The Ozone Layer

Written by Kaho Ishihara

Why is the Ozone Layer Important?

The thinning of the ozone layer has been a major global concern since the early 1980s. This is because, as is widely known, the ozone layer serves as a critical barrier in the stratosphere, preventing harmful ultraviolet radiation from the Sun from reaching the Earth’s surface. It effectively blocks 97% to 99% of the UV-B radiation. Without the ozone layer, organisms on Earth would face catastrophic consequences. For example, DNA and cells would be damaged, interfering with photosynthesis in plants and inducing the collapse of food chains. For humans specifically, it would lead to health risks such as increasing rates of skin cancer.

Good vs Bad Ozone

The protective barrier that ozone forms is the ozone layer, located in the stratosphere, about 10 to 30 miles above Earth. In contrast, ozone in the troposphere, at the ground level, harms the environment and negatively impacts our health. Tropospheric ozone is mostly formed from emissions from cars, power plants, and industrial factories, which react with ultraviolet light to form ozone.

What are Ozone Depleting Substances?

Ozone-depleting substances (ODSs) are human-made chemicals, such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Historically, these substances are most commonly found in refrigerators, air conditioners, aerosol sprays, and fire extinguishers. When these ODSs enter the stratosphere, they are broken down by UV radiation, releasing highly reactive atoms that destroy ozone molecules. This destruction happens faster than it is naturally replenished through the Chapman Cycle, leading to the thinning or holes in the ozone layer. 

The Antarctic Ozone Hole

The most prominent ozone hole is located over Antarctica, which grows in size especially from September to October. This is due to the cold stratospheric temperatures that facilitate chemical reactions that destroy ozone molecules.

The Montreal Protocol (1987)

The Montreal Protocol is a global agreement that regulates the production and consumption of ODSs. The cooperation among 197 countries has allowed this protocol to become one of the most successful environmental actions.

Good News!

A recent study led by MIT has announced that the Antarctic ozone layer is beginning to heal due to the successful global reduction of ozone-depleting substances. The World Meteorological Organization suggests that if these efforts continue, the ozone layer could recover completely by around 2066.