The Atmosphere and Climate Change

Today's atmosphere

Roughly 78% nitrogen, 21% oxygen, plus small amounts of carbon dioxide, water vapour, and noble gases (argon).

The greenhouse effect

Greenhouse gases (carbon dioxide, methane, water vapour) absorb heat radiated from Earth and re-emit it back, keeping the planet warm. Too much → enhanced effect → global warming.

Human causes of rising CO₂

• Burning fossil fuels (cars, power stations).
• Deforestation — fewer trees to absorb CO₂.
• Farming and landfill release methane.

Consequences

Rising sea levels (melting ice + thermal expansion), more extreme weather, shifting/lost habitats, changes to food supply.

Carbon footprint

The total greenhouse gases released over the life of a product/service/event. Reduce it with renewable energy, efficiency, carbon capture, and using less.

Exam tip

Link cause → gas → effect: "Burning fossil fuels releases CO₂, a greenhouse gas, which traps heat and causes global warming." Climate conclusions are based on peer-reviewed evidence.