GCSE Geography - Causes of Climate Change

Earth's orbit
1. Over a long period of time
2. Significant climate change
3. Glacial periods
  1. Glacials - temperature has been 5-6℃ cooler
    1. E.g. Pleistocene epoch
  2. Interglacials - temperature has been 2-3℃ warmer
    1. E.g. current Holocene period has persisted since Pleistocene epoch
4. Orbit changes over time - sometimes elliptical, sometimes circular
  1. This means there are times when Earth has less heat energy
  2. It can take longer for solar radiation to reach Earth
5. Earth's axis tilts - on average, 23.5º
Volcanic eruptions
1. Earth relies on gases in atmosphere to trap heat
  1. E.g. SO₂ (sulphur dioxide)
    1. SO₂ released by erupting volcanoes
      1. Eruption must be large enough so that ejected gas reaches upper atmosphere
        Once in atmosphere, gas is spread by winds in stratosphere
        Gas encircles Earth like a blanket, forming a layer reflecting radiation
2. Do not affect climate over a long period
3. E.g. Tambora, Indonesia, 1816
  1. 'Year with no summer'
  2. 200,000 deaths in Europe
  3. Sunlight reaching Earth 10% lower for next 5 years
Changes in solar activity
1. Sun's output is not constant - cycles detected
2. Records began over 2000 years ago
3. Sunspots - these darker areas can tell us about heat output
4. Black sunspots indicate that the sun is working harder and is more active
5. Number of sunspots can be linked to periods of time
Reflectivity
1. Earth reflects solar radiation (insolation)
  1. Normally about 30-70% absorbed
2. Albedo is affected by surface colour
  1. Light surfaces reflect more, dark surfaces absorb more
3. Positive feedback mechanism
MOST IMPORTANT CAUSES - REFLECTIVITY AND EARTH'S ORBIT

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GCSE Geography - Causes of Climate Change

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