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Orbital Cycles &
Long-Term Climate Changes
Orbital
Climate Cycles:
2000 Yrs |
Long-Term Climate Changes: 2 Million | Tectonic Eras or Return to Short-Term Ocean-Based Climate Oscillations & Cycles links for: Earth Changes Bulletin: SUBSCRIBE | UNSUBSCRIBE ||| Update | Archive | Almanac
Gallery
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Orbital Cycles & Long-Term Climate Changes
Abstract: [5-14-2007] This section continues the Earth Changes Storyboard about Earth's climate oscillations. The orbital cycles of the Earth-Moon System are outlined along with a summary of the long-term shifts the orbital cycles apparently produce in Earth's regional and/or global climate regimes. The primary objective of this portion of the Storyboard is to define the history of these cycles and how they combine to produce Earth's constantly changing climate regime. It is quite clear, in the historical profiles of mud and ice layers, that Earth's orbital cycles produce major swings in the prevailing climate regimes. These swings appear to far over- shadow the current and projected shifts of "Global Warming" during Century 21.
The layers of ice and mud which paleontologists study show also, quite clearly, that orbital climate shift is not the only game in town. Other natural phenomenon apparently also produce strong swings in climate of at least a few degrees Celcius. This can be seen very clearly in the wide variations of Solar Activity Cycle which have occurred during the past 1000 years in synchronicity with changes in the climates of the Northern Hemisphere. It can also be seen in many changes in average temperature in the ice sheets of Antarctica and Greenland in cycles which last from 200 to 2,000 years. These changes are far too short to be caused by the cycles of Earth's orbit, thus they must arise from a slightly unstable Sun and quite possibly from a slightly unstable Earth.
The graphs and charts of "chemistry" and deposits from the ancient past also provide considerable evidence to suspect that some of the observed climate changes in the past are produced by geophysical activity which causes periods of accelerated change. Apparently, as the fossilized records of the past make clear, the wobbling Earth itself, like the Sun, is less stable than humans would prefer to believe. There is much evidence which suggests that tectonic activity occasionally accelerates to produce rapid and radical changes in Earth's climate regimes, arising from eras of one or both of increased volcanism and/or of rapid changes in the orientation of the surface of the Earth to the equatorial plane of the solar system, ranging from small fractions of a degree up to tens of degrees.
As can be seen in the graphs of this Storyboard, the combined activity of cycles of change in the Sun, Earth's orbit, and geophysical shifts in the orientation of the Earth, can explain most of the signals in the fossil record. But alone, none of these three factors is sufficient to consistently explain the abundant evidence of frequent changes in regional and global climate regimes.
Orbital Cycles
& Long-Term Climate Changes
Note: The storyboard is under continuous development and expansion. A few links here are not working very well at the moment, and more may be added at any time.
Sunmary Of Major Findings Developed Uniquely Through This Study By MWM
Introduction To The Climate Storyboard
Table Of Contents For Climate Oscillations
Introduction To Long Term Climate Cycles
Background Information - Links to concepts, references, and major sources
Orbital Cycles
& Long-Term Climate Changes
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Orbital Cycles
& Long-Term Climate Changes
Drawing upon a wide range of graphs, charts, and analytic findings about the chemicals trapped inside the layers of polar ice sheets and many other ancient sources, the climate records in the ice and mud deposits of earth clearly demonstrate that one of the primary drivers of long term changes in Earth's climate for any given latitude are variations in Earth's orbital cycles.
The depth of orbitally-induced recurring climate change during the past several hundred years clearly over-shadows the modest changes which have become known as "Global Warming". Humans are extremely worried about the implications of a 1 Celcius shift in climate, but the North Greenland Ice Sheet has revealed recurring and relatively rapid shifts in climate of up to 15 Celcius.
The primary range of the Earth's orbital cycles is from about 20,000 to 400,000 years.
Clearly point to the Sun as the long-term modifier of the overall climate regime. Currently, these are not producing any significant trend.
Many shorter term cycles, some of which clearly point to long-term Solar Activity Cycles.
