Catalysis is relevant to many aspects of environmental science, e. g. the catalytic converter in automobiles and the dynamics of the ozone hole.

The largest Antarctic ozone hole recorded as of September 2006

The impact of these studies, the metaphor ' ozone hole ', and the colourful visual representation in a time lapse animation proved shocking enough for negotiators in Montreal to take the issue seriously.

After the discovery of the ozone hole it only took 18 months to reach a binding agreement in Montreal.

In a 2001 report, NASA found the ozone thinning over Antarctica had remained the same thickness for the previous three years, however in 2003 the ozone hole grew to its second largest size.

A 2008 study published in the Proceedings of the National Academy of Science found that a nuclear weapons exchange between Pakistan and India using their current arsenals could create a near-global ozone hole, triggering human health problems and wreaking environmental havoc for at least a decade.

However in the southern hemisphere, owing to the ozone hole phenomenon, the lowest amounts of column ozone found anywhere in the world are over the Antarctic in the southern spring period of September and October.

In the U. S., chlorofluorocarbons continued to be used in other applications, such as refrigeration and industrial cleaning, until after the discovery of the Antarctic ozone hole in 1985.

It is indeed very often said that media could be useful ( in the point of view of someone looking for a control over the forming of consensus ) in order to discipline the popular sentiments, by detracting the public from the apocalyptic problems of mankind ( e. g. global warming, ozone hole, radioactive waste, ...), and by the " psychological warfare " threatening their own public until it accepts foreign or external interventions.

* May 16 – Scientists of the British Antarctic Survey announce discovery of the ozone hole .< ref >

* The ozone hole —

Image of the largest Antarctic ozone hole ever recorded ( September 2006 ), over the Southern pole

The latter phenomenon is referred to as the ozone hole.

The details of polar ozone hole formation differ from that of mid-latitude thinning, but the most important process in both is catalytic destruction of ozone by atomic halogens.

Lowest value of ozone measured by Total Ozone Mapping Spectrometer | TOMS each year in the ozone hole.

However, the ozone hole is most usually measured not in terms of ozone concentrations at these levels ( which are typically of a few parts per million ) but by reduction in the total column ozone, above a point on the Earth's surface, which is normally expressed in Dobson units, abbreviated as " DU ".

Early models failed to take PSCs into account and predicted a gradual global depletion, which is why the sudden Antarctic ozone hole was such a surprise to many scientists.

Ozone hole in North America during 1984 ( abnormally warm reducing ozone depletion ) and 1997 ( abnormally cold resulting in increased seasonal depletion ).

The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone levels have dropped to as low as 33 % of their pre-1975 values.

Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much smaller ozone depletion through homogeneous gas phase reactions, which occurs primarily in the upper stratosphere.

The majority of tropospheric ozone formation occurs when nitrogen oxides ( NOx ), carbon monoxide ( CO ) and volatile organic compounds ( VOCs ), such as xylene, react in the atmosphere in the presence of sunlight.

Ozone in outdoor air occurs indoors at reduced concentrations because ozone is highly reactive with many chemicals found indoors.

Most of the ozone production occurs in the tropical upper stratosphere and mesosphere.

Combined chlorine and bromine in the lower stratosphere ( 10-25 km ), where most ozone loss occurs, leveled off around 1999.

Recently another pathway, via NO < sub > x </ sub >, to ozone has been found that predominantly occurs in coastal areas via formation of nitryl chloride when NO < sub > x </ sub > comes into contact with salt mist.

Three satellites and three ground stations confirmed that the upper atmosphere ozone depletion rate has slowed down significantly during the past decade.

Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.

* Primary scientific data was collected in Punta Arenas, Chile, using a Brewer spectro-photometer, and " These results indicate that during the time when ozone depletion in the Antarctica takes place, an increase in UV-B radiation reaching the Earth surface affected the American continent at latitudes about parallel 50 ° S ."

It is calculated that a CFC molecule takes an average of about five to seven years to go from the ground level up to the upper atmosphere, and it can stay there for about a century, destroying up to one hundred thousand ozone molecules during that time.

Within this polar vortex, over 50 % of the lower stratospheric ozone is destroyed during the Antarctic spring.

The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is greatest during spring.

* Many were worried that ozone holes might start to appear over other areas of the globe but to date the only other large-scale depletion is a smaller ozone " dimple " observed during the Arctic spring over the North Pole.

This avoided the ozone and nitrous oxide produced by RF decomposition of air in an earlier generation of plasma tweeters made by the pioneering DuKane Corporation, who produced the Ionovac ( marketed as the Ionofane in the UK ) during the 1950s.

Methane, a VOC whose atmospheric concentration has increased tremendously during the last century, contributes to ozone formation but on a global scale rather than in local or regional photochemical smog episodes.

Recent research has shown that mortality and morbidity increase in the general population during periods of higher outdoor ozone and that the threshold for this effect is around 20 parts per billion ( ppb ).

This limits thunderstorm activity near their center, and traps low-level pollutants such as ozone as haze under their base, which is a significant problem in large urban centers during summer months such as Los Angeles, California and Mexico City, Mexico.

STS-34 Atlantis ( October 18 to October 23, 1989 ) was a 5-day mission during which the deployed the Galileo spacecraft, on its journey to explore Jupiter, operated the Shuttle Solar Backscatter Ultraviolet Instrument ( SSBUV ) to map atmospheric ozone and performed numerous secondary experiments involving radiation measurements, polymer morphology, lightning research, microgravity effects on plants and a student experiment on ice crystal growth in space.

The largest-amplitude atmospheric tides are mostly generated in the troposphere and stratosphere when the atmosphere is periodically heated as water vapour and ozone absorb solar radiation during the day.

Partial electrical breakdown of the air causes the " fresh air " smell of ozone during thunderstorms or around high-voltage equipment.

* In some recent cold Arctic winters during the last decade, maximum total column ozone losses due to halogens have reached 30 %, but in warmer winters Arctic ozone loss is small.

Chlorine concentrations build up during the polar winter, and the consequent ozone destruction is greatest when the sunlight returns in spring.