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Topic: Milankovitch cycles

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	NOAA Paleoclimatology Program - Orbital Variations and Milankovitch Theory
		The Milankovitch or astronomical theory of climate change is an explanation for changes in the seasons which result from changes in the earth's orbit around the sun.
		The "roundness", or eccentricity, of the earth's orbit varies on cycles of 100,000 and 400,000 years, and this affects how important the timing of perihelion is to the strength of the seasons.
		The combination of the 41,000 year tilt cycle and the 22,000 year precession cycles, plus the smaller eccentricity signal, affect the relative severity of summer and winter, and are thought to control the growth and retreat of ice sheets.
	www.ncdc.noaa.gov /paleo/milankovitch.html (862 words)

	Milankovitch cycles - Wikipedia, the free encyclopedia
		Milankovitch cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian geophysicist Milutin Milanković.
		In addition, despite the relatively large 100,000 year cycle, some have argued that the length of the climate record is insufficient to establish a statistically significant relationship between climate and eccentricity variations.
		That cycle is not being detected in climate.
	en.wikipedia.org /wiki/Milankovitch_cycles (1896 words)

	Orbital forcing - Wikipedia, the free encyclopedia
		Orbital forcing, or Milankovitch theory, describes the effect on climate of slow changes in the tilt of the Earth's axis and shape of the orbit.
		A strict application of the Milankovitch theory does not allow the prediction of a "sudden" ice age (rapid being anything under a century or two), since the fastest orbital period is about 20,000 years.
		Comparisons of plate tectonic continent reconstructions and paleoclimatic studies show that the Milankovitch cycles have the greatest effect during geologic eras when landmasses have been concentrated in polar regions, as is the case today.
	en.wikipedia.org /wiki/Orbital_forcing (515 words)

	Milankovitch Theory and Climate
		It is the rocking of the plane of the Earth's orbit relative to the reference frame that produces the so-called "obliquity cycle" that averages 41 ky. For the Earth, the other main frequency that is important is that of the precession of the Earth's axis.
		This is the familiar wobble of the axis caused by the pull of both the Moon and the Sun (with similar amplitudes) on the equatorial bulge of the Earth.
		These are the modulators of climatic precession cycles and are algebraically and physically equivalent to "beat" cycles of the various climatic precession cycles, themselves.
	www.ldeo.columbia.edu /~polsen/nbcp/cmintro.html (1354 words)

	Past Climate Cycles: Ice Age Speculations
		Many things in the natural world come and go in cycles, so it was natural for people to suppose that there was a regular pattern to the ebb and flow of ice sheets.
		According to their data, the prominent cycle he had seen and attributed to the 41,000-year orbital shifts was actually the 100,000-year cycle.
		E.g., Pisias and Shackleton (1984); "The existence of the 100-kyr [kiloyear] cycle and the synchronism between Northern and Southern Hemisphere climates may have their origin in the large glacial-interglacial CO changes." Genthon et al.
	www.aip.org /history/climate/cycles.htm (8309 words)

	Milankovitch cycles
		Milankovitch cycles are cycles in the Earth's orbit that influence the amount of solar radiation striking different
		Milankovitch temporal frequencies occur at 100,000 yr, 41,000 yr, and 20,000 yr durations.
		Note that the two shorter-term Milankovitch cycles are sometimes in phase with the 100,000 yr.
	www.geocomplexity.com /milankovitch.htm (236 words)

	Milankovitch cycles Totally Explained
		Milankovitch cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković.
		The Milankovitch theory of climate change isn't perfectly worked out; in particular, the largest observed response is at the 100,000 year timescale, but the forcing is apparently small at this scale, in regard to the ice ages.
		In addition, despite the relatively large 100,000 year cycle, some have argued that the length of the climate record is insufficient to establish a statistically significant relationship between climate and eccentricity variations.
	milankovitch_cycles.totallyexplained.com (2221 words)

	Milankovitch cycles Summary
		According to the theory of the Milankovitch weather cycles, ice ages are cyclical, caused by changes in the earth's orbit.
		Milankovitch proposed that decreased sunlight prevents ice and snow from melting in the summer in the northern latitudes.
		The ice age dates for this core of calcite differed from the Milankovitch dates, and this suggested to Winograd that ice ages were tied less to orbital cycles than to an interaction of heat and moisture between the atmosphere, the ocean, and ice sheets.
	www.bookrags.com /Milankovitch_cycles (3175 words)

	Global Climate Change Student Guide
		Milankovitch (1941) considered the changing seasonal (precession) and latitudinal (obliquity) patterns of incoming radiation to be critical factors in the growth of continental ice sheets and in the initiation of ice ages.
		He hypothesised that when axial tilt was small (large latitudinal temperature gradient), eccentricity was large and perihelion occurred during the Northern Hemisphere winter (warmer winters and colder summers), such a configuration would allow the persistence of accumulated snow throughout the summer months in the Northern Hemisphere.
		Indeed, Milankovitch himself had expected the direct effects of variations in insolation to be magnified by feedback processes, such as, at high latitudes, the ice albedo effect (section 2.7).
	www.ace.mmu.ac.uk /Resources/gcc/2-5-2-4.html (444 words)

