A natural system known as the "greenhouse effect" regulates temperature on Earth.Just as glass in a greenhouse keeps heat in, our atmosphere traps the sun’s heat near earth’s surface, primarily through heat-trapping properties of certain “greenhouse gases”.Earth is heated by sunlight. Most of the sun's energy passes through the atmosphere, to warm the earth's surface, oceans and atmosphere. However, in order to keep the atmosphere's energy budget in balance, the warmed earth also emits heat energy back
to space as infrared radiation. As this energy radiates upward, most is absorbed by clouds and molecules of greenhouse gases in the lower atmosphere. These re-radiate the energy in all directions,some back towards the surface and some upward, where other molecules higher up can absorb the energy again. This process of absorption and re-emission is repeated until,finally, the energy does escape from the atmosphere to space.
However, because much of the energy has been recycled downward, surface temperatures become much warmer then if the greenhouse gases were absent from the atmosphere. This natural process is known as the greenhouse effect. Without greenhouse gases, Earth's average temperature would be -19°C instead of +14°C, or 33°C colder.
