ABSTRACT
The ozone depleting substances (ODSs) (e.g., chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs)), halons, and HFCs are part of a family of gases known as halocarbons. Halocarbons are used as refrigerants, propellants, cleaning and foam blowing agents, and fire extinguishers, etc. Molina and Rowland (1974) identified the potent stratospheric ozone depleting effects of CFCs. This was followed, within a year, by the discovery of the potent greenhouse effect of the halocarbons CFC-11 and CFC-12 (Ramanathan, 1975). Many studies confirmed this finding and estimated that the global warming potential (GWP) of CFC-11 and CFC-12 (using a 100 yr time horizon) at 4750 and 10 900 respectively, as summarized by the Intergovernmental Panel on Climate Change Fourth
Assessment Report (Forster et al., 2007). Ramanathan (1975) set the stage for identifying numerous other non-CO2 greenhouse gases (GHGs) in the atmosphere such as CH4 and O3 among others (seeWang et al., 1976 and Ramanathan et al., 1985a). The first international assessment of the climate effects of non-CO2 gases was conducted in 1985 (Ramanathan et al., 1985b) and it concluded that CO2 was the dominant contributor to greenhouse forcing until 1950s, and since the 1960s non-CO2 gases have begun to contribute as much as CO2. A more recent list of the non-CO2 GHGs can be found in Pinnock et al. (1995) and Forster et al. (2007).
