shelves which were exposed at the peak of the last glacial. Water responds differently than land to incident solar radiation. That part of incident solar radiation that is reflected from a body of water is specular and is calculated by the Fresnel equations. A graph showing the reflectivity of water vs. incident angle of light can be seen at [12]. Fresnel reflection is directional and therefore does not contribute significantly to albedo which is primarily diffuse reflection. Therefore, added water area always reduces earth’s albedo but may actually decrease the heat added to the planet.
The real water surface is wavy so reflectance assuming a flat surface as given by the Fresnel equations must be adjusted for waviness. A formula and graph for correction for waviness for two different wave energy spectrum definitions has been published. [1] With the average adjustment for the two spectrums applied for an assumed average wind speed of 5 m/s, the reflectivity of wavy water to unpolarized light increases progressively from 5% at an angle of 49.5 degrees to 20% at 72.8 deg and 50% at 83 deg. The rate of increase of reflectivity with angle then declines rapidly so that the reflectivity of wavy water is 67% at 90 deg (light parallel to surface) where it would be 100% if the water were smooth.
Reflectivity of land and various coverings is also given at [13] and does not vary significantly with the incident angle of sunlight. The reflectivity of land varies substantially depending on cover but appears to average about 0.15. Thus at incident solar radiation angles more than about 69 degrees from nadir, water absorbs less heat from the sun than does land. The effective angle for determining water reflectivity is the compound angle accounting for both latitude and time of day. Accounting for the specular reflection of wavy water and the compound angle of the added water surface to the direction of the sun, added water surface area that is further than about 60 degrees north or south latitude results in reduced heat to the planet. Closer to the equator, low reflectance of water during the day more than offsets the high reflectance near dawn and dusk so there is a net gain of heat at these locations. Thus the change in water surface area as the sea level rises provides either positive or negative feedback to ice age climate change depending on the latitude of the added water surface area.
Added water surface area towards the poles that is exposed late in an interglacial period reduces the heat added to the planet and, in concert with other factors, contributes to the toggle from interglacial to glacial. As a glacial period proceeds, lower temperatures and less exposed water area lead to less evaporation and a dryer climate with less cloudiness. The decline in cloud cover allows more solar energy to reach and be absorbed by all surfaces. The largest increase in the heat being absorbed takes place at ocean areas remote from the poles. Water areas at the equator with no cloud cover absorb about 95% of incident solar energy. The resulting net heat gain by the planet, in concert with other factors, may cause the climate to toggle from glacial to interglacial.
I think it would be an interesting (and cautionary) point to mention that the Milanković theory was dismissed as "pseudoscience" until being proven likely in recent years (and we still find some people downplaying it if I'm not mistaken?).
Obviously a section on the extent of glaciation in Europe is needed alongside the N. American treatment -- mentioning the interesting connection of Britain to continent.
Also the general issue of sea level change doesn't seem to have been dealt with in depth if I'm not forgetting something I just read. Map of coastlines at glacial maximum would be great with features like Sundaland pointed out.
Glaciation moves water from ocean to glacier resulting in sea level decline. Glacial melt during an intergalcial period moves water to the oceans producing sea level rise that covers the continental shelf. 4.232.0.79 18:53, 16 August 2006 (UTC)
I've just added a huge section discussing the Ice Ages and the myths of the Great Flood and Atlantis. I'm not really sure how to handle inclusion of this into Wikipedia, but since this is the scientific view of the myths it seems more appropriate for this to be attached to this article. I ask the more experienced editors... would this be more appropriate as a separate article?
Rursus 21:17, 27 December 2006 (UTC) says from here:
Rursus 21:17, 27 December 2006 (UTC) said to here. STOP.
Wikipedia logged me out because I took so long posting that. So no attribution and you don't know who to blame. Oh well. :) DMahalko 19:40, 23 December 2006 (UTC)
It should be a separate article, for the reasons already listed. Also the material must be supported with references - especially given that it all seems extraordinarily speculative. There are more widely-accepted explanations for the Great Flood myth (presumably you mean the Noah/Gilgamesh flood story). Raymond Arritt 22:13, 27 December 2006 (UTC)
Could use votes to save this article, thanks MapleTree 22:28, 28 September 2006 (UTC)
added section on T changes and an external link to more detailed discussion KonaScout 14:58, 16 November 2006 (UTC)
Can any one please explain why this was removed? It covered: (A) the increase in albedo initially accelerates the advance of the ice; (B) the advancing ice decreases weathering and thus causes an increase in the greenhouse effect, which brakes the advance of the ice; (C) during the Cryogenian Ice Age the unusual position of the continents (equatorial super-continent Rodinia) delayed the operation of mechanism (B) and therefore made both the ice age and the eventual increase in greenhouse effect much more severe than usual. Philcha 19:09, 5 December 2006 (UTC)
I wish there was a better picture for this article. How about a map of the world showing the areas covered by ice? I couldn't find anything on Wikicommons. Steve Dufour 04:49, 14 March 2007 (UTC)
A little background on me: I'm not an expert or anything, but I love history and although I'm only a freshman in college I have read/studied alot of subjects on my own so I have a good base knoweldge of this subject. Even though I'm not able to contribute new evidence, material or studies I feel I can contribute by pointing out what I feel are weak points in the article, in hopes someone who really knows this stuff can come in and beef them up. Anyway, I was struck by a few key points while reading this section.
Three types of evidence were discussed: geological, chemical and paleontological. Evidence is intented to convince someone of a fact, but some of the phrasing within this section seemed self defeating and unnecessary to me.
For example at the end of the paragraph explaining the geological evidence it says "Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret. It took some time for the current theory to be worked out." Is it necessary to add this? Seen from the view point of a student who is learning about ice ages for the first time, I would say this student would be confused somewhat because this statement seems to discredit the previously presented evidence.
Also, in the paragraph concerning chemical evidence: Rather than information supporting ice ages and their documentation/dating (ice cores were mentioned) here it seems this paragraph actually presents negative evidence that is not expedient towards a credible base of pro-IA evidence. "This evidence is also difficult to interpret since other factors can change isotope ratios." It basically talks about how chemical evidence is unreliable because too many other factors affect the isotopes that are studied. We should replace this paragraph with firm evidence/statistics and studies from a credible source with citations. (I would if I had the knoweledge myself)
My tertiary quibble is this: The paragraph on paleontological evidence was just as disapointing as the paragraph about chemical evidence. This paragraph states what paleontological evidence is and how it relates to glacial periods but goes no farther. Instead of bolstering the argument with successive supporting material it is followed by material that once again explains how this particular evidence is not reliable!
The last paragraph goes on to say "Despite the difficulties, analyses of ice cores and ocean sediment cores unambiguously show the record of glacials and interglacials over the past few million years." As an impartial observer I would see that and say "Hey, they just talked about how all the evidence that is used to document ice ages/glacial periods is difficult to interpret or is potentially affected by other factors, but then they say they have unambiguous records? Since this is wikipedia I have to be mindful about the legitimacy of information I find, so I think this may be fake." Come on! Beef this thing up! I don't have the knoweledge to do it myself so like I said I'm pointing out what I think are weaknesses and points that should be expounded upon and added to in order to make this article better!
The old Glaciation article has been merged in. Cleanup is now necessary. The way, the truth, and the light 10:18, 27 April 2007 (UTC)
I removed the old contents of this section because they specifically applied to Snowball Earth only and would be misleading in the context of ice ages in general; also, the information was all already found in Snowball Earth. The way, the truth, and the light 04:13, 2 May 2007 (UTC)
In the section "Causes of ice ages", the leading summary paragraph states "climate change itself can change the atmospheric composition (for example by changing the rate at which weathering removes CO2)."
Some explanation or reference on how "weathering removes CO2" from the atmosphere would be appreciated. Thank you. —The preceding unsigned comment was added by 207.7.185.129 ( talk) 03:15, 13 May 2007 (UTC).
Today's New York Times has an article on the modern ice age, which the article says was some odd years more than 8,000 years ago, but still more recently than the 10,000 year figure usually cited in places like this article. Could someone with greater experience in the hard sciences please shed light on this discrepancy? Dogru144 04:22, 16 May 2007 (UTC)
I found the primary graph to be confusing. It would not take much effort to reverse the axis, so time proceeds left to right.
But it is essential that the graph be labeled properly and the color error corrected in the text, where CO2 is printed in blue, and Temperature in red, which is manifestly incorrect.
The graph properly shows axis labels that correspond to the median value of the variable, but PLEASE label the curves redundantly anyway.
the article is excellent, and much appreciated.
