Causes of Global Climate Change

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Causes of Global Climate Change
Climate change is controlled primarily by cyclical eccentricities in Earth's rotation and orbit, as well as variations in the sun's energy output.

"Greenhouse gases" in Earth's atmosphere also influence Earth's temperature, but in a much smaller way. Human additions to total greenhouse gases play a still smaller role, contributing about 0.2% - 0.3% to Earth's greenhouse effect.

Major Causes of Global Temperature Shifts
(1) Astronomical Causes
11 year and 206 year cycles: Cycles of solar variability ( sunspot activity )
21,000 year cycle: Earth's combined tilt and elliptical orbit around the Sun ( precession of the equinoxes )
41,000 year cycle: Cycle of the +/- 1.5° wobble in Earth's orbit ( tilt )
100,000 year cycle: Variations in the shape of Earth's elliptical orbit ( cycle of eccentricity )

(2) Atmospheric Causes
Heat retention: Due to atmospheric gases, mostly gaseous water vapor (not droplets), also carbon dioxide, methane, and a few other miscellaneous gases-- the "greenhouse effect"
Solar reflectivity: Due to white clouds, volcanic dust, polar ice caps

(3) Tectonic Causes
Landmass distribution: Shifting continents (continental drift) causing changes in circulatory patterns of ocean currents. It seems that whenever there is a large land mass at one of the Earth's poles, either the north pole or south pole, there are ice ages.
Undersea ridge activity: "Sea floor spreading" (associated with continental drift) causing variations in ocean displacement.

For more details see:
http://www.ngdc.noaa.gov/paleo/milankovitch.htmlhttp://www.abc.net.au/science/news/enviro/EnviroRepublish_233658.htm