Carbon dioxide

Carbon dioxide (CO₂) is an odourless, colourless gas that is vital for natural cycles on Earth. People and animals inhale oxygen (O₂) and exhale carbon dioxide. Plants do the opposite during the day.

Plants need CO₂ in order to grow, just as people need oxygen in order to breathe. Algae in the ocean also absorb lots of CO₂ and ‘breathe out’ oxygen. Without oxygen, life on earth would not be possible.

Humankind is adding extra CO₂ to the atmosphere by burning fossil fuels, which increases the concentration of carbon dioxide. The Earth’s temperature is gradually rising because heat, which the atmosphere would otherwise release at night-time, is retained. This is called the greenhouse effect.