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.