What does albedo mean?
Albedo is a measure of how strongly a surface reflects light or radiation, expressed as the ratio of reflected to incoming energy on a scale from 0 to 1. A high albedo means a surface bounces most sunlight away — fresh snow reflects as much as 80–90% of what hits it — while a low albedo means it absorbs most of it, as dark ocean water and asphalt do. The term is central to climatology, where the ice–albedo feedback loop helps explain why melting sea ice accelerates warming, and to planetary science, where astronomers infer the size and composition of asteroids and moons from their reflectivity. Though technical in register, albedo surfaces regularly in climate journalism and even in practical design choices, since white roofs and pavements are promoted for raising urban albedo and cooling cities. Derived from the Latin word for white, it literally names the quality of whiteness in physical terms.
nounThe proportion of light or radiation reflected by a surface, expressed as a fraction or percentage of the total incident upon it; in astronomy and planetary science, a measure of how reflective a body such as a planet or moon is.
- The fraction of incoming light or radiation reflected by a surface (physics, climatology).
- In astronomy, the reflective power of a celestial body such as a planet, moon, or asteroid.
"Fresh snow has a high albedo, reflecting most of the sunlight that strikes it back into space."
"Arctic sea ice loss triggers a feedback loop: as bright ice gives way to dark ocean, the lower albedo absorbs more heat and melts still more ice."
"Astronomers use an asteroid's albedo, combined with its brightness, to estimate its size."
The standard plural, used mainly when comparing the reflectivity values of different surfaces or bodies.
"The study compared the albedos of urban rooftops before and after the white-coating program."
Painting roofs white can measurably cool a city — because raising their albedo bounces sunlight straight back into space instead of letting it turn into heat.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of albedo
Albedo comes directly from the Latin 'albedo', meaning whiteness, derived from 'albus', the Latin word for white. The term entered English scientific usage in the mid-nineteenth century, when astronomers adopted it to quantify the reflective power of celestial bodies. It shares its root with several other English words of Latin origin, including 'album' (originally a blank white book), 'albumen' (egg white), and 'albino'.
How albedo is actually used
A technical term used mainly in physics, climatology, astronomy, and planetary science; it appears rarely in everyday conversation but is common in reporting on climate science. Values range from 0 (a perfectly black, non-reflecting surface) to 1 (a perfect reflector); fresh snow is near the top of the scale, while open ocean and fresh asphalt sit near the bottom.
Easily confused with albedo
Libido means sexual desire or psychic drive, while albedo is a scientific measure of how much light a surface reflects — the two words merely sound similar.
An albino is an organism lacking pigment; albedo is a measure of reflectivity, though both derive from the Latin word for white.