The enhanced greenhouse effect and global warming
Global warming (or global heating) is attributed to the enhanced greenhouse effect. This is caused by the increased concentration of greenhouse gases in the atmosphere.
Greenhouse gases e.g. carbon dioxide (CO2), methane and nitrous oxides, act like a blanket and trap heat inside the Earth's atmosphere.
As concentrations of these gases build up, they are more effective at preventing heat being lost into space. The amount of heat being lost from the atmosphere is less than the energy entering the atmosphere. As a result the temperature of the atmosphere increases.
Enhanced greenhouse effect
| Greenhouse effect | Enhanced greenhouse effect |
| Solar radiation passes through Earth's atmosphere. | Greenhouse gases allow more solar radiation to pass through Earth's atmosphere |
| The Earth absorbs most of the radiation and warms up. | The Earth absorbs most of the radiation and warms up. |
| The Earth radiates heat energy. | The Earth radiates heat energy. |
| Some heat escapes into space. | Less heat escapes into space. |
| Some heat is absorbed by greenhouse gases in the atmosphere. | More heat is absorbed by greenhouse gases in the atmosphere. |
| Greenhouse gases radiate heat in all directions | Greenhouse gases radiate heat in all directions |
| The lower atmosphere remains warm. | The lower atmosphere heats up. |
| Greenhouse effect | Solar radiation passes through Earth's atmosphere. |
|---|---|
| Enhanced greenhouse effect | Greenhouse gases allow more solar radiation to pass through Earth's atmosphere |
| Greenhouse effect | The Earth absorbs most of the radiation and warms up. |
|---|---|
| Enhanced greenhouse effect | The Earth absorbs most of the radiation and warms up. |
| Greenhouse effect | The Earth radiates heat energy. |
|---|---|
| Enhanced greenhouse effect | The Earth radiates heat energy. |
| Greenhouse effect | Some heat escapes into space. |
|---|---|
| Enhanced greenhouse effect | Less heat escapes into space. |
| Greenhouse effect | Some heat is absorbed by greenhouse gases in the atmosphere. |
|---|---|
| Enhanced greenhouse effect | More heat is absorbed by greenhouse gases in the atmosphere. |
| Greenhouse effect | Greenhouse gases radiate heat in all directions |
|---|---|
| Enhanced greenhouse effect | Greenhouse gases radiate heat in all directions |
| Greenhouse effect | The lower atmosphere remains warm. |
|---|---|
| Enhanced greenhouse effect | The lower atmosphere heats up. |
Human activity is responsible for increasing amounts of greenhouse gases in the atmosphere. The main causes of this are:
- burning fossil fuels for heat and electricity
- fossil fuel use in transport
- agriculture
- deforestation
- cement manufacture