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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? |
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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 |
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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 |
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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% |
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Plate tectonics |
* redistribution of land masses had long term effects on climate * UK drifted to a more northerly latitude |
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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 |
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