# Milankovitch Cycles

Discussion in 'Earth Science' started by space_geek, Feb 28, 2009.

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## Your take on Milankovich Cycles

Poll closed Mar 15, 2009.

14.3%

42.9%

14.3%

42.9%
1. ### TrippyALEA IACTA ESTStaff Member

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It also happens to be one of the factors that the various models take into account.

3. ### Buffalo RoamRegistered Senior Member

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ice,your graph all end at 2000, so what have you shown?

5. ### Buffalo RoamRegistered Senior Member

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Now, that is exactly what I understood about the Thread as posted by space_geek :

Now if the Milankovitch, can be responsible for Global Cooling, they also can be responsible for Global Warming, it is just which part of the Milankovitch cycle are we in.

Now as a matter of fact, since 2000 the average trends are cooling, it will be interesting to see if they continue, and can the Milankovitch Cycle be tied to them, which from the evidence presented in publication seems plausible.

As to anthropogenic climate change, that seem top be a dying postulation, and more and more proof is out that CO2 follows the warming rather then precedes the warming, and in fact that CO2's are the regulator that cools the world, not warms it.

Prehistoric global cooling caused by CO2, research finds
... but the cause of the cooling has been the subject of scientific ... Once the team identified the global cooling, the next step was to find what caused it. ... was a major drop in greenhouse gases in the atmosphere, especially CO2. ...

http://news.uns.purdue.edu/x/2009a/090226HuberPete.html

So get your nose down to horizontal or you will walk into a lamp post.

7. ### TrippyALEA IACTA ESTStaff Member

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Show me where in this thread I have explicitly stated that I support any form of global warming, anthropogenic or not.

Oh wait, that's right, you can't, because I haven't.

The ONLY thing that I have said is that the current phase of the Milankovitch Cycles can not be responsible for Global warming - a point that you yourself have agreed with.

(Then I pointed out a bunch of flaws in your post, however, that doesn't indicate which way I lean on the issue, although you can always assume, which you seem to have been comfortable with doin so far).

Care to try again?

8. ### TrippyALEA IACTA ESTStaff Member

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Actually, I'm going to pick at this a little more.

I'm sorry. Show me where I disputed this? Oh wait, that's right, you can't because I didn't.

Go back and re-read my opening post where I said something to the effect of "The current phase of the Milankovitch Cycles can not be responsible for the current round of 'Global Warming'."

You're seriously comparing a local, short term minima to a multi thousand year cycle?

Irrelevant. You're the one that bought Anthropogenic climate change into the conversation, not me. I originally made no comments on Anthropogenic climate change.

So your citing an article which clearly states that a significant drop in temperature was caused by a reduction in atmospheric $CO_2$ as proof that the idea that dumping billions of tons of $CO_2$ into the atmosphere is erroneous?

How does that go again?

9. ### iceauraValued Senior Member

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They do not.
Al Gore claimed in the movie Inconvenient Truth that thousands of refugees were currently streaming into NZ because their islands were flooded? I missed that claim.

10. ### TrippyALEA IACTA ESTStaff Member

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Correct. That was one of the claims he made.

11. ### TrippyALEA IACTA ESTStaff Member

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I'd give you an HH:MM:SS reference, but I don't currently have access to the movie, however, it was one of 9 inconsistences that the british high court cited in Dimmock v Secretary of State for Education and Skills which was heard in September-October 2007.

Al Gore stated: " "[T]hat's why the citizens of these Pacific nations have all had to evacuate to New Zealand."

However according to Justice Burton: "There is no evidence of any such evacuation having yet happened."

And just to prove my point further, here's what a New Zealand Article has to say on the matter:
http://www.scoop.co.nz/stories/SC0708/S00012.htm

12. ### Buffalo RoamRegistered Senior Member

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Guess What I can't because I don't remember getting on it till you stuck you nose in to the Stratosphere, I didn't accuse you of supporting anthropogenic or not, what I pointed out was that the Milankovitch Cycles can be responsible for warming or cooling, because it is can be responsible for one it has to be responsible for the other when the cycle wanes.

I am not sure that is a correct assessment of my position, as all I was attempting to show was that Temperatures are on a down ward trend, and it would be interesting to see of the Milankovitch Cycle can be tied to those reductions in temperature.

Which from the stuff I have read seem very likely.

Really, you have just assumed a lot, went on a screaming fit, and got on your high horse and picked a fight that wasn't necessary, so who need to try again?

The Milankovitch Cycle, hasn't been observed long enough to know what position of the cycle we are in, if we are suppose to be in a the ascendence of the warming part of the cycle, or are we on the inferiority, cooling side of the cycle, and from the temperature averages it would seem we entering on the inferior side of the cycle.

So that is my contention, and I entered into this hoping to learn something from you not for you to try and hand me My head.

Last edited: Mar 2, 2009
13. ### TrippyALEA IACTA ESTStaff Member

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We can match the cycles, which have a 100,000 year periodicity as it's longest term* to the climate record that goes back, in some cases 65 million years or more. This has been done, and has been the subject of much study, because, among other things, by analyzing the past variations in climate, we can get further information about the variability of the earths orbit for as far back as we have a valid proxy for, and this can give us further information about the dynamics of the inner solar system.

I've seen one source that suggests that the KT extinction event coincides with some some 'phase change' that involves Jupiter, and that it was this phase change that probably resulted in the chixculub impactor being kicked out of the asteroid belt.

Modeling the Climatic Response to Orbital Variations Imbrie J, Imbrie JZ
http://www.sciencemag.org/cgi/content/abstract/207/4434/943
http://www.people.cornell.edu/pages/nrw22/astro/images/mcycle.png

Notice how the temperature is a peak, but with the possible exception of solar insolation, everything is trending downwards.

http://en.wikipedia.org/wiki/File:Orbital_variation.svg

Edit: Allow me to apologise if I have taken your first post in the wrong spirit, I am however only willing to accept part of the responsibility.

