Topic 6: Atmosphere and climate change
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6.1 Introduction to the atmosphere
6.1.1Atmosphere boundary
• Between Earth and space • Outer limit of biosphere • Composition and processes support life
6.1.2Atmospheric circulation
• Differential heating creates tricellular model • Redistributes heat from equator to poles
6.1.3Greenhouse gases and aerosols
• Absorb and re-emit infrared radiation • GHGs: water vapour, CO₂, methane, nitrous oxides • Aerosols: black carbon
6.1.4Greenhouse effect
• Keeps Earth warmer than otherwise • Natural process enabling life • Enhanced greenhouse effect: human GHG accumulation → global warming • Climate change: broader range of resulting changes
6.2 Climate change—causes and impacts
• Typical atmospheric conditions • Seasonal temperature and precipitation variations
• Atmospheric CO₂ concentration rising significantly • Accelerated since 1950 • Traced to Industrial Revolution (late 18th century)
• Positive correlation: atmospheric CO₂ and global temperatures • Data for past 800,000 years
• Anthropogenic GHG emissions • Led to global warming and climate change
• Local to global scales • Affects resilience, leads to biome shifts • Examples: coral bleaching, desertification, ocean circulation changes
• Various scales and socio-economic conditions • Impacts resilience • Health, water supply, agriculture, infrastructure
• Systems diagrams with feedback loops • Solar radiation variations, albedo changes, methane release
• Evidence suggests already passed
• Influenced by many factors • Individual and societal levels
6.3 Climate change—mitigation and adaptation
• Avoid catastrophic climate change • International cooperation needed
• Reduce/end CO₂-emitting energy sources • Replace with renewable energy • Carbon neutrality goals
• Reduce global warming: household changes, geoengineering • Reduce GHG production: energy efficiency, renewables, food changes, carbon tax • Remove CO₂: carbon sinks, rewilding, afforestation, carbon capture
• Structural: flood defences, desalination, movable infrastructure • Non-structural: agricultural adaptation, vaccination, land zoning, building codes
• National Adaptation Programmes of Action (NAPAs) • Individual to society scale
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