The theory of catastrophic anthropogenic (man-made) global warming (CAGW) as interpreted by a certain group (the warmers) is predicated on the idea that carbon dioxide (CO2) in the atmosphere has the potential to do serious harm to the Earth. Their theory goes like this: Nature releases and then recaptures CO2, thus the atmospheric CO2 content is stable. They then add, largely, through the CO2 produced from burning fossil fuels , man has upset that balance and CO2 is accumulating in the atmosphere. The chart below by the National Oceanic and Atmospheric Administration (NOAA) is a representation of the “Carbon Cycle”.
According to this chart, every year the “gross global primary production and respiration” releases 119 giga tons and then takes in 120 giga for growing vegetation. The ocean’s emit 88 giga tons and absorb 90 giga tons. Fossil fuel combustion and other industrial processes emit 6.3 giga tons and have no returns. Land use changes are small at 1.7 emited and 1.9 returned. It also tells us that 730 giga tons of carbon are in the atmosphere. In our last posting we related that the atmospheric CO2 is at 400ppm. That gives you some idea of how vast the Earth’s atmosphere is.
There are many drawings of the carbon cycle and they often have different numbers than the one shown above. But the idea is the same in all cases. The chart makers really are guessing at the numbers anyway. The fossil fuels number is the only one where data are largely available. So it is likely the best one. Another thing to know about this chart is that it is in tons of carbon. There are other sources of carbon such as methane, CH4. But because CO2 is the major carbon source you can read the chart as essentially a gross measure of CO2 for our purposes.
The net exchange by this chart results in an annual carbon accumulation of 4.1 giga tons into the atmosphere. The total from the chart of the emissions to the atmosphere are about 205 giga tons of which 8 giga tons are man-made or 4% of the total CO2 emissions. This raises the obvious question: if the big natural numbers (in blue) are no more than broad estimates, do we really know what is going on?
The next posting will examine a version of the Greenhouse Effect.