Climate science
Greenhouse Effect
The process by which greenhouse gases in the atmosphere absorb infrared radiation emitted by Earth's surface and re-radiate heat back, warming the planet.
Definition
The greenhouse effect is the warming of Earth's surface and lower atmosphere caused by greenhouse gases — water vapour, carbon dioxide, methane, and others — that absorb infrared radiation emitted by the heated surface and re-radiate it in all directions, including back toward the surface. Without this natural effect, Earth's average surface temperature would be about −18 °C rather than the life-supporting average near 15 °C; human emissions intensify it, producing global warming.
References
mechanism and baseline
mechanism
Overview
What it means
The atmosphere is largely transparent to incoming sunlight but not to the outgoing infrared. Greenhouse gases act as a partial blanket: more of them means more heat retained, raising the planet's energy budget and temperature. Despite the name, the mechanism differs from an actual greenhouse, which works mainly by trapping warmed air.
How it is used
The concept is the foundation of climate science communication, distinguishing the natural effect that makes Earth habitable from the enhanced effect driving climate change.
Why it matters
Every climate policy rests on this single piece of physics; understanding it separates the phenomenon from the politics.
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