GCSE Geography - Causes of Climate Change

GCSE Geography - Causes of Climate Change

1. Earth's orbit

   • Over a long period of time
   • Significant climate change
   • Glacial periods
     • Glacials - temperature has been 5-6℃ cooler
       • E.g. Pleistocene epoch
     • Interglacials - temperature has been 2-3℃ warmer
       • E.g. current Holocene period has persisted since Pleistocene epoch
   • Orbit changes over time - sometimes elliptical, sometimes circular
     • This means there are times when Earth has less heat energy
     • It can take longer for solar radiation to reach Earth
   • Earth's axis tilts - on average, 23.5º

2. Volcanic eruptions

   • Earth relies on gases in atmosphere to trap heat
     • E.g. SO₂ (sulphur dioxide)
       • SO₂ released by erupting volcanoes
         • 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
   • Do not affect climate over a long period
   • E.g. Tambora, Indonesia, 1816
     • 'Year with no summer'
     • 200,000 deaths in Europe
     • Sunlight reaching Earth 10% lower for next 5 years

3. Changes in solar activity

   • Sun's output is not constant - cycles detected
   • Records began over 2000 years ago
   • Sunspots - these darker areas can tell us about heat output
   • Black sunspots indicate that the sun is working harder and is more active
   • Number of sunspots can be linked to periods of time

4. Reflectivity

   • Earth reflects solar radiation (insolation)
     • Normally about 30-70% absorbed
   • Albedo is affected by surface colour
     • Light surfaces reflect more, dark surfaces absorb more
   • Positive feedback mechanism

5. MOST IMPORTANT CAUSES - REFLECTIVITY AND EARTH'S ORBIT