Greenhouse effect
The greenhouse effect is the warming of Earth's surface and lower atmosphere that occurs because certain atmospheric gases absorb and emit infrared radiation. It is a natural part of Earth's climate system; increasing concentrations of greenhouse gases from human activities enhance this effect and alter the planet's energy balance.
How the process works
Earth receives energy mainly as sunlight. Some incoming energy is reflected back to space; the rest is absorbed by the atmosphere and surface. The warmed surface emits energy as infrared radiation. Greenhouse gases, including water vapour, carbon dioxide, methane and nitrous oxide, absorb parts of this outgoing infrared radiation and emit energy in all directions. Some energy is returned toward the surface and lower atmosphere, while some escapes to space. The climate settles toward a balance between incoming and outgoing energy, and changes to that balance lead to warming or cooling.
A natural effect and its enhancement
The natural greenhouse effect keeps Earth's surface warmer than it would be without greenhouse gases. Water vapour is an important climate feedback: its concentration responds to temperature, so initial warming can lead to more water vapour and additional warming. Human activities, especially the burning of fossil fuels, have increased atmospheric carbon dioxide and other heat-trapping gases. This strengthens the greenhouse effect by reducing the rate at which energy escapes to space until the climate system adjusts. The resulting warming is not explained by the natural greenhouse effect alone, but by its human-driven enhancement and other influences on Earth's energy balance.
Greenhouse gases and climate forcing
Different gases absorb infrared radiation at different wavelengths and remain in the atmosphere for different lengths of time. Carbon dioxide, methane, nitrous oxide and halogenated gases are among the contributors to human-caused radiative forcing. The Intergovernmental Panel on Climate Change assesses effective radiative forcing as a way to quantify changes in Earth's energy balance, including relevant adjustments in the climate system. Aerosols and changes to land reflectivity can also influence the balance, sometimes offsetting part of greenhouse-gas warming.
Why the greenhouse analogy is imperfect
The name is a useful mnemonic but a glass greenhouse warms mainly by limiting the movement of air, or convection. Earth's atmospheric greenhouse effect works primarily through the absorption and emission of infrared radiation by gases. It is therefore better understood as a radiative process than as a literal atmospheric roof trapping warm air.
Key facts
- Incoming energy
- Sunlight is Earth's primary energy source; some is reflected and some is absorbed by the surface and atmosphere.
- Outgoing energy
- The warmed Earth emits infrared radiation, some of which is absorbed and re-emitted by greenhouse gases.
- Natural role
- The natural greenhouse effect helps maintain surface conditions suitable for life as we know it.
- Human enhancement
- Human emissions have increased greenhouse-gas concentrations, strengthening the effect and changing Earth's energy balance.
- Climate feedback
- Water vapour responds to temperature changes and can amplify warming initiated by other forcings.
- Analogy caveat
- Unlike a glass greenhouse, the atmospheric greenhouse effect operates mainly by altering infrared radiation, not by physically preventing convection.
Ask about this article
Answers use only “Greenhouse effect” and its references, with citations.
References
- 1.What is the greenhouse effect?
NASA Science · other · reliability: unverified · retrieved 25 October 2026
Supports: Definition, examples of greenhouse gases, natural greenhouse effect and the human-driven increase in heat trapped near Earth's surface.
- 2.Basics of the Carbon Cycle and the Greenhouse Effect
NOAA Global Monitoring Laboratory · other · reliability: unverified · retrieved 25 October 2026
Supports: Infrared absorption and re-emission, the energy flows in the greenhouse effect, and why the glass-greenhouse analogy is imperfect.
- 3.Chapter 7: The Earth’s Energy Budget, Climate Feedbacks, and Climate Sensitivity
Intergovernmental Panel on Climate Change · other · reliability: unverified · retrieved 25 October 2026
Supports: Assessment of radiative forcing, greenhouse-gas effects, climate response and feedbacks in Earth's energy budget.
- 4.Greenhouse effect
Encyclopaedia Britannica · other · reliability: unverified · retrieved 25 October 2026
Supports: Greenhouse gases absorb infrared radiation from Earth's surface and reradiate energy, contributing to warming; human activities increase their concentrations.
- 5.Climate change: evidence and causes — The Basics of Climate Change
The Royal Society · other · reliability: unverified · retrieved 25 October 2026
Supports: Greenhouse gases alter Earth's energy balance, their human-driven concentration increases, and the role of feedbacks.
References are suggested by the research engine and may be incomplete. Unverified URLs are omitted rather than guessed.
Article history
- Version 125 October 2026 · EditorCreated by Zapia