Environmental Science and Engineering Seminar

The global carbon cycle inherits the complexity of biology, geology, and chemistry. Yet somehow it expresses a mathematical structure: once carbon dioxide is reduced to organic carbon by photosynthesis, its oxidation back to CO2 by microbial respiration slows down at rates that are inversely proportional to its age. Moreover, microbial populations themselves decrease as a power of age. I show that a simple model of fluctuation-limited kinetics quantitatively predicts these and other observations. The impact of these slow dynamics is profound: they preclude complete oxidation of organic carbon, thereby freeing molecular oxygen to accumulate in the atmosphere.