CFC 13, trend

Brunke EG, Allen RJ. 1988. Tropospheric background measurements of CFC 3, CFFCCP, and CCk at Cape Point, South Africa, and their long-term trends. South African J Sci 84 266- 270. 

Figure 12.11 shows the history of the estimated annual global release rates of CFC-11 and CFC-12 from 1952 to 1980. Over this period of about three decades, the release rate into the atmosphere increased dramatically until about 1974, as these compounds found increasing use in our industrialized society. Figure 12.12 shows similar data from 1972 to 1992. The decrease in emissions as the Montreal Protocol took effect can be clearly seen (see Chapter 13.A). Data from 1986 to 1996 from the European Union show similar trends (McCulloch and Midgley, 1998). 

Figure 12.13 shows the trend in surface CFC-11 and CFC-12 concentrations in air measured at latitudes... 

Long-term trends due to CFCs must also be removed from the data to examine the effects of volcanic emissions. Finally, one must take into account the possible contributions of air that has been processed through the polar vortices and of meteorological influences that are unique to certain locations (e.g., see Ansmann et al., 1996). 

C. TRENDS IN CFCs, THEIR REPLACEMENTS, STRATOSPHERIC O, AND SURFACE UV... 

In short, the trends in the tropospheric concentrations of CFCs, halons, and their substitutes follow trends in their emissions. The effects of the controls imposed by the Montreal Protocol and its subsequent amendments are evident in the trends and have been used to show that the associated impact on ozone destruction is expected to begin about the turn of the century. The following section briefly describes the observed trends in stratospheric ozone. 

Fraser, P D. Fisher, P. Bloomfield, S. P. Sander, and M. K. W. Ko, Report on Concentrations, Lifetimes, and Trends of CFCs, Halons, and Related Species, NASA Reference Publication 1339, January 1994. 

Reactivity E10b2. 306 Reactivity-Trends E10b2. 306 CFC 11 (see also under CC13F> ElOa. 

Engel, A., Schmidt, U., McKenna, D. (1998) Stratospheric trends of CFC-12 over the past two decades Recent observational evidence of declining growth rates, Geophys. Res. Lett.. 25,3319-3322. 

The recent trend to abolish chlorofluorocarbon (CFC) blowing agents in rigid foam manufacture has prompted a new look on PMDI derived foams containing partial carbodiimide structure. Since carbon dioxide, generated in carbodiimide formation, can be used... 

Because nearly all of the chlorine and fluorine released from chlorofluorocarbons resides as HC1 and HF in the stratosphere near 50 km, observations of those two gases in this region provide an important verification of their attribution to CFC sources. Global data by Russell et al. (1996) display abundances and trends in both HC1 and HF near 50 km that are quantitatively consistent with observations of the chlorofluorocarbons at ground level these observations therefore confirm that CFCs are the key sources for stratospheric chlorine and fluorine. Such observations also suggest that the abundance of reactive chlorine reached its maximum in the late 1990s, while fluorine... 

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