“Orbital variations (eccentricity) remain the most thoroughly examined mechanism of climatic change on time scales of tens of thousands of years and are by far the clearest case of a direct effect of changing insolation (the amount of solar radiation) on the lower atmosphere of the Earth”                                  (National Research Council of the United States National Academy of Sciences 1982).

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After about 50 years, Milankovitch’s theory was largely ignored. Then, in 1976, a study published in the journal Science examined deep-sea sediment cores and found that Milankovitch’s theory did in fact correspond to periods of climate change. Specifically, the authors were able to extract the record of temperature change going back 450,000 years and found that major variations in climate were closely associated with changes in the tgeometry (eccentricity, obliquity, and Precession) of Earth’s orbit. Indeed, ice ages had occurred when the Earth was going through different stages of orbital variation. “A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next 7,000 years is toward


extensive Northern Hemisphere glaciation” J. D. Hays,  John Imbrie  and N. J. Shackleton.

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The Eccentricity of the Earth’s Orbit  Changes slowly over time from nearly zero to 0.07. As the orbit gets more eccentric (oval) the difference between the distance from the Sun to the Earth at perihelion (closest approach) and aphelion (furthest away) becomes greater and greater. Note that the Sun is not at the center of the Earth’s orbital ellipse, rather it is at one of focal points.  The eccentricty of the orbit shown in the lower image is a highly exaggerated 0.5. Even the maximum eccentricity of the Earth’s orbit—0.07—it would be impossible to show at the resolution of a web page. Even so, at the current eccentricity of .017, the Earth is 5 million kilometers closer to Sun at perihelion than at aphelion. (GSFC)

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Obliquity (change in axial tilt)  As the axial tilt increases, the seasonal contrast increases so that winters are colder and summers are warmer in both hemispheres. Today, the Earth’s axis is tilted 23.5 degrees from the plane of its orbit around the sun. But this tilt changes. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. Because this tilt changes, the seasons as we know them can become exaggerated. More tilt means more severe seasons—warmer summers and colder winters; less tilt means less severe seasons—cooler summers and milder winters. It’s the cool summers that are thought to allow snow and ice to last from year-to-year in high latitudes, eventually building up into massive ice sheets. There are positive feedbacks in the climate system as well, because an Earth covered with more snow reflects more of the sun’s energy into space, causing more cooling.

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Precession  The earth wobbles like a spinning top which is running down. This wobble follows a 26,000 year cycle. The Earth’s axis now points at Polaris, our North Star. In 13,000 years it will point towards the star Vega. Precession is caused by the gravitational effects of the Sun and Moon. If a hemisphere is pointed towards the sun at perihelion, that hemisphere will be pointing away at aphelion, and the difference in seasons will be more extreme. This seasonal effect is reversed for the opposite hemisphere. Currently, northern summer occurs near aphelion ( the Earth’s furtherest distance from the Sun.

U.S. Academy Of Sciences , Washington

1) Three indices of global climate have been monitored in the record of the past 450,000 years in Southern Hemisphere ocean-floor sediments.

2) Over the frequency range 10–4 to 10–5 cycle per year, climatic variance of these records is concentrated in three discrete spectral peaks at periods of 23,000, 42,000, and approximately 100,000 years. These peaks correspond to the dominant periods of the earth’s solar orbit, and contain respectively about 10, 25, and 50 percent of the climatic variance.

3) The 42,000-year climatic component has the same period as variations in the obliquity of the earth’s axis and retains a constant phase relationship with it.

4) The 23,000-year portion of the variance displays the same periods (about 23,000 and 19,000 years) as the quasi-periodic precession index.

5) The dominant, 100,000-year climatic component has an average period close to, and is in phase with, orbital eccentricity. Unlike the correlations between climate and the higher-frequency orbital variations (which can be explained on the assumption that the climate system responds linearly to orbital forcing), an explanation of the correlation between climate and eccentricity probably requires an assumption of nonlinearity.

6) It is concluded that changes in the earth’s orbital geometry are the fundamental cause of the succession of Quaternary ice ages.

7) A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next sevem thousand years is toward extensive Northern Hemisphere glaciation.

