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.

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.

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SaveSave</s>Positive changes in the environment are highly possible when humans come together to take action. That’s what happened to the hole on the Earth’s ozone layer, which has been found to be shrinking since the 1980s after nations agreed to ban the use of chlorofluorocarbons (CFCs), or chemicals that deplete the ozone layer.

NASA has confirmed that the ozone hole above the Antarctic is starting to close up ever since the ban was imposed through the 1987 Montreal Protocol. Data from NASA’s Aura satellite showed the success of the ban, with 20 percent less depletion of the ozone layer since 2005. In the study published in Geophysical Research Letters, chlorine levels were found to have declined by 0.8 percent each year from 2005 to 2016.

There have been previous studies conducted to analyze the changes in the size of the ozone hole to prove that there is less depletion in the layer. But this latest study, which was spearheaded by lead author Susan Strahan, was the first to look at the chemical composition inside the hole, confirming that ozone depletion has not only decreased but also that this decrease was a result of lowered levels of CFCs.

CFCs are chemicals abundant in aerosol sprays, refrigerants, and blowing agents. The radiation from the UV rays of the sun breaks down CFCs into chlorine, which will then slowly destroy the ozone layer. To arrive at their findings, the researchers used data from Microwave Limb Sounder (MLS) on the Aura satellite since 2005, which showed the levels of hydrochloric acid in the ozone layer.

Hydrochloric acid is produced when chlorine has already damaged the layer. By knowing the levels of hydrochloric acid, scientists can get a measurement of just how much chlorine is present. After comparing levels of hydrochloric acid and nitrous oxide — another gas that behaves like CFCs — it was found out that the chlorine levels were going down by 0.8 each year, on average.

With the findings, Strahan was positive that the ozone depletion was directly caused by the decline in CFCs. As to how this translates to the future of the ozone layer, co-author Anne Douglass said that the ozone layer can recover, but it can take decades.</s>Measurements show that the decline in chlorine, resulting from an international ban on chlorine-containing manmade chemicals called chlorofluorocarbons (CFCs), has resulted in about 20 percent less ozone depletion during the Antarctic winter than there was in 2005—the first year that measurements of chlorine and ozone during the Antarctic winter were made by NASA's Aura satellite.

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

CFCs are long-lived chemical compounds that eventually rise into the stratosphere, where they are broken apart by the Sun's ultraviolet radiation, releasing chlorine atoms that go on to destroy ozone molecules. Stratospheric ozone protects life on the planet by absorbing potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plant life.

Two years after the discovery of the Antarctic ozone hole in 1985, nations of the world signed the Montreal Protocol on Substances that Deplete the Ozone Layer, which regulated ozone-depleting compounds. Later amendments to the Montreal Protocol completely phased out production of CFCs.

Past studies have used statistical analyses of changes in the ozone hole's size to argue that ozone depletion is decreasing. This study is the first to use measurements of the chemical composition inside the ozone hole to confirm that not only is ozone depletion decreasing, but that the decrease is caused by the decline in CFCs.

The study was published Jan. 4 in the journal Geophysical Research Letters.

The Antarctic ozone hole forms during September in the Southern Hemisphere's winter as the returning sun's rays catalyze ozone destruction cycles involving chlorine and bromine that come primarily from CFCs. To determine how ozone and other chemicals have changed year to year, scientists used data from the Microwave Limb Sounder (MLS) aboard the Aura satellite, which has been making measurements continuously around the globe since mid-2004. While many satellite instruments require sunlight to measure atmospheric trace gases, MLS measures microwave emissions and, as a result, can measure trace gases over Antarctica during the key time of year: the dark southern winter, when the stratospheric weather is quiet and temperatures are low and stable.

The change in ozone levels above Antarctica from the beginning to the end of southern winter—early July to mid-September—was computed daily from MLS measurements every year from 2005 to 2016. "During this period, Antarctic temperatures are always very low, so the rate of ozone destruction depends mostly on how much chlorine there is," Strahan said. "This is when we want to measure ozone loss."

They found that ozone loss is decreasing, but they needed to know whether a decrease in CFCs was responsible. When ozone destruction is ongoing, chlorine is found in many molecular forms, most of which are not measured. But after chlorine has destroyed nearly all the available ozone, it reacts instead with methane to form hydrochloric acid, a gas measured by MLS. "By around mid-October, all the chlorine compounds are conveniently converted into one gas, so by measuring hydrochloric acid we have a good measurement of the total chlorine," Strahan said.

