Scientists from the Central Geophysical Observatory of the Institute of Geophysics PAS began the first regular measurements of ozone in the atmosphere 50 years ago. They record the concentration of ozone in the atmosphere above the measuring station in Belsk Duży near Grójec.

In the release sent to PAP, the institute reports that for several years, especially in the summer, scientists have been record lower concentration of ozone in the stratosphere over Belsk. "At the end of 2012 there was a few percent less than would be expected, given the decreasing concentration of pollutants in the stratosphere" - reports the Institute of Geophysics PAS.

"It is possible that a new, yet unidentified local mechanism that reduces the thickness of the protective ozone layer starts to operate in the atmosphere. Regardless of its nature, it is certain that in the near future, everyone should still be wary of the sun and avoid excessive sunbathing. And we must continue to monitor the condition of ozone over our heads" - emphasised Head of the Department of Atmospheric Physics, Institute of Geophysics PAS Prof. Janusz Krzyścin.

Molecules of oxygen we breathe have two oxygen atoms. The concentration of ozone (molecules with three atoms of oxygen) in the air is low. The maximum concentration of ozone in the atmosphere, of the order of a few parts per million air molecules, are present in the stratosphere, at about 30 km. "If we gathered all the ozone contained in a vertical column of air above our heads at ground level, the layer would have a thickness of 2 to 5 mm, depending on the time of year" - reads the message sent to PAP.

Ozone in small quantities causes cough and headache, and larger amounts lead to pulmonary edema and death. However, ozone, which is present in the stratosphere, is essential for life on Earth. It strongly absorbs ultraviolet radiation from the sun reaching the upper atmosphere, which has a protective effect on living organisms.

"In humans, excess UV radiation is harmful to the eyes and skin. It is known for its close, well documented link to the formation of skin cancers: basal and squamous" - explains Prof. Krzyścin.

Since the mid-1980s, terrestrial and satellite observations have been showing disturbingly low levels of ozone in the atmosphere over Antarctica. Its deficit over areas with surface in the tens of millions of square kilometres ranged as high as 40 percent. In some layers of the atmosphere over Antarctica, at an altitude of 15-20 km, ozone has been completely destroyed. This phenomenon has been given the name "ozone hole".

The culprit turned out to be chlorofluorocarbon gases commonly used in the second half of the twentieth century in aerosols and refrigerators, the Institute of Geophysics PAS experts explain. These compounds ended up in the atmosphere, migrated toward the equator and there they were elevated into the stratosphere, where they spread toward the poles. During their movement in the high layers of the atmosphere, CFCs disintegrated under the influence of strong UV radiation. The resulting free chlorine atoms then become a catalyst for chemical reactions leading to intensive decomposition of ozone. After about five years of wandering in the stratosphere, CFCs reached Antarctica and the Arctic.

The ozone hole is a seasonal phenomenon. It has been appearing over the Antarctic each year at the end of winter and disappearing after a few months for over 30 years. Depending on the weather conditions, it may be larger or smaller and lasts a months longer or shorter.

"As a result of the cooling of Antarctica during the polar night, in the period from June to September, in the southern hemisphere atmosphere, at an altitude of about 20 km, appear specific clouds composed of droplets of dilute nitric acid or ice crystals. With the return of sunlight over the area, at the turn of August and September, intensive ozone-depleting chemical reactions take place in the vicinity of such particle clouds. During the Arctic spring, the sun gradually warms up the atmosphere and clouds disappear, usually at the end of November, and with the ozone hole also disappears with them" - describes Prof. Krzyścin.

The researchers argue that the ozone hole over Antarctica has no effect on ozone levels over Poland. We can only be threatened by the ozone hole over the Arctic. "Over the north pole, however, the atmosphere is warmer, and only after an extremely cold winter of 2010/2011 there was the ozone hole here. It was much less extensive than its counterpart over the Antarctica" - report the researchers in the release sent to PAP.

Since the beginning of the 1970s, the stratosphere has been becoming increasingly polluted with ozone-depleting substances. In the 1990s, measurements at the Institute of Geophysics PAS observatory showed ozone deficit over Poland at the level of 6 percent in relation to the long-term average from the 1960s and 1970s. "These changes have resulted in a slight, almost harmless increase in UV radiation, comparable to the one we would experience after moving from Warsaw to Kraków" - report the researchers.

In 1987, under the so-called Montreal Protocol the international community has undertaken actions to reduce the emissions of CFCs and other ozone-depleting substances into the atmosphere. At the turn of the century many stations, including the one in Belsk, began to record the gradual increase of ozone concentrations in the atmosphere.

"It seemed that with the Montreal Protocol and its subsequent amandments, imposing further restrictions on the production of substances harmful to the ozone, the problem has been resolved. However, in the middle of the last decade, in our latitudes the trend reversed and ozone levels began to drop again" - reads the Institute of Geophysics PAS release.

The Institute of Geophysics PAS in Warsaw conducts basic research in the physics of the Earth, atmospheric physics, seismology, geomagnetism and hydrology, it also organizes polar expeditions. Belsk ozone observations are included in the global ozone monitoring system and provide valuable data for a number of scientific papers.

"The results of our observations of ozone have been used, among others to assess the accuracy of measurements of ozone made by satellites orbiting the Earth "- said Prof. Janusz Krzyścin.

„Wyniki naszych obserwacji ozonowych były używane m.in. do oceny dokładności pomiarów ozonu wykonywanych przez krążące wokół Ziemi satelity” - mówi prof. Janusz Krzyścin.

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