Greenhouse gases and climate change
The greenhouse effect
keep the Earth warm enough for life. The main ones are , and water vapour.
- Short-wavelength radiation from the Sun passes through the atmosphere and warms the Earth's surface.
- The warm Earth gives out long-wavelength infrared radiation.
- Greenhouse gases absorb some of this infrared and re-emit it in all directions, including back towards the Earth.
- This keeps the surface and lower atmosphere warmer than they would otherwise be.
More greenhouse gases means more energy is trapped, so the temperature rises.
Key terms
Human activities
Human activities increase the amounts of greenhouse gases:
| Gas | Human sources |
|---|---|
| Burning in power stations, vehicles and homes; deforestation, which leaves fewer trees to absorb CO₂ | |
| Cattle farming (from digestion), rice paddy fields, decaying waste in landfill sites |
Based on evidence, most scientists agree that human activities are increasing the average global temperature, causing .
Key terms
Evaluating climate claims
Climate is complex, so scientists use models that are simplified and uncertain. Climate stories in the media can be simplified, biased or speculative. When you read a claim, ask:
- Has the research been ?
- Is the author an expert in the field?
- Who funded the research, and could they want a particular result?
- Is it based on lots of data over a long time, or just a few measurements?
- Does it agree with other evidence?
Key terms
Effects of climate change
A rise in global temperature could cause:
- rising sea levels from melting ice and expanding water, causing flooding and coastal erosion
- more frequent and severe storms
- changes in the amount, timing and distribution of rainfall
- temperature and water stress for people and wildlife
- changes in where food can be grown, and how much
- changes in where species of wildlife can live
These effects are not shared evenly around the world.