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The Montreal Protocol, which went into effect in 1989, is a rare instance of a global agreement to solve a global problem: the release of vast quantities of ozone-destroying chemicals into the atmosphere. In the decades since, however, changes in ozone have been small and variable, making it hard to tell whether the protocol is making any difference.
But evidence has been building that the ozone layer is recovering, and a new paper claims to have directly measured the ozone hole gradually filling back in.
During the 1970s and '80s, evidence had been building that a class of industrial chemicals, the chloro-flurocarbons (CFCs), were damaging the ozone layer, a region of the stratosphere rich in this reactive form of oxygen. Ozone is able to absorb UV light that would otherwise reach the Earth's surface, where it's capable of damaging DNA. But the levels of ozone had been dropping, which ultimately resulted in a nearly ozone-free "hole" above the Antarctic.
The ozone hole spurred countries and companies into action. As companies developed replacements for CFCs, countries negotiated an international agreement that would limit and phase out their use. The Montreal Protocol codified that agreement, and it is widely credited with reducing (though not eliminating) the CFCs in our atmosphere.
But determining whether the protocol is having the desired effect on the ozone layer has been challenging. Ozone is naturally generated in the stratosphere at a very slow rate, and the amount of destruction that takes place over the Antarctic varies from year to year. Hints of a recovery have often been followed by years in which ozone levels drop again. Recovery has been so slow, in fact, that it's possible to find people who claim the whole thing was a scam—and even a conspiracy designed to test whether it was possible to create a similar agreement for greenhouse gases.
Read more here. (Ars Technica)
But evidence has been building that the ozone layer is recovering, and a new paper claims to have directly measured the ozone hole gradually filling back in.
During the 1970s and '80s, evidence had been building that a class of industrial chemicals, the chloro-flurocarbons (CFCs), were damaging the ozone layer, a region of the stratosphere rich in this reactive form of oxygen. Ozone is able to absorb UV light that would otherwise reach the Earth's surface, where it's capable of damaging DNA. But the levels of ozone had been dropping, which ultimately resulted in a nearly ozone-free "hole" above the Antarctic.
The ozone hole spurred countries and companies into action. As companies developed replacements for CFCs, countries negotiated an international agreement that would limit and phase out their use. The Montreal Protocol codified that agreement, and it is widely credited with reducing (though not eliminating) the CFCs in our atmosphere.
But determining whether the protocol is having the desired effect on the ozone layer has been challenging. Ozone is naturally generated in the stratosphere at a very slow rate, and the amount of destruction that takes place over the Antarctic varies from year to year. Hints of a recovery have often been followed by years in which ozone levels drop again. Recovery has been so slow, in fact, that it's possible to find people who claim the whole thing was a scam—and even a conspiracy designed to test whether it was possible to create a similar agreement for greenhouse gases.
Read more here. (Ars Technica)
