HAZORDOUS EARTH

• Global circulation


  1. Hot air rises at equator

  2. Causes low pressure

  3. Air cools, condenses, forms clouds, rains

  4. Air spreads out, sinks at tropics

  5. Causes high pressure, dry conditions
• ITCZ


  Band of rainfall at the equator
• ITCZ moves


  Due to tilt of Earth's axis as it orbits the Sun
• Pressure differences


  Air always moves from high pressure to low pressure
• Trade winds


  Air flowing from high pressure to low pressure, deflected by Coriolis effect
• Ocean currents


  Move heat from equator to poles, preventing overheating of the planet
• Rainfall zones


  Rain falls in areas of low pressure where air is rising, no rain in high pressure areas where air is sinking
• Hot deserts


  Form in high pressure zones at the tropics
• Cold deserts


  Form in high pressure zones at the poles
• Volcanic eruptions release sulfur dioxide and ash, causing global cooling in the short-term
• Asteroid collisions throw up dust, blocking solar radiation, causing global cooling in the short-term
• Sunspot activity


  Periods of more/less sunspot activity cause long-term heating/cooling of the planet
• Orbital theory


  Changes in Earth's orbit and axis tilt cause long-term heating and cooling of the planet
• Circular orbit


  Orbit around the sun where the distance to the sun is equal at any point
• Elliptical orbit


  Orbit around the sun where the distance to the sun varies, sometimes further away (cooler) and sometimes closer (hotter)
• Axis tilt


  The planet's axis is not straight, it is on an angle and this wobbles over a 41,000 year period, causing the planet to be closer or further from the sun
• Ice cores contain trapped carbon dioxide, which indicates past climate conditions
• High levels of carbon dioxide in ice cores indicate it was warmer in the past, low levels indicate it was colder
• Tree rings


  The gaps between tree rings indicate past growing seasons, with wider gaps showing warmer periods and narrower gaps showing cooler periods
• Historical sources like old photographs, drawings, and written accounts are less reliable for determining past climate as they may involve artistic license or exaggeration
• Satellite images are very reliable for determining current climate conditions
• Greenhouse effect


  Greenhouse gases in the atmosphere trap outgoing long-wave radiation, causing the planet to heat up
• Some greenhouse gases are naturally occurring, but human activities are enhancing the greenhouse effect and causing global warming
• Thermal expansion


  As the oceans heat up, the water molecules expand, causing sea levels to rise
• Climate change will bring more frequent and severe weather events like flooding, hurricanes, and changes to farming
• Tropical cyclones/hurricanes/typhoons


  Powerful storms that form within the tropics, measured on the Saffir-Simpson scale from 1-5 based on wind speed
• Tropical cyclones


  • Require warm sea surface temperatures of around 26.5°C
  • Form either north or south of the equator due to the Coriolis effect
  • Bring hazards like strong winds, storm surges, coastal flooding, intense rainfall, and landslides
• 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. Occurs over oceans

  8. 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
• Bangladesh


  • Very low-lying, only 2 metres above sea level
  • Located on a river delta
  • Coastal location
• Impacts are less in high-income countries, but can still be severe
• Impacts in USA


  • Hurricane Katrina in 2005 - Levees broke, flooding large areas, high death toll, criticism of government response
• Management in high-income countries


  • Better warning systems, preparation, planning, resources
• Management in low-income countries


  • Warning systems use foreign satellites, more effective in urban areas, issues with rural literacy and electricity access, shelters built but some reluctance to evacuate
• Forecasting and warning


  Satellite tracking to predict hurricane path, warnings via TV, radio, mobile phones - more effective in high-income countries
• Earth's layers


  • Crust
  • Lithosphere
  • Asthenosphere
  • Upper mantle
  • Lower mantle
  • Inner core
  • Outer core
• Continental crust


  • Thick, buoyant, light, made of granite, what we stand on
• Ocean crust


  • Newer, dense, made of basalt, gets subducted