Which one of the following is not a main greenhouse gas?

• A greenhouse is a glass building that provides optimum temperature for plants to grow in cold climates.
• The glass traps the heat inside to keep it warm.
• Greenhouse gases act in a very similar way for our atmosphere in trapping the heat.
• These gases present in the atmosphere absorbs the infrared radiation and re-emits the heat back to the surface.
• 50% of the heat is lost to space and rest 50% comes back to the Earth's surface.
• This keeps the average temperature of Earth inhabitable.
• This phenomenon is called greenhouse effect. 

Important Points

• The primary greenhouse gases include:
  • water vapour
  • carbon dioxide (CO₂)
  • methane (CH₄)
  • nitrous oxide (N₂O)
• Various human activities like burning of fossil fuels has led to a significant increase of greenhouse gases in the atmosphere over the past two centuries.
• This has in turn led to the global warming which is a global concern for life on Earth.
• Global warming causes increase in global average temperature, melting of polar ice, increase of sea-level, etc.

Additional Information

• Oxygen (O₂) may indirectly cause greenhouse effect by forming ozone (O₃) in the lower atmosphere, which may then act as a secondary greenhouse gas.