Part 1 of Essay
, in environmental science, is a popular term for the effect that certain variable constituents of the Earth's lower atmosphere have on surface temperatures. These gases--water vapor (H2O), carbon dioxide (CO2), and methane (CH4)--keep ground temperatures at a global average of about 15 degrees C (60 degrees F). Without ....

Part 2 of Essay
.... in sea level, along with other severe environmental agitation. An example of a runaway greenhouse effect is Earth's near-twin planetary neighbor Venus. Because of Venus's thick CO2 atmosphere, the planet's cloud-covered surface is hot enough to melt lead. Water vapor is an important "greenhouse" gas. It is a major reason why humid regions experience less cooling at night than do dry regions. However, variations in the atmosphere's CO2 content are what have played a major role in past climatic changes. In ....