Why is the ozone hole shrinking?

Why Is the Ozone Hole Shrinking?A time-lapse photo of an ozonesonde that measures the ozone layer depletion | Robert Schwarz/University of Minnesota

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New Delhi: The ozone hole this year is the smallest on record since its discovery in 1985, NASA and NOAA scientists have found. They, however, warned that this is not a sign that the atmospheric ozone is suddenly on a fast track to recovery.

According to satellite measurements, the ozone hole reached 16.4 million square kilometres on 8 SeptemberOzone hole shrinks to smallest on record but NASA says it doesn’t mean layer is recovering, the peak extent for the year, but then shrunk to less than 10 million square kilometres, the lowest ever on record, for the remainder of September and October.

The measurements were carried out by NASA and the National Oceanic and Atmospheric Administration (NOAA). They reveal the extent of the damage caused to the ozone layer.

The ozone layer is located in the Earth’s stratosphere — roughly 11 to 40 km above the Earth’s surface — and acts as the planet’s shield against potentially harmful ultraviolet radiation from the sun that can cause skin cancer and damage plants.

“It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA’s Goddard Space Flight Center in the US.

“But it’s important to recognise that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery,” Newman added in a statement.

During years with normal weather conditions, the ozone hole typically grows to a maximum area of about 20.7 million square miles in late September or early October.

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The ozone hole over the Antarctic forms during late winter in the Southern Hemisphere as the returning Sun’s rays start ozone-depleting reactions. These reactions take place at the stratospheric clouds due to chemically active forms of chlorine and bromine derived from man-made compounds.

  • In most years, at least some levels of the stratosphere, the region of the upper atmosphere where the largest amounts of ozone are normally found, are found to be completely devoid of ozone.
  • In warmer temperatures, however, fewer polar stratospheric clouds form and these reactions do not persist as long, limiting the ozone-depletion process.
  • The depletion is measured at the South Pole through weather balloons carrying ozone-measuring “sondes”, probes that directly sample ozone levels vertically through the atmosphere.
  • “This year, ozonesonde measurements at the South Pole did not show any portions of the atmosphere where ozone was completely depleted,” the statement quoted atmospheric scientist Bryan Johnson at NOAA’s Earth System Research Laboratory in Boulder, Colorado, as having said.
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  • This is the third time in the last 40 years that weather systems have caused warm temperatures that limit ozone depletion, the statement quoted Susan Strahan, an atmospheric scientist with the Universities Space Research Association, and who works at NASA, as having said.

Similar weather patterns in the Antarctic stratosphere in September 1988 and 2002 also produced atypically small ozone holes, she added. “It’s a rare event that we’re still trying to understand,” Strahan said.

According to the NASA statement, researchers at the British Antarctic Survey discovered the ozone hole in 1985 and NASA’s satellite estimates not only confirmed the 1985 discovery but also revealed the ozone hole’s continental scale.

In 1987, the international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer. This agreement regulated the consumption and production of ozone-depleting compounds.

Atmospheric levels of man-made ozone-depleting substances increased up to the year 2000. Since then, they have slowly declined but remain high enough to produce significant ozone loss.

The ozone hole over Antarctica is expected to gradually become less severe as chlorofluorocarbons — banned chlorine-containing synthetic compounds that were once frequently used as coolants — continue to decline. Scientists expect the Antarctic ozone to recover back to the 1980 level around 2070.

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Why Is the Ozone Hole Shrinking?

Ozone Hole Over Antarctica Shrinks to Record-Small Size

Why Is the Ozone Hole Shrinking?

The ozone hole (blue) can be seen here over Antarctica on Oct. 4, 2019.

(Image: © NASA Goddard/Katy Mersmann)

The ozone hole above Antarctica, where the sun's harmful ultraviolet (UV) rays bust through an otherwise sunscreened stratosphere, has shrunk to its smallest size on record going back to 1982, scientists have found.

Typically, at this time of year, the hole in the ozone — a layer made up of molecules containing three oxygen atoms — grows to about 8 million square miles (20 million square kilometers), NASA said. That's bigger than Russia.

But unusually warm weather in the Southern Hemisphere means that the hole only extended less than 3.9 million square miles (10 million square kilometers) for most of September until now, according to a statement from NASA. 

