The carbon cycle
Photosynthesis β respiration β combustion.
Carbon moves between four main reservoirs: ATMOSPHERE (COβ), LIVING THINGS, OCEANS, and ROCKS/FOSSIL FUELS.
The main flows:
- Photosynthesis: plants and algae take COβ from the atmosphere β glucose (and other organic compounds).
- Respiration: ALL living things (plants, animals, bacteria, fungi) release COβ back to atmosphere.
- Combustion: burning fuel (wood, coal, oil, gas) releases COβ.
- Decomposition: bacteria and fungi break down dead organisms β release COβ.
- Ocean exchange: oceans absorb ~25% of human COβ emissions.
- Fossilisation: over millions of years, some dead plants/animals get buried β coal, oil, gas.
Human disruption: burning fossil fuels (coal, oil, gas) releases carbon that was locked underground for millions of years. Atmospheric COβ has risen from ~280 ppm (1800) to ~420 ppm today β the highest in 800,000 years. This extra COβ is the main driver of climate change.
Deforestation makes it worse β fewer trees to absorb COβ AND released carbon when forests burn.
- Photosynthesis takes COβ out; respiration + combustion + decomposition put it back.
- Atmospheric COβ rose from 280 to 420 ppm in 200 years.
- Main culprit: fossil fuel burning + deforestation.