Causes of Climate Change (OCR GCSE Geography A (Geographical Themes)): Revision Notes

1.4.2 Causes of Climate Change

📌 What are the Natural Causes of Climate Change?

Orbital Changes

• The way the earth moves around the sun changes.
• These changes affect the amount of solar radiation (sun energy) the earth receives. If the earth orbits closer to the sun, like the red orbit on this diagram, the climate will be warmer.
• Orbital changes affect the glacial periods of ice ages.

Orbital Changes

Volcanic Activity

• Major volcanic eruptions eject large quantities of ash into the atmosphere.
• Some of these ash particles reflect and block the sun's rays, cooling the earth's surface.

Solar Output

• The sun's output of energy always changes (every 11 years).
• When the sun has more energy (which can be witnessed through sunspots - darker areas on the sun) the climate is warmer.

Solar Output

📌 What are the Human Causes of Climate Change?

Burning Fossil Fuels

• CO2 is released into the atmosphere when fossil fuels like coal, oil, and gas are burnt (e.g., from power stations).

Farming

• Farming of livestock produces a lot of methane.
• Rice paddies contribute to global warming because flooded fields emit methane.

Deforestation

• Plants remove CO2 from the atmosphere and convert it into organic matter.
• When trees or plants are chopped down, they stop taking in CO2.
• CO2 is also released when trees are burnt as fuel or when removed using 'slash and burn'.

The Greenhouse Effect

1. The rate of recent rise in global temperatures is alarming.
2. There is scientific agreement that human activities are causing global warming through the greenhouse effect.
3. The greenhouse effect is when greenhouse gases, such as CO2, absorb outgoing heat so less heat is lost and some is reflected back to earth.
4. Too much greenhouse gas in the atmosphere means too much sun energy is trapped and the planet warms up.