Human Causes of Climate Change
The greenhouse effect
- The Earth's atmosphere is made up of a number of gases
- Nitrogen
- Carbon dioxide
- Oxygen
- Water vapour
- Methane
- Argon
- 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 -18oC
The enhanced greenhouse effect
- Human activity is increasing the amount of certain greenhouse gases in the atmosphere:
- Carbon dioxide (CO2) levels in the atmosphere have increased by more than 100 parts per million (ppm) to 420ppm in 2020
- Methane, nitrous oxides and chlorofluorocarbons are also increasing
- Increased amounts of greenhouse gases have led to the enhanced greenhouse effect:
- Less long-wave radiation (heat) can escape the atmosphere
- Average global temperatures have increased over 1oC since pre-industrial times
The greenhouse effect vs the enhanced greenhouse effect
Human Sources of Greenhouse Gases
Greenhouse Gas | Sources from human activity |
Carbon Dioxide (CO2) |
|
Methane (CH4) |
|
Nitrous Oxide (N2O) |
|
Chlorofluorocarbons (CFCs) |
|
Exam Tip
Remember, not all scientists agree about the causes of climate change. There are a few scientists who argue that global warming is the result of the Earth's natural climate pattern and not the result of human activities.