What Is Albedo?
When it comes to Earth's climate, one of the most important feedback loops involves something called albedo. Albedo is the percentage of the Sun’s energy that is reflected off a surface. Albedo values range from 0 to 1. A pure black surface absorbs all (100%) of the incoming light and reflects none (0%), and has an albedo value of 0. On the other hand, a mirror, which absorbs no light (0%) and reflects all of it (100%), has an albedo value of 1. In general, the higher the albedo of a surface, the more light it reflects; the lower the albedo, the more light it absorbs. The following image shows the typical albedo values of some common materials.
Notice that albedo can vary even in the same type of material, depending on composition, the angle at which sunlight strikes the surface, or even how wet it is! For example, dirt and soil are darker when they get wet from rain, so they absorb more sunlight and their albedo decreases. When the Sun is shining down directly over the ocean, water can absorb much of the light, resulting in a very low albedo. But, when the Sun is setting and near the horizon, the sunlight can bounce off the surface of the ocean, making the ocean's albedo much higher. (Think of the blinding glare on the ocean surface at sunset.)
Overall, Earth has an average albedo of 0.3, reflecting back 30% of the light it receives.
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