PAPER 1

• Global circulation


  1. Hot air rises at equator

  2. Causes low pressure

  3. Air spreads out and sinks at tropics

  4. Causes high pressure

  5. Air flows back towards equator
• ITCZ


  Band of rainfall at the equator
• ITCZ moves


  Due to tilt of Earth's axis as it orbits the Sun
• ITCZ causes rainy seasons in West Africa
• Feral cell


  1. Warm air rises at mid-latitudes

  2. Causes low pressure

  3. Air spreads out and sinks

  4. Flows back towards equator
• Polar cell


  1. Cold air sinks at poles

  2. Causes high pressure

  3. Air flows outwards
• High pressure


  Dry conditions
• Air always flows from high pressure to low pressure
• Ocean currents


  Move heat from equator to poles
• Ocean currents prevent overheating of the planet
• Rainfall zones


  Areas of low pressure have rainfall, areas of high pressure are deserts
• West Africa has rainy and dry seasons due to movement in and out of the ITCZ
• Natural causes of climate change

  • Volcanic eruptions
  • Asteroid collisions
  • Sunspot activity
  • Orbital changes
• Volcanic eruptions and asteroid collisions

  • Cause short-term global cooling by blocking solar radiation
• Sunspot activity


  • Causes longer-term heating and cooling cycles
• Orbital changes


  • Cause longer-term heating and cooling cycles due to changes in Earth's distance from Sun and tilt of axis
• Circular orbit


  Equal distance to the sun at any point
• Elliptical orbit


  Not round, sometimes further away from the sun (cooler), sometimes closer to the sun (hotter)
• Axis tilt


  Planet is on an angle, this wobbles, putting us closer or further from the sun over a 41,000 year period
• The axis tilt has an impact on heating and cooling over a long period
• Ice cores


  • Contain trapped carbon dioxide, high levels indicate past warmer periods, low levels indicate past cooler periods
• Tree rings


  • Wider rings indicate longer growing seasons and warmer periods, narrower rings indicate shorter growing seasons and cooler periods
• Historical sources


  • Less reliable, may involve artistic license or exaggeration (e.g. accounts of frost fairs on the Thames)
• Satellite images


  • Very reliable, use of technology
• Greenhouse effect


  Greenhouse gases in the atmosphere trap outgoing long-wave radiation, causing the planet to heat up
• Some greenhouse gases are naturally occurring (e.g. from volcanoes, forest fires, rotting vegetation)
• Enhanced greenhouse effect


  Increased greenhouse gases from human activities (burning fossil fuels, more livestock) leading to greater heat trapping and global warming
• Thermal expansion


  Warming oceans cause water molecules to expand, leading to rising sea levels
• Future climate change scenarios

  • Option C (best case - low population growth, renewable energy, 30cm sea level rise)
  • Option B (moderate population growth, some renewable energy, 1.5°C warming)
  • Option A (worst case - high population growth, fossil fuel use, over 1m sea level rise)
• Climate change will bring more frequent and severe weather events (flooding, hurricanes, storms), disruption to farming, and climate refugees
• Tropical cyclones/hurricanes/typhoons


  • Form over warm tropical ocean waters, measured on Saffir-Simpson scale, bring strong winds, storm surges, heavy rainfall, and landslides (especially in poorer regions)
• Formation of hurricanes

  Require warm ocean water, coriolis effect, form over West Africa and move across Atlantic
• Formation of hurricanes


  1. Warm water required

  2. Coriolis effect

  3. Storms form over West Africa

  4. Storms merge due to Coriolis effect

  5. Low wind shear in upper atmosphere required

  6. Sea surface temperatures of 27 degrees required

  7. Dissipates when hits land
• Hurricanes


  • Swirling winds and clouds due to Coriolis effect
  • Very low pressure, often below 1000 millibars
• Lower the pressure


  Stronger the winds
• Hurricanes have greater impacts in low-income countries compared to high-income countries
• Bangladesh


  • Very low-lying, only 2 metres above sea level
  • Located on a river delta
  • Coastal location
• Storm surges and heavy rainfall

  Cause flooding in Bangladesh
• Impacts in Bangladesh


  • Cyclone Aila in 2009 - 190 people died, 750,000 made homeless, crops ruined by saltwater
• Impacts in high-income countries like the USA are generally less severe, but there can be exceptions