What role does Earth's surface play in the greenhouse effect?

• A. It absorbs shortwave radiation and emits longwave radiation that greenhouse gases trap
• B. It reflects all radiation back into space
• C. It only absorbs visible light
• D. It creates greenhouse gases

Answer: (A)

The main idea is that the surface is where sunlight is converted into heat and then becomes the source of infrared radiation that greenhouse gases can trap. When sunlight reaches the ground, water, and vegetation, much of it is absorbed, warming the surface. That warmth causes the surface to emit infrared (longwave) radiation. Greenhouse gases in the atmosphere absorb portions of this infrared and re-radiate it in all directions, including back toward the surface. This back-radiation traps heat near the surface, making it warmer than it would be otherwise. So the surface’s role is to absorb shortwave solar energy and emit longwave radiation that greenhouse gases capture. The other statements don’t fit because not all radiation is reflected back into space, the surface absorbs more than just visible light, and greenhouse gases aren’t created by the surface itself.