*There are possible exceptions to this, there is at least one published article that suggests that the glaciation of Antartica might have been at least partly due to a long term minima.

Last edited: Mar 1, 2009

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15. ### Buffalo RoamRegistered Senior Member

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But are we in the ascendency of the cycle, warming? or the wane of the cycle cooling?, or are we treading water in the cycle? from what I have read, in all actuality the warmest years for the last century were the period around the 1930s, and that we have been cooling ever since, that the last decade is actually a spike that now seems to be collapsing back into the cooling cycle.

THE NEW US DATA AND TOP TEN WARMEST YEARS

16. ### TrippyALEA IACTA ESTStaff Member

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Which, in all actuallity only serves to prove my point that I made in my original post - namely the hypothesis of Global warming over the last 150 years (regadless of cause) it can not be being caused by the Milankovitch cycles - unless you can find some proof of the earths orbital characteristics having changed significantly in that time, frankly, i'm not aware of having seen any.

Also note that even with the positive anomaly around the 1930's, a least squares trendline would still have a positive slope.

I contend that the '30s was an anomaly caused by some other factor that wasn't recognized at the time.

17. ### space_geekRegistered Member

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trippy is right i guess. Thread over

18. ### TrippyALEA IACTA ESTStaff Member

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Further to my post, it seems that:
The Atlantic Multidecadal Oscillation was in a warm phase in the '30s that strengthened through into the '40s
http://en.wikipedia.org/wiki/File:Amo_timeseries_1856-present.svg
In the '30s the NAO was in a transitional phase (NAO+ leads to a general warming of Europe) It should be noted that the NAO was transitioning from a strong NAO+ to a strong NAO-:
http://en.wikipedia.org/wiki/File:Winter-NAO-Index.png
The Pacific Decadal Oscillation was in a warm phase that became increasingly strong over the following few years:
http://en.wikipedia.org/wiki/File:Pdoindex_1900_present.png
The Actic Oscillation was Positive in the '30s which also leads to a warming of temperatures in continental europe.
http://jisao.washington.edu/wallace/natgeo/AOindexgraph.gif
There doesn't seem to have been anything particularly unusual about that solar cycle, although it was beginning to strengthen:

And I'll have a look when I get home for work, but it appears that the 1920's may have oppened with an El Nino warm event.

So in short, it seems like all of the various oceanic and atmospheric oscillations coincided in warm phases in the 1930's and produced an aritifically warm decade or so.

19. ### Buffalo RoamRegistered Senior Member

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I am trying to find some data on the Milankovitch cycles, but if it is a cycle, it must chang, the main question is were we are in the cycle.

The shape of Earth’s orbit becomes more or less oval (eccentricity), Earth wobbles as it spins (precession), and Earth's axis changes too (tilt). All these changes, over thousands of years, causes Earth's climate to change.

There are three ways that Earth's orbit changes over time.

Eccentricity: The shape of Earth's orbit around the Sun becomes slightly more and then less oval every 100,000 years.
Precession: Earth wobbles on it axis as it spins, completing a full wobble every 23,000 years.
Tilt: The angle of the Earth's axis relative to the plane of its orbit changes about three degrees every 41,000 years

http://jrscience.wcp.muohio.edu/climatechange04/ProposalArticles/Draft1.MilankovitchCycles.html

Introduction

http://skepticsplay.blogspot.com/2008/12/axial-tilt-milankovitch-cycles.html

Lot of questions, but it seems we are some where in the middle of the cycle headed into the aphelion of the cycle, but we have 2500 + or - a few centuries.

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21. ### TrippyALEA IACTA ESTStaff Member

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Which is precisely what i've been saying.

22. ### iceauraValued Senior Member

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Not to hijack this thing, but that struck me strange - not the sort of thing I would have missed, in that movie. But I see now why I missed it - in context, it's not quite as presented (and in particular, the point he made about the effects of a greenhouse warming is not affected by the error regardless):
from the transcript
As far as I can tell that's it. I can see, sort of, where it could be interpreted as implying thousands of refugees fleeing to New Zealand from some drowned islands, but as it stands it's a cryptic aside - could mean anything from a dozen people to millions, from drowned cities to a few salt-contaminated aquifers, from a direct false claim to a grammatically confused side reference to ordinary events like this :
A reading of the transcript did turn up a clear factual error, though, that I had forgotten: Gore repeats the frog-boil parable, which has been discredited. So that's one for sure.

Last edited: Mar 2, 2009
23. ### TrippyALEA IACTA ESTStaff Member

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No.

He claims that people are being evacuated from the pacific islands to New Zealand, because their islands are sinking, as I clarified in my next post where I copied and pasted Al Gores exact words from the movie (to the best of my knowledge) and then copied and pasted from this post here and then clarified what Justice Burton had to say about the issue in Dimmock v Secretary of State for Education and Skills.

The simple fact of the matter is that NOTHING like it has happened. There has been no evacuation of pacific islanders to New Zealand because the Islands are sinking, as Al Gore claimed.

The closest thing that has happened, is the voluntary evacuation of the inhabitants of the carteret islands in PNG to Bougainville Island as their homeland would be submerged by 2015 - something that the UN has put down to Dynamite fishing.

The fact that it might be a gramatically confused reference to it is irrelevant, it's still factually inaccurate (Bougainville is NOT part of New Zealand for a start).

Doesn't change the fact that it was one of 9 substantial inaccuracies that Justice Burton required the British Education Department to be put in the proper context in order for the movie to be legally shown in UK schools.

Even the IPCC disagrees with at least one of Al Gores POints (Another one of the points upheld by Justice Burton).