Climate 101: Ozone Depletion | National Geographic

Summary

The ozone layer, located in the stratosphere 15 to 35 kilometers above Earth, acts as a barrier against harmful UV radiation. Composed of ozone molecules, it absorbs about 98% of damaging UV light. However, pollutants like chlorofluorocarbons (CFCs) have caused the ozone layer to thin, leading to increased radiation exposure. CFCs, found in refrigerants, aerosols, and plastics, release chlorine when exposed to UV rays, which then depletes ozone. The Montreal Protocol of 1989 banned CFCs, and scientists expect the ozone layer to recover within 50 years.

Takeaways

• 🌍 15 to 35 kilometers above Earth's surface, a gas called ozone surrounds the planet.
• 🛡️ The ozone layer acts as a barrier between Earth and ultraviolet radiation from the Sun.
• 🌫️ Pollution has caused the ozone layer to thin, exposing life on Earth to dangerous radiation.
• 🌌 Earth's atmosphere is made up of six layers, with the second layer, the stratosphere, containing the ozone layer.
• 🔬 The ozone layer is made up of a highly reactive molecule called ozone, which contains three oxygen atoms.
• ⚖️ Ozone is a trace gas in the atmosphere, with only about three molecules for every 10 million molecules of air.
• ☀️ The ozone layer acts as Earth's sunscreen, absorbing about 98% of damaging ultraviolet or UV light.
• 📉 The ozone layer has gotten thinner primarily due to chemicals called chlorofluorocarbons (CFCs).
• ⚛️ CFCs are found in refrigerants, aerosols, and plastic products, and break down into chlorine when exposed to UV rays.
• ❄️ Areas of damage in the ozone layer are often called ozone holes, with the thinnest areas near the poles, especially above the Antarctic.
• 📉 About 90% of CFCs in the atmosphere were emitted by industrialized countries in the northern hemisphere.
• 📜 The 1989 Montreal Protocol banned the production of ozone-depleting substances.
• 📉 Since then, the amount of chlorine and other ozone-depleting elements in the atmosphere has been falling.
• 🔄 Scientists estimate that chlorine levels will return to their natural state in about 50 years.
• ❄️ By then, the Antarctic ozone hole will shrink to smaller than eight million square miles.

Q & A

What is the role of the ozone layer in Earth's atmosphere?

The ozone layer acts as a barrier between Earth and ultraviolet radiation from the Sun, absorbing about 98% of damaging ultraviolet or UV light, effectively acting as Earth's sunscreen.

Where is the ozone layer located in Earth's atmosphere?

The ozone layer is located in the second layer of Earth's atmosphere, called the stratosphere, which is 15 to 35 kilometers above Earth's surface.

What is the composition of the ozone molecule?

The ozone molecule is a highly reactive molecule that contains three oxygen atoms.

How prevalent is ozone in the atmosphere?

Ozone is a trace gas in the atmosphere, with only about three molecules of ozone for every 10 million molecules of air.

What causes the ozone layer to thin?

Pollution, specifically chemicals called chlorofluorocarbons (CFCs), causes the ozone layer to thin. When CFCs are exposed to ultraviolet rays in the atmosphere, they break down into substances that include chlorine, which reacts with ozone and breaks it apart.

What are chlorofluorocarbons (CFCs) and where are they commonly found?

Chlorofluorocarbons (CFCs) are molecules that contain carbon, chlorine, and fluorine. They are commonly found in refrigerants, aerosols, and plastic products.

Why is the term 'ozone hole' misleading?

The term 'ozone hole' is misleading because it suggests a complete absence of ozone. In reality, ozone layer damage is more like a thin patch, with the thinnest areas near the poles.

Why is the ozone layer above the Antarctic particularly affected by pollution?

The ozone layer above the Antarctic is particularly affected by pollution because the region's low temperatures speed up the conversion of CFCs to ozone-damaging chlorine.

What percentage of CFCs in the atmosphere were emitted by industrialized countries in the northern hemisphere?

About 90% of CFCs currently in the atmosphere were emitted by industrialized countries in the northern hemisphere.

What international agreement helped to reduce the production of ozone-depleting substances?

The Montreal Protocol, which was established in 1989, banned the production of ozone-depleting substances, leading to a decrease in the amount of chlorine and other ozone-depleting elements in the atmosphere.

When do scientists estimate that chlorine levels in the atmosphere will return to their natural state?

Scientists estimate that chlorine levels in the atmosphere will return to their natural state in about 50 years, by which time the Antarctic ozone hole will shrink to smaller than eight million square miles.