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“This warming that occurred is great news for the Southern Hemisphere because ozone is going to be higher and UV levels will be lower,” Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland, told Live Science.

Here's how it works: During the winter months in the Southern Hemisphere, clouds form in the stratosphere, which extends from about 6 to 31 miles (9.5 to 50 km) above Earth's surface.

There, even the smallest amount of visible light from the sun breaks apart chlorine gas into chlorine atoms; those atoms are considered “reactive” and can chemically destroy ozone molecules.

So, the ozone hole over Antarctica tends to be much bigger in the southern winter. 

When temperatures over Antarctica start to warm up, the polar clouds in the stratosphere dissipate, meaning that there's no place for those ozone-annihilating chemical reactions to take place. This year, exceptionally warm weather put the nix on ozone-smashing, keeping that ozone hole super-small.

“This is as small as we were seeing back in the early '80s,” Newman said. (The ozone hole was so small that it wasn't even discovered until 1985.)

The ozone-busting chlorine gas mainly comes from chlorofluorocarbons (CFCs) that were manufactured until the U.S. ban beginning in 1996. Even so, some types of CFCs can stay in the atmosphere for more than 100 years, Newman said.

The 2019 ozone hole is the smallest on record since its discovery, but there’s a catch

Why Is the Ozone Hole Shrinking? A false-color view of total ozone over the Antarctic pole. The purple and blue colors are where there is the least ozone, and the yellows and reds are where there is more ozone. (NASA)

The Antarctic ozone hole hit its smallest annual peak on record since tracking began in 1982, the National Oceanic and Atmospheric Administration and NASA announced Monday. Although we’re making progress in cutting down on the use of ozone-depleting chemicals, the milestone doesn’t mean we’ve solved the problem, the agencies cautioned.

Instead, scientists attribute the relatively tiny ozone hole to unusually mild temperatures in that layer of the atmosphere.

According to NASA and the NOAA, the annual ozone hole — which consists of an area of heavily depleted ozone high in the stratosphere above Antarctica, between seven and 25 miles above the surface — reached its peak extent of 6.3 million square miles on Sept. 8 and then shrank to less than 3.9 million square miles during the rest of September and October.

“During years with normal weather conditions, the ozone hole typically grows to a maximum of about 8 million square miles,” the agencies said in a news release.

Why is the Ozone Hole Getting Smaller?

  • Why is the Ozone Hole Getting Smaller?
  • Narration: Joy Ng
  • Transcript:

Good news! Scientists say the Antarctic ozone hole is on the road to recovery.

The amounts of ozone-depleting substances grew rapidly in our atmosphere in the 80s and early 1990s, but had stopped growing in late 90s because of the 1987 Montreal Protocol.

As levels of these manufactured chemicals have decreased in the last 14 years, the ozone hole has seen a slight improvement.

Today, satellite observations by NASA and NOAA show the peak size of this year’s ozone hole measured 9.3 million square miles—an area roughly the size of North America.

  1. This area is smaller than holes observed in past years and significantly less than the largest hole on record.
  2. But scientists say the decrease of ozone-depleting substances isn’t the only factor that has contributed to these improvements.
  3. Rising temperatures in an upper layer of the atmosphere known as the stratosphere may also play a role.
  4. Colder temperatures in the polar regions have been shown to promote ozone depletion, while warmer temperatures lead to increased ozone.
  5. Years with warmer temperatures generally had smaller holes, while colder temperatures had larger holes.
  6. So how much of the ozone hole’s recovery is due to a rising temperatures versus decreasing levels of manufactured chemicals?
  7. Scientists are looking to answer this question.

The 2019 ozone hole is the smallest ever recorded

Abnormally warm temperatures in the stratosphere over Antarctica dramatically limited ozone loss in September and October, resulting in the smallest ozone hole observed since 1982, NOAA and NASA scientists reported todayoffsite link.

The annual ozone hole reached its peak extent of 6.3 million square miles (16. 4 million square kilometers) on September 8 and then shrank to less than 3.9 million square miles (10 million square kilometers) during the remainder of September and October.

During years with normal weather conditions, the ozone hole typically grows to a maximum of about 8 million square miles.

Uncommon, but not unprecedented

This is the third time in 40 years that weather systems have caused warm temperatures that limit ozone depletion. Similar weather patterns in the Antarctic stratosphere in September 1988 and 2002 also produced atypically small ozone holes. 

