THE PAST
Changes in the carbon cycle are part of the earth’s history–in fact, as Peter Brannen documents in The Ends of World, the 5 mass extinctions each involved drastic fluctuations in carbon over a few millions years. NASA has documented the cycling nature of carbon dioxide (C02) over the last 800,000 years. As you see in the figure below, those cycles never exceeded 300 parts/million until about 1800, when the industrial revolution occurred. And since 1950, C02 levels have surpassed 400 parts/million and continuing to rise.