J. D. Hays,  John Imbrie  and N. J. Shackleton… 1976 study

Images: Milankovitch Tutorial

Thanks to “Geraldine” (4/4/18) for providing details below of the controversial Hockey Stick. The author Michael Mann is suing fellow scientist Tim Ball who claims it to be fraudulent. The case has been bogged down due to Mann not complying with the request to provide his data to the court. If Mann loses this case it will have far reaching consequences for his credibility and for those who have based their reports on his theory.

The problem for supporters of global warming, caused by man’s CO2 emissions, was that they had to “prove” that the current phase of warming that started in the late 19th century was unnatural, unique and unprecedented. If a similar or greater warming phase had occurred in the past, such as during the (MWP) Medieval Warming Period, before human CO2 emissions had caused CO2 levels to rise, then clearly any such recent warming must have been natural and not the result of CO2. To prove their theory they had to alter climate history which is what has happened when the IPCC removed the MWP they had previously documented on page 202 of their 1990 report.    ipcc_far_wg_I_full_report (1) 1990

“This period of widespread warmth is notable in that there is no evidence that it was accompanied by an increase of greenhouse gases”

The bottom section of the above chart is similar to the original IPCC version below

Page 202 IPCC 1990 Report


  1. Natural. says:

    It was unfortunate that the Global Cooling theory, claimed to have been caused by water vapor and minor greenhouse gases, like a “nuclear winter” according to Paul Ehrlich, got the green light for funding before the 1976 study that supported the Milankovitch theory, made it very difficult for scientists who had already written papers on a looming Ice Age.
    As we now know they all changed their tune when the earth started to warm slightly and they switched over to Global Warming caused by greenhouse gases also.
    You would think that if the earth’s distance from the sun can vary by five million kilometers when there is a change in its orbit then it is reasonable to assume that it would cause variations in the earth’s temperature.

    • Wayne says:

      What relevance does the Milankovitch Cycle have with the Little Ice Age 1645-1715, said to have been due solar activity as part of the Meander Minimum and the Medieval Warming in the period 950-1250, which they say was also due to the Sun’s activity?
      Climate scientists now understand that the Medieval Warm Period was much warmer than today.

    • Regalano says:

      The presence of the Medieval Warm period quickly became a problem for Michael Mann and the supporters of his Hockey Stick. If it was even warmer then, as the IPPC had previously indicated, without human influence than now at the height of industrialization, then why should today’s warming not be due to natural causes? Mann is now desperate to silence critics by threatening litigation and name calling which could finish up being a disaster for the “science”

      • Sel Murray says:

        From Independent News: “For almost a generation literally thousands of climate scientists and science publications world-wide have relied on Mann’s Hockey Stick graph as the cornerstone of the science to persuade governments to act on ‘catastrophic’ climate change”.

        “For the “world leading climate scientist” the upside is that by giving ground to Ball (who he is suing) Michael Mann dodges the deadly bullet – for now. He has bought himself time till 2019 and his lawyers can continue to deny jurors (and Joe Public) access to his disputed data in this protracted legal battle that has already eaten up six years and millions in legal fees”.

      • Realist says:

        Did Michael Mann know that Bristle Pine tree ring samples were not regarded as a reliable procedure to be used in the study of world climate temperature history? If not why didn’t the IPCC members consult other scientists before they adopted his Hockey Stick graph?. It had already been established that no matter how you feed in the tree ring data you will always get back a Hockey Stick. I think the IPCC, in their haste to prove unprecedented 20th century global warming, needed someone to produce something that could prove that the medieval warming period had never occurred and that the current warming was not natural therefore had to be anthropogenic. Why did he not seek advice before suing the likes of Tim Ball and Mark Steyn which could result in a disaster for the religion.

  2. Florida Mansions says:

    It seems more plausible than the “dangerous climate change” so why don’t they put it up for discussion? The reason is that there is no money in it. The IPPC would not be necessary and the scientist would not receive grants if the theory was adopted. This is just plain deception and greed at the expense of the taxpayer. It is the digital age that is bringing them undone where access to information is now freely available…….its over!

