Which statement best describes energy re-emission by greenhouse gases?

• A. Greenhouse gases re-emit energy in all directions, including back toward the surface
• B. Greenhouse gases only emit energy upward into space
• C. Greenhouse gases store energy indefinitely
• D. Greenhouse gases convert energy into chemical energy

Answer: (A)

Greenhouse gases trap heat by absorbing infrared radiation emitted by Earth’s surface and then re-emitting that energy in all directions. This re-emission is essentially in every direction, not just upward. Because some of the emitted photons travel downward, energy is returned toward the surface, warming it and the lower atmosphere. This downward component is what makes the greenhouse effect meaningful: it helps keep surface temperatures higher than they would be otherwise.

These gases don’t store energy indefinitely in this process, and they don’t convert the absorbed energy into chemical energy as the primary outcome here. The energy is quickly re-radiated as infrared photons, not locked away or transformed into a chemical form.