<P> A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range . Increasing greenhouse gas emissions 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 − 18 ° C (0 ° F), rather than the present average of 15 ° C (59 ° F). The atmospheres of Venus, Mars and Titan also contain greenhouse gases . </P> <P> Human activities since the beginning of the Industrial Revolution (around 1750) have produced a 40% increase in the atmospheric concentration of carbon dioxide (CO), from 280 ppm in 1750 to 406 ppm in early 2017 . This increase has occurred despite the uptake of more than half of the emissions by various natural "sinks" involved in the carbon cycle . The vast majority of anthropogenic carbon dioxide emissions (i.e., emissions produced by human activities) come from combustion of fossil fuels, principally coal, oil, and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture (including livestock). </P>

The 2 most abundant gases in our atmosphere