BALANCE
The Earth receives 84 terawatts of solar power every moment -- that's 84 million million watts. Some of that energy is directly reflected from the Earth's atmosphere and the surface of the Earth. Some is absorbed -- heating up the air, water and land. The warmer air, water and land emit invisible infrared radiation that heads back into space. But some of that infrared radiation doesn't make it to space -- it gets reflected right back to the surface. It's trapped.
A pot of heating water on the stove feels warm and it steams. The heat you feel and the steam you see are both ways the pot is getting rid of energy, but more energy comes in than goes out -- so the pot heats up. The same thing occurs with the Earth: If more energy comes in than goes out, the Earth heats up.
RADIATION BALANCE
If the Earth doesn't get rid of the 84 terawatts of power it receives at every moment, it heats up. Many factors influence the Earth's radiation balance. Snow and ice, for example, reflect sunlight right back into space. If snow and ice melt and are replaced with dark blue water or brown soil, the Earth absorbs more energy.
Another factor is that the sun has natural variations in output -- meaning that sometimes the Earth receives a little more or a little less than 84 terawatts. Volcanoes eject dust that can both make the clouds more reflective and make the atmosphere absorb more energy, depending upon the specifics of the particles.
Another factor getting a lot of attention is emission of the so-called greenhouse gases. They get that name because they function like the panes in a greenhouse -- they let light in, but they reflect the infrared radiation back toward the surface.
The Earth receives 84 terawatts of solar power every moment -- that's 84 million million watts. Some of that energy is directly reflected from the Earth's atmosphere and the surface of the Earth. Some is absorbed -- heating up the air, water and land. The warmer air, water and land emit invisible infrared radiation that heads back into space. But some of that infrared radiation doesn't make it to space -- it gets reflected right back to the surface. It's trapped.
A pot of heating water on the stove feels warm and it steams. The heat you feel and the steam you see are both ways the pot is getting rid of energy, but more energy comes in than goes out -- so the pot heats up. The same thing occurs with the Earth: If more energy comes in than goes out, the Earth heats up.
RADIATION BALANCE
If the Earth doesn't get rid of the 84 terawatts of power it receives at every moment, it heats up. Many factors influence the Earth's radiation balance. Snow and ice, for example, reflect sunlight right back into space. If snow and ice melt and are replaced with dark blue water or brown soil, the Earth absorbs more energy.
Another factor is that the sun has natural variations in output -- meaning that sometimes the Earth receives a little more or a little less than 84 terawatts. Volcanoes eject dust that can both make the clouds more reflective and make the atmosphere absorb more energy, depending upon the specifics of the particles.
Another factor getting a lot of attention is emission of the so-called greenhouse gases. They get that name because they function like the panes in a greenhouse -- they let light in, but they reflect the infrared radiation back toward the surface.
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