Avid Everyday Einstein listeners may recall that the depletion and subsequent rebound of the ozone layer is one of my favorite science stories. Scientists were able to identify a problem (the depletion of the ozone layer) and its cause (chlorofluorocarbon gases or CFCs) and within two years, politicians took swift action to reverse course to protect our planet and its inhabitants. The ozone layer has now rebounded and scientists predict that by 2060-2075, the ozone layer will be back to its pre-1950 levels. Science truly can change the world.
Unforutnately, CFCs are making a comeback in the atmosphere and scientists are not sure where they are coming from. Let’s take a look at how we know they have returned and what the leading theories are to suggest why.
What Are CFCs?
First, we cannot tell the story of ozone depletion and CFCs without highlighting the incredibly important work of Mario Molina, a Mexican immigrant to the United States. Molina was born in Mexico City and is now a Distinguished Professor of Chemistry and Biochemistry at the University of California, San Diego. Together with his former postdoctoral advisor at the University of California, Irvine, Sherwood Rowland, Molina was awarded the Nobel Prize in Chemistry for his discovery that chlorofluorocarbon gases (CFCs) contribute significantly to depletion of the ozone layer which protects us Earth inhabitants from cancer and cataract-causing harmful UV rays.
In the 1970s, CFCs were commonly used in refrigeration and as a propellant in aerosol sprays and were sold under the brand name Freon. Manufacturers first turned to CFCs because they were inflammable and nontoxic and cheap to produce. CFCs are relatively stable molecules so, once released, they almost always make their way upwards to live a long life in the Earth’s stratosphere.
However, in 1974, Molina and Rowland noted that, once in the stratosphere, CFCs become vulnerable to ultraviolet radiation from the sun which breaks them down into their constituent parts, including chlorine, fluorine, and carbon atoms. Those chlorine atoms react with oxygen atoms in the atmosphere which leads to the destruction of the molecules that make up the ozone layer. About 10 years later, a trio of British scientists found evidence of this depletion in action.
Science is a global pursuit that benefits from the free exchange of ideas and the promotion of collaboration. Mario Molina’s work is just one example of how an openness to immigration contributes to the United States’ status as a leader in scientific research. In fact, of the 78 Nobel Prizes awarded to scientists in the U.S. in chemistry, medicine, and physics since 2000, 39% were awarded to immigrants. And this is not just a trend for well-established, senior scientists. According to a study by the National Foundation for American Policy, over 80% of recent finalists in the Intel Science Talent Search (a science competition often dubbed the “Junior Nobel Prize”) were the children of immigrants.
Who is Newly Producing CFCs?
The Montreal Protocol of 1987 banned all production of CFCs by the year 2010. A recent study in the journal Nature reports that, while CFCs in the atmosphere have declined steadily from 2002 to 2012, that decline has since slowed. The scientists involved in the study found that the overall amount of ozone-harming CFCs in the atmosphere is still decreasing and the ozone is still recovering, but the levels of one particular type of CFC, known as CFC-11, have risen 25% since 2012.
The dramatic increase in CFC-11 is consistent with new production of the molecule and cannot be explained by lingering past levels. However, reported new production has been "close to zero" since 2006—the US phased out production in 1996—suggesting that whatever is causing the recent increase not only violates the international agreement set up by the Montreal Protocol but also is being done off the record.
Thanks to the work of Mario Molina and his colleagues, however, we don’t have to guess on the role these CFCs play in ozone depletion.
CFC-11 is usually found in foams, like those used for refrigeration, and can live on in the atmosphere for up to 50 years. However, cheap and effective substitutes have existed for some time making the increase in CFC-11 production an even bigger mystery. It may be possible that someone has decided to use up a stockpile of the greenhouse gas they amassed before the Montreal Protocol was instated, but the measured rate of production, 13 billion grams per year, would require an incredibly large stockpile.
The scientists involved in the study also considered less nefarious reasons for the increase, including a changing of the atmospheric patterns we rely on to remove CFCs from the atmosphere, demolition of old buildings that contained CFC-11, and accidental production. But the level of increase predicted from this combination of sources was not enough to match the observed rise in CFC-11.
Thus, someone is newly adding CFC-11 into the atmosphere and doing so in large quantities. According to the report, “the increased CFC-11 emissions arise from new production not reported to the UN Environment Program’s Ozone Secretariat, which is inconsistent with the agreed phase-out of CFC production in the Montreal Protocol by 2010.” In other words, “somebody’s cheating” as noted by Durwood Zaelke, an expert on the Montreal Protocol from the Institute for Governance and Sustainable Development.
An internationally cooperative investigation will be required to find out just who the culprit is, and until then some guesswork may be required if we want to take swift action to discourage the production of new CFCs. Thanks to the work of Mario Molina and his colleagues, however, we don’t have to guess on the role these CFCs play in ozone depletion and why their elimination is so important.
Are you a Hispanic or Latino student interested in studying science? Best Colleges has a list of scholarship resources, including financial aid for undocumented students.
Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.
Image courtesy of shutterstock.
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