Climate science

Greenhouse Effect

Meaning statusEstablishedSource recordDirect document linkedWhy these are different

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

Encyclopaedia BritannicaGreenhouse effect (absorption of infrared radiation by greenhouse gases and re-radiation back to the surface; without it Earth's average surface temperature ≈ −18 °C; human activity intensifies the effect)

mechanism and baseline

UC Berkeley Understanding Global ChangeGreenhouse effect (absorption and re-radiation cycle impedes heat loss to space; raises Earth's energy budget)

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.