    • G. Higham says:

      Yes. It could be the beginning of the end for people like Holdren and Ehrlich who helped Gore with his inconvenient truth documentary but I can assure you they won’t go quietly because there is too much money involved.
      I would like to see a body like a world committee to tackle the pollution of the world rather than wasting money on climate change that happens every day. This whole business is nothing but a rip off as far as I am concerned because they are now saying that all extremes of weather, hot or cold, are due to man’s emissions of the trace gas carbon dioxide.
      How about finding a way to clean up the the enormous plastic soup floating in the vast North Pacific spanning more than 617,000 square miles (1.6 million square kilometers), which is said to be between four and 16 times greater than previous estimates.
      They say the plastic garbage patch has more than 87,000 tons (79,000 metric tons) of plastic in it. That is said to equate to 1.8 trillion pieces, which is a hell of a lot of plastic.

  3. Refulgent says:

    The five warmest years in the global record have all come in the 2010s; The 10 warmest years on record have all come since 1998; The 20 warmest years on record have all come since 1995. So why are we, the biggest carbon polluter in the world, pulling out of the Paris agreement. I believe that the Milankovitch Theory is probably correct but we are enhancing its warming and cooling phases by the carbon dioxide we are putting into the atmosphere.

  4. Steffen says:

    A small school of scientists believe that moderate temperature increases might benefit the planet going forward. They may well be correct. Without fossil fuels, humanity would still be in a very primitive stage. Sometimes we forget the impact fossil fuels have had on the industrial age and the ensuing Fourth Industrial Age. As much criticism has been generated over the use of fossil fuels, I think our lifestyles have improved significantly in spite of many of the negative consequences attributed to the use of these forms of energy.Our capacity for innovation will provide safe and dependable fuels. Most likely, a century from now solar power will provide all the energy requirements mankind will need if not a new and more efficient power source yet to be invented.

  5. Wilson says:

    People in the U.S. seem less worried about Global Warming/Climate Change than they have ever been which is a pity. Recent studies list it at number 19 in order of concern. They might agree with it but have given up worrying about it because they have more pressing every day issues. It is our children’s children who are going to suffer as a result of our pulling out of the Paris Accord.

  6. Jumbo says:

    The Milankovitch Cycle might explain why species have become extinct during the major ice ages that occur in cycles of thousands of years….. man will be long gone by then.
    We have had remarkably stable temperatures with warming and cooling periods about equal varying by about one degree C per century so climate change should not be a concern. What is dangerous is the the world’s burgeoning population growth in developing countries where they have no power and are removing the world’s trees for fuel. Paul Ehrlich’s book, the Population Bomb is worth reading. Paul, together with John Holdren, senior science adviser to the Obama administration, had warned of an ice age during the Global Cooling period of the 70’s but changed to Global Warming when world temperatures rose slightly.

  7. Kelly and Daughter says:

    We were watching the National Geographic last night where the crew were filming the marine life around the remote Pitcairn Islands. One of the islands called Henderson, unlike Pitcairn, had long stretches of beach. Incredibly you could not walk anywhere on the island’s shore without treading on plastic garbage carried there by the ocean currents. Let’s get REAL, forget about the fear mongering and the Herd mentality associated with the global temperature scare (one degree C every 100 years) and do some thing about the plastic that is already choking our planet!

  8. Doom and Gloom says:

    The gatekeepers of global cooling and warming, notably Holdren and Ehrlich, had falsely warned of mass starvation, ecological collapse, agricultural collapse etc.. to get support of their crazy ideas they appealed to the fear of the doomsday and mob/crowd mentality of the population.. They both helped Gore, who gets a Noble Peace Prize, with his inconvenient truth and meanwhile Holdren becomes the chief science adviser to the president.

    • Nick says:

      It is remarkable that all of the many world temperature measuring authorities such as NOAA and NASA can come up with pretty much the same readings. Even more so when you consider that most of the thermometers are located in Europe and United States in areas where constant redevelopment is occurring so you would expect that allowances would have to be made for elevated readings due to the heat island effect. If you took temperature readings 500 yards apart, anywhere you care to mention, I can guarantee you they would be different, that’s why I find it extraordinary that they can detect one tenth of a degree of global warming in one year.