Nitrous oxide is a long-lived gas that behaves just like CFCs in much of the stratosphere. The CFCs are declining at the surface but nitrous oxide is not. If CFCs in the stratosphere are decreasing, then over time, less chlorine should be measured for a given value of nitrous oxide. By comparing MLS measurements of hydrochloric acid and nitrous oxide each year, they determined that the total chlorine levels were declining on average by about 0.8 percent annually.

The 20 percent decrease in ozone depletion during the winter months from 2005 to 2016 as determined from MLS ozone measurements was expected. "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 MLS data is due to declining levels of chlorine coming from CFCs. But we're not yet seeing a clear decrease in the size of the ozone hole because that's controlled mainly by temperature after mid-September, which varies a lot from year to year."

Looking forward, the Antarctic ozone hole should continue to recover gradually as CFCs leave the atmosphere, but complete recovery will take decades. "CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time," said Anne Douglass, a fellow atmospheric scientist at Goddard and the study's co-author. "As far as the ozone hole being gone, we're looking at 2060 or 2080. And even then there might still be a small hole."

More information: Susan E. Strahan et al. Decline in Antarctic Ozone Depletion and Lower Stratospheric Chlorine Determined From Aura Microwave Limb Sounder Observations, Geophysical Research Letters (2018). DOI: 10.1002/2017GL074830</s>NASA has observed that ozone layer depletion has decreased over years due to the reduction of chlorine use.

NASA's Aura satellite has identified 20 percent decline in the depletion level of ozone this year when compared with the decline during the Antarctic winter in 2005. Chlorine, which has been regarded as a major cause of ozone layer depletion was also found to be depleting.

Measures like the international ban on chlorofluorocarbons (CFCs), a human-made chemical compound of chlorine, is believed to have resulted in the lesser contribution of chlorine to the atmosphere.

Susan Strahan, an atmospheric scientist from NASA's Goddard Space Flight Center in Greenbelt, Maryland said, "We see very clearly that chlorine from CFC's is going down in the ozone hole, and that less ozone depletion is occurring because of it."

The study published in the journal Geophysical Research Letters says that CFCs are long-lived chemical compounds which rise to the stratosphere and get broken apart into its constituent elements on exposure to sun's ultraviolet radiation. The chlorine atoms released from this breakdown would destroy ozone molecules resulting in the holes.

Ultraviolet radiations from the sun could breach through the earth's atmosphere in the absence of ozone layer. It might cause skin cancer and cataract and could result in suppression of immune systems and could damage plants.

Montreal Protocol on Substances that Deplete the Ozone Layer had been signed by 196 countries and the European Union since the first agreement on September 16, 1987. This agreement was reached after the discovery of Antarctic ozone hole in 1985. Later amendments aimed to completely stop production of CFCs.

The NASA study has measured chemical compositions inside the ozone hole to confirm that the decline in CFCs has resulted in the decrease of ozone depletion. Past statistical analysis was also used to argue that ozone depletion is decreasing. Scientists had used data from NASA's JPL Microwave Limb Sounder (MLS) aboard the Aura satellite which had been continuously measuring ozone layer gases across the globe since mid-2004.

The Antarctic ozone hole usually forms during the Southern Hemisphere's winter in September. It occurs when the sun's rays catalyze ozone destruction cycles that involve the production of chlorine and bromine from the CFCs.

While many scientific instruments aboard satellites require sunlight to measure atmospheric trace gases, MLS could use microwave emissions to measure the gases over Antarctica even during dark southern winter. The Southern winter occurs between early July to mid-September when the stratospheric weather remains low and stable.

Scientists say that this period would be best suited to study ozone layer depletion as the chlorine would be the only major depleting agent of ozone present in the absence of heavy sunlight and when the Antarctic temperature remains very low. Scientists measured hydrochloric acid formed by reaction of CFC components with methane to determine the quantity of total chlorine.

Nitrous oxide, a greenhouse gas which has long-life like CFCs, also has a significant role in the stratosphere even though it does not have any role in the ozone layer depletion. The measure of nitrous oxide in the stratosphere is also a significant study of the research as declining hydrochloric acid and nitrous oxide levels could give details of the declining ozone levels.

Scientists believe that the CFCs in the ozone layer would nullify by 2060 or 2080. This would mark complete repair of the ozone layer.</s>Earth's ozone is recovering thanks to decades-old chemical ban, scientists say Data shows 20 percent less ozone depletion than a decade ago after chlorine-containing chemicals known as CFCs

Satellite data shows that the Earth's ozone layer is recovering -- and scientists say it's a direct result of a decades old international chemicals ban.

