Ozone, continued global

Halogen-atom catalyzed processes are the cause of steady and continuing global ozone decline as well as superimposed massive seasonal ozone depletion observed over polar regions during late winter/spring (see contributions by P.J. Crutzen [1], this issue). 

The alternatives are currendy acceptable because of their reduced ozone and global warming potentials. The presence of hydrogen results in a lower atmospheric lifetime. The short atmospheric lifetime also results in problems in their synthesis resulting in rapid catalyst deactivation. Longer hved catalysts have subsequently been developed. A detailed summary (8) of the catalytic chemistry reported for the preparation of the most significant CFC alternatives has been reported. Without rapid development of these new catalytic processes, CFCs would continue to be produced, resulting in further ozone depletion. 

The decrease is continuing due to global adherence to the provisions of the Montreal (1989) and London (1990) Protocols, and it is hoped that the most deleterious CFCs will eventually be phased out completely. As a result of their work, Rowland and Molina were awarded the Nobel Prize for Chemistry for 1995 (together with P. Crutzen, who showed how NO and NO2 could similarly act as catalysts for the depletion of stratospheric ozone). Several excellent accounts giving more details of the chemistry and meteorology involved are available. 

Since 1977, global ozone maps have been generated continuously by the TOMS satellite, and they are available to you here through this website. Also, be sure to check out their on-line textbook about stratospheric ozone. 

Mario Molina and Sherwood Rowland used Crutzen s work and other data in 1974 to build a model of the stratosphere that explained how chlorofluorocarbons could also threaten the ozone layer. In 1985, ozone levels over Antarctica were indeed found to be continually decreasing and had dropped to the lowest ever observed. These losses are now known to be global in extent. 

On the global-scale, the destruction of ozone by halocarbons was addressed in the U.S. by banning chlorofluorocarbons in aerosol products. The release of carbon dioxide to the atmosphere from fossil fuel combustion wil1 continue well into or through the twenty-first century. Energy requirements of nations of the temperate zone will require combustion of gas, oil and coal and the atmospheric burden of carbon dioxide will continue to increase with uncertain consequences. 

Concentrations of both ozone and particulates have increased since the early 1980s in many parts of the developing world, including cities in Asia and Latin America (e.g.. Mage et al., 1996). It is possible that continued growth will lead to increases in global background concentrations in the future (e.g., Lelieveld and Dentener, 2000). 

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