THE CARBON CYCLE: The carbon cycle describes the movement of carbon, in its many forms, between the earth, atmosphere, oceans, and the animals, plants and bacteria that live there. For example, much of the carbon stored in trees and soils is released into the atmosphere when forests are cleared and cultivated. Sometimes this release happens very quickly, like when a forest fire burns. Sometimes it happens slowly, as dead plants decompose. When forests regrow on cleared land, trees draw carbon from the atmosphere and store it again in the plants and soil. If the global totals for photosynthesis (plants taking CO2 from the air and using it for energy, giving off oxygen) and respiration (animals taking in oxygen and using it to make energy, giving off CO2) are not equal, carbon accumulates, either on land or in the atmosphere. The rates of photosynthesis and respiration are not known, and they're not measured well enough, but there does appear to be an imbalance, known as the "missing sink" of carbon. Yet the carbon cycle must be a closed system, which means there is a fixed amount of carbon; we just don't know where the missing carbon is yet. Understanding why there is an imbalance, and where it occurs, is critical to combating the threat of global warming.
OTHER WAYS TO CAPTURE CARBON: It is possible to reduce the amount of CO2 released into the atmosphere by modern power plants by as much as 80-90% through carbon capture and storage technologies. The downside is that the fuel needs of a plant would increase by 10-40% in order to capture and store the carbon dioxide, thereby increasing operating costs by 30-60%. There are three basic ways to capture carbon. One is to remove it after burning fossil fuels, an approach that is already being used on a small scale by conventional power plants. Or the fossil fuel can be turned into a gas before the burning process and captured from the exhaust stream in a purer form of CO2 and water vapor. A third emerging option is called chemical looping combustion, in which metal particles interact with the fuel and produce solid metal particles and a mix of CO2 and water vapor than can be captured and transported to a storage site.
The American Geophysical Union contributed to the information contained in the TV portion of this report.