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ozone layer (Rowland and Molina, 1974). Concern continued, and in 1985 scientists detected unexpected seasonal losses in the stratospheric ozone layer above Antarctica (Farman et al., 1985). In 1987, these concerns resulted in the Montreal Protocol—an international agreement to reduce by 1998 the production and use of CFCs, in developed countries, to 50 percent of their 1986 levels and to freeze halon production at 1986 levels by 1993. By 1988, research had shown that chlorine from man-made sources, primarily CFCs and CCs, contributed to the temporary early spring ozone losses above Antarctica. The Montreal Protocol was amended in 1990 to require a total phaseout of CFCs, halons, and carbon tetrachloride by the year 2000 in developed countries (2010 in developing countries). Not all countries have agreed to sign the Montreal Protocol, however, and this fact, along with the possibility that some countries may not comply with the agreement, has caused concern. More than 100 countries with over 67 percent of the global population and about 10 percent of current CFC use—India and China included—have not yet signed the agreement.

The United States has signed the Montreal Protocol. In addition, the 1990 amendment to the Clean Air Act will further regulate halocarbons in the United States. Figure 25.2 illustrates how CFC consumption will decline between now and 2010 because of the new Clean Air Act amendment.

Besides having a role in ozone depletion, CFCs are also greenhouse gases. Unlike the other greenhouse gases, which began to increase during the Industrial Revolution (1850), CFCs were not introduced until the early

FIGURE 25.1 CFC and halon consumption by geographic region, 1985.

SOURCE: Cogan (1988).