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MAGELLANICA: A Hole in the Sky?

January 17, 2018

Magellanica is a fictional story with invented characters; however, it is based on factual events and real science. In 1986, when the play is set, scientists knew that there was a dangerous hole in the ozone layer and were working feverishly to confirm the cause. At the same time, other scientists were beginning to notice climate-related anomalies and growing concerned about the “greenhouse effect.” Although ozone depletion and rising global temperatures are distinctly separate problems, they are both results of mankind’s actions. Magellanica is set in this historical moment when we first began to realize how extensively our choices were changing the planet.

 

What is the ozone layer?

Oxygen molecules (O2) have two oxygen atoms. When either UV rays from the sun or electrical discharges such as lightning strike an O2 molecule, it can separate the two atoms. These single atoms can then bond with an oxygen molecule, creating a new molecule that has three oxygen atoms: ozone (O3). This natural process of producing ozone is reversible, so although it is constantly being created and destroyed, the amount of ozone remains stable.

Ozone molecules are most concentrated in the stratosphere (the atmospheric layer roughly 631 miles above the earth’s surface) but even there, the amounts are miniscule: only about 0.00004%. (Oxygen makes up about 21%, and nitrogen 78%, of the atmosphere.) Nonetheless, even at such low concentration, ozone provides a vital service to life on earth by absorbing the sun’s lethal UV rays.

 

What is the ‘hole’ in the ozone layer?

Scientists began measuring the amount of ozone above Antarctica in 1957, and levels stayed relatively stable at around 300 Dobson Units (DU) for the next decade. However, beginning in the 1970s, scientists observed a regular loss of ozone in September/October of each year – a loss that increased year by year. In October 1979, the lowest level measured was 225 DU; by 1994, the level fell to 92 DU, a loss of 70% from what had been measured in the 1960s. The ‘hole’ where the loss is greatest covered an area of 1.09 million square kilometers in 1979, growing to 29.46 million square kilometers in 2006. (For comparison, the entire land mass of North America is 25.3 million square kilometers.)  

 

What causes it?

In 1974, scientists demonstrated that chlorofluorocarbons (CFCs) are able to catalytically break down ozone in the presence of high frequency UV light. CFCs were created in 1928, as non-toxic, non-flammable refrigerants, and were widely used in refrigeration, air conditioning, aerosol sprays, and plastic foams. At peak, about a million tons of CFCs were produced each year. As very stable compounds, CFCs have a very long half life. They can remain in the atmosphere for over 100 years - only breaking down when exposed to UV rays from the sun in the stratosphere.

 

Why is the ‘hole’ over Antarctica?

The sun sets at the South Pole in April and does not return until September. With the onset of winter in Antarctica, strong westerly winds are accelerated by the increasing cold, creating a vortex over the region. This wind prevents warmer, ozone-rich air from entering the region, and as the temperature in the lower stratosphere drops to -80’C, Polar Stratospheric Clouds (PSCs) begin to form. These clouds provide the surface on which CFC-related chemical reactions occur. During the dark winter months, there is little chemical activity, but when the sun returns, the UV rays striking the clouds and CFCs cause the CFCs to breakdown, releasing chlorine gas molecules that destroy the ozone. This unique combination of wind vortex that isolates the area, super-cooled air that creates PSCs, and CFCs – a compound not found in the natural world – works together to destroy the region’s ozone layer. As the temperature rises with summer, the effect is diminished and the ozone is able to partially restore.

 

What are the effects? 

A depleted ozone layer allows more UV rays from the sun to enter our part of the atmosphere. The increase in skin cancers and cataracts are significant, documented problems, but we know less about the effects on plant and animal life. There is, however, evidence that phytoplankton and zooplankton – the first links in the aquatic food chain – have a low tolerance to UV radiation. Damage to life at this level could have repercussions throughout our entire biological ecosystem.

 

What can be done?

In 1987, the Montreal Protocol, a global treaty to protect the Ozone Layer by phasing out production and consumption of CFCs and other ozone-depleting substances, was ratified by the United States and 196 other countries. The treaty was the first to achieve universal ratification by all the nations in the world and was remarkable for how quickly it came to pass with only 14 years lapsed between the discovery of CFCs’ impact on ozone and the international agreement to address the problem.

It is estimated that by 2050 the hole in the sky will be healed. Like most environmental problems, it will take longer to repair than it did to create, but it demonstrates that with global, collective action, we can avert climatic disaster.

 

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