The “greenhouse effect” of the atmosphere is named by analogy to greenhouses which become warmer in sunlight.
A greenhouse is built of any material that passes sunlight, usually glass, or plastic. It mainly warms up because the sun warms the ground and contents inside, which then warms the air in the greenhouse. The air continues to heat up because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft. Here are some easy, simple and budget-friendly ways to make greenhouses at your backyard.