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Apr 19, · The ozone layer, which lies high up in the atmosphere, shields us from harmful ultraviolet (UV) rays that come from the Sun. Unfortunately we punched a hole in it, through the use of gases like chlorofluorocarbons (CFCs) in spray cans and refrigerants, which break down ozone molecules in the upper atmosphere. Many people have heard that the ozone hole is caused by chemicals called CFCs, short for chlorofluorocarbons. CFCs escape into the atmosphere from refrigeration and .
The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which damages DNA in plants and animals including humans and leads to sunburns and skin cancer. Prior toscientists had not observed atmospheric ozone concentrations below Dobson Units. This thinning of the ozone layer over Antarctica came to be known as the ozone hole. This series of images shows the size and shape of the ozone hole each year from through no data are available for Red and yellow areas indicate the ozone hole.
Scientists use the word hole as a metaphor for the area in which ozone concentrations drop below the historical threshold of Dobson Units. These maps show the state of the ozone hole each year on the day of maximum depth—the day the lowest ozone concentrations were measured. The series begins in The maximum depth of the hole that year was Dobson Units DU —not far below the previous historical low.
For several years, the minimum concentrations stayed in the s, but then the minimums rapidly grew deeper: DU ininin Bya new threshold was passed, as the ozone concentration what is a vesa mounting pattern below DU for the first time.
Since then, concentrations below became more common. The deepest ozone hole occurred inwhen concentrations fell to just 73 DU on September Records in depth and area have never occurred during the same years the largest ozone hole occurred inbut the long-term trend in both characteristics is consistent: from through the early s, the hole rapidly grew in area and depth.
In the early years of the 21st century, annual ozone holes roughly stabilized see the Ozone Hole Watch website for annual averages. Year-to-year fluctuations in area and depth are caused by variations in stratospheric temperature and circulation.
Colder conditions result in a larger area and lower ozone values in the center of the hole. Scientists found out that chlorofluorocarbons CFCs —long-lived chemicals that had been used in refrigerators and aerosol sprays since the s—had a dark side.
In the layer of the atmosphere closest to Earth the troposphereCFCs circulated for decades without degrading or reacting with other chemicals.
When they reached the stratosphere, however, their behavior changed. In the upper stratosphere beyond the protection of the ozone layerultraviolet light caused CFCs to break apart, releasing chlorine, a very reactive atom that repeatedly catalyzes ozone destruction. The global recognition of the destructive potential of CFCs led to the Montreal Protocola treaty phasing out the production of ozone-depleting chemicals. Scientists estimate that about 80 percent of the chlorine and bromine, which has a similar ozone-depleting effect in the stratosphere over Antarctica today comes from human, not natural, sources.
Models suggest that the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre levels until the middle decades of the 21st century.
Scientists have already seen the first definitive proof of ozone recovery, observing a 20 how to remove outlook 2003 decrease in ozone depletion during the winter months from to Inabnormal weather patterns in the upper atmosphere over Antarctica dramatically limited ozone depletion, leading to the smallest hole since Models predict that the Antarctic ozone layer will mostly recover by EO Explorer.
References Carlowicz, M. Carlowicz, M. World of Change: Antarctic Ozone Hole. Subscribe to our newsletters.
Polar stratospheric clouds (PSCs) and ozone
In the s, scientists noticed that the ozone layer over the South Pole was becoming much thinner than usual. After some study, atmospheric scientists recognized that this ozone depletion was a result of air pollutants from human activities — specifically, the release of nontoxic, aerosol gas molecules called chlorofluorocarbons. Nov 11, · What caused the ozone hole? Scientists pinpointed the emissions of certain gases containing ozone-depleting substances as the main source of the problem. CFCs, short for chlorofluorocarbons, are one of the most detrimental gases to the ozone layer. Year-to-year fluctuations in area and depth are caused by variations in stratospheric temperature and circulation. Colder conditions result in a larger area and lower ozone values in the center of the hole. The ozone hole opened the world’s eyes to the global effects of human activity on the atmosphere.
