Ozone levels on the ground could increase by up to 70 percent by the year 2050, due to global climate change, a new study found.
High in the atmosphere, ozone (composed of three oxygen atoms per molecule) plays an essential role in blocking ultraviolet light generated by the sun from striking the ground and the life that flourishes on the surface. At ground level, however, the same gas is a major component in smog that can cause respiratory problems.
The National Center for Atmospheric Research (NCAR) conducted an extensive investigation of how rising temperatures could affect levels of hazardous ozone. They found the increased temperatures, combined with higher levels of atmospheric methane, could generate significant concentrations of ozone.
Research was conducted using cutting-edge computer software, running on advanced supercomputers.
The chemical process starts when nitrogen oxides and organic particles are emitted by power plants, and react together in the presence of sunlight.
Investigators ran a pair of computer simulations of future climatic conditions. In one model, these emissions continue at the present rate, while they are reduced by 60 to 70 percent in the second scenario. Both sets of conditions assumed similar levels of greenhouse gas emissions.
If left unchecked, researchers predict every region of the United States will experience at least a few days each summer with unhealthy air conditions. In cities where ozone layers are already high, the study suggests unfavorable air quality is on summer days. The most affected areas of the United States will include the East, Midwest and Pacific coast.
"It doesn't matter where you are in the United States - climate change has the potential to make your air worse. A warming planet doesn't just mean rising temperatures, it also means risking more summertime pollution and the health impacts that come with it," Gabriele Pfister, of the NCAR and the lead author of the article detailing the study, said.
Data from the study suggests that if the emission of certain pollutants is reduced or eliminated, the rise in ground-level ozone can be reduced. Without the reduction, the model predicts levels of ozone exceeding 75 parts per billion (ppb), right at the edge of what is currently considered unhealthy by the Environmental Protection Agency (EPA).
Increased temperatures increase the rate at which ozone is produced in the air. Plants also produce more volatile organic compounds in warm weather than they do during cooler conditions. These can produce additional ozone when combined with man-made pollutants. Methane also contributes to the production of hazardous ozone.
The study was funded by the National Science Foundation (NSF) and the United States Department of Energy.
Study of the role of global warming on ground-level ozone was published in the journal Journal of Geophysical Research-Atmospheres.
