CLIMATE CHANGE EAES

🌍 Drivers of Climate Change

  • Climate Change Drivers – Factors that alter Earth's energy balance and climate over time.

  • Types:

    • Natural: Variations in solar radiation, Milankovitch cycles (orbital patterns), volcanic activity, asteroid impacts.

    • Anthropogenic: Greenhouse gas emissions, deforestation, land use changes, urbanization, pollution.

    • Feedback loops: Amplify change. Example: Melting ice decreases albedo, leading to more warming.

☀ Solar Radiation – Behavior & Variability

  • Incoming Solar Radiation – Mostly shortwave UV radiation from the sun.

  • Path through Earth’s atmosphere:

    • Reflected by clouds, ice, snow, aerosols (high albedo = more reflection).

    • Absorbed by land, water, and atmospheric gases (low albedo = more absorption).

    • Re-emitted as longwave infrared radiation.

  • Natural Variability Causes:

    • Earth’s orbit (eccentricity ~100,000 yrs), tilt (~41,000 yrs), and precession (~26,000 yrs) – known as Milankovitch cycles.

    • Solar flares and volcanic aerosols also alter incoming energy.
      (Slides 7–10)

🌫 Greenhouse Gases (GHGs)

  • Definition – Gases in the troposphere that trap heat by absorbing and re-emitting infrared radiation.

  • Main GHGs (by concentration):

    • Carbon dioxide (CO₂)

    • Methane (CH₄)

    • Nitrous oxide (N₂O)

    • Water vapor (H₂O)

  • Most Potent GHGs (in terms of warming potential):

    • Methane (CH₄) is ~25x stronger than CO₂ over 100 years.

    • Nitrous oxide (N₂O) and fluorinated gases are also highly potent.

  • Atmospheric Lifetime:

    • CO₂: decades to centuries

    • CH₄: ~12 years

    • N₂O: ~114 years

  • Tropospheric Ozone (O₃):

    • Found near the Earth’s surface.

    • Formed from human-related sources: nitrous oxides + VOCs + sunlight.

    • Acts as a GHG, harmful to health.

  • Stratospheric Ozone:

    • Found high in the atmosphere.

    • Protects Earth by absorbing high-energy UV rays.
      (Slides 14–15)

⚖ Radiative Forcing

  • Definition – The measure of a factor's effect on Earth’s energy balance, in W/m².

  • Positive Forcing = warming (e.g., GHGs, black carbon on ice).

  • Negative Forcing = cooling (e.g., aerosols, volcanic ash).

  • Forcing Agents:

    • Natural: Solar variability, volcanic eruptions (aerosols), orbital cycles.

    • Anthropogenic: CO₂, CH₄, N₂O, black carbon, urbanization, deforestation.

  • Changes Over Time:

    • Past 250 years: Massive increase in anthropogenic positive forcing, especially from CO₂ and CH₄.

    • Volcanic and solar forcing have remained relatively stable or punctual.

  • Linked to Human Activity: Industrialization, fossil fuel use, agriculture, deforestation.
    (Slides 10, 16–17)

🏭 Sources of GHG Emissions

Natural Sources:

  • Respiration (CO₂)

  • Wetlands (CH₄)

  • Oceans and soils (N₂O)

  • Volcanic eruptions (CO₂ and aerosols)

Anthropogenic Sources:

  • Energy production (burning fossil fuels)

  • Transportation

  • Industry (steel, cement production)

  • Agriculture (methane from livestock, nitrous oxide from fertilizers)

  • Deforestation (loss of carbon sinks)

  • Waste management (landfills releasing CH₄)

🌲 Climate Change Predictions for BC

Temperature Changes:

  • Most warming expected in BC’s Interior.

  • All regions show a positive MAT (mean annual temperature) anomaly.

  • Projected to rise by several degrees by the 2080s.

Precipitation Changes:

  • Southwestern coast expected to become hotter and wetter.

  • Interior expected to become hotter and drier.

  • Increased precipitation variability, with more intense storms or droughts.

Biogeoclimatic Zone Shifts:

  • Zones expected to expand:

    • Bunchgrass (red) – expands into drier, hotter valleys.

    • Interior Douglas Fir – expands with warmer temps.

  • Zones expected to shrink/disappear:

    • Alpine tundra (grey) – replaced by forests at higher elevations.

    • Spruce zones – retreat to northern and higher elevation areas.