The Global Warming issue, which has become as much an interesting study in social pandemics as it is an interesting body of information about the Earth, has stimulated a large and growing number of research studies in all the of Earth Sciences and in many astrophysical endeavors during the past 25 years. When looking at the current scientific literature, it seems like scarcely a rock, ocean-bottom, cosmic cycle, or layer of ice has not been looked under for clues to the whereabouts of the Global Warming Cause.
Immeasurably more is now known about the Earth as a result of all this new research. The rapidly growing sophistication in global reporting, database archiving, and scientific communication makes possible the finding of new findings at unprecedented rates. The result is an explosion of new ideas, relationships in data, and the emergence of new paradigms which are coalescing disparate information into some detailed understandings of the history and change of the Earth's climate and tectonic activity during the past couple of million years. Scientists can now describe, with reasonable proof, the annual snowfall in Northern Greenland a million years ago, the approximate swing in temperature for the year, and whether any major volcanic eruptions occurred in any given span of time during the the last hundred thousand years or so.
The explosion of scientific inquiry has clearly identified at least a dozen major cycles in the Earth's climate patterns. Many other minor cycles also have been identified and there does not yet seem to be a count of how many distinguishable cycles there may be.
Though it might have once seemed merely obvious, science can now demonstrate in very precise terms that the Sun, both metaphorically and literally, is the center of the climate change cycles on Earth and most probably on the other planets as well. Scientists can now detect a multiplicity of both climate cycles and solar cycles in tree rings, ice layers, sedimentary deposits on the ocean floor, and in other ways, which demonstrate that the many cycles of climate change are largely driven by cycles of Solar Activity and by cycles in Earth orbit around the Sun. Rhythmic changes in the size of tree rings, or isotopic chemical compositions in layers of mud and ice and other types of layers, can now be correlated with how the orbital cycles of many planets in our solar system combine through time to influence both the activity of the Sun and the shape and size of the orbit of the Earth.
Cyclical changes in Solar Activity, which appear to range from a few weeks to a few hundred years, and the changing shape and size of the orbit of the Earth, which occurs through tens of thousands of years, combine to profoundly affect Earth's climate. The largest shifts in the orbital cycles can now be traced backwards in time for the past two million years or so while the Solar Activity cycles can be traced backwards accurately for several thousand years, even to some extent for the past 400,000 years.
Many perplexing questions are being created by the growing knowledge of cycles of change in the Earth. If we compare climate data with past levels of Solar Activity for the past 400 years, it is very clear that cool and warm periods are most likely directly connected to changes in the general level of Solar Activity. In other words, the cooler the average temperature, the lower is the Sunspot Count, and vice verse, of course.
If we compare our present trends with the trend lines of the past, it would seem that Solar Activity is now trending downward and should continue to trend downward during Century 21 and that Global Cooling should be the inevitable result during the next 50 years. This of course contradicts the Global Warming that we can see is actually happening. Thus it is apparent that something else besides just Solar Activity is driving our current trend of Global Warming. This makes the profound question of the moment: what is this "something else".
The essence of these ocean climate cycles is ultra simple. Regions of the World Ocean alternate between periods of high or low pressure gradients which are produced by surface temperatures which are cooler or warmer than average. These cycles are seasonal of course, but there are also multi-year cycles of periods warmer or cooler than normal. One of the longest ocean climate cycles, the Northern Atlantic Cycle, appears to be some 20 years in length. But this may be surpassed by a Hurricane Cycle of xxx in length and a super El Nino Cycle of 50 years or more in length. , though the Hurricane cycle is a 20 year cycle
dblecheck hurricane cycle length get terminology descriptors consistent with this below Beyond the short term Ocean Oscillation Cycles (which we can think of as ranging predominately from 3 to 21 years in length) and the Solar Activity Cycles (which we can think of as ranging predominately between 8 to 400 years in length), we encounter the vastly longer orbital cycles. The Orbital Cycles range from the relatively short term seven year cycle in the size of Earth's wobble and the lunar eclipse cycle of 18.xxx years to the 100,000 and 400,000 cycles in the shape, size, and angle of the Earth's obit about the Sun's equator. add descriptors
Nearly all of the historical climate data reflect these cycles. Why? Primarily because of variations in the light received on Earth at any given latitude. The light varies directly with changes in Earth's orbital relationships with the Sun, the Moon, and the twisting, bobbing, wobbling changes in the orientation and location of the Spin Axis of the Earth.
