World Ozone Day 2024: Safeguarding Earth's protective shield and why it's important

Ozone Day 2024: CFCs are greenhouse gases and have been studied to contribute to ozone depletion.

Today marks World Ozone Day, observed globally to raise awareness about the importance of protecting the ozone layer and recognise the milestones achieved in safeguarding this vital atmospheric shield. Established by the United Nations in 1994, the day commemorates the signing of the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987.

The ozone layer, located in the Earth's stratosphere, plays a crucial role in shielding life on the planet from the harmful ultraviolet (UV) radiation of the sun. However, in the 1970s, scientists discovered that human-made chemicals, such as chlorofluorocarbons (CFCs), were causing significant damage to the ozone, leading to the infamous "ozone hole" over Antarctica.

Layers of the Atmosphere

The Earth's atmosphere is divided into five main layers, each with distinct characteristics:

1. Troposphere:
- Extends from the Earth's surface to about 8-15 km in altitude.
- The lowest and densest layer where weather phenomena like clouds, storms, and rain occur.
- Contains most of the atmosphere's water vapor and oxygen.

2. Stratosphere:
- Lies above the troposphere, extending from about 15 km to 50 km in altitude.
- Contains the ozone layer, which absorbs and scatters UV radiation.
- Temperature increases with altitude due to ozone absorption of solar energy.

3. Mesosphere:
- Extends from about 50 km to 85 km.
- This is the coldest layer of the atmosphere, with temperatures dropping as low as -90°C.
- Meteors burn up in this layer due to friction with air molecules.

4. Thermosphere:
- Extends from about 85 km to 600 km.
- Temperatures rise significantly due to the absorption of high-energy solar radiation.
- The thermosphere contains the ionosphere, which is critical for radio communication and auroras.

5. Exosphere:
- The outermost layer, starting at around 600 km and extending into space.
- The air is extremely thin, and particles can escape into space.
- Satellites orbit within this layer.

Main Sources of CFCs Leading to Ozone Depletion

Chlorofluorocarbons (CFCs) and other ozone-depleting substances were widely used before their harmful effects were understood. Some of the primary sources of CFCs include:

1. Refrigerants:
- CFCs were commonly used in air conditioners, refrigerators, and freezers.
- When these appliances leaked or were improperly disposed of, CFCs were released into the atmosphere.

2. Aerosol Sprays:
- CFCs were used as propellants in aerosol products like hairsprays, deodorants, and household cleaners before alternatives were introduced.

3. Foam-Blowing Agents:
- CFCs were used in the production of foam products, such as insulation materials, packaging foams, and furniture cushions.

4. Solvents:
- CFCs were used as solvents in industrial processes, including the cleaning of electronic components and machinery.

5. Fire Extinguishers:
- Halons, which also contribute to ozone depletion, were commonly used in fire extinguishers, particularly for fires in electrical equipment.

Though the use of CFCs and other ozone-depleting substances has been largely phased out under the Montreal Protocol, their long atmospheric lifetimes mean that they will continue to impact the ozone layer for years to come.

How Does the Ozone Layer Deplete?

The ozone layer, located in the Earth's stratosphere, acts as a protective shield, absorbing the majority of the sun's harmful ultraviolet (UV) radiation. However, human-made chemicals, particularly chlorofluorocarbons (CFCs), are responsible for its depletion.

The process of ozone depletion occurs in the following steps:

1. Release of CFCs and Other Ozone-Depleting Substances (ODS): CFCs, halons, and other ozone-depleting chemicals are released into the atmosphere through human activities, such as industrial processes, refrigerants, and aerosol sprays.

2. Breakdown by UV Radiation: Once CFCs reach the stratosphere, they are broken down by UV radiation, releasing chlorine and bromine atoms.

3. Ozone Destruction: The released chlorine and bromine atoms react with ozone (O₃) molecules, breaking them apart into oxygen molecules (O₂) and individual oxygen atoms (O). This diminishes the concentration of ozone in the stratosphere.

4. Chain Reaction: One chlorine atom can destroy thousands of ozone molecules through a chain reaction, further depleting the ozone layer.

This thinning of the ozone layer, particularly over the polar regions, created the infamous "ozone hole," especially over Antarctica.

Montreal Protocol

Since its adoption, the Montreal Protocol has been hailed as one of the most successful environmental treaties in history. The global community came together to phase out nearly 99% of ozone-depleting substances (ODS), resulting in a remarkable recovery of the ozone layer. Scientists have predicted that the layer could return to its pre-1980 levels by the middle of this century, provided current efforts are maintained.

Significance

One key area of concern is the intersection between ozone protection and climate change. While the Montreal Protocol has been successful in curbing the release of ODS, many of these substances were replaced by hydrofluorocarbons (HFCs), potent greenhouse gases that contribute to global warming. In 2016, the Kigali Amendment to the Montreal Protocol was adopted to phase down HFCs, offering a critical step in mitigating climate change.

India, a major signatory of the Montreal Protocol and its amendments, has made significant strides in phasing out harmful substances. However, environmentalists stress that more needs to be done to transition to cleaner alternatives and reduce overall emissions.

2024 Theme

In India, the Ministry of Environment, Forest and Climate Change organised an event to mark the 30th World Ozone Day in New Delhi last week. The theme for World Ozone Day 2024 is “Montreal Protocol: Advancing Climate Actions” reflecting the Montreal Protocol's crucial role in both protecting the ozone layer and driving broader climate action initiatives globally. Leena Nandan, Union Secretary of the Ministry of Environment, Forest and Climate Change presided over the event.

Future
Experts warn that complacency could reverse the gains made over the past few decades. To ensure the long-term health of the ozone layer, countries must adhere to their commitments under the Montreal Protocol and Kigali Amendment, while also tackling related environmental challenges.