By Girish Linganna
The ozone layer is vital for life on Earth because it shields us from harmful ultraviolet rays emitted by the Sun. Without it, living organisms would be at risk of getting seriously harmed. However, our ozone layer does have a significant flaw.
The crucial ozone layer is located in the stratosphere, located in the upper atmosphere (around 10-50 km above Earth’s surface). This protective layer, primarily found in the lower portion of the stratosphere (around 20-25 km above sea level), contains about 90% of Earth’s ozone.
The ozone in Earth’s stratosphere is formed when ultraviolet light hits oxygen molecules that have two oxygen atoms (O2). This causes the oxygen molecules to split apart into individual oxygen atoms, which then combine with other intact, or unbroken, O2 molecules to create ozone (O3).
The ozone molecule, while stable in the stratosphere for a long time, becomes unstable when exposed to ultraviolet light. This causes it to break apart into an oxygen molecule (O2) and a single oxygen atom (atomic oxygen). This is the ozone-oxygen cycle, and it keeps on generating, and maintaining, the stratosphere’s ozone layer.
If all the ozone in the atmosphere were compressed to sea-level pressure, it would form only a few-millimetre thick layer.
Ozone: Safeguarding Against Harmful UV
Even though the amount of ozone in the ozone layer is quite minimal, its significance to life cannot be overstated. This layer plays a crucial role in absorbing 93-99 per cent of the harmful ultraviolet (UV) radiation emitted by the Sun, which can have detrimental effects on living organisms.
UV radiation is classified into three types—UV-A, UV-B and UV-C, depending upon their wavelengths. Here is a simplified explanation:
UV-A: A wavelength range of 400-315 nm
UV-B: A wavelength range of 315-280 nm
UV-C: A wavelength range of 280-100 nm
To protect us, the ozone layer serves as a shield against harmful UV radiation. Here are some key points:
UV-C radiation, with the shortest wavelength and the highest level of harm to humans, is completely blocked by the ozone layer
The ozone layer acts as a defence mechanism against UV-B radiation by absorbing a significant portion of it
UV-A radiation, although less harmful, is not entirely eliminated by the ozone layer and reaches Earth’s surface
In simple terms, the ozone layer acts as a protective barrier against the most dangerous UV-C radiation, while also reducing the amount of harmful UV-B radiation that reaches us. UV-B radiation poses a risk to our skin and is primarily responsible for sunburn. If we get exposed to excessive amounts of UV-B radiation, it can lead to genetic damage, potentially resulting in such conditions as skin cancer.
Ozone Discovery: Chemicals & Destruction
During the 1980s, scientists studying solar radiation in Antarctica made a startling discovery. They found a hole in Earth’s ozone layer caused by a combination of human-produced chemicals mixing with ozone molecules and causing their destruction.
The main culprits behind the damage to the ozone layer were a group of chemicals known as chlorofluorocarbons (CFCs). In the 1980s, CFCs were prevalent in many kinds of industries, mostly as refrigerants.
Fortunately, the global community took notice of the issue. In 1987, just two years after the research findings in Antarctica were made public, world leaders gathered in Montreal, Canada, and signed a treaty, called the Montreal Protocol. This historic agreement aimed to eliminate the use of ozone-depleting chemicals gradually, especially harmful chlorofluorocarbons (CFCs). The Montreal Protocol is widely recognized as the most successful environmental treaty ever established.
After four decades, recent research has raised concerns that human activities could threaten the progress made in protecting the ozone layer. While the healing process is not yet complete, there is hope that we are headed in the right direction.
In 2022, a significant achievement was reached in terms of ozone recovery. The concentration of ozone-depleting substances in the mid-latitude stratosphere returned to levels recorded in 1980. This positive development was described by the US National Oceanographic and Atmospheric Administration as “gradual, yet consistent progress”.
According to BBC Science, experts monitoring the annual formation of the ozone hole over Antarctica recently uncovered a new setback in ozone preservation. Every year, a region of significant ozone depletion forms over the polar continent due to specific chemical reactions that take place in extremely low temperatures and high atmospheric clouds. These reactions result in the breakdown of ozone, causing a substantial thinning of the ozone layer.
The formation, and disappearance, of the ozone hole follow a seasonal pattern, with peak occurrences typically observed in September and October. Thankfully, during these months, most land-based plants and animals are sheltered beneath snow cover, while many marine animals are shielded by sea ice. However, in recent times, there has been a trend of concern where the ozone hole persists until December, extending well into the Antarctic summer. This poses a greater risk to the vulnerability of plants and animals during a time when they are typically more exposed.
According to reports by experts, climate change scientist Professor Sharon Robinson from the University of Wollongong has emphasized that the prolonged existence of the ozone hole in December leads to the Antarctic continent being exposed to levels of ultraviolet (UV) radiation similar to a sunny summer day in Sydney, Australia. This elevated UV radiation exposure is regarded as extremely severe and a matter of concern. The start of summer is a critical period for many animal species as it marks the peak of their breeding season. Consequently, this stage of their lifecycle is especially vulnerable to the increased UV radiation during that time.
Similar to how we protect ourselves from the harmful effects of the Sun’s ultraviolet rays using sun-block and sunglasses to reduce the risk of skin cancer and cataracts, scientists studying UV radiation in Antarctica suggest that the same concerns may apply to the mammals and birds living on the polar continent. These animals may also be at risk from the damaging effects of UV radiation and could benefit from protective measures.
While creatures with fur and feathers enjoy natural protection for their skin, scientists believe the most significant risk to Antarctic animals lies in potential eye damage. Exposure to high levels of UV radiation poses a particular threat to their eyes, making protective measures crucial for the well-being of these animals.
Factors that help Formation of Ozone Hole
The prolonged period of ozone depletion, which poses a significant threat, can be attributed to one primary factor: Climate Change. The devastating wildfires that occurred in Australia from 2019 to 2020, intensified by severe global warming, released vast amounts of particles into the atmosphere. These particles triggered reactions that further depleted the ozone layer, exacerbating the damage caused historically. This connection between climate change, wildfires and ozone depletion underscores the urgent need for addressing and mitigating the effects of global warming to protect our ozone layer.
Ironically, certain proposed methods for climate cooling—known as geo-engineering techniques—suggest the release of sulphate particles into the upper atmosphere to create artificial clouds. However, this approach would also contribute to ozone depletion. Climate change researcher Prof. Sharon Robinson has aptly described this as a “bad idea”. These findings highlight the need for careful consideration and evaluation of any potential strategies or interventions, ensuring they do not inadvertently harm the ozone layer while attempting to address the challenges posed by climate change.
It is crucial not to become complacent when it comes to recovery of the ozone layer. The most significant action we can take to benefit Antarctica—as well as ourselves—is to address climate change and urgently reduce carbon emissions. By acting swiftly and decisively to cut down on our carbon footprint, we can contribute to safeguarding both the ozone layer and the delicate ecological balance of Antarctica. It is imperative we prioritize collective efforts in combating climate change for the sake of our planet and its vulnerable ecosystems.
The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru.
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