Naural causes of climate change

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Variations in the Earth's orbit

Stretch

  • The path of the Earth's orbit changes from an almost perfect circle to an ellipse and back around every 96,000 years.
  • Changes the distance between the Sun and Earth --> Impacts on the energy recieved from the Sun.
  • Earth's orbit is in an elliptical now - closest to the sun in January and furthest in July.
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Variations in the Earth's orbit

Tilt 

  • Earth is tilted at an angle as it orbits the Sun, called its axis.
  • Axis changes between around 21.8 degrees and 24.4 degrees over a period of 41,000 years
  • Change in tilt changes the amount of energy that different latitudes get, changing global climate.
  • When tilt is greater (24.4) areas that recieve lots of energy will be larger eg. the tropics. Other climate regions, such as the temperate regions beyond the tropics, will be smaller.
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Variations in the Earth's orbit

Wobble

  • The axis wobbles like a spinning top over 22,000 years 
  • Because the Earth is closest to the sun in January, winter in the northern hemisphere is mild and summer is cool.
  • The wobble of the axis means that this gradually changes and the seasons swap over.
  • When this happens, the Earth will be closest to the sun in Jan, but this will now be summer in the northern hemisphere. The Earth will still be furthest away from the sun in July, but this will now be winter in the northern hemisphere.
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Variations in solar output

  • The sun's output of energy isn't constant.
  • Sunspots are darker areas on the sun that increase solar output.
  • They're thought to increase and decrease in numbers over an 11 year cycle.
  • A period of cooling in the late 17th century thought to be linked to the low number of sun spots.
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Volcanic eruptions and meteor impacts

  • The impact of a meteor/astriod forms a large crater and can throw loads of material into the atmosphere. 
  • Major volcanic eruptions also eject large quantities of material into the atmosphere.
  • This results in a lot of sunight being blocked out for a long period of time, changing the climate.
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