NASA: Hole in Earth's Ozone Layer Finally Closing Up Because Humans Did Something About It

Scientists at NASA said they had located the largest ozone hole ever recorded, in a report released October 3, 2000. The Goddard Space Flight Center in Greenbelt, Maryland, said satellites had observed an 11.5 million-square-mile hole. The area is approximately three times the size of the U.S. Getty

Updated | The shrinking hole in the ozone layer has become something of a success story among all the damages humans have inflicted upon the Earth. A new NASA study based on data from the Aura satellite confirms the success, so far, through measuring the chemicals that caused the hole in the first place.

The study, published Thursday in Geophysical Research Letters, reveals that a decline in ozone-depleting chemicals has resulted in 20 percent less depletion since 2005. Specifically chlorine levels declined by 0.8 percent each year between 2005 and 2016.

"We see very clearly that chlorine from [chlorofluorocarbons] is going down in the ozone hole, and that less ozone depletion is occurring because of it," Susan Strahan, lead author and atmospheric scientist from NASA's Goddard Space Flight Center, said in a statement.

The chlorofluorocarbons (CFCs) Strahan referred to are ozone-depleting chemicals that were once used in aerosol sprays, blowing agents for foams and packing materials, and refrigerants. Chlorine causes ozone depletion as the sun's ultraviolet radiation breaks down the CFCs into chlorine.

The hole in the ozone layer was first discovered in the 1980s. This layer of the atmosphere protects the Earth from ultraviolet radiation, which can cause skin cancer and cataracts, suppress immune systems and harm plants. Just two years after the hole was discovered, the world jumped quickly to solve the problem. Several nations signed the Montreal Protocol, which would ultimately ban CFCs, the chemicals responsible for destroying the ozone. Fast-forward decades later, and the ozone hole was measured at the smallest since 1988, NASA announced last November.

Strahan's study is the first to look directly at measurements of chemicals to argue that the shrinking hole stems from the ban of CFCs. Using data since 2005 from the Microwave Limb Sounder on the Aura satellite, scientists gathered information on the amount of hydrochloric acid in the stratosphere, where the ozone layer is located. Hydrochloric acid is a chemical that forms once chlorine has destroyed the ozone itself.

Former Secretary of State John Kerry gestures as he delivers a speech during the 28th Meeting of the Parties to the Montreal Protocol in Kigali, Rwanda on October 14, 2016. Getty

Measuring hydrochloric acid, which forms when chlorine reacts with methane, allowed researchers to accurately estimate chlorine levels. Comparing hydrochloric acid levels with nitrous oxide levels—another gas that remains in the atmosphere—they determined chlorine's decline of 0.8 percent per year.

"This is very close to what our model predicts we should see for this amount of chlorine decline," Strahan said. "This gives us confidence that the decrease in ozone depletion through mid-September shown by [Microwave Limb Sounder] data is due to the declining levels of chlorine coming from CFCs." The microwave technology specifically also allowed researchers to study gases during Antarctica's dark winters, as most satellites require sunlight to measure gases.

Winter in Antarctica is the key time to measure ozone loss, according to Strahan. Temperatures are colder and more stable during July to mid-September, allowing for more accurate measurements of ozone levels, which can vary depending on temperatures and chemical levels. The researchers' findings based on chemical data closely matched what their model predicts.

A recovering ozone layer provides an example of the changes that are possible if humans take action, researchers say. Last November, some 15,000 scientists signed a letter describing how to save humanity, concluding with a positive note on what people have accomplished. "The rapid decline in ozone-depleting substances shows that we can make positive change when we act decisively," they wrote.

There is still a long way to go for a complete recovery. The hole's peak last year measured at two and a half times the size of the U.S. CFCs can linger in the atmosphere for 50 to 100 years, according to Anne Douglass, co-author and atmospheric scientist at Goddard.

"As far as the ozone hole being gone, we're looking at 2060 or 2080," Douglass said in a statement. "And even then there might still be a small hole."

This article has been updated with additional information about the NASA study and context about decreasing ozone-depleting substances.