
Ozone levels across Northern Hemisphere have been rising for 20 years
Aug. 21 (UPI) -- While emission levels for ozone-forming chemicals have fallen in some North American cities, new research suggests tropospheric ozone levels have increased across the Northern Hemisphere over the last 20 years. In the upper layers of the atmosphere, the ozone layer helps protect Earth and its inhabitants from harmful ultraviolet radiation. Advertisement But closer to Earth's surface, ozone causes problems. In addition to accelerating climate change, the greenhouse gas can harm people's lungs and damage plants. "Ozone is a secondary gas, which means that it is not directly emitted," lead researcher Audrey Gaudel, a scientist with the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, told UPI in an email. "It is formed photochemica...