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“It’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures,” said Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center. “It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”

As of October 16, the ozone hole above Antarctica was still small but stable, and it should gradually close over the next six weeks. Scientists expect the ozone hole to shrink back to the size it was in 1980 by approximately 2070, as ozone-depleting chemicals banned by the Montreal Protocol but still in the atmosphere continue to decline.

There is no identified connection between these weather patterns and climate change.

What is ozone, and why does it matter?

Ozone, comprised of three oxygen atoms, occurs naturally in exceedingly small amounts. If compressed into its pure form, all of the ozone in a column of atmosphere extending from the ground to space would be about as thick as two pennies stacked one on top of the other.

High in the stratosphere, the ozone layer is a sunscreen that shields the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and also damage plants. 

Ozone created as a byproduct of pollution close to the Earth’s surface, however, can trigger a variety of health problems such as asthma, bronchitis and difficulty breathing.

How do you measure the ozone hole?

NASA and NOAA monitor the ozone hole by using three complementary instrumental methods. 

Satellites, including NASA’s Aura satellite and NASA-NOAA Suomi National Polar-orbiting Partnership satellite, measure the size of the ozone hole from space. The Aura satellite’s Microwave Limb Sounder estimates levels of ozone-destroying chlorine. 

NOAA staff at the South Pole also launch weather balloons carrying ozone-measuring sondes that directly sample ozone levels vertically through the atmosphere. 

Most years, at least some portion of the stratosphere is found to be completely devoid of ozone. This year, ozonesonde measurements did not show any portions of the atmosphere where ozone was absent, according to NOAA scientist Bryan Johnson.

Want to know more about the ozone hole? See this helpful explainer, 20 Questions About the Ozone. 

Ozone hole near South Pole shrinks to smallest size ever seen

The ozone hole near the south pole this year is the smallest since it was discovered, but it is more due to freakish Antarctic weather than efforts to cut down on pollution, NASA reported.

This fall, the average hole in Earth's protective ozone layer is 3.6 million square miles (9.3 million square kilometers). That's down from a peak of 10.3 million square miles (26.6 million square kilometers) in 2006.

This year's hole is even smaller than the one first discovered in 1985.

“That's really good news,” NASA scientist Paul Newman said Tuesday. “That means more ozone over the hemisphere, less ultraviolet radiation at the surface.”

Earth's ozone layer shields life on the surface from harmful solar radiation, but man-made chlorine compounds that can last in the air for 100 years nibble at the ozone, creating thinning and a gap over the Southern Hemisphere.

The hole reaches its peak in September and October and disappears by late December until the next spring in the Southern Hemisphere.

The 1987 international Montreal Protocol — the only United Nations treaty ratified by every country on Earth — banned many of the chlorine compounds used in refrigerants and aerosols. The ban resulted in a slightly smaller ozone hole in recent years, but this year's dramatic shrinking isn't from those efforts, Newman said.

“It's just a fluke of the weather,” said University of Colorado atmospheric scientist Brian Toon.

Chlorine in the air needs cold temperatures in the stratosphere and clouds to convert into a form of the chemical that eats ozone, Newman said. The clouds go away when it warms up.

Ozone hole shrinks due to warmer than average air temperature

The average hole in the Earth’s protective ozone layer is 3.6 million square miles.

23rd October, 2019 at 09:00

The ozone hole near the South Pole is at its smallest since it was discovered, but that is more due to freakish Antarctic weather than efforts to cut down on pollution, NASA has said.

This autumn, the average hole in Earth’s protective ozone layer is 3.6 million square miles, down from a peak of 10.3 million square miles in 2006.

This year’s hole is even smaller than the one first discovered in 1985.

“That’s really good news,” NASA scientist Paul Newman said. “That means more ozone over the hemisphere, less ultraviolet radiation at the surface.”