  9. Nanna says:

    The Milankovitch theory concerns the long term climate climate cycle which really has no bearing on what is happening today. I would like to see carbon dioxide drastically reduced from from the earth’s atmosphere if it is really the cause of global warming at the catastrophic rate we are led to believe. Unfortunately there would be a corresponding reduction in our crop yield which we need to feed the world’s increasing population. There would also be concern at the depletion of our forests that also rely on carbon dioxide for their growth.
    We can’t count on the ever diminishing marine life for food because our oceans are being polluted also at an alarming rate.

  10. Warrigal Tom says:

    You could hardly say that one degree of warming over 100 years is a catastrophic rate of warming despite all the fear mongering using Michael Mann’s Hockey Stick. The graph shows current temperatures as unprecedented by deleting the Medieval Warming Period, an era when it was much warmer than today according to the IPCC and recent ice core samples. The Hockey Stick has therefore been regarded as fraudulent by a number of science people including Tim Ball, a highly regarded climate scientist, who has been sued by Mann himself. Mann has failed to produced certain documents in the time frame requested by the court and as a result the case has dragged on. The concern is that it a may never happen because a decision against Mann could seriously undermine the credibility of Gore’s Inconvenient Truth which had used Mann’s Hockey Stick graph as the lynch pin of the documentary. Not to mention the problem with status of all the awards it received and especially with Gore and the IPCC sharing a Nobel peace prize

  11. No Name says:

    It will be difficult to annul the academy award or the Nobel peace Prize it would be an admission that the science is crooked which they already know to be the case. It is more likely they will find some technical hitch with Mann’s libel suit preventing it from continuing any further.
    We have grown tired of all these doomsday predictions by scientists since world war two.
    There was the population bomb and compulsory castration, then acid rain, ozone hole widening, living near power lines, global cooling, the ice age, sea levels swamping our cities, global warming renamed climate change, the latter two have longer legs because of the hangers on and the huge funding they are receiving. It is now a religion, more money and jobs for the boys.

    • Tarneit says:

      The Medieval Warming Period and the Little Ice Age that had been detailed in the 1990 IPCC report disappeared after the 1995 report which downplayed them and were not mentioned in subsequent reports. The reason for this is because they were the result of natural changes in the earth’s climate cycle and not the result of greenhouse gases which have been the very basis of the global warming theory, not to mention Mann’s Hockey Stick. e.g. If greenhouse gases had engulfed the planet and caused “the period of widespread warmth” (MWP) then they would have had to disappear to enable The Little Ice Age which followed.

  12. Nick says:

    We will need all the carbon dioxide we can create to grow our crops to feed the 10 Billion people who will be living on the planet by 2050. We must also regrow the trees we have cut down over the last century because they are lungs of the earth and they also need carbon dioxide. We might also allow us to reclaim land that was once desert….. Nick Papas

  13. Adami says:

    The U.S,. who have more weather stations than anywhere else on earth, show a cooling trend in temperatures readings across the country. In fact their has been a decline since the 1930’s and the 1950’s hottest decades ever recorded in United Sates.
    Climate fraudsters frequently claim that the 1990 IPCC temperature graph showing the Medieval Warm Period (MWP) was only a representation of Central England Temperatures (CET) and was therefore not global. This is nonsense. The graph was derived from James Hansen’s 1981 study, which was taken from temperatures in England, California and Greenland.. have accused them of fraud and no one is suing the author. Much of the Inconvenient Truth documentary, currently being shown in schools, depends on the integrity of Mann’s Hockey Stick Graph which is in tatters.

  14. Gazza says:

    Body Size Shrinking Because of Global Warming
    According to scientific studies, as a result of the 0.9 C of warming this century, the shrinking victims include cotton, corn, strawberries, bay scallops, shrimp, crayfish, carp, Atlantic salmon, herring, frogs, toads, iguanas, hooded robins, red billed gulls, Californian squirrels, lynx and wood rats

  15. Peter Cross says:

    0.9 degrees celsius rise in temperatures over one hundred years is global warming…give us a break!
    Mann has used government grants to finance his Hockey Stick theory so he must not delay the release of his data any longer.
    His name calling and threats of litigation towards respected scientists is not the scientific method.

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