Why is stratospheric ozone important to life on Earth?

• A. It protects us from harmful ultraviolet light from the sun
• B. It reflects infrared radiation from the sun
• C. It stores atmospheric heat to keep Earth's surface warm
• D. It increases weather variability

Answer: (A)

Stratospheric ozone acts as a shield for life by absorbing most of the sun’s high-energy ultraviolet radiation, especially UV-B and UV-C. By filtering these harmful rays before they reach the surface, it greatly reduces DNA damage in living organisms, which lowers risks of skin cancer, cataracts, and immune suppression, and helps protect ecosystems that are sensitive to UV, such as phytoplankton in the oceans. The ozone layer sits in the stratosphere, where ozone is continually formed and destroyed, creating a protective blanket rather than a heat-trapping layer. The idea that ozone reflects infrared radiation or stores heat to warm Earth is not its primary role; those effects are associated with greenhouse gases like CO2 and water vapor. Ozone’s main importance is UV shielding, which is essential for life as we know it.