At ground level ozone is a potent pollutant and greenhouse gas. But on the edge of space, the ozone layer is the earth's sunscreen. It's no coincidence that life crept out of the primeval ocean only after that natural sunblock formed over half a billion years ago. Back then the bare surface of early earth was cooked by the equivalent of an industrial UV tanning light all day long. If the harsh UV were let through again today, forests, grasslands, and commercial crops would wither and die. Phytoplankton, the key fundamental link for much of the planet's food chain, would crash. The direct and indirect effect on our modern civilization would be immediate and catastrophic.

Chloro-fluorocarbons (CFCs) were developed in the early 20th century as an alternative to refrigerants like ammonia or sulfur dioxide. CFCs, like freon, were a huge commercial success in part because, unlike their toxic and corrosive counterparts, they were almost wholly inert. A person could inhale them by the bucketful with no ill effects. But once in the ozone layer, CFCs break apart, and the now free, reactive chlorine or fluorine particles become a catalyst capable of breaking down an unlimited number of ozone molecules. Fortunately, scientists discovered the danger posed by CFCs, and policy makers moved quickly to address it. Now, a new study by NASA suggests that that effort may have averted disaster:

Led by NASA Goddard scientist Paul Newman, a team of atmospheric chemists simulated 'what might have been' if chlorofluorocarbons (CFCs) and similar ozone-depleting chemicals were not banned through the Montreal Protocol.

The scary part? According to this projection, had the world paid heed to clowns like Tom DeLay or Rush Limbaugh who blabbed on about the 'ozone depletion myth,' this grim scenario would not just be something for our great-grandchildren to worry about. It could be happening now.