A hole lotta trouble: obliterating our ozone layer
With over 15,000 new cases reported each year, Australia and New Zealand share the dubious honour of being the world’s skin cancer capitals. Ask someone why, and there’s a good chance they’ll pin it on ‘the hole in the ozone layer’ sitting above these hapless countries. Luckily for us, this is an urban myth – the chronic failure of pasty Europeans to slip, slop, and slap is the real culprit. On the other hand, the penguins in Antarctica might need some SPF 50+, because the hole in the ozone layer there stretches across twenty million square kilometres!
Sunscreen in the sky
If you’ve ever heard of the ozone layer, you probably know that it protects our planet from the Sun’s rays. As a giant nuclear reactor, the Sun is constantly churning out excess energy as waves of radiation. Most of the radiation that escapes is harmless, but the waves with the highest energy – mainly ultraviolet (UV) rays – can irreversibly damage the DNA of living cells. Just one thing stands between us and certain death: a thin layer of ozone floating in the stratosphere, twenty kilometres above the Earth’s surface.
Ozone is just a deluxe version of the oxygen gas we breathe – instead of two oxygen atoms, ozone is made of three. But this simple difference gives ozone one very fortunate quirk: the ability to absorb the most harmful forms of UV radiation. When a UV ray crashes into an ozone molecule, its energy is sucked up into the bonds holding the ozone together. The rush of solar power ‘excites’ the bonds enough for one to break apart, and the excess energy dissipates as harmless heat. Voila! The UV ray is vanquished, and life on Earth avoids the curse of mass melanoma.
But what becomes of the ozone itself? When it breaks apart, it leaves behind a molecule of oxygen gas (O2), and a lone oxygen atom. Oxygen atoms would make fantastic cast members in a soap opera – they’re volatile, reactive, and hate being single. In a desperate bid to return to a happy marriage, they latch onto the first puff of oxygen gas that drifts by, and a new ozone molecule is born. The result is a constant cycling of oxygen particles that has allowed our ozone layer to continuously regenerate for hundreds of millions of years.
If our atmosphere’s built-in sunscreen can replenish itself, then why is there such an enormous hole above the South Pole? The blame – as usual – falls squarely on our shoulders.
Following the First and Second World Wars, many of the innovations developed by countries to aid their fight on the front line were transitioned into mainstream industries. Among these were an extremely unreactive group of chemicals known as chlorofluorocarbons (CFCs for short). Originally used to suppress fires in military aircraft, they gained popularity with private aviators throughout the 1930s. When less toxic CFCs were discovered in the 1950s, their use skyrocketed; at the peak of their popularity, CFCs could be found in just about every light aircraft, fire extinguisher, and spray can. They were also ubiquitous as coolants in household fridges, trademarked under the brand name Freon. But the same properties of stability that make CFCs so good at withstanding the fury of fires, and the pressure inside a spray nozzle, could also spell doom for our planet.
CFCs are stable due to the incredibly strong bonds that hold their atoms together; they contain chlorine and fluorine, which have the strongest ‘grips’ of any element. The iron fist these elements exert on the carbon atom at their centre gives each CFC as long as a century to move through the environment without decomposing. Over several years of heavy use, CFCs began to float out of our cities and right up into our ozone layer. But the moment they move above this protective sunshield, something happens: they break up.
The incredible power of the Sun’s UV radiation is strong enough to rip apart the bonds within these hardy molecules, sending chlorine flying into the open air. If free oxygen is an unhappy soap star, then these atoms are the mass murderers from American Horror Story. Just one chlorine atom can easily destroy one hundred thousand ozone molecules before leaving the stratosphere. With such a deep thirst for blood, it should come as no surprise that CFCs (and some related chemicals) have been named and shamed as the #1 culprits behind our sprawling ozone hole.
No hole the end goal
If we were to give CFCs free reign over our skies, the hole over Australia might not be a myth for much longer. Luckily, in a rare case of political cooperation, the rest of the world seems to agree. In 1987, just over a decade after the harmful effects of CFCs were first discovered, forty-six states signed the now-famous Montreal Protocol. Developed to restrict the use of ozone-damaging chemicals across the globe, the protocol has been described as the world’s ‘single most successful international agreement‘. Fast-forward to 2018, and an incredible 197 states are signatories to the plan. Better yet, CFC emissions have declined massively, and the hole in the ozone layer is actually closing up.
Despite our habit of ruining everything we touch, it’s clear that humanity has the power to meet lofty environmental goals. While Australians will probably never learn to apply enough sunscreen, I’m sure the cancer-free penguins waddling around Antarctica’s frosty shores will thank us in the years to come.