Which statement is true about the greenhouse effect?

Which statement is true about the greenhouse effect?

• A. Greenhouse gases deplete heat from the atmosphere.
• B. The ozone layer shields Earth from all UV radiation.
• C. Solar radiation has no effect on atmospheric warming.
• D. Greenhouse gases trap heat in the lower atmosphere and cause warming.

Answer: (D)

The greenhouse effect rests on heat being trapped by certain gases in the atmosphere. When sunlight heats Earth’s surface, the surface emits infrared radiation. Greenhouse gases such as water vapor, carbon dioxide, and methane absorb much of that infrared energy and re-radiate it, including back toward the surface, which keeps the lower atmosphere and the surface warmer than they would be otherwise. This trapping mechanism is why the statement about greenhouse gases causing warming is true. The other options misstate the process: heat isn’t depleted by these gases, the ozone layer doesn’t block all UV light and isn’t the mechanism of this warming, and solar radiation does influence warming, but the greenhouse effect explains how heat is retained after that energy reaches the surface.

The greenhouse effect rests on heat being trapped by certain gases in the atmosphere. When sunlight heats Earth’s surface, the surface emits infrared radiation. Greenhouse gases such as water vapor, carbon dioxide, and methane absorb much of that infrared energy and re-radiate it, including back toward the surface, which keeps the lower atmosphere and the surface warmer than they would be otherwise. This trapping mechanism is why the statement about greenhouse gases causing warming is true. The other options misstate the process: heat isn’t depleted by these gases, the ozone layer doesn’t block all UV light and isn’t the mechanism of this warming, and solar radiation does influence warming, but the greenhouse effect explains how heat is retained after that energy reaches the surface.