6.4 Stratospheric ozone

• Low frequency radio to high frequency gamma

• Infrared, visible light, ultraviolet (UV)

• Shorter wavelengths, higher frequencies, more energy

• UVA, UVB, UVC damage organisms

• Absorbs UV radiation from Sun

• Protects living organisms from harmful effects

• Reduces photosynthesis in phytoplankton

• DNA damage: mutations, cancer

• Humans: sunburn, premature ageing, cataracts

• Steady state between formation and destruction

• Destroy ozone molecules

• Augment natural breakdown

• Not a cause of global warming

• More UVB reaches Earth's surface

• Polar "ozone holes" in spring

• International treaty regulating CFCs and ODSs

• Most successful international environmental cooperation

• Prevented planetary boundary crossing

• Release halogens (chlorine, fluorine) into stratosphere

• Break down ozone

• Occurs in spring

• Chemical and atmospheric conditions

• Polar stratospheric clouds, active surfaces

• Replaced CFCs, less ozone depletion

• Potent GHGs

• Controlled by Kigali Amendment

• Energy-intensive, contribute to GHG emissions

• Contain ODSs

• Alternatives: building design, greening cities