Asked by: Sheila Taylor, Oxfordshire
Ozone depletion occurs when ozone molecules in the upper atmosphere are destroyed by chemical reactions with halogen gases, such as chlorine. Cold conditions above Antarctica in the winter months encourage the formation of extremely cold, high-altitude clouds.
These clouds provide the ideal conditions for chlorine that was previously trapped in stable molecules to be transformed into highly reactive chlorine gas, which accumulates over the long polar night. As winter ends, sunlight breaks apart the chlorine gas molecules, freeing billions of chlorine atoms, which go on to react with ozone molecules, causing a sharp dip in ozone levels: the ozone ‘hole’.
- Why can't we just fill in the ozone hole with man-made ozone?
- Antarctica is “getting greener” due to climate change