Ignorant in Ottawa
The difference in water surface area between the peak of glaciation and the end of an interglacial period can exceed 7%. This difference in evaporative area would have a significant effect on atmospheric water vapor quantity, average cloud cover and average cloud altitude (thus average cloud temperature). This cloud change could be a major contributor in toggling between glaciation and interglacial climates. Has this been considered? Dan Pangburn 00:21, 26 August 2007 (UTC)
Timeline of glaciation gives alternate dates for earliest hypothesized ice ages. Those dates appear to be sourced. JP 01:40, 21 September 2007 (UTC)
Hello-
I noitced that one of the references is wrong. Should be: "Frozen Earth: The Once and Future Story of Ice Ages" -- I would have corrected it, but I don't know how to change reference lists. —Preceding unsigned comment added by 129.79.184.227 ( talk) 18:17, 7 November 2007 (UTC)
In the section on mitigating factors that can lead to a worsening Ice Age, several of the items included are the prospective effects of global warming (either manmade or natural) cycles. Since global warming itself is either a mitigating factor to alleviate glaciation or is a factor to either prolong or end an interglacial period, if it can be argued to cause increased glaciation at all it should be treated as a cause of glaciation and not a mitigating factor to worsen it. It's not logical to argue that warming would worsen glaciation, only that it could trigger it, which is actually what the argument says. It's just been placed in the wrong part of the article. Anytime we get into global warming, I start to smell a rat with regard to the quality of the discussion. Too much junk science and politics (and I mean on both sides of the discussion) mixed up with a legitimate scientific concern. In the context of cause and effect in relation to glaciation cycles, a good litmus test for whether global warming is being discussed fairly and logically is to ask whether the proposed effects of global warming held true during the most severe global warming recorded, which was following the Younger Dryas period and not (at least so far, or even by the suggestions of most scientists) during the global warming uptick currently being experienced and widely attributed to the use of fossil fuels. If the earlier and more severe global warming cycle did not cause these things, it's not likely the less severe global warming forecast as a result of human activity will have a more dire effect. Ftjrwrites ( talk) 20:40, 10 December 2007 (UTC)
The section Recent glacial and interglacial phases points to Timeline of glaciation as main article, a somewhat mixed article, one half about all major episodes of glaciations in Earth's history, and the other to the Quaternary glaciation timeline. So something's wrong, the article should be Timeline of last glaciation or similar ... and there should be at least a bit of text in the corresponding section here. The section Glaciation in North America is about the Wisconsin Glaciation, which is a glacial phase of the Quaternary glaciation. This topic should be a sub-section of the preceding section as long as the other stages of the Quaternary glaciation are missing.
I renamed and moved it accordingly to third level, adding the names of all major NA glacial stages according to the Timeline-article.-- Jo ( talk) 20:49, 30 January 2008 (UTC)
I'm working on a fiction that involves the beginning of a new Ice Age, over several hundred years, and am contemplating potential causes. I was considering atmospheric change: specifically, gases released by decomposition of 9/10th (or so) of the world population, and a goodly chunk of it's non-human life, after an extinction level event like a super virus. Could such massive decomposition be enough to kick start an ice age?
-- Rencheple ( talk) 17:58, 11 April 2008 (UTC)
Ice ages can be further divided by location and time;... The examples given are glacials not ice ages. Could s.o. check and correct, please. 71.236.23.111 ( talk) 15:56, 20 May 2008 (UTC)
I removed this section which was under Volcanism:
Relatively intact wooley mammoth carcasses have been recovered from the Siberian permafrost. For this to occur freezing would have to have happened in days or perhaps even hours. Some even have been found to have undigested daisies in their stomachs, flowers that do not grow in such northern climbs. Pole shift presents a possible explaination of how this might have occured.
A review of various maps depicting the ice age depict Siberia and northern Alaska to be free of ice sheets. A possible explanation could be that the north pole had originally existed 30 degrees to the south towards greenland. In other words, possibly there was no extensive ice age, but rather a shift of the ice cap itself.
The rapid climatic change suggested by pole shift theory has many implications that need to be explored, such as the length and extent of sea level changes and if and when ice sheets existed in Panagonia. Other possible implications include the disapearance of Atlantis, worldwide peridic dinosaur extinctions, and even Noah's Ark.**
Unless there is some source cited which would pass muster at any university, this section seemed out of place here. If I'm out of line, please restore it.
209.130.192.20 ( talk) 18:12, 21 May 2008 (UTC)
If the average length of an interglacial (warm period like today), is around 10,000 years, then should our future generations start preparing to head south, or will global warming balance things out for us?
As well, if an ice age were to happen in say, 300 years from now (2308), would northern cities like Moscow, London, and Toronto expect a towering wall of ice advancing forward, scraping rocks and pushing the skyscrapers southwards, or would they be entombed in ice and snow from winter snowfalls that don't end? RingtailedFox • Talk • Contribs 03:05, 18 June 2008 (UTC)
In this article it says that the last Ice age ended 11,000 years ago in the beginning of the article but it also says at the end of the article that it ended 10,000 years ago. Which number is correct? Thank You. Maldek ( talk) 03:55, 8 July 2008 (UTC)
This Ice_age#The_Uplift_of_the_Tibetan_Plateau_and_surrounding_Mountain Areas_above_the_Snowline seems dodgy to me William M. Connolley ( talk) 22:10, 1 October 2008 (UTC)
In a few words, literally: List of ice ages...
I am not a native speaker, still -- shouldn't it rather be 'researcher' or 'scientist' ? 136.173.162.129 ( talk) 11:52, 27 November 2008 (UTC)
-Worker is common usage in the field. -Tom Bishop
"An extraordinary testimony to the widespread watery destruction of animal life...They are sometimes found in a near-perfect state of preservation, with undigested tropical vegetation in their stomachs." - Earth’s Most Challenging Mysteries.-- Standforder ( talk) 00:08, 10 December 2008 (UTC)
The "ice age" wasn't a long period, the term is misleading. The earth previous to this brief " ice age" was tropical-like. This rapid freezing put the earth in freezing [temperature]]s. The " ice age" occured nearly 4,400 years, (Compare Genesis 7:18, 21).-- Standforder ( talk) 00:08, 10 December 2008 (UTC)
"A sinking of the sea basins would cause the waters to collect there, allowing dry land to appear again. Compare Psalm 104:8. In the oceans today there is more than enough water to have accomplished what the Bible describes; 71 percent of the earth’s surface is water, with an average depth of two and a half miles."-- Standforder ( talk) 00:08, 10 December 2008 (UTC)
It does too relate to the article.-- Standforder ( talk) 23:30, 21 December 2008 (UTC)
In addition, the claim that "animal life", specifically the mummified mammoths, and horses, and other animals (in either Alaska or Siberia) are "...sometimes found in a near-perfect state of preservation, with undigested tropical vegetation in their stomachs" is a complete and utter falsehood. These mummified animals were neither in a near perfect state of preservation nor did they have tropical vegetation in their stomachs when they were found. This is discussed in Woolly Mammoths: Evidence of Catastrophe?, MOM and Atlantis, Mammoths, and Crustal Shift, and CC361.2: Quick-frozen mammoths.
Published articles that discuss the imaginary nature of claims about the "near-perfect preservation" of these animals and tropical plants being found in their stomachs are:
Brass, M., 2002, Tracing Graham Hancock's Shifting Cataclysm. Skeptical Inquirer. vol. 26, no. 4, p. 45-49. and
Farrand, W. R., 1961, Frozen Mammoths and Modern Geology: The death of the giants can be explained as a hazard of tundra life, without evoking catastrophic events. Science. vol. 133. no. 3455, p. 729-735. Paul H. ( talk) 05:37, 23 December 2008 (UTC)
The author of this section seems to rule out the possibility that volcanoes can contribute to ice ages, yet there is some evidence that reflective aerosols cause a net cooling effect on the short term (eg. mt. pinatubo). Conflicting evidence (Tuba eruption 70ka) suggests that volcanism has nothing to do with it. I am not familiar with research into the effects of supervolcanoes on climate change, but there was supposedly a massive sea level fall associated with the siberian traps volcanism 251 million years ago that could indicate the initiation of an ice age. The long term net effect of volcanism may be heating, yet that doesn't rule out it's role in the initiation of an ice age. —The preceding unsigned comment was added by Luokehao ( talk • contribs) 17:29, 21 December 2006.
I thought undersea volcanism could trigger an ice age by warming the oceans, thereby increasing precipitation. If this happens at the right part of the Milenkovich cycle, increased snowfall at high latitudes would increase albedo, and therefor cooling. —Preceding unsigned comment added by 150.195.11.24 ( talk) 19:29, 10 March 2009 (UTC)
I am an Activities Assistant at a nursing home and one of my resident would like to know, so if anyone has an answer would you please email it to me at <address removed to prevent spam>, thanks for your help—The preceding unsigned comment was added by 72.135.25.85 ( talk • contribs).
This description of the ice-albedo feedback under "Processes which make glacial periods more severe" is unclear. The use of the word "equilibrium" seems to imply that this positive feedback loop equilibrates _on its own_, which is clearly false. I suggest changing the wording to something like, "Hence, when the air temperature decreases, ice and snow fields grow, and this continues until [competition with a negative feedback mechanism forces the system to an equilibrium]."
Bradweir ( talk) 23:25, 7 May 2009 (UTC)
The CO2 reference below is conjecture and should be removed, unless someone can provide peer review substantiation for this speculation.
