Explain why carbon dioxide (CO₂) acts as a greenhouse gas. In your answer, describe its interaction with infrared radiation and its effect on Earth's temperature.
Answer
CO₂ absorbs infrared radiation emitted by Earth's surface, trapping heat and raising atmospheric temperature.
The correct answer is CO₂ absorbs infrared radiation emitted by Earth's surface, trapping heat and raising atmospheric temperature. — Conclude that this trapped IR energy increases the temperature of the lower atmosphere and the surface.
Step-by-step solution
- State that the Earth radiates infrared (IR) energy after being heated by solar radiation.
- Explain that CO₂ molecules have vibrational modes that can absorb IR photons, particularly in the 15 µm band.
- Mention that the absorbed energy is re‑emitted in all directions, sending part of it back toward the surface (the greenhouse effect).
- Conclude that this trapped IR energy increases the temperature of the lower atmosphere and the surface.
Common mistake: Thinking CO₂ reflects sunlight instead of absorbing infrared radiation
Concept tested: Greenhouse effect of carbon dioxide
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