B.2- Greenhouse Effect

• What does emissivity (e) mean?

  It quantifies the emission and absorption properties of a body as compared to a black body of equal size.
• What is the emissivity of a black body?

  e = 1
• What is the emissivity of a mirror?

  e = 0.05
• What is the formula for emissivity?

  e = power emitted by a radiating object / power emitted by a black body (same A and T)
• What is albedo?

  The proportion of incident light or radiation that is reflected off a surface
• What is the formula for albedo?

  albedo = total scattered power / total incident power
• What is the average yearly albedo value of the Earth?

  0.3
• What factors affect the albedo of the Earth?

  Latitude, season, cloud cover, and snow cover.
• What is the solar constant value?

  1360 Wm^-2
• What are the steps of the greenhouse effect?

  1. Solar radiation reaches the atmosphere.
  2. Gases absorb infrared radiation (IR).
  3. Remainder of IR reaches the ground, warming it.
  4. Solids absorb all frequencies and convert them to IR.
  5. Heat from the ground emits IR back into the atmosphere.
  6. The atmosphere traps heat, causing warming.
• What are the main 4 greenhouse gases?

  1. Carbon dioxide (CO₂)
  2. Methane (CH₄)
  3. Water vapor (H₂O)
  4. Nitrous oxide (N₂O)
• How do greenhouse gases absorb and emit radiation?

  They absorb IR radiation photons and re-emit an IR photon when de-excited.
• What is one natural process and human activity contributing to CO₂ concentrations?

  Natural- decomposition

  Human- deforestation
• What is one natural process and human activity contributing to methane concentrations?

  
  

  Natural- cattle

  Human- combustion of fossil fuels
• What is one natural process and human activity contributing to water vapour concentrations?

  
  

  Natural- water cycle

  Human- increased evaporation due to climate change
• What is the energy balance of the Earth?

  • Energy in = Energy out
• What is the difference between natural and enhanced greenhouse effects?

  Natural greenhouse effect maintains Earth's temperature, while enhanced greenhouse effect increases it due to human activities.
• What is one natural process and human activity contributing to nitrous oxide concentrations?

  Natural- nitrogen cycle

  Human- combustion of fossil fuels