These cycles are well defined and can be easily seen to be reflected in a variety of ways in the quantities of isotopes and chemical ions which are deposited in polar ice, ocean and lake sediments, tree rings, peat bogs. Scientists have learned how to use measurements of isotopes such as Oxygen-18 and Carbon-14 in various layers as "proxies" for defining changes in the warming and cooling trends of the climate. Carbon-14, for instance, can define the amount of light, the general trends in the Solar Activity Cycle, and the likely temperature changes through tens of thousands of years into the past. Oxygen-18 can track these trends backwards for millions of years. As these chemicals increase and decrease through vertical profiles of mud or ice, scientists can directly infer whether the amount of light hitting the surface of the Earth was increasing or decreasing during any given time.
As can be seen in the record of the rocks, ice, and sediments of Earth, variations in the sizes and connections between the orbital cycles produce significant climate change phenomenon on a regular cyclical basis. Cycles of 200, 40,000, 12,750, 25,500, 100000, and 400000 years have been defined during the past 10 years through a large number of studies, most especially the ice core studies on Antarctica conducted under Petrie. cite xxx please
These long range cycles range from xxx to 400,000 years in length. Three orbital cycle size, shape, and inclination of the Earth's orbit. Technically these are described by astrophysicists as the xxxx We can find the long range cycles, which range from about 12,500 years in length.
These are orbital cycles.
major cooling and warming eras.......
as much warming as... what is most interesting about these cycles is that CO2 appears to increase, AFTER the warming.
sudden shifts appear in the ice record in as little as 20 years. radical shifts,
These three are said to create what are called "the ice ages".
What makes the current climate change so extremely challenging to decipher is that there is no orbital factor which can produce any sudden shifts and nothing close to the amount of climate change we have seen in the past 100 years.
We are currently in the middle of a middling range of orbital cycles. No extremes, not much change during the last 1000 years and none to be expected during the next 1000 years. Thus, orbitally speaking, no trends here. Whatever is currently happening has no relationship to orbital factors and orbital graphs.
But, historically speaking, we have a profound mystery of substantial change which "looks like" some of the orbitally-induced climate shifts of the far past. Is it climate change induced by a very long Solar Activity Cycle, such one which is perhaps in the range of 1000 to 5000 years long? Or is it some unknown geophysical cycle? Or is this just a random fluctuation in the vast infinity of the cosmos?
Background Information & Knowledge/Data Sources:
Primary Data Series Used By MWM
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Orbital
Cycles
Of The Moon The Lunar orbit is best described by what is known as the "Saros Cycle. (Saros is ancient Hellenic for "to repeat). It describes the a recurring sequence of eclipses which occurs through a span of about 18 years, after which the sequence nearly repeats. In essence the full cycle (almost) of all the main variations in the lunar orbit is 18 years. This is the length of time it takes to grind the lunar orbit through all its main variations caused by the EMS (Earth-Moon-Sun) system. Like the Earth's orbit, the lunar orbit is not round and regular. It changes its shape, speed, and its distance from the Earth. Variations also include the degree of inclinition or tilt of the Moon above and below the Earth's equator and the progression of the "nodes" where the tilted lunar orbit intersects the Earth's equator. "Saros" is the method of computing the "full deck" of lunar orbital variations. It was worked out several millennia ago and has not been improved upon, most likely by the Egyptians, who had the world's best observatories (the Temple of the Sun composed of Thoth's (Hermes) Three Great Benbens (Pyramids)) and the best calendrical system for recording time-related events. All this they passed down to the Summerians and Chaldeans, and through them to the Hellenes and Romans. For the Earth Sciences, one of the most important orbital cycles in the Saros scheme is what the ancients called the "Draconic month". The Draconic or Dragon Cycle is the time it takes (slightly more than 13.6 days) for the Moon to move from orbital node to node directly over the Equator . This is the time it takes for the Moon to swing above or below the equator by a few degrees (about 5) as it wings out on half of its orbit around the Earth and then return to a node (position directly on the equator) on its way to winging out on the opposite side