No one paid Rowland and Molina much heed until 1985, when Joe Farman, a British researcher in Antarctica, discovered that part of the sky was missing. For decades, we’d been dissolving our UV screen by soaking it with chlorine. Since then, in unprecedented cooperation, the nations of the world have tried to phase out ozone-eating chemicals. The results are encouraging, but still mixed: Ozone destruction has slowed, but a black market in CFCs thrives, and some are still legally produced for “basic domestic needs” in developing countries. Even the replacements we commonly use today, hydrochlorofluorocarbons, HCFCs, are simply milder ozone-destroyers, scheduled to be phased out themselves—though the question of with what isn’t easily answered.
Quite apart from ozone damage, both HCFCs and CFCs—and their most common chlorine-free substitute, hydrofluorocarbons, HFCs—have many times the potential of carbon dioxide to exacerbate global warming. The use of all these alphabetical concoctions will stop, of course, if human activity does, but the damage we did to the sky may last a lot longer. The best current hope is that the South Pole’s hole, and the thinning of the ozone layer everywhere else, will heal by 2060, after destructive substances are exhausted. This assumes that something safe will have replaced them, and that we’ll have found ways to get rid of existing supplies that haven’t yet drifted skyward. Destroying something designed to be indestructible, however, turns out to be expensive, requiring sophisticated, energy-intensive tools such as argon plasma arcs and rotary kilns that aren’t readily available in much of the world.
As a result, especially in developing countries, millions of tons of CFCs are still used or linger in aging equipment, or are mothballed. If we vanish, millions of CFC and HCFC automobile air conditioners, and millions more domestic and commercial refrigerators, refrigerated trucks and railroad cars, as well as home and industry air-cooling units, will all finally crack and give up the chlorofluorocarbonated ghost of a 20th-century idea that went very awry.
All will rise to the stratosphere, and the convalescing ozone layer will suffer a relapse. Since it won’t happen all at once, with luck the illness will be chronic, not fatal. Otherwise, the plants and animals that remain in our wake will have to select for UV tolerance, or mutate their way through a barrage of electromagnetic radiation.
3. Tactical and Practical
Uranium-235, with a half-life of 704 million years, is a relatively insignificant fraction of natural uranium ore—barely .7 percent—but we humans have concentrated (“enriched”) several thousand tons of it for use in reactors and bombs. To do that, we extract it from uranium ore, usually by chemically converting it to a gas compound, then spinning it in a centrifuge to separate the different atomic weights. This leaves behind far less potent (“depleted”) U-238, whose half-life is 4.5 billion years: in the United States alone, there’s at least a half-million tons of it.
One approach to what to do with some of it involves the fact that U-238 is an unusually dense metal. In recent decades it has proved useful, when alloyed with steel, for fashioning bullets that can pierce armor, including the walls of tanks.
With so much surplus depleted uranium lying around, this is far cheaper for U.S. and European armies than buying the non-radioactive alternative, tungsten, which is mainly found in China. Depleted uranium projectiles range from 25-millimeter bullet size to three-foot-long, 120-millimeter darts with their own internal propellants and stabilizing fins. Their use kindles outrage over human health issues, on both the firing and receiving end. Because depleted uranium ordnance bursts into flames when it strikes, it leaves a pile of ash. Depleted or not, there’s enough concentrated U-238 in the bullet points that radioactivity in this debris can exceed 1,000 times the normal background level. After we’re gone, the next archaeologists to appear may unearth arsenals of several million of these super-dense, modern versions of Clovis spear points. Not only will they look considerably more fearsome, but—possibly unbeknownst to their discoverers—they’ll emit radiation for more years than the planet likely has left.