Final answer:
The ozone shield is a stratospheric layer that protects Earth from harmful UV radiation. It is endangered by chemicals like CFCs that deplete ozone. International accords like the Kyoto Protocol are critical in mitigating this threat.
Step-by-step explanation:
The Ozone Shield and Its Significance:
The ozone shield refers to a layer of ozone (ozone) gas located near the top of the stratosphere, roughly between 15 and 35 kilometers above Earth's surface. This layer, consisting of ozone molecules with three oxygen atoms, serves as a protective barrier that absorbs the majority of the sun's harmful ultraviolet (UV) radiation, thus safeguarding all life forms on Earth from potential DNA mutations and other adverse effects caused by UV exposure, such as skin cancer and eye damage.
Threats to the Ozone Shield:
The existence of the ozone shield is threatened by human activities that release industrial chemicals such as chlorofluorocarbons (CFCs) into the atmosphere, leading to ozone depletion. These chemicals react with ozone molecules and cause them to break apart, diminishing the protective layer and allowing more UV rays to reach the Earth's surface. This depletion was dramatically showcased by the discovery of the ozone hole over the Antarctic in the 1980s. However, international efforts like the Kyoto Protocol, which aims to phase out the production of ozone-depleting chemicals, have significantly contributed to slowing and reversing this damage.