Previous Year Question

After absorbing energy received from the Sun, the Earth's surface emits a large part of that energy back toward the atmosphere as longwave infrared radiation. According to NASA, atmospheric water vapour, carbon dioxide and other greenhouse gases absorb most of the longwave infrared radiation emitted by the Earth, thereby warming the lower atmosphere.

Greenhouse gases also re-emit this absorbed energy in different directions. Some of it escapes toward space, while some is radiated back toward the Earth's surface. This process keeps the surface and lower atmosphere warmer than they would otherwise be and is known as the Greenhouse Effect.

The distinction between visible light and infrared radiation is important. Much of the incoming shortwave/visible solar energy passes through the atmosphere and reaches the Earth's surface, whereas the warmed Earth emits energy mainly as infrared heat, which greenhouse gases absorb effectively.