Greenhouse gas Greenhouse gas A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about , rather than the present average of . The atmospheres of Venus, Mars and Titan also contain greenhouse gases. Human activities since the beginning of the Industrial Revolution (around 1750) have produced a 40% increase in the atmospheric concentration of carbon dioxide (), from 280 ppm
Runaway greenhouse effect feedback effect from increased atmospheric water vapor, as well as Earth being too far away from the Sun at its current luminosity for such to occur is well below that which is required to boil away the oceans. Climate scientist John Houghton has written that "[there] is no possibility of [Venus's] runaway greenhouse conditions occurring on the Earth". However, climatologist James Hansen disagrees. In his "Storms of My Grandchildren" he says that burning coal and mining shale oil will result in runaway greenhouse on Earth. A re-evaluation in 2013 of the effect of water vapor in the climate models showed