Greenhouse gases, such as carbon dioxide, methane and water vapour, let short-wavelength radiation from the Sun pass through but absorb the long-wavelength infrared radiation emitted by the Earth, keeping the planet warm. Human activities increase these gases: burning fossil fuels and deforestation add carbon dioxide, while cattle farming, rice fields and landfill release methane.
Most climate scientists agree, based on peer-reviewed evidence, that these increases are causing global climate change. Effects include rising sea levels, more extreme weather, changes in rainfall, and shifts in where species can live. The carbon footprint is the total greenhouse gas emitted over the life of a product or activity. It can be reduced by using renewable energy, improving energy efficiency, carbon capture and storage, and planting trees, although there are economic and political barriers.
Worked example
Why does methane matter even though there is much less of it than carbon dioxide?
- Methane is a greenhouse gas.
- Each methane molecule traps much more heat than a CO₂ molecule.
Answer:So small increases have a big effect on warming.
Key words
- greenhouse gas
- absorbs infrared radiation, e.g. CO₂, CH₄
- climate change
- long-term change in global weather patterns
- carbon footprint
- total greenhouse gas from a product or activity
- peer review
- checking of research by other scientists
New questions every time.
NGSS-referenced: HS-ESS2-4