What you’ll learn13 learning objectivesChoose one objective for a focused lesson, or study the complete topic.6.4.1Solar radiation spectrum• Low frequency radio to high frequency gamma• Infrared, visible light, ultraviolet (UV)Syllabus objective6.4.2UV radiation danger• Shorter wavelengths, higher frequencies, more energy• UVA, UVB, UVC damage organismsSyllabus objective6.4.3Stratospheric ozone protection• Absorbs UV radiation from Sun• Protects living organisms from harmful effectsSyllabus objective6.4.4UV radiation impacts• Reduces photosynthesis in phytoplankton• DNA damage: mutations, cancer• Humans: sunburn, premature ageing, cataractsSyllabus objective6.4.5Ozone equilibrium• Steady state between formation and destructionSyllabus objective6.4.6Ozone-depleting substances (ODSs)• Destroy ozone molecules• Augment natural breakdown• Not a cause of global warmingSyllabus objective6.4.7Ozone depletion effects• More UVB reaches Earth's surface• Polar "ozone holes" in springSyllabus objective6.4.8Montreal Protocol• International treaty regulating CFCs and ODSs• Most successful international environmental cooperationSyllabus objective6.4.9Montreal Protocol success• Prevented planetary boundary crossingSyllabus objective6.4.10(HL)—ODS mechanisms• Release halogens (chlorine, fluorine) into stratosphere• Break down ozoneSyllabus objective6.4.11(HL)—Polar stratospheric ozone depletion• Occurs in spring• Chemical and atmospheric conditions• Polar stratospheric clouds, active surfacesSyllabus objective6.4.12(HL)—HFCs• Replaced CFCs, less ozone depletion• Potent GHGs• Controlled by Kigali AmendmentSyllabus objective6.4.13(HL)—Air conditioning issues• Energy-intensive, contribute to GHG emissions• Contain ODSs• Alternatives: building design, greening citiesSyllabus objective
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