Talk:Milankovitch cycles/Archive 2

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Especially, the image at the top uses terms that are not used at all within the article. I think an overview is needed, a summary of the main points.

It's not special to wikipedia, searching for an explanation of the Milankovitch cycles, then many sites are either over simplified or they go into detail but in a confusing way so it's hard to follow.

I'm not sure what the answer is and don't feel confident to "be bold" and try to fix it myself. So raising this for discussion.

This is the best summary I've seen of it anywhere - but if you used it, would have to be in quotes

• "A) against the backdrop of the stars, the whole axis of the earth gyrates like an out-of-balance spinning top in a 25,770 year cycle
• "B) the ellipse of the earth’s orbit around the sun is itself turning against the background of the stars in a 21,000 year cycle.
• "C) the obliquity of the Earth ranges between 22.1° & 24.5° in a 41,000 year cycle, mainly under the influence of Jupiter
• "D) the eccentricity of the Earth’s orbit changes in a complicated manner in cycles of 96,000 and 413,000 years"

For details see Variation in the Equation of Time.

With the graphic at the head, I think it would be good if each of the curves was labelled in the same way as in the article itself, and also with the periodicity - this would tie it together a lot.

I've re-captioned it here, maybe it will help?

Any thoughts? Of course if I've made any mistakes in my new version also, do say.

Thanks! Robert Walker (talk) 12:41, 16 November 2015 (UTC)

No comments so I've just "been bold" and replaced the old graphic captioned with equations with the new graphic recaptioned with the ordinary language names for the cycles. Robert Walker (talk) 09:43, 21 July 2016 (UTC)

It's not a bad graphic, thanks for doing it. It would be better if it specified the latitude and time interval represented by the insolation curve (eg June/July 65 degrees N?) and NB the Antarctic palaeoclimate record now goes back to 800ka (EDC3), pity not to include it! Also consider putting eccentricity at the top, since it is the longest periodicity, then you would be working downwards from the longest to the shortest periodicities, then the summed effect in insolation at a date/latitude. Axial precession has more than one periodicity - the mean would be around 21kaOrbitalforam (talk) 17:38, 6 February 2017 (UTC)

There's a sentence at the end of the Orbital Inclination section which looks biased and illogical imo. Just because Milankovitch cycles are firmly recorded in the ice core data, it doesn't imply that an Inclination Theory couldn't additionally apply, to account for the main peaks in the climate data. The sentence in the article reads "This is an additional validation of the Milankovitch hypothesis by a relatively novel method, and is inconsistent with the "inclination" theory of the 100,000-year cycle." This statement is misleading at the least. I suggest something like "This is an additional validation of the Milankovitch hypothesis by a relatively novel method, and shows that a change in insolation plays a major role in climate change. The data gathered shows that the main driver of the ice age is in the order of 100,000 years and so can be concluded to be either eccentricity or inclination. The potential 'inclination theory' has yet to provide a suitable cause and effect model of climate change, whilst the 'eccentricity theory' relies on amplification by 'feedback'.31.54.237.165 (talk) 17:41, 3 August 2016 (UTC) Alan Lowey

There is some work on creating analytical models of the Vostok record which successfully fits nonlinear oscillations plus a stochastic process to the observed temperature record. I think it should be mentioned here because like Milankovitch's work, it is data-driven and not theory-driven. See MaslovSooku (talk) 21:59, 9 January 2017 (UTC).

