Definition
Global warming
The gradual rise in the Earth's average surface temperature caused by increasing levels of greenhouse gases.
- Global warming is the gradual rise in the Earth's average surface temperature.
- It is caused by increasing levels of greenhouse gases such as carbon dioxide and methane.
- Human activities, especially burning fossil fuels, deforestation and farming, are raising these gas levels.
Key Idea
Greenhouse gases trap heat in the atmosphere, so as their levels rise the Earth gets warmer.
Greenhouse gases
Definition
Greenhouse gas
A gas such as carbon dioxide or methane that traps heat in the atmosphere.
- A greenhouse gas traps heat that would otherwise escape from the Earth into space.
- Carbon dioxide comes mainly from burning fossil fuels and wood.
- Methane comes from cattle and rice fields, and from rotting waste in landfill.
Common Mistake
- Do not confuse the greenhouse effect with the hole in the ozone layer.
- Global warming is caused by greenhouse gases trapping heat, not by ozone.
Consequences for living things
- Rising temperatures cause climate change, with more extreme weather and shifting rainfall.
- Ice melts and sea levels rise, which floods low-lying habitats.
- Many species must move to stay in suitable conditions, changing their distribution and migration patterns.
- Species that cannot move or adapt fast enough may die out, so biodiversity falls.
Self review
- What is global warming, and what causes it?
- Name two greenhouse gases and give a source of each.
- Give two ways global warming can reduce biodiversity.
- How does global warming change where species are found?
