- The CO2 in the atmosphere comes from some natural sources, such as volcanoes erupting and plant decay. However, the Industrial Revolution brought widespread global environmental changes, including the burning of coal, oil and gas for industrial and consumer purposes. According to the National Oceanic and Atmospheric Administration, some 7 billion tons of carbon in CO2 form is released into the atmosphere annually.
- According to the NOAA, scientific measurements of the carbon dioxide in ice cores, or cylinders of ice, showed that the CO2 level prior to the Industrial Revolution was 278 parts per million. In addition, the levels did not change more than 7 ppm between 1000 and 1800 A.D. By comparison, in 2004, the atmospheric CO2 levels were 378 ppm, an increase of 36 percent. The levels were 315 ppm in 1958.
- The oceans, trees, plants and soil absorb about half of the carbon produced by humans, while the rest goes into the atmosphere. The clearing of forests means less of this carbon can be absorbed.