I have no idea how to properly add a section to the Talk page. I want to bring attention to https://m.phys.org/news/2017-01-earth-orbital-variations-sea-ice.html which suggests, rather well, that variations in Antarctic sea ice give rise to the Milankovitch cycles. I think that someone who knows what they are doing ought to add this to the main article as a proposed solution to various problems, including the 100,000 year cycle. — Preceding unsigned comment added by Dr. David B. Benson (talk • contribs) 03:10, 28 January 2017 (UTC)

I have added text and a citation (what is m.phys.org, anyway?) to the article. Spike-from-NH (talk) 02:05, 29 January 2017 (UTC)

I rewrote the third paragraph of this section to better abstract the point made by one of the papers cited. I see the 70,000-year figure in this paper, but am baffled that the cycle of orbital inclination should be 70,000 years "relative to its present orbit" but 100,000 years "relative to the invariable plane." Would variation in inclination not be a single effect with a single cycle time? Spike-from-NH (talk) 02:52, 5 February 2017 (UTC)

PS--My question boils down to this: Why is "The inclination of Earth's orbit....relative to Earth's orbit" not always zero? At any rate, with luck I may have written a useful differentiation of 70,000 and 100,000 in the section Orbital inclination, which youse are welcome to review. Spike-from-NH (talk) 13:57, 10 February 2017 (UTC)

The two failed links were both in a sequence of two links. I will delete the failed links and the other will survive. Spike-from-NH (talk) 03:10, 12 June 2017 (UTC)

I am skeptic about the statement that Neptune goes through Milankovitch Cycles, and that the evidence for it is the variation in Triton's solid nitrogen deposition.

The reference cites to a 2007 article about the effects of the sun on global warming, that doesn't suggest a connection to milankovitch cycles. It does mention Triton on 2 occasions, once in a quote from a social anthropologist, and a second time in this statement:

"The warming on Triton, for example, could be the result of an extreme southern summer on the moon, a season that occurs every few hundred years, as well as possible changes in the makeup of surface ice that caused it to absorb more of the Sun’s heat".

As far as I know, a few hundred years aren't enough time for milankovitch cycles to occur. The statement also has an embedded a link to another article, which suggests a connection between the warming observed on Triton and its volcanic activity, without any mention to milankovitch cycles.

This statement was added to the article by a non-existing user with the name Eyreland, on April 7th, 2012‎. Later, when it was challenged, he added 3 references, of which 2 were erased by now. I'm afraid this last remaining reference isn't convincing enough, so I suggest that we should erase it unless someone can suggest a better source. Omrial (talk) 12:46, 31 December 2017 (UTC)

@Omrial: I edited this text most recently by way of formatting and know nothing of the science.

You are right; seasons are not Milankovitch cycles; long-term variation in seasons is. At the least, the 2007 article is speculation (in order to flesh out polemic regarding global warming on the Earth), which the Wikipedia article renders as "Triton has a variation similar to Titan's" (the latter given not as a few hundred years but 60,000 years!). No, it is not convincing at all. For starters, does Triton's orbit have a wobble at all? Is it attributable to influence from Jupiter and Saturn, or just Neptune? Is there any science that the nitrogen deposits have migrated in the first place? Pending any additional information, I concur that the section is misleading and should come out.

PS--@Eyreland: is not a non-existing user; he is active through this month. The red simply means he has not written a user page. Usually when questioning a Wikipedian's edits, one mentions it to the editor in question, and I have now Pinged him. Spike-from-NH (talk) 13:29, 31 December 2017 (UTC)

Thanks for correcting me, I've learned something new.

Another thing which bothered me earlier was the statement about Titan. First, it has one youtube reference. I don't know whether or not it is reliable and I haven't watched the video.

More bothering was the reference to a universe today article. At the last paragraph of the article, it says:

"If Cassini would have been sent to Titan 32,000 years ago, the picture would have been reversed" - which is indeed consistent with the statement that the full cycle is about 60,000 years long. On the other hand, the nature article upon which the universe today article was based, named: "An asymmetric distribution of lakes on Titan as a possible consequence of orbital forcing" determines 2 cycles, one which is about 270,000 years long and a second one, 45,000 years long, both being caused by Saturn's orbital changes. The figures in the nature article also support that. Omrial (talk) 14:17, 31 December 2017 (UTC)

I can think of a couple other things whose "possible consequence" would be an asymmetric distribution of lakes. This has the same problem: Speculation in the literature has become fact in the Wikipedia article. Spike-from-NH (talk) 15:27, 31 December 2017 (UTC)

PS--I have edited the section generally to avoid portraying speculation as fact. I don't claim this should be the last word. Spike-from-NH (talk) 15:38, 31 December 2017 (UTC)

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The list of issues are out of date. They cycles are well understood. Modern models reproduce the climate cycles in great detail accurately. The small temperature variations are amplified by water vapour and CO2.

