The dramatic discovery of the stratospheric ozone hole has eclipsed attention to ozone increases in the troposphere, the lowest layer of the atmosphere beginning at the Earth's surface. But tropospheric ozone got equal billing with the stratosphere at a recent international symposium, suggesting that tropospheric issues have come into their own.

“Only in the past decade or so has tropospheric ozone become an important scientific concern,” said Henry Reichle of Langley Research Center. Historically, the Quadrennial Ozone Symposium, begun in 1927, dealt only with the stratosphere. But tropospheric studies shared the limelight at this year's meeting, held June 4–13 at the University of Virginia in Charlottesville. “Now we understand that tropospheric ozone can have an impact on a larger scale, not just locally,” Reichle said.