The greenhouse effect is described as?

• A. Natural situation in which heat is retained in Earth's atmosphere by carbon dioxide, methane, water vapor, and other gases; keeps earth warm but is causing too much warming
• B. Pollution of water by plastics
• C. Ozone layer depletion
• D. Cooling effect of the upper atmosphere

Answer: (A)

The greenhouse effect is a natural warming process in which heat radiated from Earth’s surface is trapped by greenhouse gases in the atmosphere, keeping the planet warmer than it would be otherwise. When sunlight heats the surface, that heat radiates back as infrared radiation, and gases like carbon dioxide, methane, and water vapor absorb much of it and re-radiate it back toward the surface, forming a warming effect.

This description fits the idea that the system is natural and heat is retained by those gases, which keeps Earth warm but is now leading to too much warming due to higher concentrations of these gases from human activities. The other options point to different issues—plastic pollution in water, ozone layer depletion, or a cooling effect—none of which describe how heat is trapped in the lower atmosphere to produce the greenhouse warming.