This page outlines the timeline with some of the main papers that lead to the modern theory THE ASTRONOMICAL THEORY OF CLIMATIC CHANGE - (The Milankovitch Hypothesis)

Lots of cites available if someone wanted to fix this article Robert Walker (talk) 21:13, 19 April 2018 (UTC)

This is a well written article, but there are many paragraphs (let alone sentences and statements of specific information) that lack any references at all. More attention to references is needed. — Preceding unsigned comment added by Neuron Doc (talk • contribs)

Another recently confirmed factor needs to be worked into the article. "It happens every 405,000 years. The Earth’s orbit gradually changes shape from almost circular to slightly elliptical over a period of 202,500 years, and then starts returning to form over the next 202,500 years...." Tests made in the US NE and in Arizona were identical. At least to 215 Mya. NYTimes. Corresponding abstract at PNAS. DOI. This appears to conform well to the article's 413k number?

Another, historical look at the question: a brief introduction to ice age theories Twang (talk) 03:38, 25 May 2018 (UTC)

I've quoted the New York Times article on the cores from Arizona and New England. (The overview of confirmation by artifact is in the Intro of the section on Problems.) On the brief introduction, it's not clear to me who wrote this or where it came from, and there are already a lot of External Links, so I'll pass. Spike-from-NH (talk) 21:56, 25 May 2018 (UTC)

Yes, thanks for that. The article & topic are complex and din't feel familiar enough with it to guess where it 'best belong'ed. Twang (talk) 01:34, 9 June 2018 (UTC)

@William M. Connolley: has removed several sentences. The section Present and future conditions ends with a numbered list whose point is to set forth the limitations of orbital models on predicting climate effects. One of the items states that anthromorphic effects are one source of deviation. This item is mostly my text but was modified by one author, who promoted cooling caused by particulates, which I had described as a "prior theory." Okay; the gist is that anthropomorphic effects could cause deviation from the mathematical models in either direction.

Yesterday, Anon edited this further, adding an assertion that "...legislation...revers[es] the cooling", improbable and uncited. Quickly Connolley reduced the entire text to "principally, increases in greenhouse gas...result in a warmer climate". Sorry, there is no control planet without anthropomorphic effects and we don't know this. We don't know much, beyond computer models. I reverted this change and he comments, "errm, pardon? this isn't the place to fight the GW wars". Well, exactly. The function of this text is to advise the reader to consider the Milankovitch cycles in full context, not to reassert the Global Warming orthodoxy. Spike-from-NH (talk) 16:56, 2 July 2018 (UTC)

The anthro effect is mostly CO2. Consult

global warming if you're in doubt. All the rest is at the level of detail, and isn't important for this article William M. Connolley (talk

) 20:09, 2 July 2018 (UTC)

There is absolutely zero anthropomorphic effect on global warming. You're essentially telling the mill owner that the river will run dry in 20 years because they lake won't be full forever. I hope you understand this analogy someday — Preceding unsigned comment added by 2601:449:8200:A430:598F:D81F:5198:CA77 (talk) 02:22, 6 September 2018 (UTC)

Looking, there's rather more wrong with that section anyway William M. Connolley (talk) 20:12, 2 July 2018 (UTC)

The section is called "Present and future conditions" and that is what it is about. Any long list of flaws in the "Milankovitch" theory belongs elsewhere. All it needs is a brief note that non-orbital forcing can be important; in the short term, the only thing fitting that is GW William M. Connolley (talk) 20:21, 2 July 2018 (UTC)