Albedo

This picture of the Andes Mountains between Chile and Argentina in South America was taken from the International Space Station in December 2000. Glaciers and snow top many of the high mountain peaks. Lakes in the valleys between mountains collect the water that melts from the snow and ice each spring and summer. Scientists have found that the smaller glaciers in this area are melting quickly as the Earth becomes warmer. Click on image for full size (156K JPG) NASA Earth Observatory

This picture shows a part of the Earth surface as seen from the International Space Station high above the Earth. A perspective like this reminds us that there are lots of different things that cover the Earth. Soil, rocks, water, forests, snow, and sand – they all look different from above. They also have different ways of dealing with the solar energy that gets to our planet. Dark colored parts of the planet surface reflect very little of the solar energy that hits them. Light colored parts of the planet surface reflect almost all of the solar that hits them.

The amount of energy reflected by a surface is called albedo. Albedo is measured on a scale from zero to one (or sometimes as a percent).

• Very dark colors have an albedo close to zero (or close to 0%).
• Very light colors have an albedo close to one (or close to 100%).

Because much of the land surface and oceans are dark in color, they have a lower albedo and absorb a large amount of the solar energy that gets to them, reflecting only a small fraction of the energy. Forests have low albedo, near 0.15. The snow and ice, on the other hand, are very light in color. They have very high albedo, as high as 0.8 or 0.9, so they reflect most of the solar energy that gets to them, absorbing very little.

The combined effect of the albedo of all these surfaces is called the planetary albedo. Earth’s planetary albedo is about 0.31. That means that about a third of the solar radiation that gets to Earth is reflected out to space and about two thirds is absorbed. The Moon’s albedo is 0.07, meaning that only 7% of the energy that gets to it is reflected. The albedo of distant planets, so distant that they are difficult to study with telescopes, can be a very helpful to scientists trying to figure out what materials are at the planet surface. Something that absorbs all radiation would have an albedo of 0 and be called a black body.

Earth’s climate is affected by the amount of solar radiation that is reflected back out to space and the amount of solar radiation that is absorbed. If Earth’s climate is colder and there is more snow and ice on the planet, more solar radiation is reflected back out to space and the climate gets even cooler. On the other hand, when warming causes snow and ice to melt, darker colored Earth surface and ocean are exposed and less solar energy is reflected out to space causing even more warming. This is known as the ice-albedo feedback.

Clouds in Earth’s atmosphere have an important effect on albedo, reflecting a large amount of solar energy out to space. While different types of clouds reflect different amounts of solar energy, their combined effect is huge. If there were no clouds in our atmosphere, Earth’s average albedo, which is about 0.31, would drop by half.

This picture of the Andes Mountains between Chile and Argentina in South America was taken from the International Space Station in December 2000. Glaciers and snow top many of the high mountain peaks. Lakes in the valleys between mountains collect the water that melts from the snow and ice each spring and summer. Scientists have found that the smaller glaciers in this area are melting quickly as the Earth becomes warmer. Click on image for full size (156K JPG) NASA Earth Observatory

This picture of the Earth surface was taken from high above the planet in the International Space Station. In this view from above, we can see that there are lots of different things that cover the Earth. All those things - like soil, rocks, water, forests, snow, and sand - look different from above. Different materials like these have different ways of dealing with the solar energy that gets to our planet. Dark colored surfaces, like ocean and forests, reflect very little of the solar energy that gets to them. Light colored parts of the planet surface, like snow and ice, reflect almost all of the solar energy that gets to them.

The amount of energy reflected by a surface is called albedo. Albedo is measured on a scale from zero to one (or sometimes as a percent).

• Very dark colors have an albedo close to zero (or close to 0%).
• Very light colors have an albedo close to one (or close to 100%).

Because much of the land surface and oceans are dark in color, they have a low albedo. They absorb a large amount of the solar energy that gets to them, reflecting only a small fraction of it. Forests have low albedo, near 0.15. Snow and ice, on the other hand, are very light in color. They have very high albedo, as high as 0.8 or 0.9, and reflect most of the solar energy that gets to them, absorbing very little.

The albedo of all these different surfaces combined is called the planetary albedo. Earth’s planetary albedo is about 0.31. That means that about a third of the solar energy that gets to Earth is reflected out to space and about two thirds is absorbed. The Moon’s albedo is 0.07, meaning that only 7% of the energy that gets to it is reflected. The albedo of distant planets, so distant that they are difficult to study with telescopes, can be a very helpful to scientists trying to figure out what a planet is made of.

Earth’s climate depends on the amount of solar radiation that is reflected back out to space and the amount that is absorbed. If Earth’s climate is colder and there is more snow and ice on the planet, more solar radiation is reflected back out to space and the climate gets even cooler. On the other hand, when warming causes snow and ice to melt, darker colored Earth surface and ocean are exposed and less solar energy is reflected out to space causing even more warming. This is known as the ice-albedo feedback.

Clouds have an important effect on albedo too. They have a high albedo and reflect a large amount of solar energy out to space. Different types of clouds reflect different amounts of solar energy. If there were no clouds, Earth’s average albedo would drop by half.

This picture is of the Andes Mountains between Chile and Argentina in South America. It was taken from the International Space Station. Do you see the glaciers and snow on top of the mountains? Do you see the lakes in the valleys between mountains? Click on image for full size (156K JPG) NASA Earth Observatory

This picture was taken from high above our planet. Looking at the Earth from very far away like this we can see that some parts of our planet look light in color, and some parts look dark.

The color of these parts affects what happens when sunshine hit them. If the Sun’s rays hit a dark part, like an ocean or forest, most of the rays are absorbed. Very few are reflected back out to space. If the Sun’s rays hit a light colored part of the Earth’s surface, like snow or ice, most of the rays are reflected back out to space. Only a few rays are absorbed. The amount of the Sun’s energy that is reflected is called albedo.

Dark colored things like oceans and forests have low albedo. Light colored things like snow and ice have very high albedo. About two out of three of the Sun’s rays that get to Earth are reflected out to space and the other one is absorbed.

The albedo of each planet or moon depends on what is at its surface. Some planets are so far away that they are difficult to see with telescopes. But scientists can figure out what the planet is made of if they can measure its albedo.

Earth’s climate depends on how many of the Sun’s rays are reflected back out to space and how many are absorbed. As our planet gets warmer, more snow and ice melt. Fewer of the Sun’s rays are reflected out to space. More are absorbed. This is causing even more warming.

Clouds affect albedo too. They have a high albedo and reflect solar energy out to space. If there were no clouds, Earth’s average albedo would drop by half.