The findings were published Thursday in the journal Geophysical Research Letters and came after scientists measured with NASA's Aura satellite the levels of ozone and ozone-destroying chlorine during an Antarctic winter. Measuring has taken place since 2005. Data showed that there was 20 percent less ozone depletion than a decade ago.

The ozone hole forms during Antarctica's winter, which is why researchers measure trace gases over the continent at this time, using an instrument on the Aura satellite known as the Microwave Limb Sounder.

Researchers have concluded that this ozone recovery is linked to the Montreal Protocol on Substances that Deplete the Ozone Layer. The protocol, signed in 1987 after the Antarctic ozone hole was discovered, eventually laid down a complete ban on chlorine-containing man-made chemicals known as chlorofluorocarbons, or CFCs, according to the Kenya-based The Ozone Secretariat at the United Nations Environment Programme.

"We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it," Susan Strahan, an atmospheric scientist at NASA's Goddard Space Flight Center in Maryland, said in a Thursday news release.

The ozone protects the planet by absorbing harmful ultraviolet radiation than can cause health problems such as skin cancer, and can damage plant life.

Scientists anticipate that the ozone hole will continue to recover as CFCs leave the atmosphere, but full recovery will take decades.

Alex Stuckey covers NASA and the environment for the Houston Chronicle. You can reach her at alex.stuckey@chron.com or Twitter.com/alexdstuckey.</s>WASHINGTON: An international ban on chlorine-containing man-made chemicals called chlorofluorocarbons (CFCs), has resulted in about 20 per cent less ozone depletion, NASA said.

CFCs are long-lived chemical compounds that eventually rise into the stratosphere, where they are broken apart by the Sun's ultraviolet radiation, releasing chlorine atoms that go on to destroy ozone molecules.

Stratospheric ozone protects life on the planet by absorbing potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plant life.

"We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it," said Susan Strahan, from the US space agency.

By comparing the Microwave Limb Sounder (MLS) measurements of hydrochloric acid and nitrous oxide each year, the scientists determined that the total chlorine levels were declining on average by about 0.8 per cent annually.

The Antarctic ozone hole forms during September in the Southern Hemisphere's winter as the returning sun's rays catalyse ozone destruction cycles involving chlorine and bromine that come primarily from CFCs.

To determine how ozone and other chemicals have changed year to year, scientists used data from the MLS aboard the Aura satellite, which has been making measurements continuously around the globe since mid-2004.

The change in ozone levels above Antarctica from the beginning to the end of southern winter - early July to mid- September - was computed daily from MLS measurements every year from 2005 to 2016.

The scientists found that ozone loss is decreasing, but they needed to know whether a decrease in CFCs was responsible.

When ozone destruction is ongoing, chlorine is found in many molecular forms, most of which are not measured. But after chlorine has destroyed nearly all the available ozone, it reacts instead with methane to form hydrochloric acid, a gas measured by MLS.

According to the study published in the journal Geophysical Research Letters, the Antarctic ozone hole should continue to recover gradually as CFCs leave the atmosphere, but complete recovery will take decades.

"CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time," said Anne Douglass, a fellow atmospheric scientist at Goddard and the study's co- author.

"As far as the ozone hole being gone, we are looking at 2060 or 2080. And even then there might still be a small hole," Douglass said.</s>An international ban on ozone-destroying chlorine that contains manmade chemicals called chlorofluorocarbons(CFCs) has led to less ozone depletion, NASA scientists have reported. CFCs are long-living chemical compounds that eventually rise into the stratosphere, where they are broken apart by the Sun’s ultraviolet radiation, releasing chlorine atoms that then go on to destroy ozone molecules. “We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it,” said lead author Susan Strahan, an atmospheric scientist from NASA’s Goddard Space Flight Centre in Maryland. The ban on the CFCs resulted in about 20 per cent less ozone depletion during the Antarctic winter from 2005 to 2016, while chlorine levels declined by an average 0.8 per cent annually, the scientists said. Stratospheric ozone protects life on the planet by absorbing potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plant life.

The Antarctic ozone hole forms during September in the Southern Hemisphere’s winter as the returning sun’s rays catalyse ozone destruction cycles involving chlorine and bromine that come primarily from CFCs. The change in ozone levels above Antarctica from the beginning to the end of southern winter — early July to mid-September — was computed daily from the Microwave Limb Sounder (MLS) aboard the Aura satellite every year from 2005 to 2016.

