One of the problems with ozone is that we don't understand how the UV-B is changing at ground level, and what fraction of the ultraviolet light really causes cancer. Happer's cautious testimony was at odds with Gore's alarmist views. Gore predicts that ozone depletion will damage crops and raise skin-cancer rates. Gore's expectation is superficially plausible. Stratospheric ozone stops much of the sun's ultraviolet-B light from reaching the earth's surface, where excessive amounts can harm plants and animals.
Sunburn is the type of UV damage with which most people are familiar.
And recent satellite data indicate that ozone declined by 3 percent to 5 percent over the United States between 1979 and 1991. But such a small decrease is hard to extract from the satellite data, since ozone levels vary widely depending upon seasons, latitude, and sunspot activity. For example, the amount of UV naturally reaching the ground in Florida is twice as great as that in Minnesota. Few people worry about moving from Philadelphia south to Baltimore because of the resulting increase in UV-B exposure. In any case, if stratospheric ozone is declining, more UV-B sunlight should be reaching the earth's surface.