Carbon Dioxide

There are three main sources of carbon dioxide discharged into the atmosphere: respiratory of plants and animals (93%), forest fires and other burning of plant materials (2%), and the burning of fossil fuels such as oil, coal, and natural gas(5%). Most (95%) of this released carbon dioxide is removed by the natural processes of photosynthesis and uptake of carbon dioxide by the oceans. There is, however, a net gain in atmospheric carbon dioxide each year.

The environmental impact of increased carbon dioxide levels is often call the greenhouse effect, an effect that could produce global warming (an increase in average air temperature). Carbon dioxide traps some of the energy radiated by the earth as it cools at night, thus preventing the radiation from escaping to outer space. The trapped energy causes an increased warming of the atmosphere.

[source: Chemical Principles by H. Stephen Stoker]