"The earliest well-documented ice age, and probably the most severe of the last 1 billion years, occurred from 850 to 630 million years ago (the Cryogenian period) and may have produced a Snowball Earth in which permanent ice covered the entire globe and was ended by the effects of the accumulation of greenhouse gases such as CO2 produced by volcanoes." —Preceding unsigned comment added by 99.241.247.201 ( talk) 23:32, 7 May 2009 (UTC)
Please note that, by a decision of the Wikipedia community, this article and others relating to climate change (broadly construed) has been placed under article probation. Editors making disruptive edits may be blocked temporarily from editing the encyclopedia, or subject to other administrative remedies, according to standards that may be higher than elsewhere on Wikipedia. Please see Wikipedia:General sanctions/Climate change probation for full information and to review the decision. -- ChrisO ( talk) 19:38, 2 January 2010 (UTC)
In the section: Variations in the Sun's energy output
The phrase: "The long-term increase in the Sun's output cannot be a cause of ice ages." needs some improvement. Oh, I see that is discussing an overall increase in the sun's energy, and not a cyclical phenomenon.
The whole section, however, needs to be updated.
Also, refer to the Wikipedia article: http://en.wikipedia.org/wiki/Sun#Possible_long-term_cycle
This Wikipedia article lists a couple of sources: http://www.newscientist.com/article/mg19325884.500-suns-fickle-heart-may-leave-us-cold.html and http://arxiv.org/abs/astro-ph/0701117
Which indicate a hypothesis that there may be long-term cycles in the sun's output energy that would generate either 41K year or 100K year (on average) cycles of the sun's output leading to the the cyclic glacial / interglacial periods, and these solar cycles may better explain the temperature variations than Milankovitch cycles.-- Keelec ( talk) 04:43, 17 January 2010 (UTC)
Shouldn't the article provide more sources for the average durations of interglacials? It appears that several sources indicate that interglacials have an average duration of 10K to 12K years. For example, this says an average of 10K years. And this says: "Over the last one million years there have been about eight Major Ice ages of about 115 kiloyears duration." Now 8 x 115K equals 920,000 and 1,000,000 - 920,000 = 80,000. 80,000/8 = 10,000 so I can see where the average is coming from. I think there are a large number of valid (e.g. actual science) sources that provide these numbers. Shouldn't we be providing that information in the article (with appropriate references of course)? Comments? (And please -- this has nothing to do with global warming etc. -- this has to do with evidence related to the past, not the present.) SunSw0rd ( talk) 14:39, 9 February 2010 (UTC)
Zeog -- what do you prefer in File:Vostok-ice-core-petit.png compared to File:Vostok Petit data.svg? I'd like to incorporate your suggestions to improve it so that we can replace the bitmap image with a vector one as part of WP:SVG. Personally I found the three separate, overlapping Y axis scales in the bitmap very difficult to read since they did not immediately appear to correspond to the different lines. -- Autopilot ( talk) 23:04, 21 June 2010 (UTC)
I see that WP has articles on Ice ages and the shorter period glacial and interglacial periods between ice ages. But what are the long-term intervals called between Ice Ages? Non-Ice Ages? Warm Ages? I can't find any research or references to these long-period intervals and what the climate, fauna, etc was like. I imagine that these "Warm Ages" also had shorter-period variations analogous to glacial and interglacial periods. Anyone want to address this? —Preceding unsigned comment added by 66.162.130.210 ( talk • contribs) 00:09, 24 October 2009
Don't know about the WP article. I have always called the 'non-ice age' as "earth normal." Since we technically live in an ice age even with the interglacial period we live in the earths average temperature is between 5 to 8 deg C warming then what it is today. -- OxAO ( talk) 00:24, 15 September 2010 (UTC)
173.165.228.33 ( talk) 15:59, 25 May 2011 (UTC) I also would like to see more definition as to the length and temperature between ice ages. Water vapor content of early atmos is essential for accurate description of ice ages. If the Med was dry until 5 mya before now, how long was it dry. Science says in order to have ice ages there must be the water vapor in the atmos to fall as snow.
This article is a load of bull, I have a pdf containing a graph that has a chart with references, please look at figure 6 on page 11 of the following pdf: http://spinonthat.com/CO2_files/CO2tdino.pdf
I have read some of the articles myself, and I feel that while wikipedia was once good, I have observed articles changing for the worse over the past couple of years. This especially includes articles which once represented skepticism towards AGW fairly, which now after having looked at them again, do not.
Wikipedia has lost alot of useful information. Indeed it is censored. I remember reading the "ammonium nitrate" article where a recipe for making it into a military grade explosive was in the article, which is now gone (and in fact, much of the rest of the information that was in the article is gone, including the synthesis of ammonium nitrate).
I don't care if this information can be used for bad things. We have a right to free learning and free information on the web and this bending over to homeland security and the UN to omit information against their global warming scam is a complete joke, and honestly, wikipedia is becoming a joke for having censored information. I deeply resent your site and I think since alex jones reported the changes to your page, who did it, and how wikipedia responded. The lack of a note on these pages about the issue that people have is offensive and I feel that people deserve to be made aware of the controversy involved. If you cannot ensure that your editors present information in a fair and unbiased way, then what good is your site? I can't learn anything about the world when so much disinformation is being given out, so much information is now omitted from your articles.
I'm not the only one that feels this way. I am personally going to lobby people to boycott your site until your site takes a more impartial presentation of information for learning purposes. Clearly the angle given on AGW and ice age, climate change, etc, is spun to such a degree as to support the UN's perspective that AGW exists. A recent article on physorg.com supports the following:
Climate change models are not accurate (aside from climategate and IPCC fraud) due to the lack of knowledge regarding the behavior of airborne particulates (and any associated reactions which may take place that we do not know about).
It can be found here: http://www.physorg.com/news180628222.html
Your articles do not state much about the "unknowns" and "alternate viewpoints", and therefore come across as heavily biased towards supporting AGW. Cherry picking the weakest counter-arguments against AGW is just as fraudulant as the IPCC doing climategate, and to be honest nobody here believes that it didn't happen considering the statements made by IPCC scientists that support the notion that they committed fraud (as some let this information slip out in video interviews which can be found on prisonplanet.com).
Can wikipedia start presenting factual information or are we supposed to accept this fraud from you as well? Should Alex Jones and I start a wiki about wikipedia articles being inaccurate? Because I am about to make a serious proposal to him to develop software to counter the disinformation your site spews out to people, starting with AGW, and anything else homeland security is paid to bully your site into making things disappear (weather the owner gets paid to allow it, or is forced to do it, or if it's hundreds of homeland security members who actually are the editors, or bribing your editors). Either way we know what's going on and we aren't dumb and you ought to present the medieval warming period information, as well as the fact that we are currently in the middle of an ice age, and that historically, 545 million years ago the co2 levels were near 8000 ppm. Start presenting some real facts, or we will start a site that will. —Preceding unsigned comment added by Stealthc ( talk • contribs) 03:04, 24 December 2009 (UTC)
It is disappointing but to be expected. Himilayas increase rainfall which must leave water vapor unaffected because the magic of CO2 ... what a load of bull. Anyway, there are some useful references in material like this in wiki if the general content is useless. —Preceding
unsigned comment added by
66.38.159.33 (
talk)
03:14, 18 February 2010 (UTC)
This article describes an Ice Age as "a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers.". I am not a scientist but to mee this definition seems a bit "wooly". What counts as long term? How far should temperatures fall below their "long term" levels before an ice age is identified? What percentage of the earth should be covered in glaciation? etc etc
I was unable to find anything better on the web so it may be that the above description is the scientific consensus, does anyone know? Alternatively perhaps people think this issue is too esoteric for an encyclopedia?
Zanzare ( talk) 14:10, 30 December 2009 (UTC)
Pluto is still there. That's the thing about labels, they don't change the facts, they're just useful handles for describing them. Tasty monster (= TS ) 18:49, 20 September 2010 (UTC)
I think it is better and more correct the new version of "Ice age",this one:
"An "Ice Age" or, more precisely, "Glacial Age" is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an existence of continental ice sheets, polar ice sheets and alpine glaciers.
The Earth's climatic history has been divided, in intervals of millions of years, into Ice Ages and Interglacial Ages. The term Ice Age refers to a long interval of time (millions years) where the Earth's poles are covered with ice sheets more or less extensive and where the average temperature of the poles remains below 0 °C) [2]. The Ice Ages are considered the Earth's climate history "seasons" and they are divided into Glacial periods (or alternatively "glacials") and Interglacial periods (or "Interglacials"). The Glacials are the stages of advancement of the ice sheets (called glaciations) and the Interglacials are the stages of retreat (these periods last for thousand years).
Interglacial Ages last millions of years, when the ice sheets have retreated to a minimum extent at the poles, and they separate two successive Ice Ages."
