Life is in the loop
The air you breathe out was once inside a leaf.
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The rule
Carbon goes round between air, living things and fuels. Life moves it fast. Fuels hold it for millions of years.
Fuels here are coal, oil and gas.
- Plants take in carbon dioxide and make glucose.
- Animals eat plants and take in the carbon.
- Breathing and decay return carbon dioxide to the air.
- Fossil fuels store carbon for millions of years. Burning frees it.
The idea
Living things are built from carbon. Proteins, fats, sugars and DNA (the instructions inside cells) all contain it. Carbon moves between air, water, rock, fuels and living things.
In the fast cycle, plants take carbon dioxide from the air. They use sunlight to make glucose, a sugar. This is photosynthesis. Breathing puts the carbon dioxide back. The decay of dead plants and animals does too. Decay is dead matter being broken down. This loop takes days to years.
The slow cycle takes millions of years. Buried plants and animals can turn into coal, oil and gas. Burning releases that carbon as carbon dioxide very fast.
Burning fuels and cutting forests add carbon dioxide. A Hawaiian mountain has measured the air's carbon dioxide since 1958. It rose from about 315 ppm to over 420 ppm. A ppm is one part in a million parts of air. The rise is 420 − 315 = 105 ppm. And 105 ÷ 315 is one third. So the amount grew by about a third. Extra carbon dioxide holds back more of the ground's heat.