It’s Back

Not that there’s much we can do about it.

There are many advantages to aging. One, of course, is that it’s much better than the only known alternative. Another is a constantly growing, personal connection with history. As Harry Truman once said, perhaps in a pessimistic moment, “The only thing new in this world is the history you don’t know.”

If you are of less than a certain age, you may never have heard of the Great Ozone Hole Debate, although there is still bad blood about it to this day. Or you may have heard of it from backyard mechanics grousing about tree-hugging hippies and the rising cost of R-22 Freon.

The GOHD was a mini-precursor to that quasi-religious battle, the Great Forced Climate Change Controversy, otherwise known as Global Warming. And it may be coming back to haunt us.

First, a primer.

Raw sunlight as it strikes the earth includes far more ultraviolet radiation (the UV of sunblock lotions) than earthly life can generally survive. As this radiation enters the stratosphere, beginning about 150,000 feet above our heads, it breaks up oxygen molecules. This absorbs some of the UV (specifically, the very energetic UVC). Further down and closer to us, oxygen atoms recombine into an ionized form called ozone. This layer of ozone absorbs still more UV (the less energetic UVB). The remaining UV radiation (some UVB and the relatively mild UVA) that gets through is what causes sunburn and, it seems, skin cancer.

Now, ozone (ionized oxygen) is not the most stable thing in the world. As a matter of fact, it’s pretty reactive in the presence of water and many other things. One of the things it likes to do is revert back to the normal molecular form of oxygen, which lets UVB pass more or less unhindered. But in the the mid-stratosperic ozone layer, new ozone is not created very rapidly because the high-energy UVC that breaks up oxygen is absorbed higher up. So it’s possible for ozone to be depleted just where we need it most.

And it turns out that a couple of elements not normally present in the stratoshpere, chlorine and bromine, catalyze the reversion of ozone back to molecular oxygen.

There is a particular chemistry involving trace amounts of water vapor, sunlight, cold temperatures, and chemicals like Freon, that releases chlorine and bromine in catalytic form. And, as catalysts, these elements are not consumed in the conversion of ozone to plain oxygen, but hang around to keep catalyzing as long as the conditions are right.

This is why, based in large part on science sponsored by NASA, the world agreed to phase out the production of certain chemicals, called CFCs, among them the old Freon. (The EPA gets to be the whipping boy because, in this country, that agency is given the thankless task of writing and enforcing the regulations.)

I think the key moment in the history of the GOHD was the decision by the venerable E. I. du Pont, chemical manufacturer and scourge of tree-huggers everywhere, to change it’s corporate policy regarding CFCs.

This was all thirty years ago. Ancient, pre-Internet history.

Now it may be back.

After years of collecting high-altitude data, a fellow by the name of Jim G. Anderson and his colleagues have published a paper, that may have du Pont thinking about getting into the sun-block business.

The observed presence of water vapor convectively injected deep into the stratosphere over the United States…

The paper’s abstract begins with what Anderrson & Co. have discovered: that large thunderstorms generate big enough updrafts to lift moist air into the normally arid lower stratosphere. Note carefully, they’re not talking about the south pole.

…can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere…

Uh-oh. The chemistry we were just discussing.

…by shifting total available inorganic chlorine into the catalytically active free-radical form…

Not what we wanted to hear!

Were the intensity and frequency of convective injection to increase as a result of climate forcing by the continued addition of CO2 and CH4 to the atmosphere…

In other words, if global warming is making thunderstorms bigger and more frequent…

…increased risk of ozone loss and associated increases in ultraviolet dosage would follow.

Great.

It’s a good paper, technical but with plenty of readable explanation. Might be a false alarm. Could be the canary in the coal mine. Interesting in its own right.

Not that there’s much we can do about it. Except wait 50 to 100 years for the CFCs already floating around up there to finally dissipate.

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