We should vote to choose the best one.-- 93.151.235.163 ( talk) 10:39, 20 September 2010 (UTC)
Anyone agree the heading image of the earth seen from space at the height of the last glaciation is not very helpful? I've been trying for fifteen minutes to match it to ordinary geography, that is to grasp from what angle it's supposed to show the earth. I supppose the N Atlantic is at the centre, but the rest? If northern Europe is the big hump on the top right, then what are the big white spots at right centre of the picture? Ethiopia and east Africa? That won't do: those ice sheets were relatively small in extent compared to those in the north. The edge outline of the ice to the left looks strange too. The lack of differentiation between non-glaciated continents and sea is a big drawback - both are shown as simply dark! I've seen much better pictures using the same idea, at the very least this one needs some captioning. Strausszek ( talk) 10:03, 20 October 2010 (UTC)
Some of the paragraphs in the article are way too long, which adversely affects readability. That's bad writing for for all but very advanced literary writers, who can sometimes pull it off. Most writers should instead break larger paragraphs into smaller ones. Especially in articles for wide public consumption.
69.171.160.110 ( talk) 02:24, 27 September 2011 (UTC)
Whoever wrote the POV push about global warming and specifically about positive and negative feedbacks seems to have very little idea what they mean. Positive feedback both warms and cools as does negative feedback. The difference is not the direction of effect but whether they increase of diminish the effect of a stimulus. Positive feedback creates a greater change than would be expected by the stimulus alone. Negative feedback reduces the effect. Although... it's more complicated in the real world due to phase changes. — Preceding unsigned comment added by 81.106.237.60 ( talk) 18:38, 18 April 2012 (UTC)
"There appears to be no geological evidence for such eruptions at the right time, but this does not prove they did not happen." That's an incredibly unscientific statement. Should it be reworded? Or eliminated? 167.206.122.66 ( talk) 17:17, 24 September 2012 (UTC)
This article surely needs to talk about, or at least link to the article on Greenhouse and icehouse Earth, since an "Ice Age" is only a period within an "Ice House", etc. -- Hibernian ( talk) 01:45, 11 March 2013 (UTC)
The latest BBC tv series Ice Age Beasts features the "elephant in the room" (pun intended) which is the conundrum of how millions of mammoths and other megafauna managed to survive the colder ice age period compared to the interglacial conditions of today. How did grass manage to grow in Siberia where it doesn't grow today? This paradox needs a mention at least, due to it putting the whole ice age theory into question. (P.S. A more common sense idea imv is that Jupiter's 100,000yr cycle increases the Earth's equatorial tidal strength which can even push warm water into the Arctic Basin). 176.24.226.120 ( talk) 21:08, 31 May 2013 (UTC) Alan Lowey
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This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 |
I think the sentence in the 'variations in solar energy output' section should be changed... "rising temperatures produce more water vapour, water vapour is a greenhouse gas (much weaker than CO2, but there will eventually be vastly more water vapour), the temperature rises, more water vapour is produced, etc." This seems to imply that water vapor is only responsible for a small part of the greenhouse effect, and it also says that their will be vastly more water vapor, when in fact their already is in relation to CO2
Semantics are important, but shouldn't we adress the blatant vandalism found in the overview?
'A minor series of glaciations occurred from 460 to 430 million years ago. Two more extensive glaciations were from 350 million years before present to 250 million, and from 4 million years ago to about 10,000 years ago (the Pleistocene period).'
Isn't there general agreement that we're still in a "series of gaciation" - that is, an Ice Age? Glaciations have come and gone regularly for the last 4 million years, and we're in between two now. As long as we're talking about "series of glaciations", I think the "to about 10k years ago" is misleading.
HERES THE LINK [1]
( William M. Connolley 20:01, 20 Jan 2004 (UTC)) SEW added some stuff, including: "Han-Shou Liu[2] and others[3] have pointed out that changes in obliquity seem to be relevant", which are:
and
The first of these appears to be about "Orbital Noise of the Earth Causes Intensity Fluctuation in the Geomagnetic Field" and doesn't seem to have any relevance to climate/ice age.
( William M. Connolley 19:19, 1 Feb 2004 (UTC)) From what I'm reading above, Liu seems to think there is a problem with the 100 kyr ecc cycle causing ice ages. Thats OK, because everyone knows that: the forcing is too weak. People invoke various geophysical explanations for this, e.g. response times for ice sheets. Jus to be clear: I've no objections to the article talking about Liu's work, but your one-sentence bit just didn't make sense to me.
The second contains useful stuff but some nonsense ("Muller and MacDonald theorize that this narrow peak in this and other data implies an astronomical origin" is true but misleading, implying they originated the idea; "They further suggest that this narrow peak has been missed due to the spectral analysis methods used" is nonsense; the peak in question is the commonplace 100 kyr peak).
I think the Rial (the pretty colour pic) work *supports* the Milank stuff and opposes Muller etc.
"However, Milankovic cycles predict an extremely cold period 400 thousand years ago which seems to have not happened." needs a ref.
"Milankovic patterns also have two peaks near 100 thousand years but not at 100 thousand years." - not sure this is v important - peaks in spectral space don't nec correspond in real time.
Following the lack of reply to the above comments, the offending para is removed to here, and a v brief summary left behind ( William M. Connolley 19:45, 25 Jan 2004 (UTC)).
However, Milankovic cycles predict an extremely cold period 400 thousand years ago which seems to have not happened. Milankovic patterns also have two peaks near 100 thousand years but not at 100 thousand years. Richard A. Muller and Gordon J. MacDonald have pointed out that those calculations are for a two-dimensional orbit of Earth but the orbital inclination in the three-dimensional orbit has a 100 thousand year peak. Earth's movements through and out of the plane of the ecliptic of all planets match the temperature patterns of the past 1 million years. He suggests this might be due to an interstellar dust cloud or increased collisions in the Themis and Koronis asteroid families causing their dust band to increase. The sudden change 1 million years ago from 41 thousand year cycles to 100 thousand cycles is not explained by unchanging two-dimensional Milankovic cycles but is explained by a cause which is affected by the inclination cycle. Han-Shou Liu [2] and others [3] have pointed out that changes in obliquity seem to be relevant.
How does this look? ( SEWilco 18:47, 2 Feb 2004 (UTC)) Again? ( SEWilco 10:07, 4 Feb 2004 (UTC))
However, Milankovic cycles have periods of 95, 125, and 400 thousand years [4]. Difficulties with Milankovic predictions include that the 400 kyr cycle is not detectable in most records, the major climate cycle has a sharp 100 thousand year peak (instead of 95 and 125 kyr), and some orbital changes which were expected to end an ice age actually took place after the ice age had already ended. Richard A. Muller [5], Gordon J. MacDonald [6], and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100 thousand year cycle of orbital inclination. Earth's movements through and out of the plane of the ecliptic of all planets match the temperature patterns of the past 1 million years. Being in the plane of Jupiter's orbit seems to have the greatest effect. Suspected causes include solar radiation or atmospheric effects due to an interstellar dust cloud or a dust band in our solar system. The change 1 million years ago, during the Middle Pleistocene Revolution, from 41 thousand year cycles to 100 thousand cycles is not explained by unchanging two-dimensional Milankovic cycles but is explained by a cause which is related to the orbital inclination cycle, such as increased collisions in the Themis and Koronis asteroid families. J.A. Rial [7] replies with more details for traditional explanations.
( William M. Connolley 18:24, 4 Feb 2004 (UTC)) OK, we're getting a bit bogged down in detail here. Instead of nit-picking yours, let me try mine again. But first, a couple of principles...
With that in mind, I propose:
The "traditional" Milankovitch explanation struggles to explain the dominance of the 100 kyr cycle over the last 1 Myr. Richard A. Muller and Gordon J. MacDonald [2] [3] [4] and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100 thousand year cycle of orbital inclination. They proposed that these variations in orbital inclination lead to variations in insolation, as the earth moves in and out of dust clouds. Although this is a different mechanism to the traditional view, the "predicted" periods over the last 400 kyr are nearly the same. The Muller and MacDonald theory, in turn, has been challenged by Rial [5].
(No room for Liu, because... I don't understand what he is saying).
We also seem to be in some uncertainty as to what the ice age periodicities are, and when. So a list of, last 1 Myr: 100 kyr; 1.5-2.5 Myr: 41 kyr; or whatever; would be useful. Hmm, actually, thats in the article, but the break is set at 0.8 Myr. This should be ref'd.
Meanwhile, I've re-arraned the paras in the Causes section to roughly chronological: ie first ice ages first, and ending with most recent, Milank. This stuff is a touch nusatisfactory at the moment as I think that 9without a good idea in your head already) you are likely to get confused by the article as to which causes fit which periods.
All of these dates assume an old earth, just as many pages assume evolution and take it as fact. I think we should get both sides of the issue. That's why I put the young earth stuff in there. Please consider it. - SamE 21:21, 3 May 2004 (UTC)
If you want to put together a page entitled something like "ice cores interpreted from a young earth perspective" then feel free. That would be OK. But I very much doubt it can be done.
The debate really belongs on the young earth pages, where it is occurring as we speak... (though of course as DJC commented on the talk pages, wiki is not a debating society).
The IPCC http://www.grida.no/climate/ipcc_tar/wg1/fig2-22.htm [8] indicate that there has been a major interglacial period every 100ky, including one at 400ky. Is this an error?
http://www.museum.state.il.us/exhibits/ice_ages/insolation_graph.html [9] shows particularly strong 400 ky cyclicity and as much as a 25% difference in insolation during one precession cycle during the more high-amplitude 100ky cycles. I would think 25% less solar energy might make a difference.
http://amper.ped.muni.cz/gw/articles/html.format/orb_forc.html [10] shows a similar pattern, though he assumes a different solar constant and therefore gets somewhat higher average fluxes, but the amplitude af the variations is on the order of 25%.
