Ground-Level Ozone Trends: Facts vs. Fantasy

Growing plants absorb some of the carbon dioxide emitted by human burning of fossil fuels for energy. However, according to a new study in the journal Nature , groundlevel ozone (AKA “smog”) will rise during the 21st Century and stunt plant growth. This will reduce CO2 uptake by vegetation, exacerbating CO2-induced greenhouse warming.

The study, which was performed by Stephen Sitch and colleagues from England’s Hadley Centre for Climate Change Research, is based on computer modeling of current and future ozone levels. To project future emissions of greenhouse gases and air pollutants, Sitch et al. relied upon the Intergovernmental Panel on Climate Change’s (IPCC) A2 scenario. The scenario includes projections of population, economic activity, energy use, and other factors that determined future emissions.

Unfortunately, comparison of Sitch et al.’s model results with actual trends in ozone and ozone-forming pollutants show that their study has nothing to do with reality. Sitch et al. conclude ozone will rise all over the world during the 21st Century. In reality, ozone levels have been dropping for decades in wealthy countries and will continue to do so. And while ozone will probably rise for a few decades in developing countries, these countries will reduce their ozone levels as they become wealthy enough to afford the necessary pollution controls—exactly as has already happened in the U.S. and Europe. Sitch et al. not only get the trends wrong. They also overstate actual ozone levels by a large margin.