In this section you will revise:

  1. The Energy Balance - description and explanation
  2. Atmospheric Circulation
  3. The ITCZ
  4. Oceanic Currents
  5. Global Warming - causes and impacts

The Energy Balance

You will be asked to describe and explain the earth's energy balance.

Describing the Earth's Energy Balance:

The graph you'll be expected to read is shown here. Pay attention to how I have included data from the graph. Also notice how I structure my answer in a manner that breaks the graph down into managable chunks.

Model Answer:

At 90°N the atmosphere is in defecit with terrestrial radiation being approximately 70 Joules greater than solar. At just past 30°N both solar and terrestrial radiation are in balance at approximately 190 Joules. At the equator the atmosphere is in energy surplus which peaks at approximately 270 Joules. The atmosphere returns to balance between solar and terrestrial radiation at just over 30°S after which it is once again in defecit as we move towards the South Pole.

Explaining the Earth's Energy Balance:

You will also be asked to explain how The Earth's energy is in defecit and surplus at the poles and equatorial regions. You should practise drawing this diagram and learn the labels.

  1. Albedo effect caused by ice and snow reflects heat back to space.
  2. Incoming radiation is concentrated more at the tropics as the earth’s surface area is less.
  3. Increased cloud cover at equator traps heat in.
  4. Some energy is reflected off of the Earth’s atmosphere due to the angle of incidence.
  5. The depth of atmosphere is greater at the Poles so energy can not get to the surface so easily.
  6. Dark surfaces such as rainforests absorb energy.
  7. Variations in solar radiation (Milankovitch cycles) cuase differences in surface temperature.

Atmospheric Circulation

In this section you will be asked to explain how energy is transferred from the equator to the poles. Having established that the poles are in energy deficit, i.e. they are losing energy and the tropics in surplus i.e. they are gaining in energy the question is then "why don't the poles keep getting colder and the tropics keep getting hotter?". Clearly this is not happening - atmospheric circulation is the process by which this energy is re-distributed.


The Inter-tropical Convergance Zone (ITCZ)

In this section you'll learn how to describe and explain the movement of the ITCZ.

Describing the ITCZ

Explaining the ITCZ



Oceanic Currents

You need to know how the oceans redistribute energy from the tropics to the poles.

Model answer:

The ocean currents in the Atlantic Ocean spin in a clockwise direction because of the coriolis force created by the spin of the Earth. They are forced to follow their path by the continents of Europe and North America which block their paths. The water is moved by surface winds. The water is warmed in the tropics and this causes it to rise. This rising water then forms a spinning gyre. Where the warm North Atlantic Drift cools as it travels north it begins to sink and becomes a denser cold current such as the Labrador or Canaries current which return to the tropical areas to be warmed up again. The process is powered by the sun.

Global Warming

You will need to know the reasons for global warming and enhanced global warming and the impacts that it may have. Watch these two clips to understand both. It is appropriate to point out that expert opinions differ as to the reasons behind and consequences of of global warming. You should watch both of these clips, take notes and then try to write a paragraph about each.

Causes of Global Warming

Impacts of Global Warming