of the equator. With respect to the Earth and all of its geophysical activities, this is the true orbital time period of the Moon. The full length of the Dragon Cycle is 27.21 days. During this cycle of 27 days , the distance of the Moon to the Earth varies fairly radically, by up to some 15%. This is why the Moon appears to change its size in the sky and occasionally look much larger than at other times. The closest approach is known as Perigee and the most distant point is called Apogee. This is a large nearly monthly variation in the shape and size of the Moon's orbit and it produces a large change in the Moon's gravity vectors acting on the Earth and the electromagnetic coupling of the Moon with Earth. To keep our minds nimble, the cosmic infintibulum makes the Perigee Cycle precess slightly from the Dragonic Cycle. The Perigee Cycle takes a few hours longer, some 27.5 days. This is probably due to the pull of the Sun attempting to retard the Moon's orbit every time it is rotating around behind the Earth away from the Sun. Or perhaps it is merely the drag of the electromagnetic bow "shock wave" which acts on the Moon every time it rotates out in between the Sun and the Earth. Here is how the numbers work on these cycles of the Moon:
Synodic Month (new moon to new moon)
29.53059 days = 29d 12h 44m For the Vortex paradigm of plate tectonics, the large variation in the Moon's gravity vector means that the Moon's pull on the Earth's continents pulses or waves in a slow moving cycle of about 27.5 days. This wave pumps the crust of the Earth, slowly pulls it apart in certain zones (The Great Rift, AKA the Mid Ocean Ridges, ) and slowly bunches it up on the eastern edges of the continents (where the greatest subduction zones are located). Since the Moon spends nearly half its time north of the Equator, and an equivalent time south of the Equator, the angle or vector of the pulling action varies constantly and is at an extreme angle relative to the Equator every 27.5 days. You have a South Moon or a North Moon for spells of 13.5 days each. This Dragon Month is different than the Synodic month, which is the length of time it takes for the Moon to return to a position of perfect alignment with the Sun and Earth, either as New at "0" degrees, or as Full at "180" degrees. The Synodic or Full Moon Cycle is what people experience as the primary Lunar orbit cycle while the Earth experiences the Draconic Month as the primary Lunar orbit cycle. The reason for the difference between the Synodic and the Dragon Months is that the Earth and Moon as a pair have completed nearly 1/13th of their combined orbit around the Sun in the time of one lunar orbit around the Earth. Since the moon is traveling more total distance than the Earth as it rotates around the Earth, it takes the Moon a little extra time to "catch up" with the Earth to achieve another perfect orbital alignment with the Sun. This time difference is nearly 2⅓ days This difference of course causes the "nodes" (where the Moon crosses the equator) to "precess" (or retard) to the west along the Equator. Each Full Moon and New Moon (solar alignments) are usually thus out of synchronization with the Dragon Nodes, only occasionally do they occur at nearly the same time during any given month. This would not matter at all if the Moon's orbit were on the same plane as the Equator. It is not, it is tilted by about 5%. This means that typically the Moon is South or North of the Equator most of the time, including during most Full and New Moons. It is only aligned on the Equator for roughly one day at a time, twice a month. It is this alignment which "precesses" by the 2.3 days each month. Consequently there cannot be eclipses twice a month, one of the Sun, the other of the Moon. Typically the Moon is a little above or below the Equator, avoiding the shadow of the Earth or off to one side of the Sun as seen from the Earth. The pattern of alignments repeats in an highly regular schedule, which makes the eclipses predictable far in advance. Known as the Saros precession, an eclipse or any given alignment sequence takes 18 years to return the nodes to the same position relative to both the Earth and the Sun. If there's an eclipse
now, in 6585.322 days from now, from Espenak http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html
Any two eclipses separated by one saros cycle share very similar
geometries. They occur at the same node with the Moon at nearly the
same distance from Earth and at the same time of year. Because the
saros period is not equal to a whole number of days, its biggest
drawback is that subsequent eclipses are visible from different
parts of the globe. The extra 1/3 day displacement means that Earth
must rotate an additional ~8 hours or ~120º with each cycle. For
solar eclipses, this results in the shifting of each successive
eclipse path by ~120º westward. Thus, a saros series returns to
