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
Future of Earth remaining life will be extinguished due to the extreme conditions. If the Earth loses its surface water by this point, the planet will stay in the same conditions until the Sun becomes a red giant. If this scenario does not happen, then in about 3–4 billion years the amount of water vapour in the lower atmosphere will rise to 40% and a "moist greenhouse" effect will commence once the luminosity from the Sun reaches 35–40% more than its present-day value. A "runaway greenhouse" effect will ensue, causing the atmosphere to heat up and raising the surface temperature to around .