Emissions of HFCs PFCs and SF6 - aggregate. The Global Warming Potential (GWP) is an index used to translate the level of emissions of various gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWPs are calculated as the ratio of the radiative forcing that would result from the emissions of one kilo-gram of a greenhouse gas to that from the emission of one kilogram of carbon dioxide over a period of time (usually 100 years). Gases involved in complex atmospheric chemical processes have not been assigned GWPs. HFCs (hydrofluorocarbons) are produced commercially as a substitute for CFCs. HFCs are used largely in refrigeration and semi-conductor manufacturing. Their GWPs range from 1300 to 11,700 times that of CO2 (over a 100 year time horizon), depending on the HFC. PFCs (Perfluorocarbons) are a by-product of aluminum smelting and uranium enrichment. They also are the replacement for CFCs in manufacturing semiconductors. The GWP of PFCs is 6500­9200 times that of CO2 (100 year time horizon). SF6 (Sulfur hexafluoride) is largely used in heavy industry to insulate high-voltage equipment and to assist in the manufacturing of cable-cooling systems. Its GWP is 23,900 times that of CO2 (100 year time horizon).