	ATM S 211 Lecture Notes #0
		We are motivated to learn about the Milankovitch cycles owing to their apparent match with climate cycles during the ice ages.
		Milankovitch claimed that variations in the incoming solar radiation at 65N during summer was key.
		The cycles are well described in the text on pages 276-277, but here the book is surprising shy on pictures.
	www.atmos.washington.edu /2004Q4/211/Lecture19_notes.html (571 words)

	Global Warming: What is Happening? (Site not responding. Last check: 2007-10-22)
		The third Milankovitch cycle is the precession of equinoxes.
		In addition to sunspot cycles and the Milankovitch cycles, another natural factor that affects climate is plate tectonics.
		There is a great deal of evidence that natural factors and cycles are causing global warming - plate tectonics causing the poles to be isolated from warm ocean currents, Milankovitch cycles affecting how the earth receives the sun's energy, and sunspot cycles affecting the sun's output of heat energy.
	www.ees.nmt.edu /~ranck/hot.html (990 words)

	Youngearth creationists believe that the earth is less than a few hundred thousand years o (Site not responding. Last check: 2007-10-22)
		The cycles pre- dicted by Milankovitch's theory and discovered in the ocean sediments turned out to have the longest variation at 100,000 years, with shorter variations superimposed at about 41,000, 23,000 and 19,000 years.
		Spectral analysis indicated that, as expected, the dominant climatic pulse was a 100,000-year cycle, which appeared on both the iso- topic and the radiolarian spectra as a large peak.
		The preceding descriptions of the confirmation of the Milankovitch theory and its correlation to ancient lake sed- iment layers is unequivocal evidence that the ice ages really occurred, and that the earth has existed for many hundreds of millions of years.
	www.skepticfiles.org /evolut/lakebeds.htm (1372 words)

	The Seasons and the Earth's Orbit - Milankovitch Cycles (Site not responding. Last check: 2007-10-22)
		There is another important cycle that has the potential to affect the Earth's climate; it is a 41,000-year variation in obliquity, the tilt of the Earth's axis with respect to a direction perpendicular to its orbital plane.
		Milankovitch's work was an attempt at explaining the ice ages, and it built upon previous astronomical theories of climate variation postulated by Joseph Adhemar and James Croll in the 19th century.
		The 21,000-year perihelion cycle and the 41,000-year obliquity cycle do in fact appear to be present in the climatological record.
	aa.usno.navy.mil /faq/docs/seasons_orbit.html (1561 words)

	Milankovitch cycles - CreationWiki (Site not responding. Last check: 2007-10-22)
		The Milankovitch cycle is the theoretical effect of changes in the Earth's movements upon its climate.
		The theory is that the eccentricity in the Earth's orbit, axial tilt, and precession of the Earth's orbit produce 100,000 year ice age cycles in Earth's climate.
		There are problems when it comes to reconciling the theory of Milankovitch cycles with reality, even if one assume uniformitarian interpretations of the data.
	www.nwcreation.net /wiki/index.php?title=Milankovitch_cycles (360 words)

	[No title]
		On the occasion of the 125th anniversary of the birth of Milutin Milankovitch, Serbian Academy of Sciences and Arts is organizing an international symposium aimed at reviewing the state-of-the-art of climate science as it relates to the scientific and professional work of Milankovitch.
		Milankovitch`s life and work, the colorful memories he has left of the events of his time, and his opus as a poetic science writer, will also be highlighted.
		Variations in the Earth's eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles for Milutin Milankovitch, the Serbian astronomer who is generally credited with calculating their magnitude.
	www.teslasociety.com /milankovic.htm (2442 words)

	MS Thesis
		Documentation of orbitally-induced (Milankovitch) cyclicity in stratigraphic sequences is useful in establishing depositional rates and in documenting climatic control of biologic, sedimentologic, and hydrologic factors in lacustrine deposition.
		Milankovitch cyclicity was documented in Cretaceous fl shale sequences from Italy (Park and Herbert, 1987) and in Triassic lacustrine deposits in New York (Van Houten, 1964; Olsen, 1984).
		This result supports earlier studies of Milankovitch cyclicity, which report that the eccentricity variation is a major driving mechanism of climatic oscillation, and show that a nonlinear climate model must be invoked to produce 100 kyr power in geologic records (Hays and others, 1976, Prentice and Matthews, 1988).
	net.indra.com /~mbennett/thesis.html (12965 words)

