Causes of Climate Change (OCR GCSE Geography B)
Revision Note
Written by: Bridgette Barrett
Reviewed by: Jenna Quinn
The Greenhouse Effect
Natural greenhouse effect
The greenhouse effect is essential to the survival of life on Earth:
Greenhouse gases in the atmosphere allow short-wave radiation from the sun through to the Earth's surface
The greenhouse gases absorb some of the long-wave radiation (heat) and stop it from radiating out into space
This maintains the Earth's average temperature
Without the greenhouse effect the average temperature would be -18°C
Greenhouse gases from natural sources
Water vapour: Evaporation from the oceans/seas and plants
Carbon dioxide: Volcanic eruptions, wildfires and respiration
Methane: Emitted from oceans and soils as part of decomposition, termites also emit methane
Nitrous oxide: Soils and oceans
Causes of Natural Climate Change
Cause | Impact |
|---|---|
Milankovitch Cycles | Long term changes to the Earth's orbit and position. This changes how much solar radiation the Earth receives |
Volcanic eruptions | Large scale eruptions lead to vast quantities of ash being ejected into the atmosphere Ash in the atmosphere blocks solar radiation leading to a decrease in temperatures |
Sunspot activity | Sunspots are dark spots appearing on the sun's surface Increased sunspot activity is linked to higher average temperatures as the sunspots indicate that the sun's effectiveness at radiating heat is increased The IPCC state the role of sunspots in climate change is minimal |
Atmospheric dust | Asteroids and meteors entering the Earth's atmosphere may increase the amount of dust which decreases temperatures |
The Greenhouse Effect
Human Sources of Greenhouse Gases
Greenhouse Gas | Sources from human activity |
|---|---|
Carbon Dioxide (CO2) | Burning of fossil fuels - power stations, vehicles |
Methane (CH4) | Decay of organic matter - manure, waste in landfill, crops |
Nitrous Oxide (N2O) | Artificial fertilisers |
Chlorofluorocarbons (CFCs) | Aerosols |
Fossil fuels
Fossil fuels account for almost 50% of global greenhouse gas emissions
Fossil fuels are used in transportation, construction, heating, manufacturing, and energy production
Agriculture
Deforestation to clear land for grazing and crops leads to less CO2 being absorbed during photosynthesis
The production of fertilisers and pesticides uses fossil fuels
Increased raising of dairy and beef cattle as well as rice cultivation increases methane emissions
Artificial fertilisers also increase the amount of nitrogen oxide released into the atmosphere
Construction
The manufacture of cement releases CO2 - it is made from limestone which contains carbon
Transport
The increasing global population has led to increased numbers of cars, lorries, and planes
Most transport uses petrol/diesel which comes from oil as fuel this releases CO2
Worked Example
Outline the theory of how sunspots are linked to climate change
(3 marks)
Answer
Sunspots are dark/ reddish spots that appear on the surface of the sun (1)
More sunspots mean the Sun is more effective at giving off heat (1)
There is an 11-year cycle for sunspots (1) which then causes variations in solar insolation depending on where it is in the cycle (1)
Increased sunspot activity may lead to higher sea temperatures (1)
The IPCC have concluded that sunspots play a very small role in climate change (1)
Examiner Tips and Tricks
Remember the greenhouse effect is a natural process without which the average temperature on Earth would be significantly lower. The cause of recent climate change is the enhanced greenhouse effect. It is important that you refer to it as the enhanced greenhouse effect in your exam and not simply the greenhouse effect.
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