The greenhouse effect is one of the things that make life on Earth possible. The light from the Sun passes through the atmosphere and reaches the earth's surface where much of it is absorbed, thereby warming the surface. Some of the infrared radiation is reflected upwards again. The greenhouse gases in the atmosphere then reflects some of this radiation back to the surface again, thus utilizing some more of the energy from it.
The greenhouse effect is necessary for life on Earth, but recent years have seen it develop into global warming. Temperatures are increasing, causing disturbances to ecosystems.
The term greenhouse effect originally came from gardening. A greenhouse is built of glass roofs and windows to keep plants warm. Sunlight passes through the glass and warms up the plants and objects inside the greenhouse. The heat is radiated back as infrared in longer wavelengths. The longer wavelength outgoing infrared cannot penetrate glass as well as the shorter wavelength incoming radiation. In a sense, a greenhouse let more of the solar energy coming in than going out. The temperature inside the greenhouse builds up over time. The greenhouse effect refers to the heat trapping characteristics of a greenhouse.
Despite the higher visibility when associated with the global warming concern, the greenhouse effect can be observed in almost any enclosure with glass windows. One very common example is a passenger car in a hot summer day. The greenhouse effect can bring the temperature in a car up to as high as 180° F within a short time. In the US, a small number of children and a larger number of pets are killed by the greenhouse effect each year when careless parents and owners leave them in cars for a long period of time.