about the same geographic region every 3 saroses (54 years and 34
days). Since there are two to five solar eclipses every year, there are approximately forty different saros series in progress at any one time. For instance, during the later half of the twentieth century, there are 41 individual series and 26 of them are producing central eclipses. As old series terminate, new ones are beginning and take their places. To illustrate, the ten central solar eclipses of 1891, 1909, 1927, 1945, 1963, 1981, 1999, 2017, 2035 and 2053 are all members of Saros 145. The series began with a partial eclipse near the north pole in 1639. The first central eclipse of the series was an annular eclipse in 1891. It was followed by another annular in 1909. The next event was the first total eclipse in 1927. The total solar eclipse of 1999 August 11 is number 21 of 77 eclipses in Saros 145, and it is the 5th of 41 total eclipses in the series. Each of the subsequent total eclipses shifts southwards. The last total eclipse occurs in 2648 near the south pole. The last eclipse of the series takes place in 3009. Table of Saros 145 gives details for every eclipse in the series.
But there is an important qualifier to this cycle. Almost. Nothing orbitally comes in whole simple numbers in simple isolated self-referential systems, thus all orbits everywhere reflect synchronicity of the cosmic infintibulum in the unitary field state. The net effect is that the return of the alignment after 18 years also precesses slightly against both the Dragon and Perigee 18 year cycles. This adds up to a Grand Saros cycle of about 1200 years during which the sequence gradually disappears and is replaced by other eclipse sequences. At any given time, the astrophysicists tell us, there are about 70 Saros Sequences in play, allowing any specific type of eclipse to be predicted every 18 years for a 1000 years. When the Moon is as high in latitude north of the Equator as it can get - about 5 degrees - it it said to be in its North Node. And so forth for the South Node. The alignments of these high nodes with the position of the Sun is of profound importance. Every 18.5 years this alignment will achieve the most extreme separation of the Moon and the Earth, a separation of about 27 degrees. This will occur during the Solstices when the Sun is as far to the South or North as it gets during any given year. When the Moon is in Perigee while the Node of the Moon's orbit is as fully separated from the position of the Sun in the opposite hemisphere on the other side of the Equator, the Earth is maximally stressed by a combination of rapidly changing gravitational and spin vectors. Truly Great Quakes tend to occur on these Saros extremes. The Great Tectonic Rupture off Sumatra, one of the greatest tectonic events ever recorded by humans during Christmas 2004 occurred during a near 18.5 year extreme on the Saros Cycle during a Full Moon Perigee. Think of this as a Four-Factor Cosmic Whammy (Full Opposition - Perigee - Perihelion - Nodal Differential), each component of which affects the gravity vectors operating on the spinning mass of the Earth. This synchronicity cannot be a coincidence. Clearly the alignment of orbital vectors induced sufficient stress to crack and move - significantly - by tens of meters vertically and hundreds of meters laterally - major sections of two large tectonic plates. When a solar eclipse occurs at a New Moon (when of course the Moon is nearly directly over the Equator), then at the next Full Moon it is likely that the the Moon has already passed over into its opposite node. It may or may not be hidden briefly by Earth's shadow in a full or partial eclipse. The next New Moon will be even further behind the transition to the opposite node, thus it is unlikely that there will be a solar eclipse. And so forth, until the two converge again. About 5 or 6 lunar cycles later the New Moon will fall close to a nodal transition over the Equator, thus another round of eclipses (one or at maximum two) can occur. Thus eclipses in the Saros Cycle occur in a 1 or 2 month period twice a year. All this has obvious implications for geophysical plate tectonics but what connection is there to climate? That is a very interesting question which is not easy to answer at this time with proof. It is possible, however, to clearly demonstrate that there is an 18.5 year cycle in the weather patterns. Clearly a lunar influence affects the Earth's atmosphere. Though it cannot be yet clearly demonstrated in this Storyboard, the most likely candidate is the same force which produces the ocean climate regimes: underwater volcanism. The extremes of the nodal relationships with the position of the Sun may produce a cycle of increasing and decreasing heat into the bottoms of the oceans, which is distinctly different than the 3.5 year El Nino Cycle.
