Concept

Albedo

The fraction of solar radiation a surface reflects rather than absorbs. Light surfaces (snow, ice, light sand) have high albedo and reflect most incoming sunlight; dark surfaces (forests, ocean, asphalt) have low albedo and absorb most. Earth's average albedo is ~0.30 (30% reflected). Albedo is a major component of the climate system: when ice melts and reveals dark ocean or land underneath, more solar energy is absorbed, accelerating warming (the ice-albedo feedback). Forests have lower albedo than the snow-covered ground they replace, partially offsetting their carbon-storage cooling effect at high latitudes — one of the complications in climate-mitigation planting strategies.

Albedo of common surfaces

Fresh snow — 0.80-0.90 (reflects 80-90% of [[sun|sunlight]])
Sea ice — 0.50-0.70
Old/dirty snow — 0.40-0.70
Dry sand (light) — 0.40
Cloud (variable) — 0.20-0.90 depending on type and depth
Earth average — 0.30
Grass — 0.20-0.25
Forests — 0.10-0.20 (very low)
Open ocean — 0.06 (very low)
Asphalt — 0.05-0.10
Wet soil — 0.10-0.20

Climate implications

Ice-albedo feedback (a major [[climate-feedback-loop|positive feedback]]):

Sea ice and snow cover have high albedo (reflect ~80% of [[sun|sunlight]])
When ice/snow melts, dark ocean or land is exposed
Dark surfaces absorb ~90% of [[sun|sunlight]], warming further
Warming melts more ice and snow
Cycle continues; this is among the most-important Arctic warming amplifiers

Forest albedo nuance:

Forests sequester carbon (cooling effect)
But forests are darker than the snow-covered or grassland surfaces they replace (warming effect from lower albedo)
At high latitudes, the albedo effect can partially offset the carbon-storage cooling
Tropical forests: net cooling (carbon storage + evapotranspiration cooling outweigh albedo)
Temperate forests: net cooling, but smaller margin
Boreal forests: net effect debated; possibly modest warming or cooling depending on conditions

Urban heat island and high-albedo surfaces:

Cities with dark asphalt and tar roofs absorb heat dramatically
“Cool roof” programs (white reflective roofing) reduce urban heating
Painting roofs and surfaces white has been proposed as a planetary-cooling intervention (Steven Chu)

Importance

Albedo is one of the major climate-system parameters. Even small albedo changes — a few percent globally — produce major climate effects. Understanding albedo:

Explains why melting ice accelerates climate change
Complicates simple “more trees = better” climate framing
Suggests interventions like high-albedo surfaces in urban environments

Sources

IPCC reports on climate-system parameters
Climate Change Science Compendium, UNEP
Multiple atmospheric-science publications

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Scientific

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Climate feedback loop ice-albedo feedback is among the most-significant positive climate feedbacks

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