This article just got moved from "ice age" to "Ice Age" and I don't think that's quite right. The article itself uses lower-case throughout. Furthermore this article is discussing ice ages in general, not a specific ice age which might have the proper name "Ice Age" (as the most recent glacial period is often called). I thought I'd bring it up here first, though, since I'm no expert. Bryan 04:20, 26 Aug 2004 (UTC)
I proposed the change a couple weeks ago, and there has been no comment on it, so regarded it as consensus. The talk on that got moved to talk at Ice Age (movie) if you want to see it. Capitalization is not the primary issue. The problem was that people looking for information on continental glaciation first got referred to a B movie about it. In this way the "main event" got the primary page. Pollinator 11:35, Aug 26, 2004 (UTC)
The end of the paragraph defining ice ages and glacial ages is very confusing. You have used ice age in two differnt ways and then you try and clarify the issues by defining glacial in terms of ice ages. I'm still not quite sure what you meant so i can't fix it. Logicnazi 05:18, 21 Dec 2004 (UTC)
The current naming conventions for glaciations and interglacials are a bit of a mess. This is more the fault of the international glaciological community that it is ours. Even so, we have lots of red links for the varying names and some duplicate entries under different regional names. From an archaeological perspective it would make more sense to give each region's name for the same glaciation its own article, each one explicitly linked with its analogues. This would permit better discussion of the relevant cultures and any other local phenomena. From a geologist's or biologist's standpoint and in the name of simplicity though it may be better to merge each name into one article as has been done in Wisconsin glaciation with lots of redirects set up. Any thoughts? adamsan 12:06, 30 Dec 2004 (UTC)
"Since the earth has significant continental glaciation in the Arctic and Antarctic, we currently are in a glacial minimum of a glaciation" doesn't quite make sense to me.
I am reverting the edits by 131.172.4.45. The user gives no citations and the stated science appears to be wrong. Veizer et al.'s strontium isotope measurements do not support a long-term relationship between continental erosion and CO2 changes. The Sr measurements suggests that the Himilayan orogeny has been uniquely profound during the Phanerozoic in it's ability to increase continental erosion (and so might contribute to recent declines in CO2), but previous mountain building events have either been too extented in time or too randomly distributed through time to significantly perturb the continental erosion budget. And as far as I know, the weak perturbations that do occur during most of the record haven't been strongly tied to CO2 changes.
Further, the CO2 declines during the Carboniferous are a biological effect (the result of the evolutionary invention of lignin bearing plants and excess carbon burial) not a geological effect. It is called the Carboniferous because so much carbon ended up in the rocks after all.
Also, while I don't know what qualifies as "extensive" mountain building, there was significant mountain builing in the Rocky Mountain range and Eastern Alps during the Paleogene, which doesn't fit the notion of "absense" of mountain building.
Dragons flight 14:22, Mar 18, 2005 (UTC)
Can anybody justify the use of TOCright on an eight item table of contents? This template has only survived deletion on the grounds that it is used sparingly and it really doesn't seem to me to improve the layout of this article at all. Joe D (t) 8 July 2005 23:52 (UTC)
"During the last few million years there have been many glacial periods, occurring at 40–100,000 year frequencies..."
If this statement is meant to say 40,000 to 100,000 years between glacial periods, this is not the way to write it -- it's too open to confusion, and omitting extra zeroes is not important enough to risk complete misunderstanding. Common sense tells me it's ridiculous to think they can happen every 40 years. DavidH 00:36, July 28, 2005 (UTC)–
Just wondering, why do we have a special section on glaciation in North America, but not for any other continent? Perhaps knowledgeable folks could add sections for each other continent. This would be a bit of a feather in Wikipedia's cap, since most other resources seem to include a bit about North America and a little about Europe, but very little about South America, Asia, Australia, or Africa. -- Securiger 09:10, 17 February 2006 (UTC)
03-28-2006
I had a dream last night. I don't recall it's parameters. But I was suddenly jolted out of bed at 3 a.m. with a thought that just has to be written down and sent to a few people for their perusal.
Once or twice (or more) in the earth's history a huge rock fell on the earth which devastated life forms at the time. Many species went extinct. This theory has a very solid scientific foundation and is understood by geologists and planetary sciences as THE explanation for the end of the dinosaurs.
My theory of the Ice Ages also involves a very large meteor. But it didn't hit the earth. It actually hit the earth's moon. The massive explosion as the meteor plowed into the moon (this probably happened several times over the millennia) ejected many, many tons of dust and debris into near earth orbit. The dust cloud encapsulated the earth. Direct sunlight was cut off by a huge percentage by the dust cloud that encased the earth. Temperatures plunged. Ice Ages resulted. Over thousands of years the dust and debris were swept up by the moon or simply fell to earth and temperatures moderated.
To test this new theory I suggest that geologists analyze the dust and debris of the period for similarities with the "moon rocks" that NASA recovered . Some large chunks must have been transferred here from an explosion that large.
24.56.162.170 16:23, 31 March 2006 (UTC)
luokehao 17:25, 21 December 2006 (UTC)
I was under the impression that one of the contending theories for ice age causes was related to a cyclic interaction between atmospheric conditions and ocean currents. My understanding was to this effect: the warming of the atmosphere (via heightened carbon dioxide levels or methane, etc.--not sure how this part is explained; possibly by geological activity?) leads to the melting of polar freshwater ice, which in turn disturbs the currents of the saltwater oceans (which are responsible for the distribution of temperate and warm air currents), causing a calming of the oceans and consummate cooling of the atmosphere, thereby lowering the overall temperature and inducing the freezing of an ice age. Is this not a widely held hypothesis, or should it receive mention in the article? --5-23-06
http://www.livescience.com/forcesofnature/050330_earth_tilt.html
As far as I can tell, the theory explained at the above link isn't mentioned here. In fact, I don't see any mention of the idea that the 100,000-yr "cycle" is actually just a mixture of 80,000- and 120,000-yr periods (is it really true?). I don't know the subject very well, so maybe I misunderstand, or maybe the stuff in the above article is unworthy of mention. But if so, I would like to know. Thanks. Xezlec 03:27, 10 June 2006 (UTC)
What does "the forcing" mean? HMAccount 22:32, 25 June 2006 (UTC)
Copyrighted text from [11] was removed from the article. Conscious 17:11, 15 July 2006 (UTC)
Since Milankovitch cycles are inadequate to explain an ice age, there must be additional contributing cause. The following, which I believe is consistant with observations, describes how conditions can be brought about by which Milankovitch could then cause the climate to toggle to the opposite climate trend. The strong effect of the incident angle of light on the reflectance of water does not appear to be widely considered in ice age study.
During the current interglacial period, sea level has risen about 120 meters and water area increased accordingly covering the continental shelves which were exposed at the peak of the last glacial. Water responds differently than land to incident solar radiation. That part of incident solar radiation that is reflected from a body of water is specular and is calculated by the Fresnel equations. A graph showing the reflectivity of water vs. incident angle of light can be seen at [12]. Fresnel reflection is directional and therefore does not contribute significantly to albedo which is primarily diffuse reflection. Therefore, added water area always reduces earth’s albedo but may actually decrease the heat added to the planet.
The real water surface is wavy so reflectance assuming a flat surface as given by the Fresnel equations must be adjusted for waviness. A formula and graph for correction for waviness for two different wave energy spectrum definitions has been published. [1] With the average adjustment for the two spectrums applied for an assumed average wind speed of 5 m/s, the reflectivity of wavy water to unpolarized light increases progressively from 5% at an angle of 49.5 degrees to 20% at 72.8 deg and 50% at 83 deg. The rate of increase of reflectivity with angle then declines rapidly so that the reflectivity of wavy water is 67% at 90 deg (light parallel to surface) where it would be 100% if the water were smooth.
Reflectivity of land and various coverings is also given at [13] and does not vary significantly with the incident angle of sunlight. The reflectivity of land varies substantially depending on cover but appears to average about 0.15. Thus at incident solar radiation angles more than about 69 degrees from nadir, water absorbs less heat from the sun than does land. The effective angle for determining water reflectivity is the compound angle accounting for both latitude and time of day. Accounting for the specular reflection of wavy water and the compound angle of the added water surface to the direction of the sun, added water surface area that is further than about 60 degrees north or south latitude results in reduced heat to the planet. Closer to the equator, low reflectance of water during the day more than offsets the high reflectance near dawn and dusk so there is a net gain of heat at these locations. Thus the change in water surface area as the sea level rises provides either positive or negative feedback to ice age climate change depending on the latitude of the added water surface area.
Added water surface area towards the poles that is exposed late in an interglacial period reduces the heat added to the planet and, in concert with other factors, contributes to the toggle from interglacial to glacial. As a glacial period proceeds, lower temperatures and less exposed water area lead to less evaporation and a dryer climate with less cloudiness. The decline in cloud cover allows more solar energy to reach and be absorbed by all surfaces. The largest increase in the heat being absorbed takes place at ocean areas remote from the poles. Water areas at the equator with no cloud cover absorb about 95% of incident solar energy. The resulting net heat gain by the planet, in concert with other factors, may cause the climate to toggle from glacial to interglacial.
