In 1987 representatives from 24 countries met in Montreal and announced to the world that it was time to stop destroying the ozone layer. In so doing, these countries committed themselves, via the Montreal Protocol on Substances that Deplete the Ozone Layer, to rid the world of substances that threaten the ozone layer.
On December 19, 1994, the UN General Assembly proclaimed September 16 to be the International Day for the Preservation of the Ozone Layer, commemorating the date when the Montreal Protocol on Substances that Deplete the Ozone Layer was signed in 1987. The day was first celebrated on September 16, 1995.
Chlorofluorocarbons (CFCs) **
Carbon tetrachloride, Methyl chloroform
Methyl bromide ~~
- Because of the high chlorine content and the ease with which the chlorine atoms can be displaced when the molecule is subject to ultraviolet light, R-11 has the highest ozone depletion potential of any refrigerant, by definition assigned the value 1.0. U.S. production was ended in 1995.
- Because bromine is 60 times more destructive to ozone than chlorine, even small amounts of bromomethane cause considerable damage to the ozone layer. In 2005 and 2006, however, it was granted a critical use exemption under the Montreal Protocol. The most recent set of 'critical use' exemptions in the US include use of Bromomethane for tomato, strawberry, and ornamental shrub growers, and fumigation of ham/pork products.
A new study led by Columbia University researchers has found that the closing of the ozone hole, which is projected to occur sometime in the second half of the 21st century, may significantly affect climate change in the Southern Hemisphere, and therefore, the global climate. The study appears in the June 13th issue of Science.
"Our results suggest that stratospheric ozone is important for the Southern Hemisphere climate change, and ought to be more carefully considered in the next set of IPCC model integrations," said Seok-Woo Son, lead-author of the study and a postdoctoral research scientist at Columbia's Fu Foundation School of Engineering and Applied Science (SEAS).
It wouldn't do for us to get complacent, however. This is a triumph, as yet, unrealized. There is much to be done to stop all air pollution. There are hazardous chemicals being used whose adverse effects still aren't fully known. At some point we will have to ask ourselves if the conveniences made possible by the substances are worth the risk to our future and that of future generations.
Until next time...become the change you imagine.