Carbon cycle
Carbon moves between the air, living things, soil, oceans and rocks. Photosynthesis takes carbon dioxide from the air into plants. Respiration, decay and burning fuels return it. Burning fossil fuels adds carbon that had been stored for millions of years.
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Analogy
A bank account where deposits and withdrawals normally balance.
In practice
Atmospheric carbon dioxide has risen from about 280 parts per million before the industrial age to over 400 today.
Practice
Flashcards
- Which process removes carbon dioxide from the air?Photosynthesis.
Questions people ask
Why does carbon dioxide cause warming?
Carbon dioxide is a greenhouse gas. It lets sunlight pass to Earth but absorbs some of the heat that the surface radiates back, and sends part of it back down. More carbon dioxide traps more heat, so the planet warms. Methane and water vapour are also greenhouse gases.
What is a carbon sink?
A carbon sink is something that takes in more carbon than it releases. Forests, oceans and soils are the main natural sinks, as plants and algae take in carbon dioxide during photosynthesis. Cutting down forests reduces this capacity, and the stored carbon can return to the air.