I think it would be an interesting (and cautionary) point to mention that the Milanković theory was dismissed as "pseudoscience" until being proven likely in recent years (and we still find some people downplaying it if I'm not mistaken?).
Obviously a section on the extent of glaciation in Europe is needed alongside the N. American treatment -- mentioning the interesting connection of Britain to continent.
Also the general issue of sea level change doesn't seem to have been dealt with in depth if I'm not forgetting something I just read. Map of coastlines at glacial maximum would be great with features like Sundaland pointed out.
Glaciation moves water from ocean to glacier resulting in sea level decline. Glacial melt during an intergalcial period moves water to the oceans producing sea level rise that covers the continental shelf. 4.232.0.79 18:53, 16 August 2006 (UTC)
I've just added a huge section discussing the Ice Ages and the myths of the Great Flood and Atlantis. I'm not really sure how to handle inclusion of this into Wikipedia, but since this is the scientific view of the myths it seems more appropriate for this to be attached to this article. I ask the more experienced editors... would this be more appropriate as a separate article?
Rursus 21:17, 27 December 2006 (UTC) says from here:
Rursus 21:17, 27 December 2006 (UTC) said to here. STOP.
Wikipedia logged me out because I took so long posting that. So no attribution and you don't know who to blame. Oh well. :) DMahalko 19:40, 23 December 2006 (UTC)
It should be a separate article, for the reasons already listed. Also the material must be supported with references - especially given that it all seems extraordinarily speculative. There are more widely-accepted explanations for the Great Flood myth (presumably you mean the Noah/Gilgamesh flood story). Raymond Arritt 22:13, 27 December 2006 (UTC)
Could use votes to save this article, thanks MapleTree 22:28, 28 September 2006 (UTC)
added section on T changes and an external link to more detailed discussion KonaScout 14:58, 16 November 2006 (UTC)
Can any one please explain why this was removed? It covered: (A) the increase in albedo initially accelerates the advance of the ice; (B) the advancing ice decreases weathering and thus causes an increase in the greenhouse effect, which brakes the advance of the ice; (C) during the Cryogenian Ice Age the unusual position of the continents (equatorial super-continent Rodinia) delayed the operation of mechanism (B) and therefore made both the ice age and the eventual increase in greenhouse effect much more severe than usual. Philcha 19:09, 5 December 2006 (UTC)
I wish there was a better picture for this article. How about a map of the world showing the areas covered by ice? I couldn't find anything on Wikicommons. Steve Dufour 04:49, 14 March 2007 (UTC)
A little background on me: I'm not an expert or anything, but I love history and although I'm only a freshman in college I have read/studied alot of subjects on my own so I have a good base knoweldge of this subject. Even though I'm not able to contribute new evidence, material or studies I feel I can contribute by pointing out what I feel are weak points in the article, in hopes someone who really knows this stuff can come in and beef them up. Anyway, I was struck by a few key points while reading this section.
Three types of evidence were discussed: geological, chemical and paleontological. Evidence is intented to convince someone of a fact, but some of the phrasing within this section seemed self defeating and unnecessary to me.
For example at the end of the paragraph explaining the geological evidence it says "Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret. It took some time for the current theory to be worked out." Is it necessary to add this? Seen from the view point of a student who is learning about ice ages for the first time, I would say this student would be confused somewhat because this statement seems to discredit the previously presented evidence.
Also, in the paragraph concerning chemical evidence: Rather than information supporting ice ages and their documentation/dating (ice cores were mentioned) here it seems this paragraph actually presents negative evidence that is not expedient towards a credible base of pro-IA evidence. "This evidence is also difficult to interpret since other factors can change isotope ratios." It basically talks about how chemical evidence is unreliable because too many other factors affect the isotopes that are studied. We should replace this paragraph with firm evidence/statistics and studies from a credible source with citations. (I would if I had the knoweledge myself)
My tertiary quibble is this: The paragraph on paleontological evidence was just as disapointing as the paragraph about chemical evidence. This paragraph states what paleontological evidence is and how it relates to glacial periods but goes no farther. Instead of bolstering the argument with successive supporting material it is followed by material that once again explains how this particular evidence is not reliable!
The last paragraph goes on to say "Despite the difficulties, analyses of ice cores and ocean sediment cores unambiguously show the record of glacials and interglacials over the past few million years." As an impartial observer I would see that and say "Hey, they just talked about how all the evidence that is used to document ice ages/glacial periods is difficult to interpret or is potentially affected by other factors, but then they say they have unambiguous records? Since this is wikipedia I have to be mindful about the legitimacy of information I find, so I think this may be fake." Come on! Beef this thing up! I don't have the knoweledge to do it myself so like I said I'm pointing out what I think are weaknesses and points that should be expounded upon and added to in order to make this article better!
The old Glaciation article has been merged in. Cleanup is now necessary. The way, the truth, and the light 10:18, 27 April 2007 (UTC)
I removed the old contents of this section because they specifically applied to Snowball Earth only and would be misleading in the context of ice ages in general; also, the information was all already found in Snowball Earth. The way, the truth, and the light 04:13, 2 May 2007 (UTC)
In the section "Causes of ice ages", the leading summary paragraph states "climate change itself can change the atmospheric composition (for example by changing the rate at which weathering removes CO2)."
Some explanation or reference on how "weathering removes CO2" from the atmosphere would be appreciated. Thank you. —The preceding unsigned comment was added by 207.7.185.129 ( talk) 03:15, 13 May 2007 (UTC).
Today's New York Times has an article on the modern ice age, which the article says was some odd years more than 8,000 years ago, but still more recently than the 10,000 year figure usually cited in places like this article. Could someone with greater experience in the hard sciences please shed light on this discrepancy? Dogru144 04:22, 16 May 2007 (UTC)
I found the primary graph to be confusing. It would not take much effort to reverse the axis, so time proceeds left to right.
But it is essential that the graph be labeled properly and the color error corrected in the text, where CO2 is printed in blue, and Temperature in red, which is manifestly incorrect.
The graph properly shows axis labels that correspond to the median value of the variable, but PLEASE label the curves redundantly anyway.
the article is excellent, and much appreciated.
Ignorant in Ottawa
The difference in water surface area between the peak of glaciation and the end of an interglacial period can exceed 7%. This difference in evaporative area would have a significant effect on atmospheric water vapor quantity, average cloud cover and average cloud altitude (thus average cloud temperature). This cloud change could be a major contributor in toggling between glaciation and interglacial climates. Has this been considered? Dan Pangburn 00:21, 26 August 2007 (UTC)
Timeline of glaciation gives alternate dates for earliest hypothesized ice ages. Those dates appear to be sourced. JP 01:40, 21 September 2007 (UTC)
Hello-
I noitced that one of the references is wrong. Should be: "Frozen Earth: The Once and Future Story of Ice Ages" -- I would have corrected it, but I don't know how to change reference lists. —Preceding unsigned comment added by 129.79.184.227 ( talk) 18:17, 7 November 2007 (UTC)
In the section on mitigating factors that can lead to a worsening Ice Age, several of the items included are the prospective effects of global warming (either manmade or natural) cycles. Since global warming itself is either a mitigating factor to alleviate glaciation or is a factor to either prolong or end an interglacial period, if it can be argued to cause increased glaciation at all it should be treated as a cause of glaciation and not a mitigating factor to worsen it. It's not logical to argue that warming would worsen glaciation, only that it could trigger it, which is actually what the argument says. It's just been placed in the wrong part of the article. Anytime we get into global warming, I start to smell a rat with regard to the quality of the discussion. Too much junk science and politics (and I mean on both sides of the discussion) mixed up with a legitimate scientific concern. In the context of cause and effect in relation to glaciation cycles, a good litmus test for whether global warming is being discussed fairly and logically is to ask whether the proposed effects of global warming held true during the most severe global warming recorded, which was following the Younger Dryas period and not (at least so far, or even by the suggestions of most scientists) during the global warming uptick currently being experienced and widely attributed to the use of fossil fuels. If the earlier and more severe global warming cycle did not cause these things, it's not likely the less severe global warming forecast as a result of human activity will have a more dire effect. Ftjrwrites ( talk) 20:40, 10 December 2007 (UTC)
The section Recent glacial and interglacial phases points to Timeline of glaciation as main article, a somewhat mixed article, one half about all major episodes of glaciations in Earth's history, and the other to the Quaternary glaciation timeline. So something's wrong, the article should be Timeline of last glaciation or similar ... and there should be at least a bit of text in the corresponding section here. The section Glaciation in North America is about the Wisconsin Glaciation, which is a glacial phase of the Quaternary glaciation. This topic should be a sub-section of the preceding section as long as the other stages of the Quaternary glaciation are missing.
