The process by which gases hold heat in air is called the greenhouse effect.

Here's why:

* Greenhouse Gases: Certain gases in the atmosphere, like carbon dioxide, methane, and water vapor, act like the glass roof of a greenhouse.

* Trapping Radiation: These gases allow sunlight to pass through, but they absorb and re-emit the infrared radiation (heat) that the Earth radiates back into space.

* Warming Effect: This trapped heat warms the Earth's atmosphere and surface, making it habitable.

Without the greenhouse effect, Earth would be much colder, and life as we know it wouldn't exist.