Introduction
This topic explores the key concepts of the Earth’s climate as they relate to:
- the composition of Earth’s atmosphere
- the ozone layer
- the greenhouse effect
- the weather.
Key concepts of Earth’s climate
The activities in this topic are designed to explore the following key concepts:
- The atmosphere consists of a thin layer of gases that surround Earth.
- The atmosphere is a mixture of gases: mostly nitrogen (78%) and oxygen (21%).
- Ozone in the atmosphere exists as a gas, the molecules of which consist of three oxygen atoms (O3).
- The atmospheric temperature does not drop further from Earth’s surface; the different layers are at various temperatures, which are independent of the altitude of the layer.
- The ozone layer is comparatively warm as it absorbs 90% of the UV radiation that reaches Earth from the Sun.
- The ozone layer is being depleted because of man-made chemical gases called chlorofluorocarbons (CFCs) produced on Earth.
- The ionosphere, an atmospheric layer, absorbs highly energetic electromagnetic radiation from the Sun, creating a region of charged particles that reflect radio waves from Earth’s surface.
- Television signals are not reflected by the ionosphere.
- The greenhouse effect keeps the average temperature of Earth at 15 °C; without the greenhouse effect, life on Earth, as we know it, would not exist.
- Atmospheric pollution has led to global warming through an enhanced greenhouse effect.
- Air pressure changes with the density and temperature of the air: the higher the temperature or density, the greater the air pressure.
- Humidity relates to the amount of water vapour in the air.
- When saturated air cools, some of the water vapour in the air condenses and it rains.
- Hot air rises as it gets displaced by denser cold air.
- Wind arises through differences in air pressure. Global wind patterns are also affected by the spinning of Earth.
Students’ alternative conceptions of Earth’s climate
Research into students’ ideas about this topic has identified the following non-scientific conceptions:
- Rain comes from holes, or funnels, in clouds.
- Rain comes from clouds sweating.
- Rain occurs because we need it.
- Rain occurs when clouds get scrambled and melt.
- Rain occurs when clouds are shaken.
- God and angels cause thunder and lightning.
- Clouds move because we move.
- The Sun boils the sea to create water vapour.
- Clouds are made of cotton, wool or smoke.
- The oxygen we breathe does not come from plants.
- Gas makes things lighter.
- All rivers flow from north to south.
- The extent of the warming likely within 50 years is approximately a 10 °C increase in average temperatures.
- There is confusion about the ozone hole problem and the greenhouse effect.
- Recent warm weather is evidence for global warming.
- Ozone depletion is causing global warming. The hole allows more sunlight and UV rays to come through and ‘warm’ Earth – hence, global warming.
- The greenhouse effect is a very bad process.