What describes the greenhouse effect?

The greenhouse effect is best described as the trapping of heat by greenhouse gases in the Earth's atmosphere. This process occurs when certain gases, such as carbon dioxide, methane, and water vapor, allow sunlight to enter the atmosphere but prevent some of the heat that the sunlight brings from leaving back into space. Consequently, this leads to a warming effect on Earth, which is crucial for maintaining a climate that can support life.

The other options are not relevant to the greenhouse effect specifically. The increase of ozone in the atmosphere relates more to ozone depletion and air quality rather than heat retention. The melting of polar ice caps is a result of global warming, which is influenced by the greenhouse effect, but it does not describe the mechanism itself. The growth of plants due to sunlight involves photosynthesis and does not pertain to the process of heat retention in the atmosphere. Overall, the trapping of heat by greenhouse gases is fundamental to understanding how energy is managed in our climate system.