Earth ozone layer due to the subsequent conversion of atmospheric into. The ozone layer blocks ultraviolet solar radiation, permitting life on land. Other atmospheric functions important to life include transporting water vapor, providing useful gases, causing small meteors to burn up before they strike the surface, and moderating temperature. This last phenomenon is known as the greenhouse effect: trace molecules within the atmosphere serve to capture thermal energy emitted from the ground, thereby raising the average temperature. Water vapor, carbon dioxide, methane, nitrous oxide, and ozone are the primary greenhouse gases in the atmosphere. Without this heat-retention effect, the average surface
Runaway greenhouse effect Runaway greenhouse effect A runaway greenhouse effect is a state in which a net positive feedback between surface temperature and atmospheric opacity increases the strength of the greenhouse effect on a planet until its oceans boil away. An example of this is believed to have happened in the early history of Venus. On the Earth, such a hypothetical state is called hothouse earth, but the IPCC states that "a 'runaway greenhouse effect'—analogous to [that of] Venus—appears to have virtually no chance of being induced by anthropogenic activities." Other large-scale climate changes are sometimes loosely called a "runaway greenhouse effect" although