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 Balancing the Carbon Cycle
Using the data given in the carbon cycle diagram, attempt to balance the carbon cycle. By balance, we mean--given the amount of carbon moving between the various sinks, as listed on the process arrows--what must be the rate at which the various sinks are changing. Are they increasing, decreasing, or remaining constant? Be sure to include the uncertainties in your calculations. Remember, the carbon cycle is a closed system, so all the carbon must be accounted for. It cannot disappear.

If scientists can figure out where the carbon from anthropogenic sources is going, then it may be possible to devise programs to enhance the uptake of carbon in these sinks. This would reduce the rate of increase of carbon in the atmosphere and perhaps slow global warming.

Hints: When scientists balance the carbon cycle, they consider only those processes and sinks which interact directly with the atmosphere, since increasing levels of CO2 in the atmosphere may cause global warming.

For decay from soil to atmosphere, use 60 GtC. This number is hotly contested, however, with many scientists believing that the soil is a significant sink for atmospheric carbon (2-3 GtC/year). Research is ongoing in this area.

Consider whether sinks are growing or shrinking. For instance, from the Mauna Loa CO2 data (You will need Excel 5.0 or higher.) or the text version we can calculate the increase in carbon in the atmosphere with a high degree of certainty. What about the other sinks? What evidence do we have that they may be growing or shrinking?

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