As we ring in the new year of 2017, let’s look at one of my favorite science stories from 2016: a story that tells us that all of that is possible. Science can save the world, with a little help, of course, from the cooperation and investment of its inhabitants.
What caused the hole in the ozone layer?
In 1985, a trio of British researchers noticed a hole in the ozone layer, our protection against harmful UV rays, over the Antarctic. Almost ten years earlier in 1974, scientists had noted a link between possible damage to the ozone layer and the release of chlorofluorocarbons in to the atmosphere, work which later earned those authors, Mario Molina and Sherwood Rowland, along with Paul Crutzen, the Nobel Prize in Chemistry.
In the 1970s and 1980s, chlorofluorocarbons or CFCs were readily used in coolants for refrigeration systems and everyday propellants like hair sprays or other aerosols. CFCs are fairly stable molecules so, once released, they almost always make their way up into the stratosphere, the layer of the Earth’s atmosphere that starts about 10-20 kilometers up (depending on where on Earth you’re located). They do not stay trapped inside the walls of your apartment, as has been incorrectly suggested by the US president elect.
Once in the stratosphere, CFCs are more exposed to ultraviolet radiation which breaks them down into their constituent parts, including chlorine atoms. These chlorine atoms in turn react with oxygen atoms, a process which leads to the destruction of the molecules that make up the ozone. Less ozone means increased risk of skin cancer and cataracts for us Earthlings.
The 1987 Montreal Protocol
In 1987, only two years after the study noting the depletion was published in the journal Nature, a global agreement was reached with the intent of phasing out the use of so-called ozone depleting substances, including CFCs. This agreement, known as the Montreal Protocol, has been ratified by 197 parties, including the European Union and all of the United Nations members, and is one of the greatest success stories in global cooperation. Kofi Annan, the former Secretary General of the United Nations, called it “perhaps the single most successful international agreement to date.”
Production of CFCs was mostly stopped in the 1990s, but they can still be found in some old appliances and in a few countries. Meeting the goals of the agreement continues to require renewed investment. The Protocol has been amended four times and billions of dollars have been spent on helping lesser-developed countries as they continue to transition away from CFCs. The CFC molecules also live in the atmosphere for as long as 50-150 years, so the emissions you released in getting those perfect feathered bangs in the 1980s? They’re still up there.
How do we know the ozone layer is healing?
Scientists found a direct link to a cause, politicians came up with a plan, and we the people took action. But did it work? In 2016, we got the first real evidence that the plan was in fact working. The hole in the ozone is getting smaller.
To understand this evidence, it helps to first note that the ozone hole expands and contracts throughout the year. This is because chlorine atoms erode the ozone layer most effectively in the right conditions: there has to be sufficient sunlight and temperatures should be cold enough. Thus the hole appears in August and is typically at its largest in October.
A group of researchers led by Susan Solomon, a climate scientist at MIT, tracked the size of the hole in the ozone layer during the month of September for 15 years from 2000 to 2015 using satellites and weather balloons. They also tracked other contributing factors that could possibly masquerade as overall healing vs increased depletion, including yearly changes in meteorological activity and sulfur dioxide levels to account for volcanic activity. The ozone hole tends to be larger in years that see significant increases in volcanic activity, not because volcanoes spew chlorine atoms but because they contribute other small particles to the atmosphere that react with the human-produced chlorine atoms.
Solomon and her team found that not only is the hole in the ozone opening later than it has in the past, it also appears to be smaller and less deep, all independent measures of the improving health of the ozone layer. Their measurements show a decrease in size of the hole by ~4 million square kilometers since 2000 which is roughly half the area of Australia or half the area of the contiguous United States. A comparison to models suggest that more than half of this shrinkage is a direct result of the reduction in chlorine in the atmosphere.
It gives us hope that we shouldn’t be afraid to tackle large environmental problems. -Susan Soloman
Science can save the world
So when people learned that their hairsprays and cooking sprays were causing significant damage to our planet, we stopped using them almost overnight. We put pressure on elected officials to ban them, and those elected officials listened. Luckily scientists came up with alternatives so that we didn’t have to give up our big 80s hair.
Now the ozone layer has rebounded, and scientists predict that by 2060-2075, the ozone layer will be back to its pre-1950s levels. The choices we make as individuals and as nations thanks to our scientific understanding have a huge impact on our quality of life and the health of our planet. So let’s remember the successful healing of the ozone as we continue to be faced with questions about our future, questions for which we need science to empower us to make the right choices in the present.
As Solomon says of her result, “It gives us hope that we shouldn’t be afraid to tackle large environmental problems.”
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 nasa.gov
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