Absorption & Reflection of Energy
Now, let’s think about absorption and reflection in relationship to Earth’s systems and the energy budget. The components of Earth’s systems (air, water, land, and living things) reflect and absorb solar radiation in ways that moderate the global energy budget.
A simple activity that you may have done with your students is to place different colors of materials in the sun to see which materials get hotter than others. For example, you can place construction paper of different colors in the sun, then measure the temperature of their surfaces (be careful to shade the thermometer when doing this), or simply feel them with your hand. Certain colors reflect sunlight (solar radiation) more than do others, and certain colors absorb sunlight and convert it into heat (infrared radiation) more than do others.
Check Your Thinking: Which colors reflect the most sunlight?
Check Your Thinking: Which colors absorb the most sunlight?
Check Your Thinking: Of the following materials on the surface of the Earth, which will reflect the most solar radiation back into space?
- Vegetation (such as, grass and trees)
- Bare ground
- Water
- Ice
- Snow
Check Your Thinking: Of the following materials on the surface of the Earth, which will absorb the most solar radiation?
- Vegetation (such as, grass and trees)
- Bare ground
- Water
- Ice
- Snow
Ice is also a good reflector. In black ice, the crystals in ice are much more uniform in their orientation than are snow crystals, which allows more light to travel through the ice than through snow. Ice that has snow mixed in it, known as snow ice, appears white and reflects more light than black ice.
For supplemental information on types of ice:
- For lake ice, refer to the Alaska Lake Ice and Snow Observatory Network,
- For sea-ice, refer to Geophysical Aspects of Sea-Ice Nomenclatures.
In addition to the fact that water is excellent at absorbing solar radiation, the fact that there is so much of it means that water is very important in the global energy budget. Roughly 71% of the surface of the Earth is covered with water. Water absorbs and stores tremendous amounts of solar radiation, and thus is one of the most important factors in moderating global temperatures.
Optional: For more information on the sources of water on the Earth, refer to the USGS Water Science School site.
