What is the “greenhouse effect” and what are the major greenhouse gases?
* A: About 30 percent of solar radiation that reaches Earth is reflected back into space by clouds, air molecules, dust, haze, and the Earth’s surface. Another 20 percent of incoming solar radiation is absorbed by the atmosphere. The remaining solar radiation reaches the Earth’s surface and is absorbed. The Earth’s surface radiates this energy back to the atmosphere in the form of infrared radiation. Most (90 percent) of this infrared radiation is trapped in the atmosphere by greenhouse gases. The energy absorbed by the greenhouse gases is reradiated in all directions. The energy that is directed back toward the Earth’s surface contributes to the warming of the planet. This phenomenon is called the greenhouse effect. Gases that absorb infrared radiation and contribute to the greenhouse effect include carbon dioxide (CO2), methane (CH4), chlorofluorocarbons (CFCs) and nitrous oxide (N2O).
