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Is Someone Cheating on the Montreal Protocol?

The Montreal Protocol regulates emissions of ozone depleting substances.  It is ratified by every nation and bans the use of chemicals including chlorofluorocarbons (CFCs), long lived substances which break down the stratosphere's protective ozone layer.  The international treaty has led to decreasing atmospheric levels of CFCs, and the ozone layer is beginning to recover.  It is now being reported, however, that atmospheric levels of one CFC (trichlorofluoromethane, CFC-11) have slowed their rate of decrease, attributed to a new CFC-11 source from Asia.

The origin of these new CFC-11 emissions are unclear, and will be difficult to pinpoint.  They may be from clandestine use of the banned substance, but could also arise from leaky CFC-11 stockpiles.  An international effort to investigate this issue now appears warranted, since it threatens to undo much of the good work of the Montreal Protocol.

CFCs are not the only threat to the ozone layer.  Recent studies have shown that the ozone levels in the lower reaches of the stratosphere are continuing to decline.  The culprit here may be very short lived substances, which decay in the atmosphere within around 6 months, yet can reach the stratosphere under the right conditions, where they eat away at ozone. Although the Montreal Protocol attempts to control some ozone depleting substances with lifetimes of several years, such as methyl bromide, it does not yet consider these very short lived substances, and continuing scientific work is required to establish if this should also happen.


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