6. How fast is Carbon Dioxide increasing?

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Unlike many pollutants, carbon dioxide is well mixed in the atmosphere. The graph above shows carbon dioxide concentrations in the atmosphere over time at an observatory on top of a dormant volcano, Mauna Loa. This location is distant from any industrial sources of pollution yet, since measurements began, carbon dioxide concentrations have been rising steadily. Currently, the number of carbon dioxide molecules among a million molecules of air (parts per million or ppm) is about 330.

You should notice two patterns. The major pattern is a trend, carbon dioxide concentration has increased by 40ppm over 35 years. (In fact, it is estimated that before the industrial revolution carbon dioxide concentrations were 270 ppm).

The second pattern evident is seasonal and shows rising and sinking values over the course of one year. What this depicts is the extraction of carbon dioxide by plants during the growing season - as there is more land and vegetation in the northern hemisphere the seasonal pattern is that of our summer and winter. In effect you are watching the vegetation of the planet 'breathe'.