What’s Ozone Got to Do With It?
Back in the late 1980s, a lot of people were confused about the relationship between two potential crises facing Earth’s atmosphere. The first was climate change — still mostly theoretical at that point, but with plenty of reason to think it would become evident all too soon in the real world.
The second was the ozone hole — not really a hole, but a thinning of ozone over Antarctica, caused by manmade chemicals wafting into the stratosphere (mostly chlorofluorocarbons, or CFCs, used as refrigerants, among other things). Less ozone in the stratosphere means that more dangerous ultraviolet radiation reaches the surface to cause skin cancers and other evils.
Because these two phenomena entered the public consciousness at the same time, lots of people mixed them up, or thought they were closely related (I may be partly to blame, thanks to this cover story I wrote for TIME in 1987).
They weren’t — but that doesn’t mean they were entirely unrelated, either. The gases that destroy ozone are also heat-trapping greenhouse gases, although there aren’t enough of them to be a major factor in global warming.
But there's another effect. Depleted ozone in the stratosphere, it turns out, results in higher wind speeds close to Earth’s surface, which loft tiny salt crystals from the ocean up into the air, according to the authors of a new paper in Geophysical Research Letters. The whiteness of the salt reflects sunlight, which helps stave off global warming (this is also the theory behind some proposed geoengineering schemes).
But cfc’s were banned by the 1987 agreement called the Montreal Protocol. As a result, the ozone hole has started to repair itself. The high-altitude salt crystals will presumably diminish, therefore, and their shielding effect will vanish.
If the analysis is correct, in short what's good for the ozone may not be so good for the climate. However there are a couple of caveats that make this result less impressive than it might seem. First, the effect is purely local — any slowdown in warming would have been local, over Antarctica, not worldwide. And second, some scientists argue that as the world warms overall, winds should pick up anyway, keeping salt crystals aloft indefinitely, so the recovery of the ozone layer (which in any case won't be complete for decades) won't necessarily change much anyway. This is where Emily Litella might have ended up saying "Never mind."