Carbon Cycle

In-depth explanation of Carbon Cycle

The carbon cycle describes how carbon moves between the atmosphere, oceans, biosphere, soils, rocks and fossil fuels. Photosynthesis removes CO2 from the air into living matter, while respiration, decomposition and combustion return it. Carbon dissolves into surface oceans and forms carbonates, and over geological timescales carbon is stored in sediments and rocks. Human burning of fossil fuels moves carbon that was stored for millions of years into the atmosphere far faster than natural sinks can absorb it. This imbalance between sources and sinks is the central cause of rising atmospheric CO2.

Going deeper: Carbon Cycle

Key ideas: Carbon moves between atmosphere (about 850 Gt C), oceans (about 38000), soils, vegetation and rocks via photosynthesis, respiration, decomposition, dissolution and combustion. Human emissions about 10 Gt C per year, with about half absorbed by oceans and land. Ocean chemistry: CO2 plus H2O in equilibrium with H2CO3, HCO3- and CO3 2-.

Common mistakes and connections: Mistake: treating the atmosphere as the main store, or assuming sinks are unlimited; warmer water holds less CO2 and acidification reduces carbonate. Fossil carbon is a slow cycle reservoir. Links to photosynthesis, carbon capture and limestone chemistry.

Visualization of Carbon Cycle

Approximate fate of annual human carbon emissions. The oceans and land absorb about half, while the rest stays in the air and raises CO2. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Oceans absorb about a quarter of the CO2 that humans emit each year.

Where Carbon Cycle fits in Biochemistry, Environment & Industry

Carbon Cycle is topic 73 of 127 in Biochemistry, Environment & Industry.

Related topics

• Greenhouse EffectBeginner
• Global WarmingBeginner
• Greenhouse GasesBeginner
• Ozone Layer DepletionIntermediate
• CFCsIntermediate
• SmogBeginner

Browse all 127 topics in Biochemistry, Environment & Industry