I renamed and moved it accordingly to third level, adding the names of all major NA glacial stages according to the Timeline-article.-- Jo ( talk) 20:49, 30 January 2008 (UTC)
I'm working on a fiction that involves the beginning of a new Ice Age, over several hundred years, and am contemplating potential causes. I was considering atmospheric change: specifically, gases released by decomposition of 9/10th (or so) of the world population, and a goodly chunk of it's non-human life, after an extinction level event like a super virus. Could such massive decomposition be enough to kick start an ice age?
-- Rencheple ( talk) 17:58, 11 April 2008 (UTC)
Ice ages can be further divided by location and time;... The examples given are glacials not ice ages. Could s.o. check and correct, please. 71.236.23.111 ( talk) 15:56, 20 May 2008 (UTC)
I removed this section which was under Volcanism:
Relatively intact wooley mammoth carcasses have been recovered from the Siberian permafrost. For this to occur freezing would have to have happened in days or perhaps even hours. Some even have been found to have undigested daisies in their stomachs, flowers that do not grow in such northern climbs. Pole shift presents a possible explaination of how this might have occured.
A review of various maps depicting the ice age depict Siberia and northern Alaska to be free of ice sheets. A possible explanation could be that the north pole had originally existed 30 degrees to the south towards greenland. In other words, possibly there was no extensive ice age, but rather a shift of the ice cap itself.
The rapid climatic change suggested by pole shift theory has many implications that need to be explored, such as the length and extent of sea level changes and if and when ice sheets existed in Panagonia. Other possible implications include the disapearance of Atlantis, worldwide peridic dinosaur extinctions, and even Noah's Ark.**
Unless there is some source cited which would pass muster at any university, this section seemed out of place here. If I'm out of line, please restore it.
209.130.192.20 ( talk) 18:12, 21 May 2008 (UTC)
If the average length of an interglacial (warm period like today), is around 10,000 years, then should our future generations start preparing to head south, or will global warming balance things out for us?
As well, if an ice age were to happen in say, 300 years from now (2308), would northern cities like Moscow, London, and Toronto expect a towering wall of ice advancing forward, scraping rocks and pushing the skyscrapers southwards, or would they be entombed in ice and snow from winter snowfalls that don't end? RingtailedFox • Talk • Contribs 03:05, 18 June 2008 (UTC)
In this article it says that the last Ice age ended 11,000 years ago in the beginning of the article but it also says at the end of the article that it ended 10,000 years ago. Which number is correct? Thank You. Maldek ( talk) 03:55, 8 July 2008 (UTC)
This Ice_age#The_Uplift_of_the_Tibetan_Plateau_and_surrounding_Mountain Areas_above_the_Snowline seems dodgy to me William M. Connolley ( talk) 22:10, 1 October 2008 (UTC)
In a few words, literally: List of ice ages...
I am not a native speaker, still -- shouldn't it rather be 'researcher' or 'scientist' ? 136.173.162.129 ( talk) 11:52, 27 November 2008 (UTC)
-Worker is common usage in the field. -Tom Bishop
"An extraordinary testimony to the widespread watery destruction of animal life...They are sometimes found in a near-perfect state of preservation, with undigested tropical vegetation in their stomachs." - Earth’s Most Challenging Mysteries.-- Standforder ( talk) 00:08, 10 December 2008 (UTC)
The "ice age" wasn't a long period, the term is misleading. The earth previous to this brief " ice age" was tropical-like. This rapid freezing put the earth in freezing [temperature]]s. The " ice age" occured nearly 4,400 years, (Compare Genesis 7:18, 21).-- Standforder ( talk) 00:08, 10 December 2008 (UTC)
"A sinking of the sea basins would cause the waters to collect there, allowing dry land to appear again. Compare Psalm 104:8. In the oceans today there is more than enough water to have accomplished what the Bible describes; 71 percent of the earth’s surface is water, with an average depth of two and a half miles."-- Standforder ( talk) 00:08, 10 December 2008 (UTC)
It does too relate to the article.-- Standforder ( talk) 23:30, 21 December 2008 (UTC)
In addition, the claim that "animal life", specifically the mummified mammoths, and horses, and other animals (in either Alaska or Siberia) are "...sometimes found in a near-perfect state of preservation, with undigested tropical vegetation in their stomachs" is a complete and utter falsehood. These mummified animals were neither in a near perfect state of preservation nor did they have tropical vegetation in their stomachs when they were found. This is discussed in Woolly Mammoths: Evidence of Catastrophe?, MOM and Atlantis, Mammoths, and Crustal Shift, and CC361.2: Quick-frozen mammoths.
Published articles that discuss the imaginary nature of claims about the "near-perfect preservation" of these animals and tropical plants being found in their stomachs are:
Brass, M., 2002, Tracing Graham Hancock's Shifting Cataclysm. Skeptical Inquirer. vol. 26, no. 4, p. 45-49. and
Farrand, W. R., 1961, Frozen Mammoths and Modern Geology: The death of the giants can be explained as a hazard of tundra life, without evoking catastrophic events. Science. vol. 133. no. 3455, p. 729-735. Paul H. ( talk) 05:37, 23 December 2008 (UTC)
The author of this section seems to rule out the possibility that volcanoes can contribute to ice ages, yet there is some evidence that reflective aerosols cause a net cooling effect on the short term (eg. mt. pinatubo). Conflicting evidence (Tuba eruption 70ka) suggests that volcanism has nothing to do with it. I am not familiar with research into the effects of supervolcanoes on climate change, but there was supposedly a massive sea level fall associated with the siberian traps volcanism 251 million years ago that could indicate the initiation of an ice age. The long term net effect of volcanism may be heating, yet that doesn't rule out it's role in the initiation of an ice age. —The preceding unsigned comment was added by Luokehao ( talk • contribs) 17:29, 21 December 2006.
I thought undersea volcanism could trigger an ice age by warming the oceans, thereby increasing precipitation. If this happens at the right part of the Milenkovich cycle, increased snowfall at high latitudes would increase albedo, and therefor cooling. —Preceding unsigned comment added by 150.195.11.24 ( talk) 19:29, 10 March 2009 (UTC)
I am an Activities Assistant at a nursing home and one of my resident would like to know, so if anyone has an answer would you please email it to me at <address removed to prevent spam>, thanks for your help—The preceding unsigned comment was added by 72.135.25.85 ( talk • contribs).
This description of the ice-albedo feedback under "Processes which make glacial periods more severe" is unclear. The use of the word "equilibrium" seems to imply that this positive feedback loop equilibrates _on its own_, which is clearly false. I suggest changing the wording to something like, "Hence, when the air temperature decreases, ice and snow fields grow, and this continues until [competition with a negative feedback mechanism forces the system to an equilibrium]."
Bradweir ( talk) 23:25, 7 May 2009 (UTC)
The CO2 reference below is conjecture and should be removed, unless someone can provide peer review substantiation for this speculation.
"The earliest well-documented ice age, and probably the most severe of the last 1 billion years, occurred from 850 to 630 million years ago (the Cryogenian period) and may have produced a Snowball Earth in which permanent ice covered the entire globe and was ended by the effects of the accumulation of greenhouse gases such as CO2 produced by volcanoes." —Preceding unsigned comment added by 99.241.247.201 ( talk) 23:32, 7 May 2009 (UTC)
Please note that, by a decision of the Wikipedia community, this article and others relating to climate change (broadly construed) has been placed under article probation. Editors making disruptive edits may be blocked temporarily from editing the encyclopedia, or subject to other administrative remedies, according to standards that may be higher than elsewhere on Wikipedia. Please see Wikipedia:General sanctions/Climate change probation for full information and to review the decision. -- ChrisO ( talk) 19:38, 2 January 2010 (UTC)
In the section: Variations in the Sun's energy output
The phrase: "The long-term increase in the Sun's output cannot be a cause of ice ages." needs some improvement. Oh, I see that is discussing an overall increase in the sun's energy, and not a cyclical phenomenon.
The whole section, however, needs to be updated.
