Final answer:
The ozone layer exists within the stratosphere and plays a critical role in absorbing UV radiation. Human-made chemicals once threatened the ozone layer, but international actions have led to a reduction in these substances and subsequent recovery of the ozone layer.
Step-by-step explanation:
The ozone layer is primarily located in the stratosphere and it is crucial for protecting the Earth from excessive ultraviolet (UV) radiation. The stratosphere hosts most of the Earth's ozone, which absorbs the harmful UV radiation, especially UVB rays that are linked to skin cancer, cataracts, and harm to marine ecosystems. The creation and destruction of the ozone involve a continuous cycle where oxygen molecules are turned into ozone by the sun's energy and then back into oxygen molecules. The presence of ozone in the stratosphere is essential for life on Earth, as it filters out most of the damaging UV rays that could otherwise cause grave effects on living organisms.
In the 1980s, we learned that the ozone layer was being depleted by human-made chemicals such as chlorofluorocarbons (CFCs). International efforts like the Montreal Protocol have since phased out the production of these ozone-depleting substances, helping to stop ozone layer degradation and allowing the ozone hole over the Antarctic to gradually shrink. The recovery of the ozone layer is a testament to how international cooperation can contribute to the preservation of our planet's habitability.