Many would agree that the Montreal Protocol of 1987, where UN member nations came together to protect the ozone layer in the atmosphere–also called the “sunshield”–against pollutants is perhaps, the most ambitious–and successful plan ever taken against an environmental issue.
Since the chlorine from dangerous gases such as chlorofluorocarbons have now reduced dramatically, the ozone hole is in a state of recovery. However, Quirin Schiermeier reports in Nature that the original estimate, which predicted that the ozone hole will be completely repaired by 2050, will likely not be reached. Greenhouse gases in the atmosphere have altered conditions in such drastic ways that there are many other contributing factors that need to be considered now.
The Antarctic ozone hole is probably going to take decades longer to repair, even while the shield in other parts of the world—such as the mid-latitude regions–might recover much sooner than anticipated, according to the report. In an ironic twist to the earth’s environmental troubles, the faster recovery in this region is thanks to greenhouse gases, which trap the heat in the lower atmosphere, thus allowing the stratosphere to cool and cause ozone recovery.
In the Antarctic region, however, this cooling has an opposite effect because it leads to stratospheric cloud formation; these clouds allow a surface for ozone-depleting chemical reactions to occur. What also happens in the polar regions is that the rising air from the tropics, which drifts upward; the sinking of this air in the higher latitudes causes compression and then warming, which in turn prevents ozone depletion.
This interplay between ozone depletion and recovery is what makes these estimates even harder.
In addition, some threats to the ozone layer due to chemicals still remain. Methyl bromide, an ingredient in pesticides, whose use was supposed to be phased out by developed countries in 2005 is still in use. Also, chlorine and bromine from air-conditioning and fire-fighting systems are expected to be released into the atmosphere over time, continuing the depletion of ozone.
This interplay is further complicated by the fact that hydrofluorocarbons, which we used to replace CFCs to prevent ozone depletion can act as super greenhouse gases that can be over four thousand times more harmful than carbon dioxide in their heat-trapping power.
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