Also, refer to the Wikipedia article: http://en.wikipedia.org/wiki/Sun#Possible_long-term_cycle
This Wikipedia article lists a couple of sources: http://www.newscientist.com/article/mg19325884.500-suns-fickle-heart-may-leave-us-cold.html and http://arxiv.org/abs/astro-ph/0701117
Which indicate a hypothesis that there may be long-term cycles in the sun's output energy that would generate either 41K year or 100K year (on average) cycles of the sun's output leading to the the cyclic glacial / interglacial periods, and these solar cycles may better explain the temperature variations than Milankovitch cycles.-- Keelec ( talk) 04:43, 17 January 2010 (UTC)
Shouldn't the article provide more sources for the average durations of interglacials? It appears that several sources indicate that interglacials have an average duration of 10K to 12K years. For example, this says an average of 10K years. And this says: "Over the last one million years there have been about eight Major Ice ages of about 115 kiloyears duration." Now 8 x 115K equals 920,000 and 1,000,000 - 920,000 = 80,000. 80,000/8 = 10,000 so I can see where the average is coming from. I think there are a large number of valid (e.g. actual science) sources that provide these numbers. Shouldn't we be providing that information in the article (with appropriate references of course)? Comments? (And please -- this has nothing to do with global warming etc. -- this has to do with evidence related to the past, not the present.) SunSw0rd ( talk) 14:39, 9 February 2010 (UTC)
Zeog -- what do you prefer in File:Vostok-ice-core-petit.png compared to File:Vostok Petit data.svg? I'd like to incorporate your suggestions to improve it so that we can replace the bitmap image with a vector one as part of WP:SVG. Personally I found the three separate, overlapping Y axis scales in the bitmap very difficult to read since they did not immediately appear to correspond to the different lines. -- Autopilot ( talk) 23:04, 21 June 2010 (UTC)
I see that WP has articles on Ice ages and the shorter period glacial and interglacial periods between ice ages. But what are the long-term intervals called between Ice Ages? Non-Ice Ages? Warm Ages? I can't find any research or references to these long-period intervals and what the climate, fauna, etc was like. I imagine that these "Warm Ages" also had shorter-period variations analogous to glacial and interglacial periods. Anyone want to address this? —Preceding unsigned comment added by 66.162.130.210 ( talk • contribs) 00:09, 24 October 2009
Don't know about the WP article. I have always called the 'non-ice age' as "earth normal." Since we technically live in an ice age even with the interglacial period we live in the earths average temperature is between 5 to 8 deg C warming then what it is today. -- OxAO ( talk) 00:24, 15 September 2010 (UTC)
173.165.228.33 ( talk) 15:59, 25 May 2011 (UTC) I also would like to see more definition as to the length and temperature between ice ages. Water vapor content of early atmos is essential for accurate description of ice ages. If the Med was dry until 5 mya before now, how long was it dry. Science says in order to have ice ages there must be the water vapor in the atmos to fall as snow.
This article is a load of bull, I have a pdf containing a graph that has a chart with references, please look at figure 6 on page 11 of the following pdf: http://spinonthat.com/CO2_files/CO2tdino.pdf
I have read some of the articles myself, and I feel that while wikipedia was once good, I have observed articles changing for the worse over the past couple of years. This especially includes articles which once represented skepticism towards AGW fairly, which now after having looked at them again, do not.
Wikipedia has lost alot of useful information. Indeed it is censored. I remember reading the "ammonium nitrate" article where a recipe for making it into a military grade explosive was in the article, which is now gone (and in fact, much of the rest of the information that was in the article is gone, including the synthesis of ammonium nitrate).
I don't care if this information can be used for bad things. We have a right to free learning and free information on the web and this bending over to homeland security and the UN to omit information against their global warming scam is a complete joke, and honestly, wikipedia is becoming a joke for having censored information. I deeply resent your site and I think since alex jones reported the changes to your page, who did it, and how wikipedia responded. The lack of a note on these pages about the issue that people have is offensive and I feel that people deserve to be made aware of the controversy involved. If you cannot ensure that your editors present information in a fair and unbiased way, then what good is your site? I can't learn anything about the world when so much disinformation is being given out, so much information is now omitted from your articles.
I'm not the only one that feels this way. I am personally going to lobby people to boycott your site until your site takes a more impartial presentation of information for learning purposes. Clearly the angle given on AGW and ice age, climate change, etc, is spun to such a degree as to support the UN's perspective that AGW exists. A recent article on physorg.com supports the following:
Climate change models are not accurate (aside from climategate and IPCC fraud) due to the lack of knowledge regarding the behavior of airborne particulates (and any associated reactions which may take place that we do not know about).
It can be found here: http://www.physorg.com/news180628222.html
Your articles do not state much about the "unknowns" and "alternate viewpoints", and therefore come across as heavily biased towards supporting AGW. Cherry picking the weakest counter-arguments against AGW is just as fraudulant as the IPCC doing climategate, and to be honest nobody here believes that it didn't happen considering the statements made by IPCC scientists that support the notion that they committed fraud (as some let this information slip out in video interviews which can be found on prisonplanet.com).
Can wikipedia start presenting factual information or are we supposed to accept this fraud from you as well? Should Alex Jones and I start a wiki about wikipedia articles being inaccurate? Because I am about to make a serious proposal to him to develop software to counter the disinformation your site spews out to people, starting with AGW, and anything else homeland security is paid to bully your site into making things disappear (weather the owner gets paid to allow it, or is forced to do it, or if it's hundreds of homeland security members who actually are the editors, or bribing your editors). Either way we know what's going on and we aren't dumb and you ought to present the medieval warming period information, as well as the fact that we are currently in the middle of an ice age, and that historically, 545 million years ago the co2 levels were near 8000 ppm. Start presenting some real facts, or we will start a site that will. —Preceding unsigned comment added by Stealthc ( talk • contribs) 03:04, 24 December 2009 (UTC)
It is disappointing but to be expected. Himilayas increase rainfall which must leave water vapor unaffected because the magic of CO2 ... what a load of bull. Anyway, there are some useful references in material like this in wiki if the general content is useless. —Preceding
unsigned comment added by
66.38.159.33 (
talk)
03:14, 18 February 2010 (UTC)
This article describes an Ice Age as "a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers.". I am not a scientist but to mee this definition seems a bit "wooly". What counts as long term? How far should temperatures fall below their "long term" levels before an ice age is identified? What percentage of the earth should be covered in glaciation? etc etc
I was unable to find anything better on the web so it may be that the above description is the scientific consensus, does anyone know? Alternatively perhaps people think this issue is too esoteric for an encyclopedia?
Zanzare ( talk) 14:10, 30 December 2009 (UTC)
Pluto is still there. That's the thing about labels, they don't change the facts, they're just useful handles for describing them. Tasty monster (= TS ) 18:49, 20 September 2010 (UTC)
I think it is better and more correct the new version of "Ice age",this one:
"An "Ice Age" or, more precisely, "Glacial Age" is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an existence of continental ice sheets, polar ice sheets and alpine glaciers.
The Earth's climatic history has been divided, in intervals of millions of years, into Ice Ages and Interglacial Ages. The term Ice Age refers to a long interval of time (millions years) where the Earth's poles are covered with ice sheets more or less extensive and where the average temperature of the poles remains below 0 °C) [2]. The Ice Ages are considered the Earth's climate history "seasons" and they are divided into Glacial periods (or alternatively "glacials") and Interglacial periods (or "Interglacials"). The Glacials are the stages of advancement of the ice sheets (called glaciations) and the Interglacials are the stages of retreat (these periods last for thousand years).
Interglacial Ages last millions of years, when the ice sheets have retreated to a minimum extent at the poles, and they separate two successive Ice Ages."
We should vote to choose the best one.-- 93.151.235.163 ( talk) 10:39, 20 September 2010 (UTC)
Anyone agree the heading image of the earth seen from space at the height of the last glaciation is not very helpful? I've been trying for fifteen minutes to match it to ordinary geography, that is to grasp from what angle it's supposed to show the earth. I supppose the N Atlantic is at the centre, but the rest? If northern Europe is the big hump on the top right, then what are the big white spots at right centre of the picture? Ethiopia and east Africa? That won't do: those ice sheets were relatively small in extent compared to those in the north. The edge outline of the ice to the left looks strange too. The lack of differentiation between non-glaciated continents and sea is a big drawback - both are shown as simply dark! I've seen much better pictures using the same idea, at the very least this one needs some captioning. Strausszek ( talk) 10:03, 20 October 2010 (UTC)
Some of the paragraphs in the article are way too long, which adversely affects readability. That's bad writing for for all but very advanced literary writers, who can sometimes pull it off. Most writers should instead break larger paragraphs into smaller ones. Especially in articles for wide public consumption.
69.171.160.110 ( talk) 02:24, 27 September 2011 (UTC)
Whoever wrote the POV push about global warming and specifically about positive and negative feedbacks seems to have very little idea what they mean. Positive feedback both warms and cools as does negative feedback. The difference is not the direction of effect but whether they increase of diminish the effect of a stimulus. Positive feedback creates a greater change than would be expected by the stimulus alone. Negative feedback reduces the effect. Although... it's more complicated in the real world due to phase changes. — Preceding unsigned comment added by 81.106.237.60 ( talk) 18:38, 18 April 2012 (UTC)
"There appears to be no geological evidence for such eruptions at the right time, but this does not prove they did not happen." That's an incredibly unscientific statement. Should it be reworded? Or eliminated? 167.206.122.66 ( talk) 17:17, 24 September 2012 (UTC)
This article surely needs to talk about, or at least link to the article on Greenhouse and icehouse Earth, since an "Ice Age" is only a period within an "Ice House", etc. -- Hibernian ( talk) 01:45, 11 March 2013 (UTC)
The latest BBC tv series Ice Age Beasts features the "elephant in the room" (pun intended) which is the conundrum of how millions of mammoths and other megafauna managed to survive the colder ice age period compared to the interglacial conditions of today. How did grass manage to grow in Siberia where it doesn't grow today? This paradox needs a mention at least, due to it putting the whole ice age theory into question. (P.S. A more common sense idea imv is that Jupiter's 100,000yr cycle increases the Earth's equatorial tidal strength which can even push warm water into the Arctic Basin). 176.24.226.120 ( talk) 21:08, 31 May 2013 (UTC) Alan Lowey
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