Hazardous earth

• What happens at the equator?

  The sun warms the earth causing heat to rise creating a low pressure belt. As air rises, it cools and condenses forming clouds and rain.
• Where does the cool dry air move to?

  30 degrees north or south of the equator.
• What happens at 30 degrees north or south of the equator?

  Cool air shrinks creating a high pressure belt with cloudless skies and low rainfall.
• What happens when the cool air when it reaches the ground surface?


  It moves as surface winds back to the equator or towards the poles.
• What are surface winds that blow towards the equator known as?

  Trade winds.
• Where do trade winds blow from?

  Either the southern hemisphere or the northern hemisphere.
• What happens when trade winds meet at the equator?

  They are heated by the sun causing them to form clouds.
• What are surface winds that blow towards the poles known as?

  Westerlies.
• Where do westerlies blow?

  They blow from the north west in the southern hemisphere and from the south west in the northern hemisphere.
• What happens at 60 degrees north and south of the equator?

  Warmer surface winds meet colder air from the poles.
• Why does warmer air rise?

  Because it is less dense than cooler air.
• What's another way heat can be transferred?

  Ocean currents.
• What are surface currents caused by?

  Winds.
• What do surface currents help do?

  Transfer heat away from the equator.
• What is the cooling and sinking of water known as?

  Thermohaline circulation.
• Acid (dry)

  1. Sinking air from the hadley and ferrel cells meeting causes high pressure and prevents rainfall.
  2. Rainfall is very low throughout most of the year.
  3. Temperatures are hot or warm.
• Polar.

  1. Sinking air from polar cells creates an area of high pressure at the poles.
  2. Temperatures are low all year round and there is very low rainfall.
• Tropical.

  1. Rising air from the two hadley cells meeting causes low pressure and lots of rainfall.
  2. Temperatures are hot all the time and rainfall is high.
• Volcanic activity.

  1. Major volcanic eruptions eject large quantities of material such as ash into the atmosphere.
  2. Some of these particles reflect the suns rays back out to space causing the earth's surface to cool.
  3. Volcanic activity can cause short term changes in the climate.
• Solar output.

  1. The suns output of energy isn't constant it changes in short cycles of around 11 years.
  2. Periods when solar output is reduced may cause the earths climate to become cooler.
• Asteroid collisions.

  1. Asteroids hitting the earths surface can throw up huge amounts of dust into the atmosphere.
  2. These particles prevent the suns energy from reaching the earths surface so global temperatures will fall.
• Tree rings

  1. Most tress produce one ring within their trunks every year.
  2. the thickness of the ring depends on the climate when the ring was formed when its warmer the rings are thicker.
  3. Scientists take cores through tree trunks and date each ring by counting them back to when the core was taken.
  4. The thickness of the rings gives them an idea of the climate at the time.
• Ice cores

  1. Ice sheets are made of layer of ice and one is formed each year.
  2. Scientists drill into ice sheets to get long cores of ice.
  3. By analysing gases trapped in the layers of ice they can tell what the temperature was like in that year.
• What is the greenhouse effect?

  When gases in the atmosphere naturally act like an insulating layer and let short wave radiation in but trap long wave radiation helping keep the earth at the right temperature.
• Examples of greenhouse gases.

  1. Carbon dioxide.
  2. Methane.
• What happens when a greenhouse gas is strong?

  Stays in the atmosphere for longer and contributes to global warming.
• What makes the greenhouse effect stronger?

  Human activites.
• Farming.

  1. Farming of livestock produces a lot of methane.
  2. Rice paddies contribute to global warming because flooded fields emit methane.
  3. Trees absorb and store carbon dioxide so when cut down for agriculture it stops the absorption of carbon dioxide leaving more of it in the atmosphere.
• Industrial processes.

  1. Cement is made from limestone containing carbon, when cement is produced lots of carbon dioxide is released into the atmosphere.
  2. Industrial waste may end up in landfill sites where it decays releasing methane.
• Energy.

  1. Carbon dioxide is released into the atmosphere when fossil fuels like coal, oil and natural gas are burnt in power stations etc.
• Transport.

  1. Most cars, lorries, ships and planes run on fossil fuels which release greenhouse gases when burnt.
  2. Car ownership is also increasing in developing countries such as China.
  3. Therefore there are more cars on the road increasing congestion and traffic leading to more pollution and global warming.
• Declining arctic ice.

  1. The extent of arctic sea ice in winter has decreased by more than 3% each decade over the past 35 years.
• Global temperature rise.

  1. Temperature has increased by nearly 1 degree celsius since 1880 and is expected to rise by 0.3 - 4.8 degree celsius between 2005 and 2100.
• Sea level rise and warming oceans.

  1. Since 1901 sea levels have risen by almost 0.2m.
  2. Warmer temperatures are causing glaciers to shrink and ice sheets to melt. This means that water stored on land is now going into the oceans causing sea levels to rise.
  3. Water expands in the oceans as it gets warmer known as thermal expansion.
• Impacts of climate change on people.

  1. Damaged crops from flooding.
  2. More extreme weather which is expensive to protect against.
• Where do tropical storms develop?

  Over warm water typically in the tropic of cancer.
• When are tropical cyclones most frequent in the northern hemisphere?

  June to November.
• When are tropical cyclones most common in the southern hemisphere?

  November to April.
• What is a tropical cyclone?

  Intense low pressure weather systems with heavy rain and strong winds that spiral around the centre.
• What latitudes do tropical cyclones form in?

  Usually low latitudes between 5 and 30 degrees north and south.