The ozone layer acts as Earth's natural sunscreen, absorbing up to 98% of the sun's harmful ultraviolet radiation.

The ozone layer is located within the stratosphere, roughly 9 to 18 miles (15 to 30 kilometers) above the Earth's surface. It contains a high concentration of ozone (O3) molecules, which are formed when solar ultraviolet (UV) radiation hits regular oxygen (O2) molecules and breaks them apart into individual atoms. These atoms then bond with other O2 molecules to create O3.This process is known as the Chapman Cycle, first described by British physicist Sydney Chapman in 1930. The ozone layer is critical because it absorbs 97% to 99% of medium-frequency ultraviolet light (UV-B), which is biologically harmful. Without this protection, life on land would be nearly impossible due to severe DNA damage and cellular mutations in plants and animals.In 1985, researchers from the British Antarctic Survey, including Joseph Farman, Brian Gardiner, and Jonathan Shanklin, published a study in 'Nature' revealing a massive 'hole' in the ozone layer over Antarctica. They identified chlorofluorocarbons (CFCs), commonly used in aerosol sprays and refrigerators, as the primary culprits. When CFCs reach the stratosphere, UV light breaks them down to release chlorine atoms, which can destroy over 100,000 ozone molecules each.The international community responded by signing the Montreal Protocol in 1987, which remains one of the most successful environmental treaties in history. According to a 2022 United Nations-backed report, the ozone layer is on track to recover to 1980 levels by approximately 2040 for most of the world. The recovery over the Antarctic is expected to take longer, potentially reaching completion by 2066.