What is the primary function of the greenhouse effect regarding Earth's thermal energy?

• A. To trap heat in the atmosphere
• B. To reflect heat away from the planet
• C. To generate heat through chemical reactions
• D. To convert heat into kinetic energy

Answer: (A)

The greenhouse effect mainly serves to trap heat in the lower atmosphere and on the surface by absorbing infrared radiation and re-emitting it in all directions. When sunlight warms the Earth, the surface emits infrared energy, and greenhouse gases like water vapor and carbon dioxide absorb much of that infrared heat and then radiate it back toward the surface. This slows heat escape to space and keeps the planet warmer than it would be otherwise. It isn’t about reflecting heat away, generating heat from chemical reactions, or converting heat into kinetic energy—the key idea is energy retention through absorption and re-radiation of infrared energy by atmospheric gases.