Carbon Dioxide
Atmospheric concentrations of carbon dioxide have ranged from 200 to 280 ppm over the last 160,000 years. During the 1,000 years before the industrial revolution, in a time of stable global climate, the range was within 10 of 280 ppm. However, since 1850 there has been a 30 percent increase in carbon dioxide concentration, with much of this increase occurring in the last 30 years. In 1994, carbon dioxide levels were at 358 ppm and rising at a rate of 1.6 ppm/yr. The reason for this recent increase can be attributed almost entirely to anthropogenic (man-made) sources such as burning of fossil fuels and deforestation.
The following are sources of carbon dioxide:
- Respiration: All living organisms respire and during this process give off carbon dioxide.
- Decomposition of organic material.
- Anthropogenic sources: Fossil fuel burning; deforestation and burning of rain forest; land-use conversion; and cement production.
Of the direct radiative forcing of the long-lived greenhouse gases, which combined is 2.45Wm-2 (watts per square meter), carbon dioxide accounts for 1.56 Wm-2, or about 64 percent. In other words, carbon dioxide accounts for 64 percent of the global warming due to the long-lived greenhouse gases. As a matter of fact, historical records in ice core samples have shown lockstep increases in global temperature with carbon dioxide increases. So it seems that carbon dioxide has been a very important greenhouse gas. If you couple this with the fact that human activities cause the increases in carbon dioxide levels then we see a need to control anthropogenic output of dioxide to the atmosphere.
Predictions for the future carbon dioxide levels are that it will continue to increase in our atmosphere for the next century or two and then stabilize. The point of stabilization is not certain but is expected to be somewhere between a minimum of 450 ppm and a maximum of 1000 ppm. The wide range is of expectations depends on how much we can reduce increasing sources of anthropogenic carbon dioxide and how soon this happens.
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