THE ROLE OF CARBON DIOXIDE
Human burning of fossil fuels (coal, oil, and natural gas) causes about three-quarters of man-made carbon emissions. Greenhouse gases such as carbon dioxide (CO₂) and other trace gases, such as methane, chlorofluorocarbons (CFCs), nitrous oxide (N₂O), and surface ozone, are increasing in the atmosphere.

Land conversion (deforestation by burning or logging of tropical forests) also releases CO₂ into the atmosphere, both directly as the fire releases CO₂ and indirectly by reducing the number of trees available to remove the CO₂ from the atmosphere during photosynthesis. Slash-and-burn agriculture causes about 60% of tropical deforestation; commercial logging accounts for about 20%; and 12% of rain forests are destroyed to provide open rangelands for cattle.