CNN: Ozone depletion has now reached the highest level observed to date in the northern hemisphere. The World Meteorological Organization stated Tuesday that the Arctic region lost 40% of its ozone layer from the beginning of this winter to late March. The usual winter ozone loss there is about 25%; the highest ozone loss previously recorded was approximately 30%. Although cuts in the production of chlorofluorocarbons and other ozone-destroying chemicals have been made, and the concentration of them in the atmosphere is slowly falling, the chemicals stay in the atmosphere for several decades. When temperatures in the stratosphere fall below −78 °C, chemical reactions turn the ozone-destroying chemicals into highly reactive substances that break apart the three oxygen atoms of ozone, leading to an ozone hole.
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