Almost 40 years ago, scientists discovered that human activities were depleting the ozone layer and that a hole had formed over Antarctica. These sobering discoveries brought the world together to tackle an environmental challenge of a lifetime.
Decades later, the ozone hole has come a long way since its dire outlook in the s. But it's not a cause for celebration just yet. There are still ongoing efforts between policymakers and scientists to ensure the ozone in the atmosphere is protected. At ground level, ozone is a poisonous molecule to humans and can damage the lungs when inhaled.
At the stratospheric level, it connects with other ozone molecules in a cover known as the ozone layer. These ozone molecules absorb UV radiation , acting as a sunscreen for life on Earth. In the s and 70s, researchers began discovering that certain substances — particularly manmade industrial chemicals — disrupt ozone molecules.
These substances break down ozone molecules by stripping away one of the oxygen atoms. Over time, these reactions can make the ozone layer less stable. In , this threat became known to the public. Scientist Joseph C. Farman and his colleagues discovered that atmospheric ozone over Antarctica had reduced by 40 percent.
Certain human-made substances had reached the stratosphere and disrupted the ozone layer to the point of depletion, creating an extremely thin section commonly known as the ozone hole. The hole formed at the South Pole due to the region's unique meteorological and chemical conditions. Scientists pinpointed the emissions of certain gases containing ozone-depleting substances as the main source of the problem.
CFCs, short for chlorofluorocarbons, are one of the most detrimental gases to the ozone layer. CFCs were widely used in previous decades, peaking in the late s. Many refrigerators, air conditioners and foam-blowing equipment used to emit dangerous levels of chlorine gas into the atmosphere. Once chlorine reaches the ozone layer, ultraviolet radiation from the sun converts it into a reactive substance, which then destroys ozone molecules.
Other compounds, such as bromine, have also played a role in depleting the ozone layer. Even though levels of these substances in the atmosphere reduced drastically over the years, the ozone hole will only fully recover in coming decades. Ozone layer thinning is a human health risk.
Excess UVB radiation is particularly worrisome, as it can cause skin cancer and cataracts. UVB radiation also can harm marine life and plants , and reduce the productivity of rice, wheat and soybean crops.
The effects of CFCs might go beyond the ozone layer. CFCs are potent greenhouses gases and could have a broader impact on climate change outcomes. While CFCs don't seem to cause global warming, a different picture emerges with regional warming. Recent research has shown that these same gases have sped up the warming of the Arctic, contributing to a sea level rise and surface warming in the North Pole. Fixing the ozone hole is a matter of ensuring that no ozone-depleting gases reach the stratosphere.
In , the United Nations established the Montreal Protocol to regulate the quantities of these gases in the atmosphere. The Montreal Protocol was signed by countries, and is the only UN treaty in history to achieve universal ratification. Over time, the protocol has been updated to include more substances that could cause harm to the ozone layer and the climate. For example, in , hydrofluorocarbons were added to the list of controlled substances, because these gases have been identified as potent greenhouse gases.
The treaty is considered to be one of the most successful protocols to tackle an environmental challenge caused by humans. Yes and no. As a result of the Montreal Protocol, concentrations of ozone-depleting gases in the atmosphere have significantly declined. But according to Laura Revell, an environmental physics professor at the University of Canterbury, the issue isn't solved yet.
Stephen Montzka, a research chemist at the National Oceanic and Atmospheric Administration, says they've detected possible illegal CFCs in the atmosphere. In , Montzka coauthored a report in Nature that showed unexpected levels of CFC, a type of chlorofluorocarbons, were present. This concentration of CFC was perhaps the result of unauthorized industrial production, going against the Montreal Protocol. Further research by Montzka showed that the recovery of the ozone hole could be delayed because of these emissions.