When ozone destruction is ongoing, chlorine is found in many molecular forms, most of which are not measured. But after chlorine has destroyed nearly all the available ozone, it reacts instead with methane to form hydrochloric acid — a gas measured by MLS. The Antarctic ozone hole should continue to recover gradually as CFCs leave the atmosphere, but complete recovery will take decades, the researchers said, in the paper published in the journal Geophysical Research Letters. “CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time,” said Anne Douglass, a fellow atmospheric scientist at the Goddard Centre.”As far as the ozone hole being gone, we’re looking at 2060 or 2080. And even then there might still be a small hole.”</s>The hole in the ozone layer has shrunk thanks to low levels of chlorine in the stratosphere – a drop brought about by the ban on CFCs, according to the latest NASA research.

Scientists from the agency’s Jet Propulsion Laboratory (JPL) in California used the Microwave Limb Sounder (MLS) aboard the Aura satellite to measure the amount of chlorine in the stratosphere. The resultant study, published in the journal Geophysical Research Letters, found that there has been around 20 percent less ozone depletion during the Antarctic winter than there had been when the Aura was launched in 2005.

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NASA credits the decline to the worldwide ban on chlorofluorocarbons (CFCs) enacted in 1987. "We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it," Susan Strahan, an atmospheric scientist from NASA's Goddard Space Flight Center in Maryland, said in a statement.

The ozone layer acts as a protective shield around the Earth, absorbing the Sun’s harmful ultraviolet radiation which can cause cancers, suppress the immune system in humans and damage plant life. CFCs are man-made chemical compounds that, when exposed to ultraviolet radiation in the stratosphere, break up and release chlorine atoms that destroy ozone molecules.

The MLS measures microwave emissions and trace gases over the Antarctic. The southern winter period, which goes from early July to September, is seen as ideal for monitoring stratospheric conditions as the temperatures are low and stable. Daily readings taken every year from 2005 to 2016 revealed that ozone loss is decreasing.

READ MORE: Hole in ozone layer shrank to smallest size since 1988 – NASA (VIDEO)

Despite the encouraging results, Anne Douglass, a fellow atmospheric scientist at Goddard, believes a complete ozone recovery is still a long way off. "CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time,” Douglass said. “As far as the ozone hole being gone, we're looking at 2060 or 2080. And even then there might still be a small hole."</s>The ozone hole in the upper atmosphere has shrunk by about 20 percent since 2005, and scientists are crediting the international ban on manmade chemicals containing chlorine.

The chemicals, called chlorofluorocarbons, left chlorine in the atmosphere, a main contributor to the hole in the protective ozone layer that surrounds the earth.

“We see very clearly that chlorine from CFCs is going down in the ozone hole, and that less ozone depletion is occurring because of it,” said Susan Strahan, an atmospheric scientist from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

CFCs are long-lived chemical compounds that eventually rise into the stratosphere, where they are broken apart by the Sun’s ultraviolet radiation, releasing chlorine atoms that go on to destroy ozone molecules, NASA said on its website.

Stratospheric ozone protects life on the planet by absorbing potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plant life.

Two years after the discovery of the Antarctic ozone hole in 1985, nations of the world signed the Montreal Protocol on Substances that Deplete the Ozone Layer, which regulated ozone-depleting compounds, according to NASA.</s>About 30 years since the Montreal Protocol was signed, which prohibited using ozone-destroying chemicals, NASA scientists say they have hard proof the hole in Earth's ozone layer is shrinking.

In the past, researchers determined ozone layer health by tracking how much the hole grew in a given time. But now, NASA scientists wanted to see specifically if the man-made, ozone-destroying chemicals in the atmosphere around the Antarctic ozone hole were declining.

For example, researchers measured the levels of chlorine, a primary source of ozone depletion, and found it's falling almost 1 percent a year.

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Although the results of the new study are encouraging, they seem to contradict other recent findings about the hole in the ozone, like one that said it wasn't growing or shrinking. While the ozone hole did shrink to its smallest size since 1988, scientists say it was thanks to an unstable and warm atmosphere — not a drop in harmful chemicals.

Even if the results of the new study do hold true, scientists say it will take until at least 2060 for the hole in the ozone to vanish.
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NASA research, published in Geophysical Research Letters, implies that the ozone layer is starting to recover due to man's actions. The decline in ozone-depleting chemicals, specifically chlorine from chlorofluorocarbon (an effect from the 1980's CFC ban, say the scientists), has resulted in 20 percent less depletion since 2005.