WEBVTT FILE

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The Earth is constantly hit by solar radiation.

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That radiation is the driving force for life on Earth.

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However, not all of the radiation that reaches the Earth is absorbed.

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In fact, the Earth's ability to reflect a portion of the solar radiation is vital

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to sustain the balance that allows life as we know it to thrive.

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The fraction of solar radiation a surface reflects

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is called its "albedo." An albedo of 1 means that

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100% of incoming radiation is reflected. An albedo of 0

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means that 0% of incoming radiation is reflected and all of it

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is absorbed. On sunny days, you may have noticed that if you walk

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barefoot on dark asphalt, it burns your feet more than the lighter concrete.

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This is because the dark surface of the black asphalt has a lower albedo

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than the lighter-colored concrete. It absorbs more of the incoming radiation and

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is much warmer as a result.

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Surfaces throughout the Earth have different albedos. NASA is able to measure these differences

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with many instruments, including those on the Aqua satellite. These measurements

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can tell scientists essential information about the Earth's environment.

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Snow-covered ice in the polar regions has a high albedo.

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It reflects the majority of incoming radiation, which helps to cool the Earth.

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As the Earth's temperature rises with the increase in greenhouse gases,

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sea ice in the polar regions can be expected to retreat.

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This replaces an ice surface with a water surface, which has a much lower

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albedo. This causes more energy to be absorbed, and accelerates the warming

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process. The low albedo of dark

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green vegetation allows it to absorb sunlight and use it in photosynthesis,

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a fundamental process necessary to bring energy into the biosphere.

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Satellite imagery helps scientists to see how the albedo of these areas

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changes over time, through both natural processes and human alteration.

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As we move from rural to urban areas, many factors change,

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including the albedo. This causes urban areas to generally be

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warmer than their surroundings, a phenomenon known as the "urban heat island effect."

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Understanding albedo can lead to suggestions to help reduce

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this effect. One possibility would be to paint roofs white in hot regions,

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thereby reflecting solar radiation. Though it may not

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feel like it's affecting you directly, abledo is critical to the climate of the

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entire planet. By measuring and understanding albedo, we can see how our environment

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is changing in response to our alterations and how it may impact the

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relationship between solar radiation and the Earth.