Energy > Climate Change
February 2022
The role of ozone in global warming
This article is the twelfth in a series focused on the causes and consequences of a warming planet
Ozone is a modest greenhouse gas. It accumulated in significant concentrations in two regions of the atmosphere: at ground level (bad ozone) and stratospheric (good ozone). Ground level ozone comes from motor vehicle exhaust, gasoline vapors, industrial facility emissions, and other sources. Breathing ozone can also cause a variety of health problems.
Stratospheric ozone, the good ozone, occurs naturally and forms a protective layer that shields us from the sun’s harmful ultraviolet rays. You can think of stratospheric ozone as Earth’s "sunscreen".
Remember the hole in the ozone layer over Antarctica? It caused great concern that stratospheric ozone depletion would allow more ultraviolet rays from the sun to reach the Earth, leading to greatly increased incidences of human skin cancer and damage to many sensitive micro-organisms.
Researchers found that certain substances such as chlorofluorocarbons, when emitted into the atmosphere, were destroying stratospheric ozone. Chlorofluorocarbons are man-made substances developed for a variety of uses including refrigerants in air conditioning (Freon).
In 1987, an international treaty called the Montreal Protocol was created to protect the ozone layer by phasing out ozone depleting substances like chlorofluorocarbons. Signed by 197 countries, it is the first treaty in the history of the United Nations to achieve universal ratification.
Hydrofluorocarbons, substances that don’t destroy ozone, have been replacing ozone depleting substances. However, hydrofluorocarbons are powerful and long-lasting greenhouse gases. They are over 3000 times more potent than carbon dioxide. Although the concentration of hydrofluorocarbons in the atmosphere is very small, it does have a global warming impact.
To meet this new challenge, the parties to the Montreal Protocol adopted an amendment that is paving the way for the phase down of hydrofluorocarbons by using other substances. The phase down of hydrofluorocarbons is expected to avoid almost 1 degree Fahrenheit of global temperature rise by 2100.
With the elimination of ozone depleting substances, atmospheric ozone will gradually increase and the hole in the ozone will eventually disappear. Although ozone is a mild greenhouse gas, the ultraviolet shielding value of good ozone will more than offsets its negative impact on global warming.
See the Ag Decision Maker website for more from this series.
Don Hofstrand, retired extension agricultural business specialist, agdm@iastate.edu
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University
