Greenhouse effect is a warming of the lower atmosphere and surface of a planet by a complex process involving sunlight, gases, and particles in the atmosphere. On Earth, the greenhouse effect began long before human beings existed. However, recent human activity may have added to the effect. The amounts of heat-trapping atmospheric gases, called greenhouse gases, have greatly increased since the mid-1800's, when modern industry became widespread. Since the late 1800's, the temperature of Earth's surface has also risen. The greenhouse effect is so named because the atmosphere acts much like the glass roof and walls of a greenhouse, trapping heat from the sun.