Why Is the Ozone Hole Shrinking?

What caused the hole in the ozone layer? And how has science helped us begin to shrink the hole?

Sabrina Stierwalt, PhD
4-minute read
Episode #220

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


About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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