Orbital forcing
Orbital forcing is the effect on climate of slow changes in the tilt of the Earth's axis and shape of the Earth's orbit around the Sun (see Milankovitch cycles). These orbital changes modify the total amount of sunlight reaching the Earth by up to 25% at mid-latitudes (from 400 to 500 W/(m2) at latitudes of 60 degrees)[citation needed]. In this context, the term "forcing" signifies a physical process that affects the Earth's climate.
This mechanism is believed to be responsible for the timing of the ice age cycles. A strict application of the Milankovitch theory does not allow the prediction of a "sudden" ice age (sudden being anything under a century or two), since the fastest orbital period is about 20,000 years. The timing of past glacial periods coincides very well with the predictions of the Milankovitch theory, and these effects can be calculated into the future.
Milankovitch cycles are also associated with environmental change during
Overview
It is sometimes asserted that the length of the current interglacial temperature peak will be similar to that of the preceding interglacial peak (
Note in the graphic, the strong
Orbital mechanics require that the length of the seasons be proportional to the swept areas of the seasonal quadrants, so when the eccentricity is extreme, the seasons on the far side of the orbit can last substantially longer. Today, when autumn and winter in the Northern Hemisphere occur at closest approach, the Earth is moving at its maximum velocity and therefore autumn and winter are slightly shorter than spring and summer.
Today in the Northern Hemisphere, summer is 4.66 days longer than winter and spring is 2.9 days longer than autumn.
The arrangements of land masses on the Earth's surface are believed to reinforce the orbital forcing effects. Comparisons of
See also
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References
- S2CID 134068136. Retrieved 12 January 2023.
- . Retrieved 5 April 2023.
- . Retrieved 22 January 2023.
- . Retrieved 2 January 2023.
- . Retrieved 5 April 2023.
- S2CID 128923481.
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- ^ Benson, Gregory (11 December 2007). "Global Warming, Ice Ages, and Sea Level Changes: Something new or an astronomical phenomenon occurring in present day?".
Further reading
- Hays, J. D.; Imbrie, John; Shackleton, N. J. (1976). "Variations in the Earth's Orbit: Pacemaker of the Ice Ages". Science. 194 (4270): 1121–1132. S2CID 667291.
- Hays, James D. (1996). Schneider, Stephen H. (ed.). Encyclopedia of Weather and Climate. New York: Oxford University Press. pp. 507–508. ISBN 0-19-509485-9.
- Lutgens, Frederick K.; Tarbuck, Edward J. (1998). The Atmosphere. An Introduction to Meteorology. Upper Saddle River, N.J.: Prentice-Hall. ISBN 0-13-742974-6.
- National Research Council (1982). Solar Variability, Weather, and Climate. Washington, D.C.: National Academy Press. p. 7. ISBN 0-309-03284-9.
- Cionco, Rodolfo G., and Pablo Abuin. "On planetary torque signals and sub-decadal frequencies in the discharges of large rivers." Advances in Space Research 57.6 (2016): 1411–1425.
External links
- The NOAA page on Climate Forcing Data includes (calculated) data on orbital variations over the last 50 million years and for the coming 20 million years
- The orbital simulations by Varadi, Ghil and Runnegar (2003) provide another, slightly different series for orbital eccentricity