Stratospheric ozone depletion

The ozone layer in the upper atmosphere protects the Earth from harmful solar ultraviolet radiation. Additionally, ozone plays an important role in atmospheric energy balance. Because of the release of ozone depleting substances (ODS), the ozone layer has substantially declined over the second half of the 20th century.

Since the mid-1990s, thanks to the international agreements limiting ODS release, the ozone layer has largely recovered, and it is expected to stay within the safe limits. The ozone layer depletion and its subsequent recovery had measurable effects on atmospheric circulation, particularly in the Southern Hemisphere.

Control variables

The Planetary Boundary for Stratospheric Ozone Depletion tracks the amount of ozone (O₃) in the upper atmosphere, where it forms a protective layer that blocks most of the Sun’s harmful ultraviolet (UV) radiation. Thanks to the Montreal Protocol, which phased out ozone-depleting chemicals like CFCs, the ozone layer has been recovering. Overall, it remains within the safe zone, but the recovery is uneven and still vulnerable. New pressures are emerging from rising nitrous oxide (N₂O) emissions and increasing space activity, both of which could slow or even reverse the gains made over the past decades.

Impacts

A thinner ozone layer means more UV radiation reaches the ground. This affects people, ecosystems, and even weather patterns. While the most dramatic ozone hole over Antarctica is slowly closing, the ozone layer’s health remains essential for life and climate stability.

More UV radiation and health risks

When ozone levels drop, the Earth’s surface gets more intense UV radiation. This raises the risk of skin cancer, cataracts, and other health problems in people, and it can also harm animals and microscopic life.

Ecosystem damage on land and at sea

Extra UV light can reduce crop yields, weaken trees, and damage tiny marine organisms called phytoplankton that form the base of ocean food webs. These changes ripple through ecosystems, affecting biodiversity and food production.

Shifts in weather and wind patterns

Ozone loss over Antarctica cooled the air above the South Pole, strengthening the polar vortex and shifting southern wind belts farther toward the pole. This changed rainfall patterns in parts of the Southern Hemisphere. As the ozone layer has slowly recovered since 2000, these effects have started to ease.

Key drivers

Ozone-depleting chemicals (CFCs)

CFCs were once widely used in refrigerators, aerosols, and fire-fighting systems. They break down in the upper atmosphere, releasing chlorine that destroys ozone. Although now largely banned, these chemicals remain in the air for decades, continuing to cause some depletion.

Nitrous oxide from agriculture

Today, nitrous oxide (N₂O) is the main human-made gas still depleting ozone. It comes mostly from fertilizers and animal waste on farms. Once it reaches the stratosphere, it breaks apart and reacts with ozone, reducing its concentration.

Growing space and industrial activity

Rocket launches and re-entering debris can release ozone-damaging gases high in the atmosphere. Some new industrial chemicals that replaced CFCs also have uncertain long-term effects. Monitoring these emerging sources is becoming increasingly important.