Scary autumn tales about the Antarctic ozone “hole” have become an annual media ritual that treats the phenomenon of ozone thinning as an ominous threat to human health and the environment. Thus far, 2001 is proving to be no exception. A recent NASA press release announced that “this year's Antarctic ozone hole peaked at about 26 million square kilometers — roughly twice the size of North America,” and warned that ozone loss “contributes to skin cancer and cataracts in humans.” Indeed, Al Gore's bestseller Earth In The Balance claims that due to the ozone hole, “hunters [in Patagonia] now report finding blind rabbits; fishermen catch blind salmon.” Such terrifying claims have been repeated so often that most people think they have been scientifically proven. But what is really going on? It is true that the ozone layer — a concentration of ozone molecules in the stratosphere — protects the earth from excessive ultraviolet-B radiation (UVB). And scientists agree that the ozone layer thins by 50 percent or more above the Antarctic region between September and November, before reverting back to normal. This annual occurrence — termed the Antarctic “ozone hole” — results in a temporary increase in UVB reaching ground level in that region. And most scientists also agree that chlorofluorocarbons (CFCs, a once-widely used class of refrigerants) and other man-made compounds are responsible for furnishing stratospheric chlorine, one of the ingredients that can lead to a breakdown of ozone molecules. But from these acorns of scientific truth, mighty oaks of costly nonsense have developed. The one published study that has actually attempted to document the effects of Antarctic ozone thinning on people and animals comes from a team of Johns Hopkins University researchers. In the mid-1990s, they traveled to Punta Arenas, Chile, the largest city in the vicinity of the ozone hole to study the effects of ozone thinning. After studying local medical and veterinary records, the researchers concluded that there is absolutely no truth to many of the claims made about health hazards attributed to temporary ozone depletion. “The lack of observed adverse health effects is consistent with our estimation of an excess annual UVB exposure in the region of 1 percent,” the 1995 study said, and “the cumulative UVB exposure in Punta Arenas, even within the context of an ozone hole, is exceeded by that in many temperate climates and is far surpassed by that in tropical locations.” Despite an absence of “adverse health effects,” ozone alarmism eventually led the U.S. and other countries to ban the use of CFCs. Although this ban is probably irreversible, there still are valuable lessons to be learned before far costlier policy mistakes are made. For example, concerns about global warming are peddled in a remarkably similar manner today, as proponents of radical reductions in energy use try to generate public support for restrictions on the emissions of carbon dioxide and other so-called greenhouse gases. Indeed, these fears form the backdrop for the current conference underway in Marrakech, Morocco, as nations meet for another round of discussions to hammer out the specifics of the Kyoto Protocol, the 1997 treaty on greenhouse gas emissions. If our experience with the ozone scare is any guide, a healthy dose of scientific skepticism is justified.