The ozone layer is no longer disappearing. Depletion of stratospheric ozone, which defends the planet from harmful levels of ultraviolet rays, was first detected 25 years ago and stems mostly from industrial pollutants, especially chlorofluorocarbons. Atmospheric scientists analyzed data on the entire ozone layer from satellites and ground stations and found ozone level decline plateaued between 1996 and 2002. The ozone layer has even increased a small amount in parts of the Northern Hemisphere, including much of the area over North America, Europe and Asia. Study co-author Betsy Weatherhead of the University of Colorado at Boulder says that more recent data, through this past August, “absolutely are in agreement with the general conclusions of the paper,” which appears in the August 31 Journal of Geophysical Research. Overall, however, ozone will remain seriously depleted worldwide, especially at the poles, because ozonedestroying chemicals persist in the atmosphere for decades.