the name given to the phenomenon by which transparent gasses of the atmosphere allow sunlight to warm the Earth's surface, and then prevent that warmth from escaping back into space. Like the inside of a greenhouse on a sunny winter day, the Earth is warmer because of this effect than it would be if the atmosphere did not hold heat. Carbon dioxide and other gasses responsible for this heat-trapping effect constitute less than 1% of the atmosphere's volume. [fn]Source: (IISD 2005) from IISD website; http://www.iisd.org/sd/glossary.asp (updated: Aug 2005)[/fn]