Ozone: stabilization but no all-clear

Record to the International Day of the Ozone

Ozone density over the northern hemisphere DLR
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Every year on 17 September, the international focus is on an invisible but indispensable protective cover in our earth's atmosphere - the ozone layer. The UN International Day of the Ozone Layer is the catalyst for the annual "Health Check" on the ozone envelope, without which life on earth would hardly be possible.

The day commemorates the entry into force of the Montreal Convention in 1987 and aims to underline the importance of ozone protection. "This was the beginning of the unique success story of the joint efforts of the global community to protect the life-preserving ozone layer, " said Federal Environment Minister Jürgen Trittin.

Ozone is concentrated mainly in the second floor of the atmosphere, the stratosphere, in the altitude range between 10 and 30 kilometers. The ozone layer is extremely important for life on earth. It blocks the hostile, skin cancer-promoting, ultraviolet radiation of the sun and thus serves the earth as a natural UV protection.

Scientists sounded the alarm

After the end of the 1980s, when scientists sounded the alarm and drew attention to the seemingly inexorable shrinking density of the ozone layer, it was time to act. The culprits were already clearly identified: halogen-containing propellants and coolants acted as catalysts for ozone depletion.

The most well-known ozone pollutants are the so-called CFCs, which are mainly used in sprays as propellants. Another group of ozone-depleting substances are HCFCs. They are primarily used as refrigerants in air-conditioning and refrigeration systems and, in contrast to CFCs, are much less hazardous to the ozone layer. In addition, they are usually in closed systems. display

Measures begin to take effect

The safeguards adopted by the Montreal Convention and ratified by 198 countries are beginning to take hold today. Since then, the ozone layer has been recovering globally and has even stabilized, according to new results from American science teams.

According to the Federal Statistical Office, only about 2, 050 tonnes of ozone-depleting substances were used by German companies in 2003. Their use has more than halved in the last five years (- 56.3 percent). In 1999, about 4, 687 tonnes were still used in the production of products. Germany is thus adhering to the timetable of the internationally agreed exit periods.

Nevertheless, record fading over the Arctic

But there is still no reason to be completely clear: Although the ozone layer has recovered globally since the entry into force of the Montreal Agreement of 1987, unfavorable weather conditions at both poles of the earth this year led to a temporarily extremely high ozone depletion. Both over the North Pole and over the South Pole, the ozone hole in 2005 was the largest ever.

The evaluation of the data of the atmosphere sensor SCIAMACHY, which is operated by the German Aerospace Center (DLR), showed that the ozone layer had reached a worrying decrease, especially over Europe in February 2005. At some points in the stratosphere, chemical ozone erosion across the Arctic reached nearly 50 percent, the second highest values ​​ever recorded.

However, a recovery was already observed in March 2005, as the ozone destruction was stopped by the increase in the temperature in the stratosphere. In addition, ozone-depleted air masses are normally transported to the ozone-depleted areas at the end of winter.

and over the Antarctic

Also, the ozone hole over the S dpol was this year as big as ever. This was the result of analyzes by scientists of the European Space Agency ESA, who had analyzed data from the satellite ENVISAT. Thereafter, in the summer of 2005, the Antarctic ozone hole covered an area of ​​ten million square kilometers, which is roughly equivalent to the size of Europe. The main reason for the ozone hole over the Antarctic is still the emission of chemicals such as chlorofluorocarbons, in this year also an unfavorable weather situation, which promoted the depletion of ozone.

(BMU, Federal Statistical Office, NOAA, NASA, 16.09.2005 - NPO)