and most likely the ocean climate regimes. Most likely through the lunar For additional information on the Saros Cycle: Access To Info On Eclipses: http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html Five Thousand Years of Lunar Eclipses - A NASA Catalog - here is the master catalog to the Lunar events which so worried the ancients that they invented the science of astronomy to keep track of them http://sunearth.gsfc.nasa.gov/eclipse/LEcat/LEcatalog.html Fred Espenak at NASA: "Eclipses and the Saros"; http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.htmlMore exact numbers provided by Espenak. These are averages - keep in mind that there are variations in all of the orbits) Synodic Month: 29.530589 days Dragon Month: 27.21222 days Perigee or the
"Anomalistic Month": 27.55455 days. The precession of the Moon's Nodes (backwards) of 19-20 degrees a year makes the Dragon year shorter than the usual calendar year. It's average length is 346.62005 days. Any particular eclipse cycle: 47 synodic months (1387.938 days) corresponding with 51 draconic months (1387.822 days), featuring an eclipse every 3.8 years. These cycles all repeat
nearly exactly every 18+ years because: 223 synodic months (6585.321 days) almost equal 242 draconic months (6585.357 days), a period of 18 years 10 and 1/3 (or 11 and 1/3) days -- depending on the number of intervening leap years. The second Saros (446
full Moons) afterwards, the eclipse comes some 16 hours later and
240 degrees westward. The third Saros (669 full Moons) finds the
eclipse coming full circle, happening at about the same time and
place. This Triple Saros is called an Exeligmos, a period
representing some 54 years and 34 days. A typical Saros series consists of 69 to 86 eclipses spanning well over a thousand years. Eventually the eclipses produce no shadow and the sequence is considered dead. There are around 40 different Saros series in operation at any one given time.
But, unlike the Sun, the maximum and minimum declination reached by the Moon also varies. This is because the orbit of the Moon's revolution about the Earth is inclined by about 5° to the orbit of the Earth's revolution around the Sun, and so the maximum declination of the Moon varies from (23.5°-5°)=18.5° to (23.5°+5°)=28.5°. The effect of this is that at one particular time (the minor lunar standstill), the Moon will change its declination during the month from +18.5° to -18.5°, which is a total movement of 37°. This is not a particularly big change, and may not be very noticeable in the sky. However, 9.3 years later, during the major lunar standstill, the Moon will change its declination during the month from +28.5° to -28.5°, which is a total movement of 57°, and which is enough to take it from high in the sky to low on the horizon in just two weeks.
Inclination: 5.145° to
ecliptic Angular size: from 29′to 33′ Perigee: 363,104 km (0.0024 AU) Apogee: 405,696 km (0.0027 AU) Axial tilt: 1.5424° (to ecliptic) Obliquity: 6.687° (to orbit plane) |
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Long Term Climate Cycles
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2000 Year Climate Cycles Climate
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The 200 Year
"deVries" Solar Activity Cycle
Solar or
Geophysical? "It is commonly believed that the ~200- year deVries cycle is one of the most intense solar cycles (Vasil’ev et al., 1999, Wagner et al., 2001). This is evidenced, for instance, by the occurrence of pronounced solar activity minima (Maunder, Spörer, Wolf ) in approx. 200-year intervals during the last millennium. The temporal coincidence between the Maunder (AD 1645-1715), Spörer (AD 1416-1534), and Wolf periods (AD 1280-1350) and the expansion of Alpine glaciers indicates a climatic response to these solar minima (Eddy, 1976). A similar conclusion was recently inferred from an analysis of glacier expansion in Alaska (Wiles et al., 2004)." (Raspopov et al, 2006) Here, we aim to reveal the deVries
O. Raspopov :
SPbF IZMIRAN, St. Petersburg, Russia;
oleg@OR6074.spb.edu
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Chart
of Temperature Proxy Variations For Holocene Era This
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Orbital Cycles Eccentricity: shape of the Earth's Orbit
If the Earth's orbit were a perfect circle, the amount of insolation or sunlight hitting the Earth would vary only with the Solar Activity Cycles. But the Earth's orbit is not a perfect circle, it is slightly distorted into an egg- shape, which the astrophysicists define as an ellipse. The amount of this distortion is called the eccentricity of the Earth's orbit and it is measured as a unit of ellipsicity, which indicates the amount of variation from a perfect circle. The eccentricity of the Earth's orbit varies between nearly 0 (a perfect circle to almost 0.05, currently it is 0.0167 and it is getting smaller.
