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6 Cards in this Set

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Orbital Theory


Milankovitch cycles

* Surface temps change due to orbit and tilt of the earth over time, affecting the amount and distribution of solar radiation received




Eccentricity (over 100,000 years)


--> earth's orbit changes from circular to elliptical and back




Obliquity (41,000)


--> earth's axis tilts from 22.5˚ to 24.5˚ and back




Precession (22,000)


--> axis wobbles and changes the point in the year when it's closest to the sun




* When the tilt of the earth is at its most and coincides with the earth being the furthest from the sun on its orbit, winters are 20% colder

why do surface temps change?




3 types of cycle


- over how long they occur


- what happens during the cycle




when are the coldest winters?

Albedo effect

* reflection of incoming solar radiation --> reduces global temps


* when the earth is at its most elliptical orbit there is an ice advance


* greater albedo effect --> more solar radiation reflected --> ice advances further

Variation in solar output

* sun's output is not constant --> cycles in solar energy output


* sun spots: dark spots on the sun which represent more solar activity


* more sun spots --> more solar energy being fired out from the sun (increased solar luminosity) --> temps rise

Volcanic activity

* ash and SO2 spread around earth in the stratosphere by high level winds


* sunlight reflected off ash and gas back into space --> temps decrease


* 1991 --> Mt Pinatubo, Philippines --> 17mill tonnes of SO2 --> reduced global sunlight by 10%, cooling planet by 0.5C for a year


* 1815 --> Tambora, Indonesia --> biggest eruption ever


1816 --> "the year with no summer" --> 200,000 died in Europe as harvest failed --> effects lasted 4-5 years --> sunlight reduced by 10%

Plate tectonics

* redistribution of land masses had long term effects on climate


* UK drifted to a more northerly latitude

Changes in ocean currents

* THERMOHALINE CIRCULATION --> movement of ocean waters around the world


* warm water from equator moved N or S --> as warmer water moves N it cools and sinks back to equator


* if too much fresh water from melting ice is put in the ocean, the circulation could shut down and the northern hemisphere could go into an ice age