Natural Causes
Geography: Edexcel A Level, topic 2.1.2
Milankovitch Cycles
Long-term climate change has been due to a range of natural causes, including Milankovitch cycles. Milankovitch cycles refer to the 'wobble, roll and stretch' changes in the Earth’s orbit around the sun.
Stretch (eccentricity)
- The 'stretch' part of the Milankovitch cycles describes the Earth’s orbit changes from circular to elliptical.
- This affects how much solar radiation is received on the Earth's surface.
Roll (tilt)
- The 'roll' part of the Milankovitch cycles describe the axis tilting from 21 to 24 degrees and back again, over a period of 41,000 years.
- This leads to changes in the amount of solar radiation received at the Earth's surface.
Wobble (precession)
- The Earth's axis is said to ‘wobble’, altering the distance between the sun and the Earth.
Diagram
Other Natural Causes of Climate Change
Long-term climate change has been due to a range of natural causes, including sunspot activity and volcanic activity.
Sunspot activity
- Sunspots are temporary spots on the Sun's photosphere that send more solar radiation towards the Earth.
- They happen on a range of cycles, the smallest being every 11 years.
- The net increase in radiation with sunspots is 0.1%.
Volcanic activity
- Volcanoes emit ash, sulphur dioxide, carbon dioxide and water into the atmosphere.
- These gases and ash reduce the amount of solar radiation received at the surface by forming a buffer between the sun's rays and the Earth's surface.
- A recent example was Mt Pinatubo, which erupted in 1991.
Test yourself on Natural Causes
Over how many years does the 'roll' part of the Milankovitch cycle happen?
What is the word for temporary spots on the Sun's photosphere that send more solar radiation towards the Earth?
Which of these is an example of a recent climate-altering volcanic eruption?