By Maitphang Syiem
Starting with an amusing note from what actor, wrestler John Cena says, “Sunscreen you can’t see,” literally reminds us how important it is to protect our skin and generally speaking sunscreen with various SPF categories have become inevitable for any outdoor activities. However, diving deeper, the aforementioned catchphrase literally reminds us of a natural phenomena (Chapman Cycle) not visible to our naked eyes which requires a deep scientific thought to understand its importance. This cycle is vital for the present and future generation, else sustaining life on this Earth will be difficult.
Dear readers, by this time you must have gained something from the cues mentioned. Can you guess what it is? Yes, friends it’s the ozone layer, the Earth’s natural sunscreen protecting us from the harmful UV rays of the Sun. September 16, is always commemorated as the international day for the preservation of the ozone layer with this year’s theme “From Science to Global Action” to emphasizes on the critical role of the ozone layer in sustaining life on this planet, highlighting the commitment to eliminate those substances which deplete the ozone layer through the Montreal Protocol which was adopted on the September 16, 1987 and enforced on January 1, 1989. As we commemorate World Ozone Day 2025 with the theme “From Science to Global Action,” the theme reminds us of humanity’s remarkable environmental success stories that span from a Swiss chemist’s curious laboratory observation to current ozone global monitoring networks. This year’s theme exhibits the extraordinary transformation from scientific discovery to committed international cooperation that has initiated the healing process of our planet’s protective shield.
The story begins in the basement laboratory of Christian Friedrich Schönbein at the University of Basel in 1839. While conducting experiments with electrical sparks and water, the German-Swiss chemist noticed a peculiar, pungent odour that resembles after-lightning strikes. Schönbein recognized its significance. He named the mysterious substance “ozone,” derived from the Greek word “ozein,” which means “to smell”. Little did he know that his basement discovery would eventually save the world. Ozone was a molecule composed of three oxygen atoms rather than the familiar two, but its planetary importance remained hidden. However, its atmospheric revelation came in 1913 when French physicists Charles Fabry and Henri Buisson revolutionized our understanding of Earth’s atmosphere. Through innovation they were able to make precise measurements of the solar spectrum reaching Earth’s surface which led to the discovery of something remarkable, a sharp cutoff in ultraviolet radiation around 310 nanometres. It was speculated that the missing radiation wasn’t lost in space, it was being absorbed by something in the atmosphere. When they matched the spectrum of the missing radiation to known chemicals, only one fit perfectly which is Ozone. This thin shield absorbs 97-99% of the sun’s harmful ultraviolet-B radiation and protects us from the sterilization effect.
British meteorologist G.M.B. Dobson revealed that ozone distribution defied simple photochemical predictions, leading to the discovery of massive atmospheric circulation patterns that transport ozone from tropical production zones to polar regions.
It was only in the 1970s that F. Sherwood Rowland and Mario Molina at the University of California, Irvine, made a chilling discovery of chlorofluorocarbons (CFCs), wonder chemicals used in refrigeration and aerosols since the 1930s and found that these chemicals were destroying the ozone. CFCs appear to be benign in Earth’s lower atmosphere, non-toxic, non-reactive, and seemingly harmless. However their long stability proved dangerous. When these chemicals reach the stratosphere after decades of atmospheric transport, the solar ultraviolet radiation breaks their structure apart, releasing chlorine atoms and through the photochemical reaction each chlorine atom can catalytically destroy up to 100,000 ozone molecules. This threat became visible in 1985 when British Antarctic Survey scientists Joe Farman and his colleagues reported shocking measurements from Antarctica. In every spring, it was found that an area of severely depleted ozone was appearing over the South Pole. The Antarctic ozone hole grew larger each year, creating a stark visual reminder of human impact on atmospheric chemical conditions.
Scientific investigation revealed an unexpected dimension to the ozone crisis because the CFCs weren’t just ozone destroyers, they were also extraordinarily potent greenhouse gases. Despite their minuscule atmospheric concentrations of just four parts per billion, CFCs possess global warming potentials (GWPs) thousands of times greater than carbon dioxide. Their unique molecular structure allows them to absorb infrared radiation in the “atmospheric window” where the atmosphere is relatively transparent creating what scientists term a “super greenhouse effect. CFCs contribute approximately 16% of the warming effect of all human produced greenhouse gases, demonstrating how ozone protection and climate action are fundamentally linked.
The chemicals threatening our UV shield were simultaneously accelerating global warming which prompted immediate action. This thin veil of molecules maintains the delicate balance that allows life to flourish on Earth’s surface. Without it, increased UV exposure would cause dramatic increases in skin cancer and cataracts in humans, while disrupting plant photosynthesis and marine ecosystems. This invisible shield doesn’t just protect life, it helps regulate the entire atmospheric system that sustains our planet’s habitability.
Today’s ozone monitoring represents a technological leap from Dobson’s ground-based spectrophotometers to advanced satellite instruments like NASA’s Ozone Monitoring Instrument on the Aura satellite, ISRO’s INSAT 3DR and the Ozone Mapping and Profiler Suite on NOAA’s polar satellites provide unprecedented global coverage. These advances revealed unexpected discoveries, including global-scale ozone reductions during COVID-19 lockdowns, the lowest levels recorded since 2005. Such findings demonstrate how satellite technology continues expanding our understanding of atmospheric dynamics and human environmental impacts.
From science emerged unprecedented global action. This landmark agreement achieved something extraordinary: virtually universal participation in addressing a global environmental threat. The committed phased approach proved remarkably effective and in 2005, consumption of ozone-depleting chemicals had fallen by 90-95% in participating countries. The 2016 Kigali Amendment extended controls to hydrofluorocarbons (HFCs), powerful greenhouse gases used as CFC replacements, projecting avoidance of up to 0.5°C of global warming by 2100. Evidence confirms the protocol’s success. The Antarctic ozone hole, which reached its maximum size of 29.9 million square kilometres in 2000, had shrunk significantly by recent years. Scientists projected that the Antarctic ozone layer will largely recover by 2040 with global ozone returning to pre-1980 levels.
The theme “From Science to Global Action” perfectly captures achievements and ongoing responsibilities. The international agreement with frameworks will support the cause but ozone protection will also require citizen and individual participation with environmental centric motives. Grassroots educational initiatives play a crucial role in sustaining progress. Schools, universities, and community organizations have a big role to play in educating the new generation about atmospheric and environmental protection These grassroots efforts will complement formal governmental programs, creating a global network of environmental stewardship.
The story From Schönbein’s laboratory observations to today’s global monitoring networks, from the discovery of the ozone hole to its gradual healing, reminds us that environmental protection is not just a policy challenge it’s a shared human responsibility, requiring both scientific understanding and participatory commitment to ensure that Earth’s invisible shield continues protecting life for generations to come.
(The writer is a Geo-spatial expert and avid citizen science practitioner)