  • Read more about the Earth’s atmosphere:
  • Earth’s ozone layer shields life on the surface from harmful solar radiation, but man-made chlorine compounds that can last in the air for 100 years eat away at the ozone, creating thinning and a gap over the Southern Hemisphere.
  • The hole reaches its peak in September and October and disappears by late December until the next spring in the Southern Hemisphere.
  • The 1987 international Montreal Protocol — the only United Nations treaty ratified by every country on Earth — banned many of the chlorine compounds used in refrigerants and aerosols.
  • The ban resulted in a slightly smaller ozone hole in recent years, but this year’s dramatic shrinking is not from those efforts, Mr Newman said.
  • “It’s just a fluke of the weather,” said University of Colorado atmospheric scientist Brian Toon.
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Chlorine in the air needs cold temperatures in the stratosphere and clouds to convert into a form of the chemical that eats ozone, Mr Newman said. The clouds go away when it warms up.

But this September and October, the southern polar vortex — a swirl of cold high-speed winds around the pole — started to break down.

At 12 miles high in the atmosphere, temperatures were 16°C warmer than average. Winds dropped from a normal 161mph to about 67mph, NASA reported.

This is something that happens on occasion, occurring in 1988 and 2002, but not this extreme, Mr Newman said.

Asked by: Rob Munton, Poole

The main ozone-depleting gases are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The Montreal Protocol, which came into force in 1989, lists 56 CFCs and 34 HCFCs, and production of almost all of them is now completely banned. There are a few exceptions where there isn’t an alternative, such as the fire suppression systems on submarines.

However, a study at the University of East Anglia found three new CFCs and one HCFC that have recently been released into the atmosphere.

The amounts aren’t large – less than one per cent of the total release of ozone-depleting compounds before the Montreal Protocol was signed. But the source of these new compounds is currently unknown and the levels of two of them are rising rapidly.

These chemicals will also take several decades to break down naturally, so they will continue to be a problem, even if their production is stopped immediately.

Read more:

Alexander is the Online Editor at BBC Science Focus and is the one that keeps sciencefocus.com looking shipshape and Bristol fashion. He has been toying around with news, technology and science on internet for well over a decade, and sports a very fetching beard.

A Warming Planet Is Helping Shrink The Ozone Hole To Smallest Since 1988

Size of the ozone hole form 1979 to 2016

NASA

One upside to a warming planet is the gradual shrinking of the ozone hole over Antarctica. NASA measurements found that the ozone hole is approximately the same size that it was in 1988 and 1.3 million square miles smaller than it was last year.

The reason behind the significant decrease in the ozone layer is unusually warm weather conditions in Antarctica's stratosphere, which helped push away ozone-depleting chemicals. However, the overall trend of a shrinking ozone hole is a result of the global effort to eliminate ozone attacking chemicals such as chlorofluorocarbons, previously used in refrigerants.

The global effort was put in place by the Montreal Protocol On Substances that Deplete the Ozone Layer, which regulated ozone-depleting chemicals from manufacturing.

While the use of harmful compounds for the ozone has decreased dramatically, chlorofluorocarbons remain in the atmosphere for quite a long time and estimates are that the ozone hole won't fully recover back to 1980 levels until the 2070s.

The ozone hole reached its maximum extent in 2017 on September 11th, at 7.6 million square miles or approximately 2.5 times the size of the United States. While the ozone hole still remains large, NASA indicates it is much smaller than the ozone hole's peak in 2000 at 11.5 million square miles.

However, the extent to which the ozone hole decreases due to warmer weather can just as easily swing the other direction if the stratosphere over Antarctica were to experience a cooler than normal year.

This year's unusually warm weather caused a warm Antarctic vortex to minimize stratospheric cloud formation.

This cloud formation is required in order for chlorine-catalyzed and bromine-catalyzed reactions to deplete the ozone.

In 2016 the ozone hole reached its maximum extent of 8.9 million square miles, yet that was still significantly lower than the average of about 10 million square miles the ozone hole had been since the late 1990's.

Size of the ozone hole over Antarctica through time.

NASA

The reduction in the ozone hole in the last couple years is largely due to natural variability in temperature and does not indicate the sudden “healing” of the ozone hole. However, recent upticks in the slope of average global temperatures could help play a role in the short term diminishing of the hole.

Global Land-Ocean Temperature Index

NASA

The ozone layer helps protect humans, animals, and plants from harmful ultraviolet radiation. Depletion of the ozone layer causes an increased risk of skin cancer, cataracts, suppresses the immune system and can damage plants. While we'll have to wait until the 2070s to get back to pre-1980s conditions, it's good to see progress and positive news.

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