Fourier continued to rationalize how the sun could continually warm the earth, without the heat trapped by the greenhouse effect overheating the planet. According to American Institute of Physics, he concluded that the earth's heated surface emits invisible infrared radiation which allowed the heat to escape the atmospheric layer and be carried away into space. Science has since determined that earth emits enough longwave radiation into space to equal the solar radiation absorbed. According to NASA's Earth Observatory, it's this radiative equilibrium that keeps the earth's temperature relatively constant over time.
Greenhouse gases are the atmospheric gases that include carbon dioxide and water vapor that are trapped within the earth's atmosphere. The greenhouse gases absorb the sun's highly-active shortwave radiation, which according to the University Corporation for Atmospheric Research is capable of breaking apart stable biological molecules and causing sunburn and skin cancers. The greenhouse gases transform shortwave radiation into the less active longwave radiation and bounce it around in many directions, including back toward the earth which maintains temperatures at night. Not only does the earth benefit from constant temperatures, the "greenhouse effect" allows for the recirculation of water vapors as rain.
When Fourier first described the greenhouse effect, it was an innocent term to explain what he believed to occur in the atmosphere. However, the earth's atmosphere really is nothing like a greenhouse with disagreements in the scientific community as to "greenhouse effect" being an inaccurate term. In Fourier's time, it was believed that the atmosphere was comprised of a single barrier much like a pane of glass. Since then science has learned that the atmosphere is made-up of a series of layers. The earth, even with its atmospheric layers is an open environment into space, while a greenhouse is a closed and often controlled environment.
Without the natural processes involved in the greenhouse effect, life could not exist on planet earth. However, ACAR notes that in the 1950s the term was linked to concerns of dramatic climate changes, and began to take on negative connotations. Today it is linked with the threat of global warming and the beneficial greenhouse gases of carbon dioxide and water vapor are discussed as hazardous elements. In 2011, the polarizing debate as to the legitimacy of global warming and its proposed dangers has yet to find a neutral grounds for agreement among scientists, politicians and economists.