How does carbon cycle through earth's four spheres?

Carbon dioxide constantly moves into and out of the atmosphere through several major pathways. Over short time scales, the processes of photosynthesis, respiration, organic decomposition (decay), and combustion (burning of organic material) increase or decrease the concentration of atmospheric CO2. Carbon dioxide is also exchanged between the atmosphere and oceans by gas exchange over short time scales. Each year, approximately one-fifth of the carbon (in the form of CO2) in the atmosphere is cycled in and out.