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Topic 6: Atmosphere and climate change

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  1. 6.1 Introduction to the atmosphere

    1. • Between Earth and space • Outer limit of biosphere • Composition and processes support life

    2. • Differential heating creates tricellular model • Redistributes heat from equator to poles

    3. • Absorb and re-emit infrared radiation • GHGs: water vapour, CO₂, methane, nitrous oxides • Aerosols: black carbon

    4. • Keeps Earth warmer than otherwise • Natural process enabling life • Enhanced greenhouse effect: human GHG accumulation → global warming • Climate change: broader range of resulting changes

    5. • Physical processes: global warming, air movements • Chemical processes: ozone production from oxygen

    6. • Gravity pulls molecules to surface • Atmosphere thins with altitude • Standard lapse rate: ~1°C per 100m

    7. • Affect solar radiation reaching Earth • Climate cycles over tens to hundreds of thousands of years • Three types: orbit shape, tilt angle, axis rotation • Do not explain current warming

    8. • Moving away from glacial-interglacial cycle • Quaternary period (2.5 million years) • Current changes: rapid and anthropogenic (Anthropocene epoch)

    9. • Life changed atmospheric composition • Photosynthesis: decreased CO₂, increased O₂ • Allowed stratospheric ozone formation, metal oxidation

  2. 6.2 Climate change—causes and impacts

    1. 6.2.1Climate definition

      • Typical atmospheric conditions • Seasonal temperature and precipitation variations

    2. 6.2.2Anthropogenic CO₂ emissions

      • Atmospheric CO₂ concentration rising significantly • Accelerated since 1950 • Traced to Industrial Revolution (late 18th century)

    3. 6.2.3Ice core, tree ring, sediment data

      • Positive correlation: atmospheric CO₂ and global temperatures • Data for past 800,000 years

    4. 6.2.4Enhanced greenhouse effect

      • Anthropogenic GHG emissions • Led to global warming and climate change

    5. 6.2.5Climate change impacts on ecosystems

      • Local to global scales • Affects resilience, leads to biome shifts • Examples: coral bleaching, desertification, ocean circulation changes

    6. 6.2.6Climate change impacts on societies

      • Various scales and socio-economic conditions • Impacts resilience • Health, water supply, agriculture, infrastructure

    7. 6.2.7Climate change models

      • Systems diagrams with feedback loops • Solar radiation variations, albedo changes, methane release

    8. 6.2.8Climate change planetary boundary

      • Evidence suggests already passed

    9. 6.2.9Perspectives on climate change

      • Influenced by many factors • Individual and societal levels

    10. 6.2.10(HL)—Climate data collection

      • Weather stations, observatories, radar, satellites • Direct measurements: temperature, GHG concentrations • Indirect (proxies): ice core isotopes, dendrochronology, peat pollen

    11. 6.2.11(HL)—Global climate models

      • Manipulate inputs to predict outputs • Uncertainty in inputs and outputs • Hindcasting: test validity

    12. 6.2.12(HL)—Climate model scenarios

      • Predict impacts: sea-level rise, temperature, precipitation

    13. 6.2.13(HL)—Critical thresholds and tipping points

      • Earth may approach critical threshold → new equilibrium • Examples: Antarctic ice sheet melting, Atlantic circulation slowing, Amazon-Cerrado transition

    14. 6.2.14(HL)—Tipping cascades

      • Two or more tipping points interact • Predictions very uncertain

    15. 6.2.15(HL)—Climate justice

      • Countries vary in responsibility and vulnerability • Least responsible often most vulnerable • Political, economic, equity implications

  3. 6.3 Climate change—mitigation and adaptation

    1. • Avoid catastrophic climate change • International cooperation needed

    2. • Reduce/end CO₂-emitting energy sources • Replace with renewable energy • Carbon neutrality goals

    3. • Reduce global warming: household changes, geoengineering • Reduce GHG production: energy efficiency, renewables, food changes, carbon tax • Remove CO₂: carbon sinks, rewilding, afforestation, carbon capture

    4. • Structural: flood defences, desalination, movable infrastructure • Non-structural: agricultural adaptation, vaccination, land zoning, building codes

    5. • National Adaptation Programmes of Action (NAPAs) • Individual to society scale

    6. • Led by governments or non-governmental stakeholders • Economic measures: carbon pricing, emissions trading, subsidies, tariffs • Legislation: reduce carbon emissions • Goal setting: B Corp, company goals • Personal changes: reduce waste, meat, energy consumption

    7. • UNFCCC, IPCC, COP summits • Stabilize GHG concentrations • Kigali Amendment controls HCFCs

    8. • Five scenarios for future GHG emissions • Targets to reduce catastrophic change risk

    9. • Aid climate change mitigation

    10. • There are challenges to overcome in implementing climate management and intervention strategies • Include: the following challenges and barriers • Lack of belief that climate change is a serious problem • Lack of financial resources or planning strategies from national governments

    11. • Geoengineering is a mitigation strategy for climate change, treating the symptom not the cause • Geoengineering is a deliberate and large-scale intervention in the Earth’s climate system, including but not limited to measures such as space mirrors, ocean fertilization • However, it has disadvantages, such as potential high costs, uncertainty of impacts, political hesitancy, lack of convincing trials and the potential for geopolitical conflict • Consider: arguments for and against the potential of geoengineering

    12. • A range of stakeholders play an important role in changing perspectives on climate change • Consider: how a range of stakeholders can influence an individual’s perspectives on climate change • For example, stakeholders can include a charismatic individual, a local community group, NGOs, media and educational institutions

    13. • Perspectives on the necessity, practicality and urgency of action on climate change will vary between individuals and between societies • Consider: differences in perspective between age groups, developed and developing societies, coastal and inland communities, and economies that profit from fossil fuels

    14. • The concept of the tragedy of the commons suggests that catastrophic climate change is likely unless there is international cooperation on an unprecedented scale • The atmosphere is common to all, but when one nation benefits from an action that harms the atmosphere (e.g., burning of fossil fuels), the costs are shared by all nations • The reverse scenario is also true: the costs of restoring the atmosphere (e.g., by carbon capture and storage) might be borne by a single nation

  4. 6.4 Stratospheric ozone

    1. • Low frequency radio to high frequency gamma • Infrared, visible light, ultraviolet (UV)

    2. • Shorter wavelengths, higher frequencies, more energy • UVA, UVB, UVC damage organisms

    3. • Absorbs UV radiation from Sun • Protects living organisms from harmful effects

    4. • Reduces photosynthesis in phytoplankton • DNA damage: mutations, cancer • Humans: sunburn, premature ageing, cataracts

    5. • Steady state between formation and destruction

    6. • Destroy ozone molecules • Augment natural breakdown • Not a cause of global warming

    7. • More UVB reaches Earth's surface • Polar "ozone holes" in spring

    8. • International treaty regulating CFCs and ODSs • Most successful international environmental cooperation

    9. • Prevented planetary boundary crossing

    10. • Release halogens (chlorine, fluorine) into stratosphere • Break down ozone

    11. • Occurs in spring • Chemical and atmospheric conditions • Polar stratospheric clouds, active surfaces

    12. • Replaced CFCs, less ozone depletion • Potent GHGs • Controlled by Kigali Amendment

    13. • Energy-intensive, contribute to GHG emissions • Contain ODSs • Alternatives: building design, greening cities