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 1879 in the rural village of Dalj (then part of the Austro-Hungarian Empire, today located in Croatia), Milankovitch attended the Vienna Institute of Technology and
graduated in 1904 with a doctorate in technical sciences. After a brief
stint as the chief engineer for a construction company, he accepted a
faculty position in applied mathematics at the University of Belgrade in
1909a position he held for the remainder of his life.
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. Now known as the Milankovitch Theory, it states that as the Earth travels through space around the sun, cyclical variations in three elements of Earth-sun geometry combine to produce variations in the amount of solar energy that reaches Earth:
Together, the periods of these orbital motions have become known as Milankovitch cycles.
next: Orbital Variations
Obliquity (change in axial tilt)
return to: Orbital Variations
return to: Orbital Variations
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. He then attempted to correlate these changes with the growth and retreat of the Ice Ages. To do this, Milankovitch assumed that radiation changes in some latitudes and seasons are more important to ice sheet growth and decay than those in others. Then, at the suggestion of German Climatologist Vladimir Koppen, he chose summer insolation at 65 degrees North as the most important latitude and season to model, reasoning that great ice sheets grew near this latitude and that cooler summers might reduce summer snowmelt, leading to a positive annual snow budget and ice sheet growth.
But, for 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 (Hays et al. 1976). 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 geometry (eccentricity, obliquity, and precession) of Earth's orbit. Indeed, ice ages had occurred when the Earth was going through different stages of orbital variation.
Since this study, the National Research Council of the U.S. National Academy of Sciences has embraced the Milankovitch Cycle model.
Links and References
Alaska Science Forum: The Earth's Changing Orbit
J.D Hays, John Imbrie, and N.J. Shackleton, "Variations in the Earth's Orbit: Pacemaker of the Ice Ages," Science, 194, no. 4270 (1976), 1121-1132.
Hays, James D., 1996: Encyclopedia of Weather and Climate, Oxford University Press, Stephen H. Schneider, ed. pp 507-508.
Lutgens, Frederick K. and Edward J. Tarbuck, 1998: The Atmosphere, Prentice-Hall, Inc., 434pp.
National Research Council, Solar Variability, Weather, and Climate, Washington, D.C.: National Academy Press, 1982, p. 7.