Carbon dioxide enters the atmosphere when wood or fossil fuels such as oil, coal and natural gas are burned. As the rate of fossil fuel use has increased over the last century, the amount of carbon dioxide in the atmosphere has also increased by 20 - 25%.

Atmospheric carbon dioxide is considered to be a contributor to the greenhouse effect. Along with other greenhouse gases including Methane, CFC's (chlorofluorocarbons) Nitrous oxide and Hydrofluorocarbons, carbon dioxide prevents heat from leaving the Earth's atmosphere. As more heat is trapped, the Earth's surface will become warmer. This process is called Global warming.

Computer models suggest that global warming could cause the following changes:

As a result of these concerns in December 1997 the Kyoto protocol, which set limits for the emission of greenhouse gases including carbon dioxide was negotiated. Countries which have ratified the Kyoto Protocol are expected to have met their agreed target rate of emissions by 2012. As of November 2004, 127 countries have ratified the agreement.

Changes in carbon dioxide emissions since 1990 can be investigated by comparison between this data and the 1990 rate of emissions.