Scientists know that ozone can be both bad and good for us. Ozone is a pollutant in the lower atmosphere, or troposphere, the atmospheric layer nearest the ground. However, in the stratosphere, approximately 6 to 11 miles above Earth’s surface, ozone plays a critical role, protecting us from the Sun’s harmful ultraviolet radiation.

The "ozone layer," located in the stratosphere, contains 90% of Earth’s ozone and is beneficial to us because it absorbs ultraviolet (UV) radiation from the Sun. Ultraviolet rays can damage living things and increase rates of skin cancer and cataracts in humans. By blocking most of the ultraviolet radiation before it reaches the Earth's surface, the stratospheric ozone layer is critical to our survival.

British Antarctic Survey researchers first noticed the loss of ozone in the stratosphere during the 1970s.

Chemicals produced by humans, including chlorofluorocarbons (CFCs) once used in refrigeration and as propellants in spray cans, have damaged the ozone layer by releasing chlorine and bromine into the atmosphere. These chemicals prevent the formation of ozone, which creates “ozone holes." A diminished ozone layer allows more UV rays to reach Earth’s surface.

Scientists continue to study the ozone layer and ozone holes using satellite and ground-based data. To protect the ozone layer, many countries including the U.S. have signed an international treaty, The Montreal Protocol on Substances that Deplete the Ozone Layer, to reduce the amount of CFCs in the atmosphere. While the ozone hole over Antarctica continues to open and close, the ozone layer around the rest of the planet seems to be mending. Emissions of ozone-depleting substances are falling and predictions are that the ozone layer will recover by 2050. Even though the ozone hole and global warming are different problems, the ozone hole recovery may be affected by increases in the primary greenhouse gases, such as CO₂.

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