	The Milankovitch Theory
		Milankovitch, being a mathematician, took Croll's work and set out to develop a mathematical theory of climate change.
		Precession is caused by two factors: a wobble of the Earth's axis and a turning around of the elliptical orbit of the Earth itself (Thomas, 2002).
		"Using these three orbital variations, Milankovitch was able to formulate a comprehensive mathematical model that calculated latitudinal differences in insolation and the corresponding surface temperature for 600,000 years prior to the year 1800"(Kaufman, 2002).
	www.emporia.edu /earthsci/student/howard2/theory.htm (724 words)

	Climate Change \| Milankovitch Cycles \| Ice Ages
		Milankovitch (1941) considered the changing seasonal (precession) and latitudinal (obliquity) patterns of incoming radiation to be critical factors in the growth of continental ice sheets and in the initiation of ice ages.
		He hypothesised that when axial tilt was small (large latitudinal temperature gradient), eccentricity was large and perihelion occurred during the Northern Hemisphere winter (warmer winters and colder summers), such a configuration would allow the persistence of accumulated snow throughout the summer months in the Northern Hemisphere.
		Indeed, Milankovitch himself had expected the direct effects of variations in insolation to be magnified by feedback processes, such as, at high latitudes, the ice albedo effect (section 2.7).
	www.global-climate-change.org.uk /2-5-2-4.php (444 words)

	Online-Course Stratigraphy
		In shallowing-upward sequences with tidal flat caps the difficulty of establishing unambiguous criteria for distinguishing Fischer's Milankovitch cycles from Ginsburg's autocycles remains.
		Therefore these cycles must be the result of sea-level oscillations of either eustatic or tectonic origin, or some combination of the two.
		Plots of cumulative cycle thickness versus stratigraphic position show that individual cycles are bundled into asymmetrical clusters of 5, distinguishable by a thick basal cycle followed by a progressive upward decrease in thickness in the remaining 4 cycles of the cluster.
	www.geologie.uni-stuttgart.de /online_kurse/Online-Course/NewFiles/Lecture2_Chapter6.html (447 words)

	Wildlife News: Rare climate event linked to Milankovitch cycles
		Although the concept of such relationships is not new, some of the results were surprising, said James Zachos, a professor of Earth sciences at the University of California, Santa Cruz, and lead author of the paper.
		The combination of a low-amplitude "node" in the obliquity cycle and a minimum in eccentricity would have caused only several degrees difference in summer temperatures at the poles, but it was probably enough to allow the Antarctic ice sheet to expand, Zachos said.
		In the period they examined, the late Oligocene and early Miocene, Zachos and his collaborators found evidence of several climate cycles with frequencies corresponding to the Milankovitch cycles.
	www.wildlifenews.co.uk /articles2001/april/1401h.htm (834 words)

	Views of the National Parks
		Milutin Milankovitch recognized that minor changes in Earth’s orbit around the sun and in the tilt of Earth’s axis causes slight but important variations in the amount of solar energy that reaches any given latitude on Earth’s surface.
		By reconstructing and dating the history of climatic variations over hundreds of thousands of years, scientists have shown that fluctuations of climate on glacial-interglacial time scales match the predictable cyclic changes in Earth’s orbit and axial tilt.
		In the case of the Milankovitch Cycles, orbit is used to describe the path the Earth follows as it circles the Sun.
	www2.nature.nps.gov /views/KCs/Milankovitch/ET_Milankovitch.htm (578 words)

	Ice Age
		Milankovitch said the ice ages are caused by variations in sunlight hitting the continents.
		To visualize the different astronomical cycle that Muller and MacDonald have found to match that of the climatic record, imagine a flat plane with the sun in the center and nine planets circling close to the plane.
		age probably are controlled by the Milankovitch cycle (a periodic change in the tilt of the Earth's axis and the ellipticity of the Earth's orbit).
	www.newagedatabase.com /IceAge.htm (7758 words)

	Extinction: Proposed Law of Nature Linking Impacts, Plume Volcanism, and Milankovitch Cycles to Terrestrial Vertebrate ...
		Natural fluctuations of the carbon cycle such as rapid releases of carbon dioxide from the mantle, or oceans, disrupt steady state S-E-S flow.
		A major carbon cycle perturbation involves readjustment of the outer physiochemical spheres of the earth: the atmosphere, hydrosphere, and lithosphere, and by necessity, the biosphere.
		Milankovitch cycles drive the Cenozoic ice age cycles, and also seem to influence mammalian bioevolution and extinctions.
	filebox.vt.edu /artsci/geology/mclean/Dinosaur_Volcano_Extinction/pages/ghreplon.html (1282 words)

	EO Library: Milutin Milankovitch
		The Serbian astrophysicist Milutin Milankovitch is best known for developing one of the most significant theories relating Earth motions and long-term climate change.
		Born in the rural village of Dalj, Serbia, Milankovitch attended the Vienna Institute of Technology and graduated in 1904 with a doctorate in technical sciences.
		Milankovitch dedicated his career to developing a mathematical theory of climate based on the seasonal and latitudinal variations of solar radiation received by the Earth.
	earthobservatory.nasa.gov /Library/Giants/Milankovitch (240 words)

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