Astrophysicists believe that gravitational attractions between the planets produce some eccentricity in all the orbits of the planets, and the amount of course varies widely.
Through time, the eccentricity of the Earth's orbit slowly changes f(see graph [1]). This graph shows the variation in the eccentricity of the Earth's orbit over the last 750,000 years. The blue line traces the eccentricity of the elliptical orbit as it varies from from circular (0.0).. The orange line shows today's value for comparison. The data are from Berger and Loutre (1991). In other values, Mercury (with an eccentricity of 0.2056) holds the title as the largest value among the planets of the Solar System. Orbital mechanics require that the duration of the seasons be proportional to the area of the Earth's orbit swept between the solstices and equinoxes, so when the orbital eccentricity is extreme, the seasons that occur on the far side of the orbit (aphelion) can be substantially longer in duration. Today, northern hemisphere fall and winter occur at closest approach (perihelion), when the earth is moving at its maximum velocity. As a result, fall and winter are slightly shorter than spring and summer. In 2006, summer is 4.66 days longer than winter and spring is 2.9 days longer than fall [2]. Axial precession slowly changes the place in the Earth's orbit where the solstices and equinoxes occur. Over the next 10,000 years, northern hemisphere winters will become gradually longer and summers will become shorter. Any cooling effect, however, will be counteracted by the fact that the eccentricity of Earth's orbit will be almost halved, reducing the mean orbital radius and raising temperatures in both hemispheres closer to the mid-interglacial peak.
Milankovitch_Variations.png
Inclination: t This figure shows the variations in Earth's orbit, the resulting changes in solar energy flux at high latitude, and the observed glacial cycles. According to Milankovitch Theory, the precession of the equinoxes, variations in the tilt of the Earth's axis (obliquity) and changes in the eccentricity of the Earth's orbit are responsible for causing the observed 100 kyr cycle in ice ages by varying the amount of sunlight received by the Earth at different times and locations, particularly high northern latitude summer. These changes in the Earth's orbit are the predictable consequence of interactions between the Earth, its moon, and the other planets. The orbital data shown is from Quinn et al. (1991). Principal frequencies for each of the three kinds of variations are labeled. The solar forcing curve (aka "insolation") is derived from July 1st sunlight at 65 °N latitude according to Jonathan Levine's insolation calculator [1]. The glacial data is from Lisiecki and Raymo (2005) and gray bars indicate interglacial periods, defined here as deviations in the 5 kyr average of at least 0.8 standard deviations above the mean. This figure shows the variations in Earth's orbit, the resulting changes in solar energy flux at high latitude, and the observed glacial cycles. This image is intended to replace Image:Milankovitch_patterns.jpg. http://en.wikipedia.org/wiki/Image:Milankovitch_patterns.jpg
Milankovitch_patterns.jpg (406 × 247 pixel, file size: 92
KB, MIME type: image/jpeg)
Calculated Milankovitch variations and actual glacial and thermal pattern. USGS; posted at Wikipedia Image from Global Warming Art
Obliquity & Precession.
In astronomy, Axial tilt is the inclination angle of a planet's rotational axis in relation to a perpendicular to its orbital plane. It is also called axial inclination or obliquity. The axial tilt is expressed as the angle made by the planet's axis and a line drawn through the planet's center perpendicular to the orbital plane.
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