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
Atmospheric carbon cycle lifetime of about eight years. This keeps the concentration of methane in the atmosphere relatively low and is the reason that it currently plays a secondary role in the greenhouse effect to carbon dioxide, despite the fact that it produces a much more powerful greenhouse effect per volume. Carbon dioxide () has a large warming effect on global temperatures through the greenhouse effect. Although individual CO molecules have a short residence time in the atmosphere, it takes an extremely long time for carbon dioxide levels to sink after sudden rises, due to e.g. volcanic eruptions or human activity and among