Ozone Depletion

Ozone Depletion:

Ozone is a gas that exists naturally in our atmosphere. It is most heavily concentrated in a region of the atmosphere that scientists refer to as the ozone layer, and its function is to absorb the Sun’s ultraviolet radiation before it reaches the earth’s surface, protecting both us as well as all other living things from the sun’s harmful ultraviolet rays. In this way the ozone layer acts as a shield, making life possible on our planet by absorbing the ultraviolet rays, and keeping them from doing damage to the life thriving on the Earth’s surface. In a way, the effect of the ozone layer is the opposite of the greenhouse effect: while the greenhouse effect holds energy and heat in, keeping the Earth’s temperature warm, (in the case of global warming, potentially too warm), the function of the ozone layer is that it blocks something out, namely,-ultraviolet radiation. It filters it and blocks harmful ultraviolet radiation from reaching the planet’s surface.

The Hole in the Ozone Layer

What do experts mean when they refer to a hole in the ozone layer? The significance of ozone in maintaining life on our planet makes it critically important to address this phenomenon. A hole can occur in the ozone because the layer varies in its density around the globe, with its density being the thinnest at the north and south pole. As a result, when the ozone layer is damaged and becomes too thin, the damage shows up first and is most noticeable at the poles. This ozone depletion is what scientists refer to as the “hole in the ozone layer”. Ozone depletion has generated worldwide concern over the increased risk of cancer and other negative side effects that can result from when too much of the sun’s ultraviolet radiation reaches the planet surface.

“The Ozone layer protects humans, plants, and wildlife from the sun’s harmful ultraviolet radiation…”


Under normal circumstances, a healthy ozone layer prevents most harmful UV wavelengths of ultraviolet light (UV light) from reaching the Earth’s surface. These wavelengths have been linked to skin cancer, sunburn, and cataracts in humans, all of which have been projected to increase as a result of thinning ozone, not to mention the harming of plants and animals. Without the ozone layer, humans would also be susceptible to damage to our genetic and immune systems as well. Fortunately in 1974, two researchers pinned down the damage to the ozone layer to one major human activity. Chemists Mario Molina and F. Sherwood Rowland of the University of California at Irvine recognized that human-produced chlorofluorocarbons were a major source of damage to the ozone layer. Ozone depletion occurs when chlorofluorocarbons, (at the time found primarily in aerosol spray cans and refrigerants), get released into the atmosphere, causing chemical reactions that break down the ozone layer and reduce its radiation-absorbing capacity.

The Montreal Protocol

As a result of this research, the Montreal Protocol was ratified in 1987, the first of several comprehensive international agreements enacted to halt the production and use of ozone-depleting chemicals. The ban came into effect in 1989. Since then, while the recovery has been slow, ozone levels reportedly stabilized by the mid-1990s, and then began to recover in the 2000s. In 2019, NASA announced that the “ozone hole” over Antarctica was the smallest it has ever been since it was first discovered in 1982. This gradual process of recovery is projected to continue over the next century. If progress continues it would make the Montreal Protocol one of the most successful international environmental agreements of all time, engendering hope for a future where the environmental law students of today can participate in negotiating and implementing ecologically sound international agreements in the future.

References and Resources:

The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which damages DNA in plants and animals (including humans) and leads to sunburns and skin cancer. (NASA).

Climate Prediction Center’s Stratosphere Home Page

NOAA organization’s UV Index forecasts and maps of stratospheric ozone depletion, daily hemispheric ozone, and stratospheric temperature time series.

The Centre for Atmospheric Science is a joint venture within the University of Cambridge between the University Departments of Chemistry, Applied Mathematics and Theoretical Physics and Geography. Post-doctoral researchers and students from the UK and abroad carry out world-leading research with international collaborations.

Ozone (O3) depletion does not cause global warming, but both of these environmental problems have a common cause: human activities that release pollutants into the atmosphere altering it. Article from the Union of Concerned Scientists.

Despite a ban on chemicals like chlorofluorocarbons, the ozone hole over Antarctica remains nearly as large as it did when the Montreal Protocol was signed in 1987. Scientists now warn of new threats to the ozone layer,.. (YaleEnvironment360).