Activity	Percent Contribution to Global Warming
Energy use and production	57%
Chlorofluorocarbons	17%
Agricultural practices	14%
Changes in land use	9%
Other industrial activities	3%

Source: C&EN, March 27, 1989, p. 22, from the US Environmental Protection Agency.

The above table shows the major causes of global warming, and lists them in order based on the percentage of global warming they have caused.

At the top is energy production, which far outranks any other source of global warming and accounts for more than half of all global warming.

Energy production creates greenhouse gases through the burning of fossil fuels.  Until renewable, non-polluting methods of energy production are developed, energy production will likely remain at the top of this list.

Chlorofluorocarbons, or CFCs, rank second in the list.  In recent times, public awareness about the dangers of CFCs has increased in some of the more developed countries.  As a result, people are beginning to call for decreases in the consumption of products that produce CFCs.